Final Report Summary - MUJULIMA (Innovative Materials for Multiple Junction OPVs and for Improved Light Management)
Executive Summary:
The focus of MUJULIMA is the development of innovative materials for multiple junction OPVs and for improved light management in order to achieve high energy conversion efficiencies (above 17% cell efficiency required for the 15% module efficiency). The lifetime (10 years) and stability of the modules will be enhanced by identifying and remediating the degradation mechanisms at material level and by improving the outdoor performance of encapsulation materials.
Solar photovoltaic (PV) technology is one of the fastest growing sustainable, renewable energy conversion technologies that can help meet the increasing global energy demands. Organic photovoltaic (OPV) technologies are particularly attractive due to their compatibility with low-cost roll-to-roll and printing processing at low temperatures on a wide variety of substrate materials and the lack of scarce or toxic materials rendering them environmentally friendly. OPVs can also benefit from a larger selection of functional materials as the required properties (high semi-conductor mobility, suitable band-gap, good intrinsic stability, good barrier properties, etc.) can be tuned by careful design and synthesis.
Currently, the highest cell efficiencies reported in Europe for solution processed single, double and triple junction cells as well as the lowest water vapor transmission rates for transparent flexible barriers were obtained by the partners of MUJULIMA. In this project we show how with new and innovative materials we will increase the module efficiencies and outdoor stability to make OPVs a commercially competitive viable technology.
The innovative materials and technologies developed within MUJULIMA are demonstrated via three applications powered by OPVs: (a) in-house electrical automation devices, (b) off-grid charging, and (c) flexible OPV modules on bus roof.
Project Context and Objectives:
Solar photovoltaic (PV) technology is one of the fastest growing sustainable, renewable energy conversion technologies that can help meet the increasing global energy demands. Organic photovoltaic (OPV) technologies are particularly attractive due to their compatibility with low-cost roll-to-roll and printing processing at low temperatures on a wide variety of substrate materials and the lack of scarce or toxic materials rendering them environmentally friendly. OPVs can also benefit from a larger selection of functional materials as the required properties (high semi-conductor mobility, suitable band gap, good intrinsic stability, good barrier properties, etc.) can be tuned by careful design and synthesis.
Currently, the highest cell efficiencies reported in Europe for solution processed single (>9%), double (8.9%) and triple (9.6%) junction cells as well as the lowest water vapor transmission rates for transparent flexible barriers (WVTR 10-6 g/m2/day) were obtained by the partners of MUJULIMA. In this project we show how with new and innovative materials we will increase the module efficiencies ≥15%) and outdoor stability to make OPVs a commercially competitive viable technology.
The general objective of MUJULIMA is to develop high performance commercially competitive materials with excellent intrinsic stabilities for the cost-effective production of double and triple junction OPVs, for improved light management and for enhanced outdoor stability to achieve high module efficiencies (15%) and lifetime (10 years).
A) Design and synthesis of innovative photoactive materials as well as novel interlayer materials and their functional performance (molecular weight, polydispersity, crystallinity, morphology with fullerenes, charge carrier mobility, etc.) followed by characterization and optimization in order to produce multiple junction OPVs.
1) Innovative photoactive materials will focus on novel donor-acceptor conjugated polymers with sufficient variation in optical band gaps to achieve high efficiencies in single, double and triple junction devices.
2) Novel interlayer materials will comprise of organic (e.g. polyelectrolytes) and inorganic (e.g. metal oxides) materials to increase charge selectiveness of the contacts and to adjust the work function to improve the ohmicity of the contact.
These materials will first be tested in single junction OPV cells, measuring the energy conversion efficiencies of the cells and performing stability and lifetime tests. To reach high energy conversion cell efficiencies (17% or higher) needed to achieve high module efficiencies (15% or larger) the new photoactive and interlayer materials will be employed in architectures with double and triple junctions.
B) Development of materials for better light management within the module by employing up- and down-converter materials (IR to VIS/NIR and UV to VIS) for enhanced spectral usage of the solar spectrum. This will provide an additional relative efficiency increase of at least 15%. Cost efficient use of materials will be ensured by low cost printing/coating technologies and laser scribing. To achieve the highest possible efficiencies the optimum thickness of the different layers within the multiple junction cells will be predicted by electro-optical modelling. Optical modelling will be used to find the best arrangements of (plasmonic) micro- and nanostructures for improved light incoupling (enhanced absorption).
C) Improvement of the lifetime and stability of the modules by identifying and remediating the degradation mechanisms at material and stack level (layer/material interfaces) will be achieved by developing accelerated ageing test protocols and by improving the outdoor performance of encapsulation materials using special coatings.
The innovative materials and technologies developed within MUJULIMA will enable the realization of three applications (the first 2 will be demonstrated during the project, the 3rd one is a virtual demonstrator that will be mature and commercially available technology by 2030):
1) Electrical automation devices for in-house application will be equipped with a small (25 cm²) high efficiency OPV module. This OPV equipment will enable devices to communicate with each other (data exchange) without grid connected electricity.
2) Urban furniture (information desk for example) will be equipped with a medium sized (225 cm2) high efficiency OPV module. Using adequate charger and battery, this system will enable the full equipment to run without grid connection.
3) A roof of a commercial bus will be fully equipped (20 m2) with high efficiency custom made OPV flexible module. The aim of the demonstrator will be to run a dedicated electrical air conditioning system. The system will enable the vehicle to stop its engine when expecting passengers/clients. With such equipment the bus will consume less gasoline and reduce pollution.
In the above described applications the common need is to have OPV modules with excellent stability and lifetime, capable for high efficiency solar energy conversion (15% and above) with low cost. To create such OPVs high performance stable materials (e.g. photoactive, electro-active, interlayer, barrier etc. materials) and technologies are needed that will ensure cost effective production and commercialization.
Project Results:
Work package 2: Specifications
Work Package 2 provides the specifications of the material and demonstrators developed in the project and the influence of cost and environmental impact of the studied materials. The initial specifications for five experimental topics (photoactive polymer development, charge extraction and recombination material development, light management, stability, and upscaling) have been done at the beginning of the project. The baseline stacks have been defined for the different tasks within the work packages. Every half year the progress was re-evaluated to converge activities from the different experimental topics as much as possible. The initial specification of the materials is presented in the Deliverable Report D.2.1 and the revised specification is presented in the Deliverable Report D.2.3.
The influence of the individual novel materials developed within MUJULIMA on the cost and environmental impact of tandem and triple junction modules has been evaluated by using a SimaPro LCA tool and a home-built CoO tool. The photoactive, charge extraction and recombination, and hardcoat material price and environmental impact have been varied to investigate the impact on the total cost and environmental impact of the modules.
Task 2.1: Specification of materials and formulations thereof
The essential requirements and characteristics have been developed for all five experimental topics: Photoactive polymer development, Charge extraction and recombination material development, Light management, Stability and Upscaling. In order to accommodate all targets, two simultaneous approaches have been chosen: one for upscaling towards industrial production limited by the above registered specifications and one for record cells where these requirements may be violated for higher things.
Task 2.2: Life cycle analysis and cost of ownership calculations
- The photoactive polymer was found to be potentially critical component in terms of environmental impacts and cost. The critical factor in this context is the synthesis complexity. A minimization of synthesis complexity is desirable.
- Device performance parameters such as “service lifetime” and “annual degradation rate” are of utmost importance in the overall evaluation of environmental impacts and cost. These parameters can easily overshadow effects related to changes in materials or production parameters. A maximization of service lifetime and minimization of annual degradation rate are desirable.
- Design rules for the materials to which cost and environmental impacts are most sensitive (photoactive polymer and fluorinated polymer in encapsulation structure) have been derived. These are useful as a “first order” materials selection tool.
Task 2.3: Specifications and design of demonstrators
- Photoactive components which can be produced at low cost at the Kg scale, with a target cost of less than 100€/g.
- Highly efficient & stable donor/acceptor blends capable of withstanding 1 sun light soaking for > 2 years, with acceptor components also at less than 100€/g at scaled cost.
- Photoactive components which can be formulated using non-chlorinated solvents
- Good device performance and lifetime achieved ideally at around 300nm dried dried layer thicknesses for manufacturing yield.
- An additional factor worth pursuing is suitability for indoor & low light applications as early market opportunity for OPV.
WP2 Conclusions
The goal of WP2 is achieved. All Milestone and Deliverables have been achieved and realized in the project. The specifications of the different experimental topics have been described in D2.1. It was revised in the second period and has been described in the D.2.3. The sensitivity on the cost and environmental impact of the newly developed materials in tandem and triple junction solar cells has been studied and documented in D2.2. The material selection tool which covers materials properties, the cost and environmental footprint of OPV modules is described in MS11 report. The specifications for the demonstrators, realized in WP6, are described in D2.4.
Work package 3: Innovative materials for multiple junction OPV
Task 3.1: Synthesis of novel photoactive materials
- The effect of side chain length on the photovoltaic properties of conjugated polymers have systematically been investigated with two sets of polymers that bear different alkyl side chain length based on benzodithiophene and benzo[2,1,3]thiadiazole or 5,6-difluorobenzo[2,1,3]thiadiazole.
- Replacing thiophene by thiazole in conjugated polymers based on benzo[2,1,3]thiadiazole give significant enhancement in open-circuit voltage by about 0.2 V in solar cells. A high Voc approaching 0.95 V was achieved for the polymers with optical band gap below 1.75 eV.
- Random copolymerization of two electron deficient monomers, alternating with one electron rich monomer, forms a successful approach to synthesize state-of-the-art semiconducting copolymers for organic solar cells. A PCE over 8% could also be achieved when the active layer was deposited from non-halogenated solvents at room temperature.
- Introducing additional thiophene rings in conjugated polymers increases the fill factor and efficiency of thick polymer:fullerene solar cells, by creating a more favorable polymer chain packing and a finer phase separation.
- A series of new ultra-small band gap polymers has been synthesized in which the HOMO energy level of ultra-small band gap polymers has successfully been tuned by the ratio of the co-monomers in the main chain. Regioregular polymer P4, exhibits a PCE of 3.5% at a bandgap as low as 1.25 eV.
Several important results have been obtained regarding the design of conjugate polymers for solar cells:
Side chains: The data show that insufficient side chain length yields low molecular weight polymers or even insoluble polymers that cannot be used. The low molecular weight results in poor phase interconnectivity, low domain purity, unfavorable structural orientation and so on, which have already been well studied. On the other hand, too long side chains produce too soluble polymers, which will affect drying kinetics and self-organization of the BHJ films during spin-coating as well as the compatibility between polymer and fullerene. As a result, a suboptimal BHJ film morphology with serious phase separation and large domain size will be formed. In these liquid-liquid phase separated blends, charge generation mainly occurs in the continuous mixed polymer-fullerene phase, but because most fullerenes are assembled in the droplet domains, the electron transport in the mixed phase is hampered which results in significant bimolecular recombination. An optimal side chain length is thus required to balance solubility such that the right microstructure can be formed in BHJ films.
Increasing Voc: Replacement of thiophene by thiazole can effectively downshift the frontier orbital levels of the polymers without significantly changing the optical bandgap. Consequently, the Voc of the PSCs is enhanced by about 0.2 V. The PCE however, is only significantly improved for IDT-DTzBT compared to IDT-DTBT, but not for BDT-DTzBT with respect to BDT-DTBT. In the latter case, the low Mn and higher solubility cause a sub-optimal morphology for BDT-DTzBT:[70]PCBM blends. The results evidence that the thiazole-implementing strategy can be a fruitful approach.
Random colpolymers: Semiconducting random copolymers offer a significant prospect for application in highly efficient PSCs. The beneficial effect originates from the fact that the random polymers possess structurally different monomers, but these do not result in strong variations of the energy levels along the chain. The random polymers do not suffer from batch-to-batch variation or strong dependence on the precise composition. The reduced crystallinity and π-π stacking provides the random copolymers with good solubility and processability. As a result, random copolymers allow fabricating highly efficient PSCs with low sensitiveness to processing history, even from non-halogenated solvents at room temperature. The successful demonstration of these random copolymers for PSCs represents a reliable methodology for developing practical useful photovoltaic polymers in future manufacturing of PSCs.
Thick cells with high FF: A set of conjugated polymers based with a systematic increase of thiophene rings in the polymer main repeating unit was designed and synthesized. Interestingly, for thick photoactive layers based on these materials there is a monotonic relation between the relative number x of thiophene rings in the conjugated polymer main chain and fill factor, which is a dominant factor that determines the performance of PSCs. The steady increase of fill factor results in a rising overall efficiency with increasing content of thiophene rings. A detailed investigation revealed that the “thiophene ring effect” is a combined result of an enhanced hole mobility and suppressed bimolecular charge recombination, which we attribute to a more favorable polymer chain packing and a finer phase separation. The rationale behind the beneficial effect is that the additional unsubstituted thiophene rings allow for a reduced π-stacking distance and a reduced lamellar distance which improve charge transport, and reduce the solubility of the polymer chain which results in finer phase separation in blends with fullerenes. The discovery also provides an explicit guideline for designing and developing practical useful polymers for application in PSCs in future. Moreover, the correlations between molecular structure and fill factor observed in this paper are a motivation to search for methods that can enhance charge carrier mobility, suppress charge recombination, tune polymer packing, and optimize morphology to achieve high PCE at large active layer thickness, which in turn favors large-scale processing and multi-junction PSCs.
Ultra-low band gaps: Polymers with ultra-low band gaps (1.15 eV) can be made to function in organic solar cells. Via co-polymerization it is possible to tune the Voc. Although relatively high EQEs and Jsc can be reached, the common energetic loss between band gap and Voc of 0.7 to 0.8 eV, prevents obtaining high Voc’s. The low Voc also results in a low FF and hence the original objective of a PCE of 8% at 1.15 eV has not been reached.
Task 3.2: Functional materials for charge extraction and recombination
We have shown that photoinduced shunting upon UV illumination (h¬ > Eg) is a general phenomenon in OSCs comprising neat or electrically doped ZnO-based electron extraction layers. As a result, a significant deterioration of Voc and FF is found. We have provided a clear correlation of increasing carrier density in the EEL and a loss of electron selectivity in the EEL. In stark contrast to ZnO, we have demonstrated that the photoinduced shunting problem can be overcome by the use of EELs based on tin oxide (SnOx). In an in-depth assessment using XPS and Kelvin probe techniques, we have shown that the surface electronic structure of SnOx is substantially different from that of ZnO or AZO. The surface of ZnO-based EELs is dominated by negatively charged chemisorbed oxygen causing a depletion layer. UV illumination (h¬ > Eg) activates oxygen desorption, which leads to a lowered WF and a significant increase of carrier density. As a cathode interlayer in OSCs, this is found to result in a loss of electron selectivity. On the contrary, the surface of SnOx shows an accumulation layer, most likely caused by oxygen deficiency and H2O adsorbates. As a result, UV illumination was shown to leave the WF and carrier density of the SnOx essentially unaffected. In OSCs, the electron selectivity of the SnOx EEL persisted even upon UV illumination and thereby photoinduced shunting could be avoided. This finding is extremely important for the design of organic solar cells with a superior operational stability.
