Periodic Reporting for period 1 - PerSiSTanCe (Low-cost and Large-Area Perovskite-Silicon Solar Tandem Cells)
Reporting period: 2019-05-01 to 2021-04-30
As the world population grows, the total energy demanded increases, despite the limited reserves of fossil fuels. Energy sources based on new technologies, such as the photovoltaic cells are a sustainable and environmentally clean option. Most of the photovoltaic cells produced are based in silicon, a material that even though presents several advantages for the industry, fails to absorb the energy of the entire solar spectrum. One interesting option to increase device efficiencies is to produce stacks of complementing cells, known as tandem cells, thus taking advantage of the full solar spectrum. Tandems of Si and novel perovskite cells are a feasible alternative and can be synthesized from cheap and abundant materials.
On the other hand, the main requirements in industry are low cost, high throughput and process reliability. Thus, production techniques and materials should be selected bearing in mind a compromise between cost reduction, acceptable efficiencies and process yield.
The aim of the project PerSiSTanCe (Low-cost and Large-Area Perovskite-Silicon Solar Tandem Cells) was producing large area and low cost perovskite tandem solar cells with industry friendly methods and materials, selected bearing in mind the most appropriate for their implementation in tandem Si/perovskite cells. The priority was the substitution of layers whose use would involve scarce/strategic materials or difficult and/or expensive processes. The result should be more robust and reliable processes and devices, contributing to reducing the gap between laboratory devices and the future mass production tandem cells.
Big steps have been given in this direction, all the components of the standard cell have been subject of analysis and optimization, resulting in a control standard device of around 21% efficiency. On the other hand, planar and inverted devices, the most favourable architecture for tandem devices was developed for the first time at the Adolphe Merkle Institute, achieving an efficiency of 17.4% thanks to a low cost solution processed nickel oxide hole transport layer, improved passivation interlayers and an optimized perovskite absorber. This result paves the way towards the in-house production of semi-transparent and perovskite-in-perovskite tandem devices.
On the other hand, the main requirements in industry are low cost, high throughput and process reliability. Thus, production techniques and materials should be selected bearing in mind a compromise between cost reduction, acceptable efficiencies and process yield.
The aim of the project PerSiSTanCe (Low-cost and Large-Area Perovskite-Silicon Solar Tandem Cells) was producing large area and low cost perovskite tandem solar cells with industry friendly methods and materials, selected bearing in mind the most appropriate for their implementation in tandem Si/perovskite cells. The priority was the substitution of layers whose use would involve scarce/strategic materials or difficult and/or expensive processes. The result should be more robust and reliable processes and devices, contributing to reducing the gap between laboratory devices and the future mass production tandem cells.
Big steps have been given in this direction, all the components of the standard cell have been subject of analysis and optimization, resulting in a control standard device of around 21% efficiency. On the other hand, planar and inverted devices, the most favourable architecture for tandem devices was developed for the first time at the Adolphe Merkle Institute, achieving an efficiency of 17.4% thanks to a low cost solution processed nickel oxide hole transport layer, improved passivation interlayers and an optimized perovskite absorber. This result paves the way towards the in-house production of semi-transparent and perovskite-in-perovskite tandem devices.
Given that silicon solar cells are generally produced on p-type substrates with an n-type emitter on top, the necessity to create a series connection with a perovskite solar cell in order to produce monolithic tandem device mandates the use of a so-called inverted architecture of perovskite solar cells. This inverted architecture consists on the deposition in the substrate (silicon for tandems or a transparent conductor coated glass for standalone PSC), of a transparent conductive oxide (TCO) between both devices, the HTM followed by the active perovskite absorber, an ETL and finalizing with the metallic electrodes evaporation. The sequence is summarized with the acronym p-i-n by the order in which the materials are deposited, the p for the HTM that would make the series connection with the n-type emitter of the silicon solar cell.
The tasks fulfilled towards the achievement of the main objective have been:
- Protocols and methods for low cost hole transport materials like NiO have been developed and optimized.
- The sputter deposition protocols for ITO and indium-free (AZO) transparent conductive oxides have been developed and optimized.
