Towards New Generation of Solid-State Photovoltaic Cell: Harvesting Nanotubular Titania and Hybrid Chromophores

Project Information

CHROMTISOL

Grant agreement ID: 638857

DOI

10.3030/638857

Project closed

EC signature date 16 February 2015

Start date 1 March 2015

End date 31 August 2020

Funded under

• EXCELLENT SCIENCE - European Research Council (ERC)

Total cost

€ 1 644 380,00

EU contribution

€ 1 644 380,00

Coordinated by

UNIVERZITA PARDUBICE
Czechia

Periodic Reporting for period 4 - CHROMTISOL (Towards New Generation of Solid-State Photovoltaic Cell: Harvesting Nanotubular Titania and Hybrid Chromophores)

Reporting period: 2019-09-01 to 2020-08-31

Summary of the context and overall objectives of the project

The issue addressed was the lack of solar cell technology fulfilling stringent criteria of efficiency, stability, low prize, flexibility, transparency, tunable cell size, esthetics.
The aim of this project was to develop a new solar cell concept, with fast and loss-reduced photo-generated carrier to boost the solar-to-electricity conversion efficiency and to power so far unpowerable devices and objects.
The CHROMTISOL solar cell concept bears a large potential to outperform existing thin film photovoltaic technologies and concepts due to unique combination of materials and their complementary properties.

The research focus was given to extremely promising materials, yet unseen and unexplored in a joint device, whose combination may solve traditional solar cells drawbacks (carrier recombination, narrow light absorption). It featured a high surface area interface (higher than any other known PVs concept) based on ordered anodic TiO2 nanotube arrays, homogenously infilled with nanolayers of high absorption coefficient crystalline chalcogenide or organic chromophores using different techniques, yet unexplored for this purpose. After addition of supporting constituents, a solid-state solar cell with an extremely large incident area for the solar light absorption and optimized electron pathways was created.

Secondary goal was the development of advanced techniques for infilling of high-aspect ratio nanotubular TiO2 arrays with inorganic and organic chromophores. The filling method of the first choice was the Atomic Layer Deposition (further noted as ALD). However, there were at least 3 other methods employed (electrodeposition, solution processing, in-situ synthesis).

Conclusion of this action:
Fully functional, robust and stable solid-state solar cell according to the proposed CHROMTISOL concept was realized. The details are described below and in the scienfic report.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

Workpackage 1: Development and Synthesis of TiO2 Nanotube layers
Development of nanotube layers suitable for their employment in the proposed solar cells concept was carried out already. In particular, uniform nanotube layers with different aspect ratios were realized using new anodization protocols allowing to tailor tube diameters, lengths, wall. We have also understanding how crystalline structures (obtained by various treatments) influences the nanotube properties. The developed nanotube layer are used in WP3.
In the remaining time, we plan to scale up of the nanotube production by synthesis of developed anodic TiO2 nanotube arrays on rigid titanium as well as flexible substrates (PET foils or similar) of different sizes, dimensions and formats.

Workpackage 2: Development of Chromophores
Development of chromophores suitable for the purpose of the deemed solar cell concept was carried out. Two classes of materials were developed - inorganic crystalline semiconductors and organic push-pull sensitizers. They have shown sufficient light absorption capability, optimized HOMO-LUMO fit with TiO2, good anchorage to TiO2 and reasonable stability. Chromophores are chemically and thermally compatible with other constituent creating deemed solar cell. The as-synthesized chromophores are used in WP3.

Workpackage 3: Nanotube Infilling Routes
Deposition of a range of chromophores developed in WP2 inside the TiO2 nanotubes synthesized in WP1 was carried out. For that a broad range of deposition techniques has been employed including Atomic Layer Deposition (ALD), electrochemical deposition, spin-coating and direct in-situ synthesis. For the purpose of homogenous nanotube coating/ infilling, especially ALD was used to a great extent for the first time. During these efforts, some specific challenges connected with the filling efforts had to be overcome. However, due to significant drive of the whole team and efforts spent on this topic, we are ready to proceed to infill inside the nanotubes all necessary parts of the futue solar cells – topic of WP4.

Workpackage 4: Creation of the Solar Cell
Samples produced in WP 3 will receive remaining elements to function as the solar cell. Solar cells prepared in the laboratory will be tested on the photovoltaic performance by photocurrent measurements and solar cell simulator. Strong feedback on the materials development (WP1-2) and filling routes (WP3) is expected that will influence optimization of all components towards solar cells with highest conversion efficiency and stability possible.

For all WPs, numerous publications in highly ranked international peer-reviewed journals were published during the action- see the relevant section PUBLICATIONS of this report, please. They were all disseminated in the open-access green or gold way. The main result of this action - the pioneering publication on the whole complete CHROMTISOL based solar cell - is to be published in the highest possible class journal after the planned end of the action. Some remaining cross-check measurements and data validation need to be performed to be extremely well sure about the performance and endurance of the solar cells, before dissemination of that results.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

Progress beyond the state of art (understood as the time before the beginning of this action):

Achieved results during the Action:
1) Important novel findings on the synthesis of nanotube layers, their aspect ratios, morphologies and post-treatments necessary for the solar cells function
E.g. we have shown the relationship between the microstructure of the substrates and the nanotube growth, we were able to demonstrate the anodization of electrodeposited Ti towards nanotubes, which is extremely
hand for the realization of transparent solar cell devices, we were able to produce really high aspect ratio nanotube layers, we were able to reduce the usual annealing time of the nanotube layers from hours to seconds (by intense laser treatment),we showed also the possiblity to make single-wall nanotube layers with better performance than traditional double wall nanotube layers, and many more...

2) Important novel findings in the deposition of secondary materials within nanotubes - in particular ALD (See attached photograph) has been super cool tool for deposition of other materials inside nanotubes for solar cells, but also for batteries, sensors, biomedical devices, etc.The team developed significant skills in ALD and developed unique know-how, how to use the technique for the purpose of the project. This was very successfull and we plan to utilize / develop it even more and stronger in the future.

3) fully functional solid-state solar cell according to the proposed CHROMTISOL design. This is main result of this action - the pioneering publication on the whole complete CHROMTISOL based solar cell - is to be published in the highest possible class journal after the planned end of the action. Some remaining cross-check measurements and data validation need to be performed to be extremely well sure about the performance and endurance of the solar cells, before dissemination of that result.

Overall,the results published so far have attracted significant attention. Based on the number of papers, presentations (incl.invited) given at conferences, one can state that we became world leaders in the deposition of various materials into high aspect ratio nanostructures. This knowledge is liked and we are increasingly asked to participate to take a leading role in some complementary follow-up activities to this action.

SEM image of the TiO2 nanotubes with coating of secondary material

photograph of the ALD tool - key instrument for the realization of research agenda of CHROMTISOL