Moreover the new SnO2 formulations provided by Nanograde have been the subject of recent experiments. With those nanoparticle dispersions we were able to realize a room temperature solution process for light-soaking and photo-shunting free EELs.
In the first period of the project new recombination architecture for inverted tandem devices has been realized by combining the un-doped metal oxides eMoO3 and ALD-SnOx. This interconnect does not show major electronic problems without the need of additional thin metal layers or PEDOT:PSS. Now, using XPS/UPS and Klevin probe analysis, the formation of a dipole of about 0.7eV at the MoO3/SnOx interface could be found. The consequential alignment of the conduction bands makes a nearly barrier free electron transfer from SnOx into MoO3 possible. Due to the n-type characteristics of both oxides the electrons are carried through the MoO3 and the recombination takes place at the donor/MoO3 interface.
Investigations on solution processed metal oxides stated the resilience against solvents as a decisive challenge heading towards solution processed all-oxide interconnects. The combination of sol-gel VOx and ZnO nanoparticles showed first good results concerning protection against solvents and functionality in tandem devices. Perfect addition of Voc is achieved but slightly s-shaped J-V-curve results in a lowered FF of the tandem device. Nonetheless the tandem devices show a significant enhancement in power conversion efficiency with respect to the single junctions. For tandems with such recombination architecture comprising only solution room temperature processes under ambient conditions this has not been reported so far. With an optimized processing approach for the provided SnO2 nanoparticles we were even able to create an improved room temperature solution processed all-oxide recombination contact, that provides perfect addition of Voc and a higher FF than reached with ZnO. As an additional advantage towards the ZnO based interconnection layer, devices with the new sVOx/SnO2 architecture do no longer need UV activation.
Task 3.3: Triple junction cells with efficiency up to 17%
- Fully solution processed triple-junction polymer solar cells with PCE = 10% has been achieved by combining three different band gap polymers in an inverted solar cell configuration employing modified PEDOT:PSS and ZnO nanoparticles in the recombination layers.
- The polymer triple junction cell was fully characterized for the EQE of the three sub-cell which matched remarkably well with the predicted values based on optical modelling and data for the single junction solar cells.
- The polymer triple junction was implemented in a four cell module without any appreciable loss in efficiency.
- Hybrid tandem and triple junction solar cells were made using a near-infrared absorbing polymer and amorphous silicon. PCE of 11.6% for the tandem and 13.2% for the triple junction represents world records at this time for these types of cells.
A 10% efficient triple junction solar cell has been made. The performance is very close to the properties expected based on those of the sub cell. This demonstrates that the solution processed interconnects work perfectly. The main limiting losses are related to the quality (energy efficiency, IQE) of the sub cells. The efficient triple junction cells have effectively been applied in a 4-cell module with very similar efficiency (cell-area based).
We further demonstrated highly efficient hybrid multijunction photovoltaic devices by combining vacuum-deposited a-Si:H and solution-processed polymer solar cells. The best PCEs of 11.6% and 13.2% have been obtained for the hybrid tandem and triple-junction configurations, respectively. The combined merits from both a-Si:H and polymer solar cells can significantly enhance the PCE in reference to all polymer based counterparts. The effects of the optical characteristics of the interconnecting layer between a-Si:H and polymer sub-cells were analysed in-depth and optimized to achieve a higher photocurrent in the polymer sub-cell. In order to achieve a high balanced photocurrent in the triple-junction solar cells, a well-chosen mildly textured front electrode was used. The solution processing of polymer solar cells is fully compatible with the vacuum deposition of a-Si:H solar cells, which makes the hybrid devices applicable for the low-cost roll-to-roll mass production. The hybrid concept studied here can ultimately drive the PCE of polymer solar cell based photovoltaic devices to 15% and beyond in the near future, making low-cost, non-toxic, earth abundant, light weight and large-area photovoltaic modules available for clean electricity generation.
The ultimate goal of the project, which is to demonstrate a 17.5% triple junction cell, has not been reached. The main reason is the lack of efficient wide band gap and efficient ultra-small gap materials. Despite the vigorous attempts described under task 3.1 the desired results were not obtained. We note that with a fully characterized 10% all polymer triple and a fully characterized 13.2% hybrid triple cell we have advance the state of the art in this field.
Task 3.4: Large area processing of functional materials
- Non-chlorinated solvent system were investigated for four polymers
- PCDTBT and P17 show significant efficiency drop using non-chlorinated solvents.
- Both P15 and Th15 demonstrates at list 90% of devices performance using non-chlorinated solvents compare to the performance of the devices produces from o-DCB.
- Slot die coating process was developed for several polymers and was used for the manufacturing of the demonstrators.
The polymers PCDTBT and P17 perform well only when the photoactive layer produced from chlorobenzene or ortho-dichlorobenzene. Non-chlorinated solvents lead to the significant performance drop. While, other two polymers P15 and Th35 show reasonable results when processed from non-chlorinated solvents. Although P15 show reasonable performance using non-chlorinated solvents, this result is not very reproducible due to high polydispersity of the polymer molecular weight. For the manufacturing of large area demonstrators (D.6.5 and D.6.6.) the polymer Th35 is selected using non-chlorinated solvents.
WP3 Conclusions
Synthesize of innovative material has reached noticeable results: Random copolymerization of two electron deficient monomers forms a successful approach to synthesize state-of-the-art semiconducting copolymers for organic solar cells. A PCE over 8% is achieved when the active layer was deposited from non-halogenated solvents at room temperature. Photoactive material with ultra-small band gap reported in D.3.7. It is noteworthy that the PCE of 3.5% is among the highest efficiencies reported for a polymer solar cell with a band gap < 1.3 eV.
Variety of inorganic charge extraction and recombination materials (ETL and HTL nanoparticle dispersions) was developed in the project.
Fully solution processed triple-junction polymer solar cells with PCE = 10% has been achieved by combining three different band gap polymers in an inverted solar cell configuration employing modified PEDOT:PSS and ZnO nanoparticles in the recombination layers.
The polymer triple junction was implemented in a four cell module without any appreciable loss in efficiency. We note that with a fully characterized 10% all polymer triple and a fully characterized 13.2% hybrid triple cell we have advance the state of the art in this field.
Non-chlorinated inks for the polymers developed in the project were developed and used for manufacturing of the demonstrators using slot die coating.
Work package 4: Innovative materials and structures for light management
Task 4.1: Optical simulations and modelling of innovative light-management concepts
In the first period of the project, several methodologies have been developed to model and simulate optically the device stacks in which light management (LM) techniques can be incorporated. In this second period these methodologies were implemented throughout the developments of the other tasks.
Task 4.2: Innovative light-conversion concepts
- 1 Polyfluorene soluble in polar solvents was synthesised
- 1 Polymer incorporating red-emitting dye units and also soluble in polar solvents was synthesised which shows an intense solid-state photoluminescence at 612 nm upon excitation at 380 nm
- 3 Polymers incorporating red-emitting dye units were synthesised, which show an intense solid-state photoluminescence at 604 nm (PFR1a, 10 mol%), 597 nm (PFR1a; 30 mol%) and 621 nm (PFR1b) upon excitation at 380 nm.
- Different polymers incorporating BSe units were synthesised, which show an intense photoluminescence at 580 nm – 603 nm upon excitation at 380 nm.
- PFO, BN-PFO and DPAVB are promising materials for the preparation of guest host systems to down-shift the spectral region λ <425 nm to λ >450 nm with an efficiency of more than 50%.
- BNPFO:DPAVB successfully applied on OPV single junction device
Development and synthesis of novel down-shifting materials and material systems is well achieved. Therefore, new synthesis routines have been developed to follow different approaches of the down-shifting concept. On the one hand materials for host-guest systems have been studied, evaluating samples that are already commercially available (PFO, DPAVB) as well as materials synthesized by the Scherf-Group at BUW (BNPFO). In addition to the known host-guest approach the novel concept of down-shifting copolymers has been studied. Therefore multiple new copolymers (PF-PEG1, PFR1, PFR2, PFBSe) have been developed, synthesized and already tested at BUW. Moreover a new down-shifting copolymer has been developed, that has a good solubility in polar solvents.
Both approaches, guest-host systems and copolymers, provide materials with down-shifting properties required for the desired applications. Remarkably the new developed BN-PFO showed increased photoluminescence quantum efficiency in contrast to the commercially available PFO.
The copolymer approach already leads to a collection of possible materials with slightly different emission spectra around 600 nm. Thus they all have potential for application in OPV devices.
After selection it turned out that best candidate is the doped BNPFO:DPAVB combination, which has been tried in OPV single junction device. However, no overall improvement could be obtained in the performance of OPV single junction device. Reduced photoshunting could be observed due to UV-filtering.
Task 4.3: Innovative light-reflecting concepts
- Low-n nanoparticle dispersion development is complete
- This material has been evaluated as ARC in multiple architectures
- The first DBRs were calculated and made using known OPV transport layers, which showed reflection around 500 nm as calculated.
- In a second stage known intermediate reflectors from other fields in thin film PV were used and working devices were obtained.
While in the first period both anti-reflective as retro-reflective layers have been considered, the latter was only available from sources outside of the consortium. Therefore more focus was on the anti-reflective materials developed within the project in this second period. Another approach, specifically focusing for use in multijunction structures is the incorporation of intermediate reflectors.
As presented in the first periodic report Nanograde has developed a synthesis of low refraction index SiO2 nanoparticles and further dispersed it into a coatable formulation. In the second part of the MUJULIMA project, Nanograde was focused on further improvement of the ink formulation in order to improve its stability, coating properties and reducing the refraction index of the dried film. This allowed selecting the optimal dispersing parameters and the formulation composition.
This material has been evaluated as anti-reflective coating (ARC) in multiple device architectures. However, no significant improvement in the device performance could be obtained.
For the intermediate reflectors in multijunction devices, two different approaches were tested: the Distributed Bragg Reflector (DBR), consisting of several sets of transport layers that have high and low refractive indices and the Intermediate Reflector (IR), which is a single layer of aSiO:H combined with the regular OPV recombination contact.
Optical simulations were done and DBR stacks build and measured. Testing the DBR in OPV devices was foreseen, but first experiments showed that it was highly challenging to maintain a good optical performance and high conductivity in the DBR layer.
Optical simulations were also done to optimize the thicknesses of the IR and the calculated optimal thickness was integrated in full multi junction OPV solar cells. The results showed that though these layers can reflect part of the spectrum back to the front cell, however, the conductivity remained a challenge leading to S-shaped J-V curves of the devices limiting the solar cell power output instead of enhancing.
The use of a Distributed Bragg Reflector (DBR) or other Intermediate Reflector (IR) for multi junction OPV can be considered to still be in the exploratory phase of research. It has shown to be challenging to find material combinations that work both optically as well as electrically in two terminal multi junction OPV solar cells.
Task 4.4: Innovative light-scattering concepts
- Innovative light scattering nano and microstructured structures has been produced onto rigid (glass) substrates:
· use of a single layer of silica beads as a physical mask for TCO grid deposition
· sheet-to-sheet nanoimprint lithography (NIL) of a UV lacquer layer
Light scattering structures have been produced by TCO (ZnO:Al as an example) patterning in the 0.5- 10 μm range. Light scattering nano and microstructured structures have been produced onto rigid (glass) substrates.
Concerning Textured TCO, only the double texturation applied on AZO allow a gain of +0.6mA/cm² (from 14.4mA/cm² with AZO to 15mA/cm² with textured AZO). This gain represents an increase of 4.2% of Jsc. Nevertheless, the increase of Haze factor traducing a potential increase of light trapping is not sufficient to compensate the lowering of Voc and fill factor. The high roughness of these TCOs could induce high rate of defect for the collection of charges at TCO/absorbent layers interfaces.
Concerning nano imprinted structures of ITO the conclusion is that building OPV devices both SJ and MJ on top of a structured surface that acts as light management layer for light scattering, the performance of these devices is not improved, but rather deteriorated. Also taking into account the higher difficulty of processing thin layers on top of these structured layers it therefore is not recommended to use this type of light management for OPV devices.
Task 4.5: Optimisation of combined light management concepts in multiple junction devices
• Two light management material upscale approaches:
o Nanoimprinted hard coat
o Antireflection nanoparticle-based coating
In summary, the consortium has selected the ARC and nano-imprint hardcoat as the two light management approaches for further use and has proven the feasibility of upscaling both of the selected light management strategies. The pilot R2R instrument located at TNO already enables production of 1m2/min nanoimprinted hardcoat material. There are no obvious difficulties of scaling the process further up. Nanograde with their antireflection coating could already reach 10ton/year production scale. Such an amount would enable coating of 200000 m2 substrate.
WP4 Conclusions
A broad range of LM techniques has been investigated in this WP for use in single an multijunction OPV devices. It turns out however to be very challenging to simultaneously achieve optical and electrical improvements in the devices when applying such techniques without destroying the overall device operation. Finally, two main approaches have been selected for further use and upscaling: the ARC and nano-imprint hardcoat.
Work package 5: Stability of materials and devices
Task 5.1: Evaluation and development of hardcoat materials for barrier integration
Deliverable 5.1 described the specifications, selection and testing of commercially available hardcoats and hardcoats developed by TNO. Deliverable 5.2 elaborates on the tests in the last evaluation phase of the hardcoats and additional properties to make a final selection for a hardcoat that can be combined with a barrier coating. Being in the fortunate position of having multiple hardcoat candidates after all tests of evaluation phase, some additional properties are evaluated to make a final selection.
Materials selected in this task were used during the second half of the project for:
- manufacturing combined light management structures (see Task 4.5)
- evaluation a stability of the OPV devices with combined innovative materials (see Task 5.6)
- manufacturing of the demonstrators (see Task 6.3).
Task 5.2: Stability of photoactive, charge extraction and recombination layers
In this task, investigations of mono-stress tests of photoactive layers and charge transport layers are performed. The materials selection is based on stability assessment of single junctions. The impact of materials combination is assessed in task 5.4. All results are reported in detail in deliverable D5.3 and D5.5.
Regarding the photoactive layer stability, three different single junctions are investigated. The materials tested are:
- the best performing new wide band gap material BDT-FBT-2T from WP3;
- the reference DPP polymer pDPP5T from BASF that has a large resemblance to the small band gap polymers that are being developed in WP3;
- P3HT:ICBA that is used as a well-known wide band gap reference material.
- Different ETL were also evaluated, within pDPP5T solar cells.
- Single junctions with varying photoactive layers and ETL were evaluated against light, heat and air. Air appeared as the most critical stress factor but encapsulation can prevent damage to the cells.
- Zinc oxide appeared as the most promising ETL.
- pDPP5T and P3HT:ICBA appeared as the most stable photoactive layers.
Task 5.3: Stability of light management materials
Stability of different light management materials has been investigated and results gathered in deliverable D5.4. Down-shifting coatings, anti-reflective layers as well as light scattering materials were tested under mono-stress conditions (light, heat or air). Optical and electrical characterizations are reported before and after ageing.
- Down-shifting materials, anti-reflective coatings and light scattering materials were evaluated against light, heat and air stability.