- Deposition protocols for ZnO and SnO low cost inorganic electron transport layers developed.
- Planar and inverted perovskite solar cells were produced with high stabilities and efficiencies of up to 17.4%
- Successful perovskite deposition on industrial silicon textured substrates through Flash Infra-Red Annealing.
- Optimization of meso n-i-p control devices, achieving efficiencies of approximately 21%.
Part of these results have already been published in peer-reviewed publications and scientific conferences. There have been four publications with contributions from the current project, while there is an additional paper currently accepted, and two other manuscripts under preparation.
Regarding the conferences I participated with oral or graphical contributions in 4 of them, with a potential accumulated audience of hundreds to thousands of researchers.
The dissemination aspect of the grant was mainly focalized in local work within the City of Fribourg, with primary and secondary schools students taking part in simple solar energy expositions and laboratory practices. Through the workshops the students had the opportunity of not only getting in touch with solar and renewable energy specific aspects, but with science in general, giving them in many cases their first contact with how science is made.
The tasks fulfilled towards the achievement of the main objective have been:
- Protocols and methods for low cost hole transport materials like NiO have been developed and optimized.
- The sputter deposition protocols for ITO and indium-free (AZO) transparent conductive oxides have been developed and optimized.
- Deposition protocols for ZnO and SnO low cost inorganic electron transport layers developed.
- Planar and inverted perovskite solar cells were produced with high stabilities and efficiencies of up to 17.4%
- Successful perovskite deposition on industrial silicon textured substrates through Flash Infra-Red Annealing.
- Optimization of meso n-i-p control devices, achieving efficiencies of approximately 21%.
Part of these results have already been published in peer-reviewed publications and scientific conferences. There have been four publications with contributions from the current project, while there is an additional paper currently accepted, and two other manuscripts under preparation.
Regarding the conferences I participated with oral or graphical contributions in 4 of them, with a potential accumulated audience of hundreds to thousands of researchers.
The dissemination aspect of the grant was mainly focalized in local work within the City of Fribourg, with primary and secondary schools students taking part in simple solar energy expositions and laboratory practices. Through the workshops the students had the opportunity of not only getting in touch with solar and renewable energy specific aspects, but with science in general, giving them in many cases their first contact with how science is made.
During the development of the PerSiSTanCe project there was work performed in all the components of semi-transparent perovskite solar cell, from the transparent electrode, to both transport layers (electron and hole), the metal back electrode and the perovskite active absorbing material itself. Most of the time has been devoted to develop a reliable solution process approach for the deposition of nickel oxide (NiO) as HTM on one hand, and to improve in general the performance and reliability of the perovskite material. The work with the NiO has been successful since a relatively simple solution process approach of nanoparticles formation and deposition has been optimized. This process is suitable for transfer to industry, which was part of the main goals of the project. On the other hand, the perovskite material and overall device reliability produced at the host institution have been greatly increased during the 2 years project. In this time the efficiency of the devices produced passed from average 15% efficiency to averages close to 20%.
The use of the Flash Infra-Red Annealing (FIRA) has allowed creating pseudo-conformal layers on texturized substrates. The combination of FIRA with an in-line solution process method like blade-coating, spray-coating or inkjet printing could result in an industrially feasible and vacuum-less method for Si/PSC tandems on texturized substrates. The specific conditions of perovskite solution molarity, substrate preparation and FIRA settings were optimized, the result is a uniform and conformal perovskite coating layer on texturized silicon, an achievement not out of reach for practically all the groups working on solution processing perovskite.
The use of the Flash Infra-Red Annealing (FIRA) has allowed creating pseudo-conformal layers on texturized substrates. The combination of FIRA with an in-line solution process method like blade-coating, spray-coating or inkjet printing could result in an industrially feasible and vacuum-less method for Si/PSC tandems on texturized substrates. The specific conditions of perovskite solution molarity, substrate preparation and FIRA settings were optimized, the result is a uniform and conformal perovskite coating layer on texturized silicon, an achievement not out of reach for practically all the groups working on solution processing perovskite.