- PFO layers (down-conversion layers) showed good heat and light stability. Air combined with light leads to degradation of the layers (damage of the absorption). Such down-shifting materials need to be encapsulated. Thus they should be deposited on the front side of the devices before encapsulation.
- The hard coats, retroreflective foils, and antireflective coatings show no change in optical transmission upon light soaking for 200 h.
- Nanoimprinted lacquers (light scattering) with and without ITO do not show any degradation in optical parameters upon mono- and multistress ageing. Samples with ITO electrode on nanoimprinted lacquers show a small increase in sheet resistance over time when exposed to air and heat. AMA layers showed good heat and light stability. Their exposure to air must be prevented through a proper encapsulation.
- No dramatic degradation of any of the layers was observed, thus all of the tested layers appear as good candidates for integration into devices.
Task 5.4: Stability of combined innovative materials
This task aims at assessing the stability of stacks combining multiple innovative materials. This part of the work comprised the following experiments:
- pDPP5T single junctions were combined with several light management materials and their stability was assessed as compared to the single junction alone ;
- tandems stability was compared to single junctions stability ;
- also the introduction on the one hand of novel interlayer materials in the tandem configurations, as on the other hand light management (LM) techniques on such tandem architectures was attempted.
- Tandems were fabricated with Th35 and pDPP5T polymer. Monostress tests were performed on those tandems. Based on an assessment with single junction devices, no mutual or additional interactions were observed.
- Light management coatings and foils do not influence the degradation mechanisms for pDPP5T solar cells on glass.
- Hard-coat imprinting can be done on barrier foils but lamination (which is needed for cells encapsulation) leads to transmission decrease. Therefore their implementation onto flexible devices was not successful.
Task 5.5: Accelerated test protocol
The objective of this task is to conduct multi-stress ageing tests and compare their outcome to mono-stress (so as to identify synergetic effects) as well as outdoor ageing (in order to be able to propose an accelerated test that is adapted to outdoor lifetime prediction).
- Mono and multistress tests were conducted on low band-gap and high band-gap solar cells. Air was clearly identified as the most severe stress factor of low band-gap pDPP5T solar cells. For encapsulated pDPP5T solar cells, no pronounced synergistic degradation effects when exposed to light and heat were found. For encapsulated high band-gap P3HT:ICBA solar cells, no synergistic degradation mechanism was observed when combining light and air.
- Multi-stress tests as well as outdoor ageing were conducted on flexible encapsulated devices with pDPP5T absorber. The accelerated conditions which mimic the best the outdoor ageing are the ISOS-L-1 protocol (1 sun, ambient air and moisture).
- These solar cells show remarkable stability, with no degradation after 2000 hours ageing outdoors, and an average PCE of 3.7% after 2000 hours. The devices also pass the damp heat and thermal cycling tests described in IEC-61646 standard (T90 > 1000 hours at 85°C 85% RH, and no PCE loss after 200 thermal cycles).
Task 5.6: Stable OPV devices with combined innovative materials
In this task, multi-stress and outdoor ageing tests were conducted on flexible tandem solar cells comprising light management materials. The light management material was selected from WP4, it is an anti-reflective coating provided by Nanograde and deposited on the device front side (external side of the gas-barrier film). The ageing protocols were selected according to deliverable D5.6. A comparison is made for cells with and without the anti-reflective layer.
- Flexible tandems were prepared with efficiencies of 5.91%.
- Efficiency of flexible encapsulated tandems comprising the AR coating was 6.21%.
- Stability of these devices is promising, with:
· a T90 higher than 1300 hours outdoors (PCE > 5.5%)
· a T80 of more than 1300 hours under 1 sun, in ambient air
· a T80 of more than 200 thermal cycles (for devices without AR).
- The benefit of the AR coating is observed in ageing conditions without a too high relative humidity. In these conditions, AR-coated cells end up with higher efficiencies.
- The accelerated conditions which mimic the best the outdoor ageing so far are the ISOS-L-1 protocol (1 sun, ambient air and moisture).
WP5 Conclusions
The hardcoat material for barrier integration have been develop in the project and reported in D.5.1 and D5.2.
Innovative materials developed in the project have passed mono-stress stability tests (D.5.3). The results were compared with multi-stress ageing results (D.5.5) and the identification of synergistic failure mechanism was realized in the project. The comparison of mono-stress aging results has been performed on individual and combined innovative materials in order to identify mutual interactions (D.5.7).
Flexible tandems were prepared, encapsulated and aged in outdoor as well as accelerated conditions (D.5.8).
Work package 6: Demonstration
This work package number 6 dedicated to Demonstration has two main objectives. The first one is to develop industrial scale synthesis of materials (charge extraction and recombination layers materials, and also active polymers) selected from workpages number 3 and number 4 and the second one to demonstrate efficient OPV modules for three different applications, i.e. rigid module on 5x5cm2 for indoor application, 15x15cm2 flexible substrate fulfilling the requirements for off-grid charging, 15x15cm2 flexible substrate fulfilling the requirements for bus roof application. Nanograde has successfully up-scaled the syntheses of the charge extraction and recombination materials by implementing at their plant new reactors capable of producing more than a ton per year of nanoparticles and more than ten tons per year of formulations containing nanoparticles. PCAS has synthesized for demonstration activities larger batches of a wide band gap polymers developed by TU/e within work package number 4. The feasibility study concerning the up-scaling of this polymer has also been regarded in terms of security and toxicity. Regarding the second objective of the work package, 5x5 cm2 modules for indoor application were produced by sheet-to-sheet slot die coating on glass substrate which provide 3.24% performance (3.9% active area efficiency), with the voltage of 6.579 Volts, FF of 40.45 % and the current of 24.32 mA.
In terms of task 6.3 Eight19 has produced large scale TANDEM demonstrators at 15x15cm on flexible web using green solvent processing with a geometric fill factor of over 80%. The two demonstrator modules generate 400mW and 600mW respectively and the IV curve fill factors are high. The demonstrator containing the TH35 donor material had an active area efficiency of 1.9%, whereas the P3HT demonstrator had an active area efficiency of 3.9%, which dropped to 3.25% after encapsulation and hardcoat layer application.
Task 6.1: Upscaling synthesis of functional materials from WP3 and WP4
- Upscale of nanoparticle synthesis and formulation successful
- Scale-up of a newly developed wide band gap polymer, Th35, with a security study of the process, a toxicity study on the polymer concerning acute dermal irritation and the preparation of large batches of Th35.
The nanoparticle materials selected within WP3 and WP4 were successfully up-scaled in Nanograde lab.
The scale-up synthesis of one of the newly developed wide band gap polymer, Th35, has been successfully achieved. The larger samples prepared within the course of this study are going to be used in the demonstration activities of Task 6.2 and Task 6.3.
Task 6.2: OPV demonstrator for indoor application
- 5x5 cm2 modules were produced by sheet-to-sheet slot die coating on glass substrate (D.6.2)
- The modules provides 3.24% performance (3.9% active area efficiency), with the voltage of 6.579 Volts, FF of 40.45 % and the current of 24.32 mA.
Slot die coated 5x5 cm2 modules with high geometrical fill factor were demonstrated. The interconnection in the modules was realized by laser patterning. Performance of the slot die coated modules using PCBTBT:PC[70]BM as a photoactive layer was 3.24 % (active area efficiency is 3.9%). The total area of the modules was 25cm2, with the busbars area of 5 cm2 and module are of 20 cm2 (active area 16.8 cm2). Geometrical FF of the modules was 80%. The modules consist of 8 serially interconnected cells and have Voc of 6.579 V, Isc of 24.32 mA and FF of 40.5 %. Material selected for this demonstrator meets the requirements of indoor application.
Task 6.3: OPV demonstrator for outdoor application
Two demonstrators of 15x15cm were produced directed to the requirements of D6.5 (off-grid charging module) and D6.6 Bus-roof demonstrator.
- D6.5 Off-grid charging Tandem OPV module was produced with Project donor material TH35 with a size greater than 225cm2 and a 1 sun cell area efficiency of 1.9% after encapsulation and a power output of just over 400mW.
- D6.6 Bus-roof demonstrator Tandem OPV module with P3HT in the first photoactive layer was produced which incorporated a hardcoat material. It was >225cm2 and 1 sun cell area efficiency was measured at 3.9% - this dropped to 3.25% efficiency after encapsulation due to optical losses through the additional hardcoat layer. The power output was measured at just over 600mW.
Tandem solar module demonstrators for off grid charging comprising the project donor TH35 (D6.5) and a bus roof demonstrator with hardcoat (D6.6) were fabricated. The demonstrator module stack delivered 400mW and 600mW of power under 1 Sun illumination, and were completed with a geometric fill factor of >80% in line with the target. The efficiency was measured at 1.9% and 3.9% respectively. At low light there was some promising performance, which was good to see given the relatively thin layers and related deposition and yield challenges involved.
WP6 Conclusions
During the course of this work package number 6, the syntheses of a variety of functional materials developed within work package 3 and work package number 4 have been successfully scaled-up. All these scaled-up materials have been used to produce either charge and extraction layers and/or active layers in the demonstrators developed and set up within this work package 6. As an example, the OPV modules prepared on a 20 cm2 for indoor application provide 3.24% performance, and tandem outdoor demonstrators >225cm2 were produced with 1.9% efficiency using project photoactive donor material and 3.9% using P3HT as the first donor material.
Potential Impact:
Strategic impact
MUJULIMA will result in next generation high performing innovative materials for multiple junction OPV cells with improved light management. These cells will show higher efficiencies and higher outdoor lifetime than present state-of-the-art. More importantly a convincing roadmap will be built during the project that will show that the results of MUJULIMA will contribute to realize a cost effective production of industrial modules for a commercially competitive price with efficiencies of OPV modules of at least 15%, with outdoor lifetime of at least 10 years before 2030.
In order to realize such an ambitious roadmap, a number of results have to be accomplished in MUJULIMA. On the technical side these include: lab-scale multiple junction OPV cells, novel light management materials and structures, study of intrinsic stabilities and stress factors, and coupling of this know-how to improved materials and device structures, increased stability achievement by incorporating needed protective functionalities on the Holst Centre barrier, OPV modules using non-vacuum based printing technologies. To determine the market size, CoO calculations of OPV modules based on the concepts developed in MUJULIMA will be performed, including the production cost of the novel materials and light management techniques developed in the project. The performance of OPV materials and devices will be validated in a number of demonstrators, where it is believed that low cost flexible and in some applications transparent OPV modules will find a market before 2030.
The consortium will further strengthen European scientific and technological leadership in the fields of materials for organic based devices, specifically organic PV, device structures for high efficient single, double and triple junction organic solar cells, and full working OPV demonstrators, leading to a solid basis for production and employment of OPV cells and modules. Thus, it will create employment and future industrial solutions.
Renewable energy sources like PV play an important role in reducing the need for environmentally unwanted sources of energy producing large quantities of CO2. Organic photovoltaics among all of the PV technologies has by far the lowest carbon foot print. Both these aspects on future OPV products are believed to have a positive impact on European welfare and will support the European efforts to reach the environmental European goals.
MUJULIMA has brought together a strong consortium of universities and research institutes in combination with strong industrial companies. Two partners (PCAS and Nanograde) who are active in development and production of materials for applying several layers necessary for polymer electronic devices, especially OPV, fill up almost the complete value chain for production of OPV devices. Substrates and barrier manufacturers are outside the scope of the project, but substrates are abundantly available, and barrier coatings and stacks are within the project available through one of the partners (TNO/Holst Centre). As the development of new and improved materials is the primary focus of this project, the consortium further consists of a strong and world leading group of universities and research institutes. Development of OPV demonstrators with the intention to produce OPV cells and modules and to apply these in a range of products will be done by the industrial partner Eight 19 is exploring several markets for the application of flexible photovoltaic films. Near term opportunity is off-grid charging in developing countries, but also indoor energy harvesting which relates to the emerging internet of things. Eight19 is currently working with customers to develop specific solutions for outdoor and indoor applications. This existing customer base, PV know-how and printing technology, combined with a road map to OPV production within a few years makes them essential in the MUJULIMA consortium.
Economic Impact (Direct & Indirect Market)
The ultimate market of OPV modules is in high level high power energy production. MUJULIMA will show that this ultimate market will be within reach by 2030, as long lifetime and high efficiency are considered necessary for this market. But, light weight flexible, (semi-)transparent OPV modules in different colours will by themselves create new markets and opportunities to use OPVs in areas which are not possible or extremely difficult or costly for present day c-Si rigid panels, or even not-possible for other non-transparent thin film PV modules based on thin film-Si or CIGS. Applications include transparent OPV within office building double glazing units, shades, bus and truck roofs, textile based tents, umbrellas, airplane wings, sails etc.
Solar photovoltaic (PV) technology is one of the fastest growing sustainable, renewable energy conversion technologies that can help meet the increasing global energy demands. EPIA showed a cumulative installed total solar generating capacity of almost 70 GWp by the end of 2011, and showed an average cumulative growth over the last ten years of 44% and an average yearly growth of 75%. Although growth predictions for the coming decade are lower than in the past decade, for Europe alone a cumulative installed base between 130-260 GW is predicted by 2020. Thin Film PV production accounted for generating 3.6 GWp in 2011 and a total installed base of over 9 GWp.
Main stream thin film PV explores the high temperature stability of glass substrates. However, flexible non-breakable large area inorganic thin film devices on foils are emerging. Furthermore organic PV technology that has the potential to challenge the inorganic PV performance (expressed in price/kWh) is showing great potential. The development of OPV concentrates on the use of polymer substrates to take leverage of the roll-to-roll production option on flexible substrates to bring down the production costs (< €0.5/Wp).
A number of market research companies have recently published updated figures of the OPV market. Market Research Company IDTechEx forecasts that the market will rise to $630 million in 2022. The market growth will be predominantly driven by electronics in apparel, posters and PoP smart labels, and off-grid developing world applications. Nanomarkets are a little bit more optimistic in their market predictions estimating a market size of over $700 million in 2019; they do state that this market is heavily limited by the expected module efficiency of less than 6% and lifetime of less than 10 years by commercially available products. Nanomarkets estimates that more than 300 M$ of this 700 M$ market will be in portable charging devices, in BIPV/ BAPV Glass and other application areas like BIPV/BAPV Roofing, AIPV etc.
Another research company (Lux research) has made the lowest market prediction, also based on the present situation, with low efficiency modules with limited lifetime, they predict the OPV market in 2020 to be $ 159 million in the most likely case. Lux research sees five market segments where already now OPV products could be introduced: signage, consumer electronics, defence, developing world (off-grid) and most importantly BIPV.
Earlier predictions by IDTechEx based on faster introduction of more efficient and longer lasting OPV modules on the market predicted that OPV would have about 30% of the thin film PV market in 2023, the thin film section was estimated to be about 20-30% of the total PV market, leading to an estimate of about 10% of the total PV market for OPV. With an estimate of a total market size for PV beyond 2020 exceeding 1000 billion EUR, even a small percentage in the market for production of OPV would lead to large numbers. Considering that production of high efficient OPV modules of at least 15% with outdoor lifetime of at least 10 years as an outcome of MUJULIMA can be accomplished before 2030 it is believed that far larger market sizes will be within reach than predicted at this point in time.
With still 10-20 years before OPV can seriously compete with mainstream PV modules of today, in combination with the fact that PV modules are already becoming rather low in price some criticasters doubt whether there will be a substantial market for OPV in future. To the opinion of the MUJULIMA partners there is no doubt that a substantial market will be possible for OPV products. This belief is based on a number of observations. For one it is based on the already very fast development of materials, technology, equipment and pilot and production facilities. See section 1.2 for the state-of the art world records, where cell efficiencies in the lab already are 12%, and on module level beyond 8%. Noteworthy these records do not come from universities and institutes, who are usually far from commercial production but from companies, who do want to commercialise their R&D efforts within a short time period, as is the case with the industrial partners of MUJULIMA, PCAS, Nanograde and Eight 19. Eight19 plans to increase the production capacity initially to 10.000 and then to 200.000m2/yr during the next three years. This is a key step to prove the markets and applications. The second reason we believe that there will be a substantial market is by the unique properties of OPV, which none of the other PV technologies have in common in its totality. These properties being, light weight, unbreakable (as compared to glass and Si based PV devices) with lowest CoO and lowest LCA making them the most sustainable form of PV. In addition the aesthetic properties with the possibility to tune the colour and the transmission wavelength in general, to make them transparent and to produce them in any shape thinkable. On top of that the fact that OPV already has an energy output with low light intensities making more energy with lower efficiencies and making them suitable for indoor use and the inversely proportional temperature slope of OPV, making them more effective with increased temperature. This makes them interesting in a number of applications such as:
- Buildings; BIPV, BAPV, integrated roof structures, facades, semi-transparent windows, with the possibility to design and manufacture custom made and aesthetically pleasing, as is standard practice in the building industry, and is one of the greatest wishes of architects designing PV in buildings. Pike Research has published a report examining the expanding global market for BIPV products and they predict a strong growth with almost $2.5 billion revenue in 2016 with a growth of approximately 20% year. Nanomarkets has an even larger prediction for the BIPV market, they predict an enormous market size of $8.5 billion in 2016, although this prediction is much lower than a few years ago due to the present economic crises. They predict also that 2/3 of the systems installed will be thin film based. OPV modules with their low weight, flexible colour and transparency, and extreme low energy payback times, will have an enormous impact on this market.
- Transparent OPV can be applied inside a double glazing unit, still leaving sufficient light to enter a building but at the same time produce energy cost effectively. Even though it will not be applicable to every double glazing unit, even a small percentage of the global market for double glazing is enormous. Office buildings are often equipped with reflective glazing units, which only transmit 20-25% of the light inside the building. A major part of this market can be replaced with OPV units. For existing windows OPV can be applied on the inside (or outside) in shades, luxaflex and curtains.
- Greenhouses; OPV devices can be tuned to transmit light needed to grow products and to use the rest of the light to produce energy. A product/market analyses shows that especially for plastic greenhouses in southern countries, where the greenhouses are often white coated, because of an excess of solar light, the use of OPV foil with a double function, transmitted the right wavelength for controlled crop growth in combination with energy harvesting at wavelengths not needed for crop growth would be very cost effective. Currently the market for plastic greenhouses is large. In Spain 30.000 hectares of plastic greenhouses exist, in Africa 1.000.000 hectares, in China: 2.000.000 hectares etc. For bowed OPV greenhouses, this would mean a potential for Spain of 1.35 billion m2, in Africa 45 billion m2, China: 90 billion m2 etc. According to Markets and Markets. The global agricultural films market was worth $4.8 billion in 2011 and is estimated to reach $7.1 billion by 2017, growing at a CAGR of 6.7% from 2012 to 2017.
- Transportation sector; integration of OPV in vehicles, like trains, trucks, cars, airplanes, boats, camping cars to reduce energy consumption and battery usage for climate control, illumination etc. Light weight, flexibility and aesthetically pleasant are important aspects here.
- Interior use; mobile chargers, window shades and blinds. The low light intensity properties are important here in combination with flexibility and aesthetics.
- A report by ABI projects that the portable power industry, called the “Advanced Charging Technologies” industry which includes portable solar chargers, is currently estimated at $1.5 billion in revenue and is expected a grow to $34 billion by 2015. That is a Compound Annual Growth Rate(CAGR) of 86%.
- Textiles; tents, sails, umbrellas, car park roofs, backpacks etc., with light weight and aesthetics as most important properties here. Especially refugee and military tents are an interesting market case. Worldwide approximately 50 million people are displaced every year due to natural disasters and conflicts according to UN OCHA. A total of 33.9 million refugees are under UNHCR care alone. UNHCR procures 300.000+ tent/year. In refugee camps nowadays, generators with enormous amounts of fuel are needed which are often transported expensively with airplanes. Solar cells on the tents can help reduce the fuel need in disaster and conflict areas drastically. Refugee tent surface areas are in the millions of m2. Military tent applications in conflict areas are a multiple of the refugee tent market.
- A report by Pew Charitable Trusts states that the U.S. Department of Defence will invest heavily in clean energy projected to eclipse $10 billion annually by 2030. The majority of the spending will be for portable base applications including portable “soldier power.” In fact, the total market for renewable mobile power for forward military bases and temporary installations is forecast to reach $6.1 billion by 2030.
- Urban furniture; off-grid energy.
- Security; local off-grid energy in clothes and tents for first responders (fireman), red cross, army. Low weight, flexibility and low-light conditions are important aspects.
It is clear that the potential markets where OPV will most definitely play a role, when 15% efficiency and lifetime > 10 years is reach, will be enormous. From the above figures rough but conservative estimates have been made for the yearly m2 needed in 10-20 years from now. This totals to more than 600 million m2 per year for OPV (with 50 Mm2/yr in BIPV (conservative estimate due to assumed limited lifetime), 400 Mm2/yr for plastic greenhouses, 120 Mm2/yr for truck roofs, etc. etc.). CoO calculations show that at least 70% of the total cost of OPV are in materials, in total 8.4 tonnes are needed for 1 Mm2 of OPV modules, totalling to a need of more than 5000 tonnes/year. With the total cost of a module around 50 EUR/m2, the total yearly value comes to 30 billion EUR. The CoO show that the functional materials like photo-active polymers, interlayer materials, light management and hard coats are approximately 40% of the total materials cost, adding to a total market value of 8 billion EUR/year.
Although this program concentrates on the development of materials, devices and demonstrators for Organic PV cells and modules, a number of the materials and technologies developed have a much wider application scope. Transparent conductors, interlayers, light management and encapsulation are needed in organic based and inorganic based electronic systems on foil and even on glass based substrates. OLED light emitting devices, other thin film PV devices like thin film-Si and CIGS based solar cells could benefit from the developments in MUJULIMA.
The market for Organic Large Area Electronics (OLAE) is although still relatively small, rapidly expanding. A market size by 2027 of 330 billion US$ for the OLAE sector as a whole is forecast by the leading market research company IDTechEx. The market for OLED lighting is forecast to be 4-6 billion dollars in the 2015-2020 timeframe.
The market size for alternatives for ITO based Transparent Conductors (TC) is predicted by the market research company Nanomarkets to exceed 2 billion $. They also predict the market size for TC’s in general for OLED lighting of more than 430 M$ and thin film photovoltaics 340 M$.
Societal Impact (Social, Health, Employment, Environment)
OPV will enable an increase in alternative energy sources. It will reduce the need for polluting energy plants and nuclear energy plants. In Germany the effect of PV is already visible in the daily load curve on the energy grid. PV installations reduce the peaks in daily energy consumption, resulting in a levelling of energy prices to a lower level, and a considerable reduction of stand-by power plants which are only needed in peak times.84
The technologies and processes that will be developed in this project will bring the competence and skill level of the European companies, research institutes and universities involved to an exceptionally high and competing level compared to the rest of the world. This is extremely important in the view of the general strategy to develop Europe further into a knowledge-based economy (KBE).
MUJULIMA will also contribute to the implementations of the European Strategic Energy Technology plan (SET plan). The SET-plan wants to accelerate the development and deployment of cost-effective low carbon technologies. From all the PV technologies, OPV is estimated to be the best choice as cost-effective low carbon technology. The estimated energy payback time (regarding the carbon foot print) for OPV is 0.2 years, while for conventional solar cells this is still about 2.
In a recent study LCA analyses have been made on OPV devices, with a focus on critical components like TCO layer and encapsulation components. The result of the study is that LCA values did not change much for OPV. Krebs and his team showed that with efficiency improvements of the OPV cells even further reduction of the LCA time is possible, he predicts an LCA time of 1-3 days for a 15% effective OPV cell. The MUJULIMA team will critically watch that the LCA values will stay low despite the more complicated double and triple OPV cells, with alternative TC and with light management structures.
National and International Impact
Today there is less and less mass production of PV cells and panels within the EU. However, Europe is still the source of high-end technology, equipment and materials. Also, for organic and large area technology Europe has so far a strong position. However, here we also recognize competition from the Far East and from the US and have to respond by European initiatives to keep our leading edge in the near and longer future.
The project will help to keep or even to expand that level with respect to materials for OPVs. Considering production of OPV cells, for large scale products where millions of square meters of products are needed these will be produced eventually by roll-to-roll methods using printing technologies. The operational costs of these R2R lines are very low, so there is no reason to move this production to low wages countries. Furthermore Europe has an excellent know-how and skill level at equipment companies for building these production lines. As OPV cells and modules can be made by print technology, there is a huge possibility for SME’s in Europe to produce lucrative products on smaller scale by Sheet to Sheet (S2S) or sometimes small scale Roll to Roll (R2R) production (slower speed, small width). These will be customised products with a high level of uniqueness and integration possibilities. Local production and the possibility to make unique products will give a huge opportunity to other local European SME’s who can integrate these modules in all kinds of products.
Eight 19 ultimate goal is to manufacture plastic photovoltaic films in large volume. Due to high degree of automation Roll-to-Roll manufacturing can be done cost effectively in Europe. We are currently exploring various market sectors for short term and longer term entry. We are already in the process of developing specific solutions for volume customers.
Another large advantage of OPV is the absence of rare metals. By enabling the mass production of OPVs within the EU an alternative energy source will be made available, which does not depend on high-tech metals as needed for example for CIGS solar cells. Those expensive materials not only need to be imported into the EU, but they are environmentally non-friendly.
Partners
PCAS is already for 20 years recognized as a major European player for the production of active molecules in the microelectronics industry. The company opens up new areas of competence outside the core business areas and sustainably supports technological changes by developing new products. PCAS focuses on markets with above average long-term growth rates such as organic and printed electronics (e.g. OLEDs, organic semiconductors and dielectrics, OPVs, etc.). PCAS develops organic semiconductor materials with high thermal and photochemical stability. Their excellent light-absorption properties allow them to be applied in thin layers by printing technologies. PCAS and its subsidiary, Saint Jean photochemistry, are specialists in industrial production of semiconducting polymers for organic electronics, and are already offering commercial products and innovative new materials in the market.
On this promising market, PCAS has the advantage to bring their strong expertise in organic chemistry and, their technical and commercial knowledge of various sectors of high tech as well as future technologies, such as OLED for flat display, printed electronic. They will bring their existing market knowledge (existing partnerships with some leader market players) and industrial knowledge thanks to their subsidiary Saint Jean in Quebec. And last but not least their know-how in the development of methods of synthesis from the laboratory stage to pilot and industrial scale production. PCAS is able to produce pure materials with low contents of metals and is very flexible in terms of volumes (from small to industrial scale volumes).
In parallel, PCAS provides the new industries forming in the energy and environment sectors with innovative solutions for a smooth transition towards clean and safe energies, and towards the more efficient, economical and sustainable environmental technologies of the future. In that scope, the PCAS Group is strongly committed in the development of fourth-generation photovoltaics.
On a chemistry point of view, the competition is rare, some players having stopped investments on OPV. At the present time, the main competitors outside EU are American (Dupont) but new Asian competition is emerging (Taiwan, Korea, China). Through the product and technology knowledge improvement, this project will help PCAS to increase their competitiveness in addition to their flexibility and quality process and products as well as enlarge his presence on additional markets (such as construction (BIOPV, greenhouses), transportation).
Nanograde is a young SME and high-tech spin-off of the ETH Zurich. Nanograde is worldwide leader in custom-made development of specialty nanoparticles and inorganic inks. nanograde has the production capacity of about 1 metric ton of nanoparticles and plans to scale up to 10 metric tons of formulations. The main market for the developed materials is R&D departments in industry and academia. Nanograde expects to secure its position as leading manufacturer of OPV materials in the coming 3 years and anticipates therefore a significant expansion of its activities in OPVs with regards to sales volume and personnel.
Eight19 Ltd was spun-out from the University of Cambridge in 2010 in order to take to market world leading work on OPV. Eight19 is owned by a number of high profile industrial shareholders, including a £4.5M investment in 2010 from Solvay and the Carbon Trust and more recently further investment primarily from IP Group. The company’s mission is to develop the large scale-roll-to roll production technology for organic photovoltaic modules, and during the past 4 years it has established a significant infrastructure directed at commercial development of OPV based products.
This infrastructural capability covers the full range running from efficient evaluation of materials and components for organic solar cells in sheet fed processes to the development of the roll-to-roll processes on a pre-production pilot machine.
Eight19 sees its role as a developer of the roll-to-roll production technology for organic photovoltaic modules that will meet the demanding cost, stability and performance requirements of volume markets in off grid applications and large scale power generation. The deep knowledge of organic solar cell technology, roll-to-roll production processes and experience of roll to roll product development and commercialization enables Eight19’s team to deliver on the project goals.
Holst Centre/TNO, IMEC, TUe, ECN, CEA, BUW. Participation in the project will give the R&D partners new research and commercialization opportunities in public and private sectors. New partner relationships are brought in this project which can extend in future collaborations. New foreground being created can open up new research fields and applications, or additional exploitation routes through e.g. licensing agreements etc. Showing and developing further our research expertise can also result in new research projects, either publicly funded or by third parties.
As a university of technology the TUe performs scientific research in areas that are relevant for new technologies and society. The TUe has defined Energy, Health, and Smart Mobility as its strategic areas for the future. Within the area Energy, the TUe has invested strongly in research in thin film solar cells and by participating in MUJULIMA it is possible to advance some of the discoveries that have been and will be made at the TUe in the field of OPV into new technologies and products, creating new jobs and business in Europe. Educating young people and developing new technologies that can find their way into the market, are important goals for the TUe.
NEN is the only institute in the Netherlands that may officially publish standards. As such it is the Dutch representing member in international standardisation organisations such as ISO, IEC, CEN and CENELEC. NEN has held for many years held the position of secretariats of the CENELEC. Within this project NEN, is responsible for communication with CEN/CENELEC on progress of standardisation.
List of Websites:
The project website:
http://www.mujulima.eu/
The progress and new achievements in the project were communicated to the wider audience via Social Media:
https://www.linkedin.com/company/mujulima
https://twitter.com/MUJULIMA
The focus of MUJULIMA is the development of innovative materials for multiple junction OPVs and for improved light management in order to achieve high energy conversion efficiencies (above 17% cell efficiency required for the 15% module efficiency). The lifetime (10 years) and stability of the modules will be enhanced by identifying and remediating the degradation mechanisms at material level and by improving the outdoor performance of encapsulation materials.
Solar photovoltaic (PV) technology is one of the fastest growing sustainable, renewable energy conversion technologies that can help meet the increasing global energy demands. Organic photovoltaic (OPV) technologies are particularly attractive due to their compatibility with low-cost roll-to-roll and printing processing at low temperatures on a wide variety of substrate materials and the lack of scarce or toxic materials rendering them environmentally friendly. OPVs can also benefit from a larger selection of functional materials as the required properties (high semi-conductor mobility, suitable band-gap, good intrinsic stability, good barrier properties, etc.) can be tuned by careful design and synthesis.
Currently, the highest cell efficiencies reported in Europe for solution processed single, double and triple junction cells as well as the lowest water vapor transmission rates for transparent flexible barriers were obtained by the partners of MUJULIMA. In this project we show how with new and innovative materials we will increase the module efficiencies and outdoor stability to make OPVs a commercially competitive viable technology.
The innovative materials and technologies developed within MUJULIMA are demonstrated via three applications powered by OPVs: (a) in-house electrical automation devices, (b) off-grid charging, and (c) flexible OPV modules on bus roof.
Project Context and Objectives:
Solar photovoltaic (PV) technology is one of the fastest growing sustainable, renewable energy conversion technologies that can help meet the increasing global energy demands. Organic photovoltaic (OPV) technologies are particularly attractive due to their compatibility with low-cost roll-to-roll and printing processing at low temperatures on a wide variety of substrate materials and the lack of scarce or toxic materials rendering them environmentally friendly. OPVs can also benefit from a larger selection of functional materials as the required properties (high semi-conductor mobility, suitable band gap, good intrinsic stability, good barrier properties, etc.) can be tuned by careful design and synthesis.
Currently, the highest cell efficiencies reported in Europe for solution processed single (>9%), double (8.9%) and triple (9.6%) junction cells as well as the lowest water vapor transmission rates for transparent flexible barriers (WVTR 10-6 g/m2/day) were obtained by the partners of MUJULIMA. In this project we show how with new and innovative materials we will increase the module efficiencies ≥15%) and outdoor stability to make OPVs a commercially competitive viable technology.
The general objective of MUJULIMA is to develop high performance commercially competitive materials with excellent intrinsic stabilities for the cost-effective production of double and triple junction OPVs, for improved light management and for enhanced outdoor stability to achieve high module efficiencies (15%) and lifetime (10 years).
A) Design and synthesis of innovative photoactive materials as well as novel interlayer materials and their functional performance (molecular weight, polydispersity, crystallinity, morphology with fullerenes, charge carrier mobility, etc.) followed by characterization and optimization in order to produce multiple junction OPVs.
1) Innovative photoactive materials will focus on novel donor-acceptor conjugated polymers with sufficient variation in optical band gaps to achieve high efficiencies in single, double and triple junction devices.
2) Novel interlayer materials will comprise of organic (e.g. polyelectrolytes) and inorganic (e.g. metal oxides) materials to increase charge selectiveness of the contacts and to adjust the work function to improve the ohmicity of the contact.
These materials will first be tested in single junction OPV cells, measuring the energy conversion efficiencies of the cells and performing stability and lifetime tests. To reach high energy conversion cell efficiencies (17% or higher) needed to achieve high module efficiencies (15% or larger) the new photoactive and interlayer materials will be employed in architectures with double and triple junctions.
B) Development of materials for better light management within the module by employing up- and down-converter materials (IR to VIS/NIR and UV to VIS) for enhanced spectral usage of the solar spectrum. This will provide an additional relative efficiency increase of at least 15%. Cost efficient use of materials will be ensured by low cost printing/coating technologies and laser scribing. To achieve the highest possible efficiencies the optimum thickness of the different layers within the multiple junction cells will be predicted by electro-optical modelling. Optical modelling will be used to find the best arrangements of (plasmonic) micro- and nanostructures for improved light incoupling (enhanced absorption).
C) Improvement of the lifetime and stability of the modules by identifying and remediating the degradation mechanisms at material and stack level (layer/material interfaces) will be achieved by developing accelerated ageing test protocols and by improving the outdoor performance of encapsulation materials using special coatings.
The innovative materials and technologies developed within MUJULIMA will enable the realization of three applications (the first 2 will be demonstrated during the project, the 3rd one is a virtual demonstrator that will be mature and commercially available technology by 2030):
1) Electrical automation devices for in-house application will be equipped with a small (25 cm²) high efficiency OPV module. This OPV equipment will enable devices to communicate with each other (data exchange) without grid connected electricity.
2) Urban furniture (information desk for example) will be equipped with a medium sized (225 cm2) high efficiency OPV module. Using adequate charger and battery, this system will enable the full equipment to run without grid connection.
3) A roof of a commercial bus will be fully equipped (20 m2) with high efficiency custom made OPV flexible module. The aim of the demonstrator will be to run a dedicated electrical air conditioning system. The system will enable the vehicle to stop its engine when expecting passengers/clients. With such equipment the bus will consume less gasoline and reduce pollution.
In the above described applications the common need is to have OPV modules with excellent stability and lifetime, capable for high efficiency solar energy conversion (15% and above) with low cost. To create such OPVs high performance stable materials (e.g. photoactive, electro-active, interlayer, barrier etc. materials) and technologies are needed that will ensure cost effective production and commercialization.
Project Results:
Work package 2: Specifications
Work Package 2 provides the specifications of the material and demonstrators developed in the project and the influence of cost and environmental impact of the studied materials. The initial specifications for five experimental topics (photoactive polymer development, charge extraction and recombination material development, light management, stability, and upscaling) have been done at the beginning of the project. The baseline stacks have been defined for the different tasks within the work packages. Every half year the progress was re-evaluated to converge activities from the different experimental topics as much as possible. The initial specification of the materials is presented in the Deliverable Report D.2.1 and the revised specification is presented in the Deliverable Report D.2.3.
The influence of the individual novel materials developed within MUJULIMA on the cost and environmental impact of tandem and triple junction modules has been evaluated by using a SimaPro LCA tool and a home-built CoO tool. The photoactive, charge extraction and recombination, and hardcoat material price and environmental impact have been varied to investigate the impact on the total cost and environmental impact of the modules.
Task 2.1: Specification of materials and formulations thereof
The essential requirements and characteristics have been developed for all five experimental topics: Photoactive polymer development, Charge extraction and recombination material development, Light management, Stability and Upscaling. In order to accommodate all targets, two simultaneous approaches have been chosen: one for upscaling towards industrial production limited by the above registered specifications and one for record cells where these requirements may be violated for higher things.
Task 2.2: Life cycle analysis and cost of ownership calculations
- The photoactive polymer was found to be potentially critical component in terms of environmental impacts and cost. The critical factor in this context is the synthesis complexity. A minimization of synthesis complexity is desirable.
- Device performance parameters such as “service lifetime” and “annual degradation rate” are of utmost importance in the overall evaluation of environmental impacts and cost. These parameters can easily overshadow effects related to changes in materials or production parameters. A maximization of service lifetime and minimization of annual degradation rate are desirable.
- Design rules for the materials to which cost and environmental impacts are most sensitive (photoactive polymer and fluorinated polymer in encapsulation structure) have been derived. These are useful as a “first order” materials selection tool.
Task 2.3: Specifications and design of demonstrators
- Photoactive components which can be produced at low cost at the Kg scale, with a target cost of less than 100€/g.
- Highly efficient & stable donor/acceptor blends capable of withstanding 1 sun light soaking for > 2 years, with acceptor components also at less than 100€/g at scaled cost.
- Photoactive components which can be formulated using non-chlorinated solvents
- Good device performance and lifetime achieved ideally at around 300nm dried dried layer thicknesses for manufacturing yield.
- An additional factor worth pursuing is suitability for indoor & low light applications as early market opportunity for OPV.
WP2 Conclusions
The goal of WP2 is achieved. All Milestone and Deliverables have been achieved and realized in the project. The specifications of the different experimental topics have been described in D2.1. It was revised in the second period and has been described in the D.2.3. The sensitivity on the cost and environmental impact of the newly developed materials in tandem and triple junction solar cells has been studied and documented in D2.2. The material selection tool which covers materials properties, the cost and environmental footprint of OPV modules is described in MS11 report. The specifications for the demonstrators, realized in WP6, are described in D2.4.
Work package 3: Innovative materials for multiple junction OPV
Task 3.1: Synthesis of novel photoactive materials
- The effect of side chain length on the photovoltaic properties of conjugated polymers have systematically been investigated with two sets of polymers that bear different alkyl side chain length based on benzodithiophene and benzo[2,1,3]thiadiazole or 5,6-difluorobenzo[2,1,3]thiadiazole.
- Replacing thiophene by thiazole in conjugated polymers based on benzo[2,1,3]thiadiazole give significant enhancement in open-circuit voltage by about 0.2 V in solar cells. A high Voc approaching 0.95 V was achieved for the polymers with optical band gap below 1.75 eV.
- Random copolymerization of two electron deficient monomers, alternating with one electron rich monomer, forms a successful approach to synthesize state-of-the-art semiconducting copolymers for organic solar cells. A PCE over 8% could also be achieved when the active layer was deposited from non-halogenated solvents at room temperature.
- Introducing additional thiophene rings in conjugated polymers increases the fill factor and efficiency of thick polymer:fullerene solar cells, by creating a more favorable polymer chain packing and a finer phase separation.
- A series of new ultra-small band gap polymers has been synthesized in which the HOMO energy level of ultra-small band gap polymers has successfully been tuned by the ratio of the co-monomers in the main chain. Regioregular polymer P4, exhibits a PCE of 3.5% at a bandgap as low as 1.25 eV.
Several important results have been obtained regarding the design of conjugate polymers for solar cells:
Side chains: The data show that insufficient side chain length yields low molecular weight polymers or even insoluble polymers that cannot be used. The low molecular weight results in poor phase interconnectivity, low domain purity, unfavorable structural orientation and so on, which have already been well studied. On the other hand, too long side chains produce too soluble polymers, which will affect drying kinetics and self-organization of the BHJ films during spin-coating as well as the compatibility between polymer and fullerene. As a result, a suboptimal BHJ film morphology with serious phase separation and large domain size will be formed. In these liquid-liquid phase separated blends, charge generation mainly occurs in the continuous mixed polymer-fullerene phase, but because most fullerenes are assembled in the droplet domains, the electron transport in the mixed phase is hampered which results in significant bimolecular recombination. An optimal side chain length is thus required to balance solubility such that the right microstructure can be formed in BHJ films.
Increasing Voc: Replacement of thiophene by thiazole can effectively downshift the frontier orbital levels of the polymers without significantly changing the optical bandgap. Consequently, the Voc of the PSCs is enhanced by about 0.2 V. The PCE however, is only significantly improved for IDT-DTzBT compared to IDT-DTBT, but not for BDT-DTzBT with respect to BDT-DTBT. In the latter case, the low Mn and higher solubility cause a sub-optimal morphology for BDT-DTzBT:[70]PCBM blends. The results evidence that the thiazole-implementing strategy can be a fruitful approach.
Random colpolymers: Semiconducting random copolymers offer a significant prospect for application in highly efficient PSCs. The beneficial effect originates from the fact that the random polymers possess structurally different monomers, but these do not result in strong variations of the energy levels along the chain. The random polymers do not suffer from batch-to-batch variation or strong dependence on the precise composition. The reduced crystallinity and π-π stacking provides the random copolymers with good solubility and processability. As a result, random copolymers allow fabricating highly efficient PSCs with low sensitiveness to processing history, even from non-halogenated solvents at room temperature. The successful demonstration of these random copolymers for PSCs represents a reliable methodology for developing practical useful photovoltaic polymers in future manufacturing of PSCs.
Thick cells with high FF: A set of conjugated polymers based with a systematic increase of thiophene rings in the polymer main repeating unit was designed and synthesized. Interestingly, for thick photoactive layers based on these materials there is a monotonic relation between the relative number x of thiophene rings in the conjugated polymer main chain and fill factor, which is a dominant factor that determines the performance of PSCs. The steady increase of fill factor results in a rising overall efficiency with increasing content of thiophene rings. A detailed investigation revealed that the “thiophene ring effect” is a combined result of an enhanced hole mobility and suppressed bimolecular charge recombination, which we attribute to a more favorable polymer chain packing and a finer phase separation. The rationale behind the beneficial effect is that the additional unsubstituted thiophene rings allow for a reduced π-stacking distance and a reduced lamellar distance which improve charge transport, and reduce the solubility of the polymer chain which results in finer phase separation in blends with fullerenes. The discovery also provides an explicit guideline for designing and developing practical useful polymers for application in PSCs in future. Moreover, the correlations between molecular structure and fill factor observed in this paper are a motivation to search for methods that can enhance charge carrier mobility, suppress charge recombination, tune polymer packing, and optimize morphology to achieve high PCE at large active layer thickness, which in turn favors large-scale processing and multi-junction PSCs.
Ultra-low band gaps: Polymers with ultra-low band gaps (1.15 eV) can be made to function in organic solar cells. Via co-polymerization it is possible to tune the Voc. Although relatively high EQEs and Jsc can be reached, the common energetic loss between band gap and Voc of 0.7 to 0.8 eV, prevents obtaining high Voc’s. The low Voc also results in a low FF and hence the original objective of a PCE of 8% at 1.15 eV has not been reached.
Task 3.2: Functional materials for charge extraction and recombination
We have shown that photoinduced shunting upon UV illumination (h¬ > Eg) is a general phenomenon in OSCs comprising neat or electrically doped ZnO-based electron extraction layers. As a result, a significant deterioration of Voc and FF is found. We have provided a clear correlation of increasing carrier density in the EEL and a loss of electron selectivity in the EEL. In stark contrast to ZnO, we have demonstrated that the photoinduced shunting problem can be overcome by the use of EELs based on tin oxide (SnOx). In an in-depth assessment using XPS and Kelvin probe techniques, we have shown that the surface electronic structure of SnOx is substantially different from that of ZnO or AZO. The surface of ZnO-based EELs is dominated by negatively charged chemisorbed oxygen causing a depletion layer. UV illumination (h¬ > Eg) activates oxygen desorption, which leads to a lowered WF and a significant increase of carrier density. As a cathode interlayer in OSCs, this is found to result in a loss of electron selectivity. On the contrary, the surface of SnOx shows an accumulation layer, most likely caused by oxygen deficiency and H2O adsorbates. As a result, UV illumination was shown to leave the WF and carrier density of the SnOx essentially unaffected. In OSCs, the electron selectivity of the SnOx EEL persisted even upon UV illumination and thereby photoinduced shunting could be avoided. This finding is extremely important for the design of organic solar cells with a superior operational stability.
Moreover the new SnO2 formulations provided by Nanograde have been the subject of recent experiments. With those nanoparticle dispersions we were able to realize a room temperature solution process for light-soaking and photo-shunting free EELs.
In the first period of the project new recombination architecture for inverted tandem devices has been realized by combining the un-doped metal oxides eMoO3 and ALD-SnOx. This interconnect does not show major electronic problems without the need of additional thin metal layers or PEDOT:PSS. Now, using XPS/UPS and Klevin probe analysis, the formation of a dipole of about 0.7eV at the MoO3/SnOx interface could be found. The consequential alignment of the conduction bands makes a nearly barrier free electron transfer from SnOx into MoO3 possible. Due to the n-type characteristics of both oxides the electrons are carried through the MoO3 and the recombination takes place at the donor/MoO3 interface.
Investigations on solution processed metal oxides stated the resilience against solvents as a decisive challenge heading towards solution processed all-oxide interconnects. The combination of sol-gel VOx and ZnO nanoparticles showed first good results concerning protection against solvents and functionality in tandem devices. Perfect addition of Voc is achieved but slightly s-shaped J-V-curve results in a lowered FF of the tandem device. Nonetheless the tandem devices show a significant enhancement in power conversion efficiency with respect to the single junctions. For tandems with such recombination architecture comprising only solution room temperature processes under ambient conditions this has not been reported so far. With an optimized processing approach for the provided SnO2 nanoparticles we were even able to create an improved room temperature solution processed all-oxide recombination contact, that provides perfect addition of Voc and a higher FF than reached with ZnO. As an additional advantage towards the ZnO based interconnection layer, devices with the new sVOx/SnO2 architecture do no longer need UV activation.
Task 3.3: Triple junction cells with efficiency up to 17%
- Fully solution processed triple-junction polymer solar cells with PCE = 10% has been achieved by combining three different band gap polymers in an inverted solar cell configuration employing modified PEDOT:PSS and ZnO nanoparticles in the recombination layers.
- The polymer triple junction cell was fully characterized for the EQE of the three sub-cell which matched remarkably well with the predicted values based on optical modelling and data for the single junction solar cells.
- The polymer triple junction was implemented in a four cell module without any appreciable loss in efficiency.
- Hybrid tandem and triple junction solar cells were made using a near-infrared absorbing polymer and amorphous silicon. PCE of 11.6% for the tandem and 13.2% for the triple junction represents world records at this time for these types of cells.
A 10% efficient triple junction solar cell has been made. The performance is very close to the properties expected based on those of the sub cell. This demonstrates that the solution processed interconnects work perfectly. The main limiting losses are related to the quality (energy efficiency, IQE) of the sub cells. The efficient triple junction cells have effectively been applied in a 4-cell module with very similar efficiency (cell-area based).
We further demonstrated highly efficient hybrid multijunction photovoltaic devices by combining vacuum-deposited a-Si:H and solution-processed polymer solar cells. The best PCEs of 11.6% and 13.2% have been obtained for the hybrid tandem and triple-junction configurations, respectively. The combined merits from both a-Si:H and polymer solar cells can significantly enhance the PCE in reference to all polymer based counterparts. The effects of the optical characteristics of the interconnecting layer between a-Si:H and polymer sub-cells were analysed in-depth and optimized to achieve a higher photocurrent in the polymer sub-cell. In order to achieve a high balanced photocurrent in the triple-junction solar cells, a well-chosen mildly textured front electrode was used. The solution processing of polymer solar cells is fully compatible with the vacuum deposition of a-Si:H solar cells, which makes the hybrid devices applicable for the low-cost roll-to-roll mass production. The hybrid concept studied here can ultimately drive the PCE of polymer solar cell based photovoltaic devices to 15% and beyond in the near future, making low-cost, non-toxic, earth abundant, light weight and large-area photovoltaic modules available for clean electricity generation.
The ultimate goal of the project, which is to demonstrate a 17.5% triple junction cell, has not been reached. The main reason is the lack of efficient wide band gap and efficient ultra-small gap materials. Despite the vigorous attempts described under task 3.1 the desired results were not obtained. We note that with a fully characterized 10% all polymer triple and a fully characterized 13.2% hybrid triple cell we have advance the state of the art in this field.
Task 3.4: Large area processing of functional materials
- Non-chlorinated solvent system were investigated for four polymers
- PCDTBT and P17 show significant efficiency drop using non-chlorinated solvents.
- Both P15 and Th15 demonstrates at list 90% of devices performance using non-chlorinated solvents compare to the performance of the devices produces from o-DCB.
- Slot die coating process was developed for several polymers and was used for the manufacturing of the demonstrators.
The polymers PCDTBT and P17 perform well only when the photoactive layer produced from chlorobenzene or ortho-dichlorobenzene. Non-chlorinated solvents lead to the significant performance drop. While, other two polymers P15 and Th35 show reasonable results when processed from non-chlorinated solvents. Although P15 show reasonable performance using non-chlorinated solvents, this result is not very reproducible due to high polydispersity of the polymer molecular weight. For the manufacturing of large area demonstrators (D.6.5 and D.6.6.) the polymer Th35 is selected using non-chlorinated solvents.
WP3 Conclusions
Synthesize of innovative material has reached noticeable results: Random copolymerization of two electron deficient monomers forms a successful approach to synthesize state-of-the-art semiconducting copolymers for organic solar cells. A PCE over 8% is achieved when the active layer was deposited from non-halogenated solvents at room temperature. Photoactive material with ultra-small band gap reported in D.3.7. It is noteworthy that the PCE of 3.5% is among the highest efficiencies reported for a polymer solar cell with a band gap < 1.3 eV.
Variety of inorganic charge extraction and recombination materials (ETL and HTL nanoparticle dispersions) was developed in the project.
Fully solution processed triple-junction polymer solar cells with PCE = 10% has been achieved by combining three different band gap polymers in an inverted solar cell configuration employing modified PEDOT:PSS and ZnO nanoparticles in the recombination layers.
The polymer triple junction was implemented in a four cell module without any appreciable loss in efficiency. We note that with a fully characterized 10% all polymer triple and a fully characterized 13.2% hybrid triple cell we have advance the state of the art in this field.
Non-chlorinated inks for the polymers developed in the project were developed and used for manufacturing of the demonstrators using slot die coating.
Work package 4: Innovative materials and structures for light management
Task 4.1: Optical simulations and modelling of innovative light-management concepts
In the first period of the project, several methodologies have been developed to model and simulate optically the device stacks in which light management (LM) techniques can be incorporated. In this second period these methodologies were implemented throughout the developments of the other tasks.
Task 4.2: Innovative light-conversion concepts
- 1 Polyfluorene soluble in polar solvents was synthesised
- 1 Polymer incorporating red-emitting dye units and also soluble in polar solvents was synthesised which shows an intense solid-state photoluminescence at 612 nm upon excitation at 380 nm
- 3 Polymers incorporating red-emitting dye units were synthesised, which show an intense solid-state photoluminescence at 604 nm (PFR1a, 10 mol%), 597 nm (PFR1a; 30 mol%) and 621 nm (PFR1b) upon excitation at 380 nm.
- Different polymers incorporating BSe units were synthesised, which show an intense photoluminescence at 580 nm – 603 nm upon excitation at 380 nm.
- PFO, BN-PFO and DPAVB are promising materials for the preparation of guest host systems to down-shift the spectral region λ <425 nm to λ >450 nm with an efficiency of more than 50%.
- BNPFO:DPAVB successfully applied on OPV single junction device
Development and synthesis of novel down-shifting materials and material systems is well achieved. Therefore, new synthesis routines have been developed to follow different approaches of the down-shifting concept. On the one hand materials for host-guest systems have been studied, evaluating samples that are already commercially available (PFO, DPAVB) as well as materials synthesized by the Scherf-Group at BUW (BNPFO). In addition to the known host-guest approach the novel concept of down-shifting copolymers has been studied. Therefore multiple new copolymers (PF-PEG1, PFR1, PFR2, PFBSe) have been developed, synthesized and already tested at BUW. Moreover a new down-shifting copolymer has been developed, that has a good solubility in polar solvents.
Both approaches, guest-host systems and copolymers, provide materials with down-shifting properties required for the desired applications. Remarkably the new developed BN-PFO showed increased photoluminescence quantum efficiency in contrast to the commercially available PFO.
The copolymer approach already leads to a collection of possible materials with slightly different emission spectra around 600 nm. Thus they all have potential for application in OPV devices.
After selection it turned out that best candidate is the doped BNPFO:DPAVB combination, which has been tried in OPV single junction device. However, no overall improvement could be obtained in the performance of OPV single junction device. Reduced photoshunting could be observed due to UV-filtering.
Task 4.3: Innovative light-reflecting concepts
- Low-n nanoparticle dispersion development is complete
- This material has been evaluated as ARC in multiple architectures
- The first DBRs were calculated and made using known OPV transport layers, which showed reflection around 500 nm as calculated.
- In a second stage known intermediate reflectors from other fields in thin film PV were used and working devices were obtained.
While in the first period both anti-reflective as retro-reflective layers have been considered, the latter was only available from sources outside of the consortium. Therefore more focus was on the anti-reflective materials developed within the project in this second period. Another approach, specifically focusing for use in multijunction structures is the incorporation of intermediate reflectors.
As presented in the first periodic report Nanograde has developed a synthesis of low refraction index SiO2 nanoparticles and further dispersed it into a coatable formulation. In the second part of the MUJULIMA project, Nanograde was focused on further improvement of the ink formulation in order to improve its stability, coating properties and reducing the refraction index of the dried film. This allowed selecting the optimal dispersing parameters and the formulation composition.
This material has been evaluated as anti-reflective coating (ARC) in multiple device architectures. However, no significant improvement in the device performance could be obtained.
For the intermediate reflectors in multijunction devices, two different approaches were tested: the Distributed Bragg Reflector (DBR), consisting of several sets of transport layers that have high and low refractive indices and the Intermediate Reflector (IR), which is a single layer of aSiO:H combined with the regular OPV recombination contact.
Optical simulations were done and DBR stacks build and measured. Testing the DBR in OPV devices was foreseen, but first experiments showed that it was highly challenging to maintain a good optical performance and high conductivity in the DBR layer.
Optical simulations were also done to optimize the thicknesses of the IR and the calculated optimal thickness was integrated in full multi junction OPV solar cells. The results showed that though these layers can reflect part of the spectrum back to the front cell, however, the conductivity remained a challenge leading to S-shaped J-V curves of the devices limiting the solar cell power output instead of enhancing.
The use of a Distributed Bragg Reflector (DBR) or other Intermediate Reflector (IR) for multi junction OPV can be considered to still be in the exploratory phase of research. It has shown to be challenging to find material combinations that work both optically as well as electrically in two terminal multi junction OPV solar cells.
Task 4.4: Innovative light-scattering concepts
- Innovative light scattering nano and microstructured structures has been produced onto rigid (glass) substrates:
· use of a single layer of silica beads as a physical mask for TCO grid deposition
· sheet-to-sheet nanoimprint lithography (NIL) of a UV lacquer layer
Light scattering structures have been produced by TCO (ZnO:Al as an example) patterning in the 0.5- 10 μm range. Light scattering nano and microstructured structures have been produced onto rigid (glass) substrates.
Concerning Textured TCO, only the double texturation applied on AZO allow a gain of +0.6mA/cm² (from 14.4mA/cm² with AZO to 15mA/cm² with textured AZO). This gain represents an increase of 4.2% of Jsc. Nevertheless, the increase of Haze factor traducing a potential increase of light trapping is not sufficient to compensate the lowering of Voc and fill factor. The high roughness of these TCOs could induce high rate of defect for the collection of charges at TCO/absorbent layers interfaces.
Concerning nano imprinted structures of ITO the conclusion is that building OPV devices both SJ and MJ on top of a structured surface that acts as light management layer for light scattering, the performance of these devices is not improved, but rather deteriorated. Also taking into account the higher difficulty of processing thin layers on top of these structured layers it therefore is not recommended to use this type of light management for OPV devices.
Task 4.5: Optimisation of combined light management concepts in multiple junction devices
• Two light management material upscale approaches:
o Nanoimprinted hard coat
o Antireflection nanoparticle-based coating
In summary, the consortium has selected the ARC and nano-imprint hardcoat as the two light management approaches for further use and has proven the feasibility of upscaling both of the selected light management strategies. The pilot R2R instrument located at TNO already enables production of 1m2/min nanoimprinted hardcoat material. There are no obvious difficulties of scaling the process further up. Nanograde with their antireflection coating could already reach 10ton/year production scale. Such an amount would enable coating of 200000 m2 substrate.
WP4 Conclusions
A broad range of LM techniques has been investigated in this WP for use in single an multijunction OPV devices. It turns out however to be very challenging to simultaneously achieve optical and electrical improvements in the devices when applying such techniques without destroying the overall device operation. Finally, two main approaches have been selected for further use and upscaling: the ARC and nano-imprint hardcoat.
Work package 5: Stability of materials and devices
Task 5.1: Evaluation and development of hardcoat materials for barrier integration
Deliverable 5.1 described the specifications, selection and testing of commercially available hardcoats and hardcoats developed by TNO. Deliverable 5.2 elaborates on the tests in the last evaluation phase of the hardcoats and additional properties to make a final selection for a hardcoat that can be combined with a barrier coating. Being in the fortunate position of having multiple hardcoat candidates after all tests of evaluation phase, some additional properties are evaluated to make a final selection.
Materials selected in this task were used during the second half of the project for:
- manufacturing combined light management structures (see Task 4.5)
- evaluation a stability of the OPV devices with combined innovative materials (see Task 5.6)
- manufacturing of the demonstrators (see Task 6.3).
Task 5.2: Stability of photoactive, charge extraction and recombination layers
In this task, investigations of mono-stress tests of photoactive layers and charge transport layers are performed. The materials selection is based on stability assessment of single junctions. The impact of materials combination is assessed in task 5.4. All results are reported in detail in deliverable D5.3 and D5.5.
Regarding the photoactive layer stability, three different single junctions are investigated. The materials tested are:
- the best performing new wide band gap material BDT-FBT-2T from WP3;
- the reference DPP polymer pDPP5T from BASF that has a large resemblance to the small band gap polymers that are being developed in WP3;
- P3HT:ICBA that is used as a well-known wide band gap reference material.
- Different ETL were also evaluated, within pDPP5T solar cells.
- Single junctions with varying photoactive layers and ETL were evaluated against light, heat and air. Air appeared as the most critical stress factor but encapsulation can prevent damage to the cells.
- Zinc oxide appeared as the most promising ETL.
- pDPP5T and P3HT:ICBA appeared as the most stable photoactive layers.
Task 5.3: Stability of light management materials
Stability of different light management materials has been investigated and results gathered in deliverable D5.4. Down-shifting coatings, anti-reflective layers as well as light scattering materials were tested under mono-stress conditions (light, heat or air). Optical and electrical characterizations are reported before and after ageing.
- Down-shifting materials, anti-reflective coatings and light scattering materials were evaluated against light, heat and air stability.
- PFO layers (down-conversion layers) showed good heat and light stability. Air combined with light leads to degradation of the layers (damage of the absorption). Such down-shifting materials need to be encapsulated. Thus they should be deposited on the front side of the devices before encapsulation.
- The hard coats, retroreflective foils, and antireflective coatings show no change in optical transmission upon light soaking for 200 h.
- Nanoimprinted lacquers (light scattering) with and without ITO do not show any degradation in optical parameters upon mono- and multistress ageing. Samples with ITO electrode on nanoimprinted lacquers show a small increase in sheet resistance over time when exposed to air and heat. AMA layers showed good heat and light stability. Their exposure to air must be prevented through a proper encapsulation.
- No dramatic degradation of any of the layers was observed, thus all of the tested layers appear as good candidates for integration into devices.
Task 5.4: Stability of combined innovative materials
This task aims at assessing the stability of stacks combining multiple innovative materials. This part of the work comprised the following experiments:
- pDPP5T single junctions were combined with several light management materials and their stability was assessed as compared to the single junction alone ;
- tandems stability was compared to single junctions stability ;
- also the introduction on the one hand of novel interlayer materials in the tandem configurations, as on the other hand light management (LM) techniques on such tandem architectures was attempted.
- Tandems were fabricated with Th35 and pDPP5T polymer. Monostress tests were performed on those tandems. Based on an assessment with single junction devices, no mutual or additional interactions were observed.
- Light management coatings and foils do not influence the degradation mechanisms for pDPP5T solar cells on glass.
- Hard-coat imprinting can be done on barrier foils but lamination (which is needed for cells encapsulation) leads to transmission decrease. Therefore their implementation onto flexible devices was not successful.
Task 5.5: Accelerated test protocol
The objective of this task is to conduct multi-stress ageing tests and compare their outcome to mono-stress (so as to identify synergetic effects) as well as outdoor ageing (in order to be able to propose an accelerated test that is adapted to outdoor lifetime prediction).
- Mono and multistress tests were conducted on low band-gap and high band-gap solar cells. Air was clearly identified as the most severe stress factor of low band-gap pDPP5T solar cells. For encapsulated pDPP5T solar cells, no pronounced synergistic degradation effects when exposed to light and heat were found. For encapsulated high band-gap P3HT:ICBA solar cells, no synergistic degradation mechanism was observed when combining light and air.
- Multi-stress tests as well as outdoor ageing were conducted on flexible encapsulated devices with pDPP5T absorber. The accelerated conditions which mimic the best the outdoor ageing are the ISOS-L-1 protocol (1 sun, ambient air and moisture).
- These solar cells show remarkable stability, with no degradation after 2000 hours ageing outdoors, and an average PCE of 3.7% after 2000 hours. The devices also pass the damp heat and thermal cycling tests described in IEC-61646 standard (T90 > 1000 hours at 85°C 85% RH, and no PCE loss after 200 thermal cycles).
Task 5.6: Stable OPV devices with combined innovative materials
In this task, multi-stress and outdoor ageing tests were conducted on flexible tandem solar cells comprising light management materials. The light management material was selected from WP4, it is an anti-reflective coating provided by Nanograde and deposited on the device front side (external side of the gas-barrier film). The ageing protocols were selected according to deliverable D5.6. A comparison is made for cells with and without the anti-reflective layer.
- Flexible tandems were prepared with efficiencies of 5.91%.
- Efficiency of flexible encapsulated tandems comprising the AR coating was 6.21%.
- Stability of these devices is promising, with:
· a T90 higher than 1300 hours outdoors (PCE > 5.5%)
· a T80 of more than 1300 hours under 1 sun, in ambient air
· a T80 of more than 200 thermal cycles (for devices without AR).
- The benefit of the AR coating is observed in ageing conditions without a too high relative humidity. In these conditions, AR-coated cells end up with higher efficiencies.
- The accelerated conditions which mimic the best the outdoor ageing so far are the ISOS-L-1 protocol (1 sun, ambient air and moisture).
WP5 Conclusions
The hardcoat material for barrier integration have been develop in the project and reported in D.5.1 and D5.2.
Innovative materials developed in the project have passed mono-stress stability tests (D.5.3). The results were compared with multi-stress ageing results (D.5.5) and the identification of synergistic failure mechanism was realized in the project. The comparison of mono-stress aging results has been performed on individual and combined innovative materials in order to identify mutual interactions (D.5.7).
Flexible tandems were prepared, encapsulated and aged in outdoor as well as accelerated conditions (D.5.8).
Work package 6: Demonstration
This work package number 6 dedicated to Demonstration has two main objectives. The first one is to develop industrial scale synthesis of materials (charge extraction and recombination layers materials, and also active polymers) selected from workpages number 3 and number 4 and the second one to demonstrate efficient OPV modules for three different applications, i.e. rigid module on 5x5cm2 for indoor application, 15x15cm2 flexible substrate fulfilling the requirements for off-grid charging, 15x15cm2 flexible substrate fulfilling the requirements for bus roof application. Nanograde has successfully up-scaled the syntheses of the charge extraction and recombination materials by implementing at their plant new reactors capable of producing more than a ton per year of nanoparticles and more than ten tons per year of formulations containing nanoparticles. PCAS has synthesized for demonstration activities larger batches of a wide band gap polymers developed by TU/e within work package number 4. The feasibility study concerning the up-scaling of this polymer has also been regarded in terms of security and toxicity. Regarding the second objective of the work package, 5x5 cm2 modules for indoor application were produced by sheet-to-sheet slot die coating on glass substrate which provide 3.24% performance (3.9% active area efficiency), with the voltage of 6.579 Volts, FF of 40.45 % and the current of 24.32 mA.
In terms of task 6.3 Eight19 has produced large scale TANDEM demonstrators at 15x15cm on flexible web using green solvent processing with a geometric fill factor of over 80%. The two demonstrator modules generate 400mW and 600mW respectively and the IV curve fill factors are high. The demonstrator containing the TH35 donor material had an active area efficiency of 1.9%, whereas the P3HT demonstrator had an active area efficiency of 3.9%, which dropped to 3.25% after encapsulation and hardcoat layer application.
Task 6.1: Upscaling synthesis of functional materials from WP3 and WP4
- Upscale of nanoparticle synthesis and formulation successful
- Scale-up of a newly developed wide band gap polymer, Th35, with a security study of the process, a toxicity study on the polymer concerning acute dermal irritation and the preparation of large batches of Th35.
The nanoparticle materials selected within WP3 and WP4 were successfully up-scaled in Nanograde lab.
The scale-up synthesis of one of the newly developed wide band gap polymer, Th35, has been successfully achieved. The larger samples prepared within the course of this study are going to be used in the demonstration activities of Task 6.2 and Task 6.3.
Task 6.2: OPV demonstrator for indoor application
- 5x5 cm2 modules were produced by sheet-to-sheet slot die coating on glass substrate (D.6.2)
- The modules provides 3.24% performance (3.9% active area efficiency), with the voltage of 6.579 Volts, FF of 40.45 % and the current of 24.32 mA.
Slot die coated 5x5 cm2 modules with high geometrical fill factor were demonstrated. The interconnection in the modules was realized by laser patterning. Performance of the slot die coated modules using PCBTBT:PC[70]BM as a photoactive layer was 3.24 % (active area efficiency is 3.9%). The total area of the modules was 25cm2, with the busbars area of 5 cm2 and module are of 20 cm2 (active area 16.8 cm2). Geometrical FF of the modules was 80%. The modules consist of 8 serially interconnected cells and have Voc of 6.579 V, Isc of 24.32 mA and FF of 40.5 %. Material selected for this demonstrator meets the requirements of indoor application.
Task 6.3: OPV demonstrator for outdoor application
Two demonstrators of 15x15cm were produced directed to the requirements of D6.5 (off-grid charging module) and D6.6 Bus-roof demonstrator.
- D6.5 Off-grid charging Tandem OPV module was produced with Project donor material TH35 with a size greater than 225cm2 and a 1 sun cell area efficiency of 1.9% after encapsulation and a power output of just over 400mW.
- D6.6 Bus-roof demonstrator Tandem OPV module with P3HT in the first photoactive layer was produced which incorporated a hardcoat material. It was >225cm2 and 1 sun cell area efficiency was measured at 3.9% - this dropped to 3.25% efficiency after encapsulation due to optical losses through the additional hardcoat layer. The power output was measured at just over 600mW.
Tandem solar module demonstrators for off grid charging comprising the project donor TH35 (D6.5) and a bus roof demonstrator with hardcoat (D6.6) were fabricated. The demonstrator module stack delivered 400mW and 600mW of power under 1 Sun illumination, and were completed with a geometric fill factor of >80% in line with the target. The efficiency was measured at 1.9% and 3.9% respectively. At low light there was some promising performance, which was good to see given the relatively thin layers and related deposition and yield challenges involved.
WP6 Conclusions
During the course of this work package number 6, the syntheses of a variety of functional materials developed within work package 3 and work package number 4 have been successfully scaled-up. All these scaled-up materials have been used to produce either charge and extraction layers and/or active layers in the demonstrators developed and set up within this work package 6. As an example, the OPV modules prepared on a 20 cm2 for indoor application provide 3.24% performance, and tandem outdoor demonstrators >225cm2 were produced with 1.9% efficiency using project photoactive donor material and 3.9% using P3HT as the first donor material.
Potential Impact:
Strategic impact
MUJULIMA will result in next generation high performing innovative materials for multiple junction OPV cells with improved light management. These cells will show higher efficiencies and higher outdoor lifetime than present state-of-the-art. More importantly a convincing roadmap will be built during the project that will show that the results of MUJULIMA will contribute to realize a cost effective production of industrial modules for a commercially competitive price with efficiencies of OPV modules of at least 15%, with outdoor lifetime of at least 10 years before 2030.
In order to realize such an ambitious roadmap, a number of results have to be accomplished in MUJULIMA. On the technical side these include: lab-scale multiple junction OPV cells, novel light management materials and structures, study of intrinsic stabilities and stress factors, and coupling of this know-how to improved materials and device structures, increased stability achievement by incorporating needed protective functionalities on the Holst Centre barrier, OPV modules using non-vacuum based printing technologies. To determine the market size, CoO calculations of OPV modules based on the concepts developed in MUJULIMA will be performed, including the production cost of the novel materials and light management techniques developed in the project. The performance of OPV materials and devices will be validated in a number of demonstrators, where it is believed that low cost flexible and in some applications transparent OPV modules will find a market before 2030.
The consortium will further strengthen European scientific and technological leadership in the fields of materials for organic based devices, specifically organic PV, device structures for high efficient single, double and triple junction organic solar cells, and full working OPV demonstrators, leading to a solid basis for production and employment of OPV cells and modules. Thus, it will create employment and future industrial solutions.
Renewable energy sources like PV play an important role in reducing the need for environmentally unwanted sources of energy producing large quantities of CO2. Organic photovoltaics among all of the PV technologies has by far the lowest carbon foot print. Both these aspects on future OPV products are believed to have a positive impact on European welfare and will support the European efforts to reach the environmental European goals.
MUJULIMA has brought together a strong consortium of universities and research institutes in combination with strong industrial companies. Two partners (PCAS and Nanograde) who are active in development and production of materials for applying several layers necessary for polymer electronic devices, especially OPV, fill up almost the complete value chain for production of OPV devices. Substrates and barrier manufacturers are outside the scope of the project, but substrates are abundantly available, and barrier coatings and stacks are within the project available through one of the partners (TNO/Holst Centre). As the development of new and improved materials is the primary focus of this project, the consortium further consists of a strong and world leading group of universities and research institutes. Development of OPV demonstrators with the intention to produce OPV cells and modules and to apply these in a range of products will be done by the industrial partner Eight 19 is exploring several markets for the application of flexible photovoltaic films. Near term opportunity is off-grid charging in developing countries, but also indoor energy harvesting which relates to the emerging internet of things. Eight19 is currently working with customers to develop specific solutions for outdoor and indoor applications. This existing customer base, PV know-how and printing technology, combined with a road map to OPV production within a few years makes them essential in the MUJULIMA consortium.
Economic Impact (Direct & Indirect Market)
The ultimate market of OPV modules is in high level high power energy production. MUJULIMA will show that this ultimate market will be within reach by 2030, as long lifetime and high efficiency are considered necessary for this market. But, light weight flexible, (semi-)transparent OPV modules in different colours will by themselves create new markets and opportunities to use OPVs in areas which are not possible or extremely difficult or costly for present day c-Si rigid panels, or even not-possible for other non-transparent thin film PV modules based on thin film-Si or CIGS. Applications include transparent OPV within office building double glazing units, shades, bus and truck roofs, textile based tents, umbrellas, airplane wings, sails etc.
Solar photovoltaic (PV) technology is one of the fastest growing sustainable, renewable energy conversion technologies that can help meet the increasing global energy demands. EPIA showed a cumulative installed total solar generating capacity of almost 70 GWp by the end of 2011, and showed an average cumulative growth over the last ten years of 44% and an average yearly growth of 75%. Although growth predictions for the coming decade are lower than in the past decade, for Europe alone a cumulative installed base between 130-260 GW is predicted by 2020. Thin Film PV production accounted for generating 3.6 GWp in 2011 and a total installed base of over 9 GWp.
Main stream thin film PV explores the high temperature stability of glass substrates. However, flexible non-breakable large area inorganic thin film devices on foils are emerging. Furthermore organic PV technology that has the potential to challenge the inorganic PV performance (expressed in price/kWh) is showing great potential. The development of OPV concentrates on the use of polymer substrates to take leverage of the roll-to-roll production option on flexible substrates to bring down the production costs (< €0.5/Wp).
A number of market research companies have recently published updated figures of the OPV market. Market Research Company IDTechEx forecasts that the market will rise to $630 million in 2022. The market growth will be predominantly driven by electronics in apparel, posters and PoP smart labels, and off-grid developing world applications. Nanomarkets are a little bit more optimistic in their market predictions estimating a market size of over $700 million in 2019; they do state that this market is heavily limited by the expected module efficiency of less than 6% and lifetime of less than 10 years by commercially available products. Nanomarkets estimates that more than 300 M$ of this 700 M$ market will be in portable charging devices, in BIPV/ BAPV Glass and other application areas like BIPV/BAPV Roofing, AIPV etc.
Another research company (Lux research) has made the lowest market prediction, also based on the present situation, with low efficiency modules with limited lifetime, they predict the OPV market in 2020 to be $ 159 million in the most likely case. Lux research sees five market segments where already now OPV products could be introduced: signage, consumer electronics, defence, developing world (off-grid) and most importantly BIPV.
Earlier predictions by IDTechEx based on faster introduction of more efficient and longer lasting OPV modules on the market predicted that OPV would have about 30% of the thin film PV market in 2023, the thin film section was estimated to be about 20-30% of the total PV market, leading to an estimate of about 10% of the total PV market for OPV. With an estimate of a total market size for PV beyond 2020 exceeding 1000 billion EUR, even a small percentage in the market for production of OPV would lead to large numbers. Considering that production of high efficient OPV modules of at least 15% with outdoor lifetime of at least 10 years as an outcome of MUJULIMA can be accomplished before 2030 it is believed that far larger market sizes will be within reach than predicted at this point in time.
With still 10-20 years before OPV can seriously compete with mainstream PV modules of today, in combination with the fact that PV modules are already becoming rather low in price some criticasters doubt whether there will be a substantial market for OPV in future. To the opinion of the MUJULIMA partners there is no doubt that a substantial market will be possible for OPV products. This belief is based on a number of observations. For one it is based on the already very fast development of materials, technology, equipment and pilot and production facilities. See section 1.2 for the state-of the art world records, where cell efficiencies in the lab already are 12%, and on module level beyond 8%. Noteworthy these records do not come from universities and institutes, who are usually far from commercial production but from companies, who do want to commercialise their R&D efforts within a short time period, as is the case with the industrial partners of MUJULIMA, PCAS, Nanograde and Eight 19. Eight19 plans to increase the production capacity initially to 10.000 and then to 200.000m2/yr during the next three years. This is a key step to prove the markets and applications. The second reason we believe that there will be a substantial market is by the unique properties of OPV, which none of the other PV technologies have in common in its totality. These properties being, light weight, unbreakable (as compared to glass and Si based PV devices) with lowest CoO and lowest LCA making them the most sustainable form of PV. In addition the aesthetic properties with the possibility to tune the colour and the transmission wavelength in general, to make them transparent and to produce them in any shape thinkable. On top of that the fact that OPV already has an energy output with low light intensities making more energy with lower efficiencies and making them suitable for indoor use and the inversely proportional temperature slope of OPV, making them more effective with increased temperature. This makes them interesting in a number of applications such as:
- Buildings; BIPV, BAPV, integrated roof structures, facades, semi-transparent windows, with the possibility to design and manufacture custom made and aesthetically pleasing, as is standard practice in the building industry, and is one of the greatest wishes of architects designing PV in buildings. Pike Research has published a report examining the expanding global market for BIPV products and they predict a strong growth with almost $2.5 billion revenue in 2016 with a growth of approximately 20% year. Nanomarkets has an even larger prediction for the BIPV market, they predict an enormous market size of $8.5 billion in 2016, although this prediction is much lower than a few years ago due to the present economic crises. They predict also that 2/3 of the systems installed will be thin film based. OPV modules with their low weight, flexible colour and transparency, and extreme low energy payback times, will have an enormous impact on this market.
- Transparent OPV can be applied inside a double glazing unit, still leaving sufficient light to enter a building but at the same time produce energy cost effectively. Even though it will not be applicable to every double glazing unit, even a small percentage of the global market for double glazing is enormous. Office buildings are often equipped with reflective glazing units, which only transmit 20-25% of the light inside the building. A major part of this market can be replaced with OPV units. For existing windows OPV can be applied on the inside (or outside) in shades, luxaflex and curtains.
- Greenhouses; OPV devices can be tuned to transmit light needed to grow products and to use the rest of the light to produce energy. A product/market analyses shows that especially for plastic greenhouses in southern countries, where the greenhouses are often white coated, because of an excess of solar light, the use of OPV foil with a double function, transmitted the right wavelength for controlled crop growth in combination with energy harvesting at wavelengths not needed for crop growth would be very cost effective. Currently the market for plastic greenhouses is large. In Spain 30.000 hectares of plastic greenhouses exist, in Africa 1.000.000 hectares, in China: 2.000.000 hectares etc. For bowed OPV greenhouses, this would mean a potential for Spain of 1.35 billion m2, in Africa 45 billion m2, China: 90 billion m2 etc. According to Markets and Markets. The global agricultural films market was worth $4.8 billion in 2011 and is estimated to reach $7.1 billion by 2017, growing at a CAGR of 6.7% from 2012 to 2017.
- Transportation sector; integration of OPV in vehicles, like trains, trucks, cars, airplanes, boats, camping cars to reduce energy consumption and battery usage for climate control, illumination etc. Light weight, flexibility and aesthetically pleasant are important aspects here.
- Interior use; mobile chargers, window shades and blinds. The low light intensity properties are important here in combination with flexibility and aesthetics.
- A report by ABI projects that the portable power industry, called the “Advanced Charging Technologies” industry which includes portable solar chargers, is currently estimated at $1.5 billion in revenue and is expected a grow to $34 billion by 2015. That is a Compound Annual Growth Rate(CAGR) of 86%.
- Textiles; tents, sails, umbrellas, car park roofs, backpacks etc., with light weight and aesthetics as most important properties here. Especially refugee and military tents are an interesting market case. Worldwide approximately 50 million people are displaced every year due to natural disasters and conflicts according to UN OCHA. A total of 33.9 million refugees are under UNHCR care alone. UNHCR procures 300.000+ tent/year. In refugee camps nowadays, generators with enormous amounts of fuel are needed which are often transported expensively with airplanes. Solar cells on the tents can help reduce the fuel need in disaster and conflict areas drastically. Refugee tent surface areas are in the millions of m2. Military tent applications in conflict areas are a multiple of the refugee tent market.
- A report by Pew Charitable Trusts states that the U.S. Department of Defence will invest heavily in clean energy projected to eclipse $10 billion annually by 2030. The majority of the spending will be for portable base applications including portable “soldier power.” In fact, the total market for renewable mobile power for forward military bases and temporary installations is forecast to reach $6.1 billion by 2030.
- Urban furniture; off-grid energy.
- Security; local off-grid energy in clothes and tents for first responders (fireman), red cross, army. Low weight, flexibility and low-light conditions are important aspects.
It is clear that the potential markets where OPV will most definitely play a role, when 15% efficiency and lifetime > 10 years is reach, will be enormous. From the above figures rough but conservative estimates have been made for the yearly m2 needed in 10-20 years from now. This totals to more than 600 million m2 per year for OPV (with 50 Mm2/yr in BIPV (conservative estimate due to assumed limited lifetime), 400 Mm2/yr for plastic greenhouses, 120 Mm2/yr for truck roofs, etc. etc.). CoO calculations show that at least 70% of the total cost of OPV are in materials, in total 8.4 tonnes are needed for 1 Mm2 of OPV modules, totalling to a need of more than 5000 tonnes/year. With the total cost of a module around 50 EUR/m2, the total yearly value comes to 30 billion EUR. The CoO show that the functional materials like photo-active polymers, interlayer materials, light management and hard coats are approximately 40% of the total materials cost, adding to a total market value of 8 billion EUR/year.
Although this program concentrates on the development of materials, devices and demonstrators for Organic PV cells and modules, a number of the materials and technologies developed have a much wider application scope. Transparent conductors, interlayers, light management and encapsulation are needed in organic based and inorganic based electronic systems on foil and even on glass based substrates. OLED light emitting devices, other thin film PV devices like thin film-Si and CIGS based solar cells could benefit from the developments in MUJULIMA.
The market for Organic Large Area Electronics (OLAE) is although still relatively small, rapidly expanding. A market size by 2027 of 330 billion US$ for the OLAE sector as a whole is forecast by the leading market research company IDTechEx. The market for OLED lighting is forecast to be 4-6 billion dollars in the 2015-2020 timeframe.
The market size for alternatives for ITO based Transparent Conductors (TC) is predicted by the market research company Nanomarkets to exceed 2 billion $. They also predict the market size for TC’s in general for OLED lighting of more than 430 M$ and thin film photovoltaics 340 M$.
Societal Impact (Social, Health, Employment, Environment)
OPV will enable an increase in alternative energy sources. It will reduce the need for polluting energy plants and nuclear energy plants. In Germany the effect of PV is already visible in the daily load curve on the energy grid. PV installations reduce the peaks in daily energy consumption, resulting in a levelling of energy prices to a lower level, and a considerable reduction of stand-by power plants which are only needed in peak times.84
The technologies and processes that will be developed in this project will bring the competence and skill level of the European companies, research institutes and universities involved to an exceptionally high and competing level compared to the rest of the world. This is extremely important in the view of the general strategy to develop Europe further into a knowledge-based economy (KBE).
MUJULIMA will also contribute to the implementations of the European Strategic Energy Technology plan (SET plan). The SET-plan wants to accelerate the development and deployment of cost-effective low carbon technologies. From all the PV technologies, OPV is estimated to be the best choice as cost-effective low carbon technology. The estimated energy payback time (regarding the carbon foot print) for OPV is 0.2 years, while for conventional solar cells this is still about 2.
In a recent study LCA analyses have been made on OPV devices, with a focus on critical components like TCO layer and encapsulation components. The result of the study is that LCA values did not change much for OPV. Krebs and his team showed that with efficiency improvements of the OPV cells even further reduction of the LCA time is possible, he predicts an LCA time of 1-3 days for a 15% effective OPV cell. The MUJULIMA team will critically watch that the LCA values will stay low despite the more complicated double and triple OPV cells, with alternative TC and with light management structures.
National and International Impact
Today there is less and less mass production of PV cells and panels within the EU. However, Europe is still the source of high-end technology, equipment and materials. Also, for organic and large area technology Europe has so far a strong position. However, here we also recognize competition from the Far East and from the US and have to respond by European initiatives to keep our leading edge in the near and longer future.
The project will help to keep or even to expand that level with respect to materials for OPVs. Considering production of OPV cells, for large scale products where millions of square meters of products are needed these will be produced eventually by roll-to-roll methods using printing technologies. The operational costs of these R2R lines are very low, so there is no reason to move this production to low wages countries. Furthermore Europe has an excellent know-how and skill level at equipment companies for building these production lines. As OPV cells and modules can be made by print technology, there is a huge possibility for SME’s in Europe to produce lucrative products on smaller scale by Sheet to Sheet (S2S) or sometimes small scale Roll to Roll (R2R) production (slower speed, small width). These will be customised products with a high level of uniqueness and integration possibilities. Local production and the possibility to make unique products will give a huge opportunity to other local European SME’s who can integrate these modules in all kinds of products.
Eight 19 ultimate goal is to manufacture plastic photovoltaic films in large volume. Due to high degree of automation Roll-to-Roll manufacturing can be done cost effectively in Europe. We are currently exploring various market sectors for short term and longer term entry. We are already in the process of developing specific solutions for volume customers.
Another large advantage of OPV is the absence of rare metals. By enabling the mass production of OPVs within the EU an alternative energy source will be made available, which does not depend on high-tech metals as needed for example for CIGS solar cells. Those expensive materials not only need to be imported into the EU, but they are environmentally non-friendly.
Partners
PCAS is already for 20 years recognized as a major European player for the production of active molecules in the microelectronics industry. The company opens up new areas of competence outside the core business areas and sustainably supports technological changes by developing new products. PCAS focuses on markets with above average long-term growth rates such as organic and printed electronics (e.g. OLEDs, organic semiconductors and dielectrics, OPVs, etc.). PCAS develops organic semiconductor materials with high thermal and photochemical stability. Their excellent light-absorption properties allow them to be applied in thin layers by printing technologies. PCAS and its subsidiary, Saint Jean photochemistry, are specialists in industrial production of semiconducting polymers for organic electronics, and are already offering commercial products and innovative new materials in the market.
On this promising market, PCAS has the advantage to bring their strong expertise in organic chemistry and, their technical and commercial knowledge of various sectors of high tech as well as future technologies, such as OLED for flat display, printed electronic. They will bring their existing market knowledge (existing partnerships with some leader market players) and industrial knowledge thanks to their subsidiary Saint Jean in Quebec. And last but not least their know-how in the development of methods of synthesis from the laboratory stage to pilot and industrial scale production. PCAS is able to produce pure materials with low contents of metals and is very flexible in terms of volumes (from small to industrial scale volumes).
In parallel, PCAS provides the new industries forming in the energy and environment sectors with innovative solutions for a smooth transition towards clean and safe energies, and towards the more efficient, economical and sustainable environmental technologies of the future. In that scope, the PCAS Group is strongly committed in the development of fourth-generation photovoltaics.
On a chemistry point of view, the competition is rare, some players having stopped investments on OPV. At the present time, the main competitors outside EU are American (Dupont) but new Asian competition is emerging (Taiwan, Korea, China). Through the product and technology knowledge improvement, this project will help PCAS to increase their competitiveness in addition to their flexibility and quality process and products as well as enlarge his presence on additional markets (such as construction (BIOPV, greenhouses), transportation).
Nanograde is a young SME and high-tech spin-off of the ETH Zurich. Nanograde is worldwide leader in custom-made development of specialty nanoparticles and inorganic inks. nanograde has the production capacity of about 1 metric ton of nanoparticles and plans to scale up to 10 metric tons of formulations. The main market for the developed materials is R&D departments in industry and academia. Nanograde expects to secure its position as leading manufacturer of OPV materials in the coming 3 years and anticipates therefore a significant expansion of its activities in OPVs with regards to sales volume and personnel.
Eight19 Ltd was spun-out from the University of Cambridge in 2010 in order to take to market world leading work on OPV. Eight19 is owned by a number of high profile industrial shareholders, including a £4.5M investment in 2010 from Solvay and the Carbon Trust and more recently further investment primarily from IP Group. The company’s mission is to develop the large scale-roll-to roll production technology for organic photovoltaic modules, and during the past 4 years it has established a significant infrastructure directed at commercial development of OPV based products.
This infrastructural capability covers the full range running from efficient evaluation of materials and components for organic solar cells in sheet fed processes to the development of the roll-to-roll processes on a pre-production pilot machine.
Eight19 sees its role as a developer of the roll-to-roll production technology for organic photovoltaic modules that will meet the demanding cost, stability and performance requirements of volume markets in off grid applications and large scale power generation. The deep knowledge of organic solar cell technology, roll-to-roll production processes and experience of roll to roll product development and commercialization enables Eight19’s team to deliver on the project goals.
Holst Centre/TNO, IMEC, TUe, ECN, CEA, BUW. Participation in the project will give the R&D partners new research and commercialization opportunities in public and private sectors. New partner relationships are brought in this project which can extend in future collaborations. New foreground being created can open up new research fields and applications, or additional exploitation routes through e.g. licensing agreements etc. Showing and developing further our research expertise can also result in new research projects, either publicly funded or by third parties.
As a university of technology the TUe performs scientific research in areas that are relevant for new technologies and society. The TUe has defined Energy, Health, and Smart Mobility as its strategic areas for the future. Within the area Energy, the TUe has invested strongly in research in thin film solar cells and by participating in MUJULIMA it is possible to advance some of the discoveries that have been and will be made at the TUe in the field of OPV into new technologies and products, creating new jobs and business in Europe. Educating young people and developing new technologies that can find their way into the market, are important goals for the TUe.
NEN is the only institute in the Netherlands that may officially publish standards. As such it is the Dutch representing member in international standardisation organisations such as ISO, IEC, CEN and CENELEC. NEN has held for many years held the position of secretariats of the CENELEC. Within this project NEN, is responsible for communication with CEN/CENELEC on progress of standardisation.
List of Websites:
The project website:
http://www.mujulima.eu/
The progress and new achievements in the project were communicated to the wider audience via Social Media:
https://www.linkedin.com/company/mujulima
https://twitter.com/MUJULIMA