Joint project "Next generation photovoltaics"

The crystalline Si (c-Si) and copper indium gallium selenide (CIGS) photovoltaic (PV) technologies are likely only a first step in the solarisation of energy systems as they fail to convert efficiently high-energy photons. Increased power output can be achieved by adding a higher bandgap top cell on their front side to form a tandem device. As balance of system (BOS) costs dominate the PV electricity price, increasing efficiency directly reduces it. Solar cells based on a perovskite absorber are likely the ideal top cell thanks to their high single-junction performance, tuneable bandgap, potential low costs and soft processing conditions. Such tandems may achieve efficiencies of 27%-30% (>5%abs higher than what is currently achievable with c-Si and CIGS), which in the long term could provide Switzerland with 13-14 TWh/year of PV electricity using well-orientated roofs and façades.

The major objective of the project was to design the next-generation of high-efficiency photovoltaics (PV) technologies. The project spanned the synthesis of novel materials, their integration in high-efficiency single- and multi-junction solar cells with c-Si and CIGS, the development of solar façade concepts, grid management strategies and analysis of the life cycles and social acceptance of these new technologies. The main aim was to develop the technological building blocks that could help to realise the Energy Strategy 2050.

Combining advanced simulation and characterisation techniques with thin film processing, the project team was able to design perovskite, c-Si as well as CIGS single-junction solar cells with improved optoelectronic properties. By combining them in multi-junction devices, the project partners were able to achieve world record efficiencies, notably the first perovskite/c-Si tandem featuring a texture on the front side for optimal light management, or flexible thin film perovskite/CIGS 4-terminal tandems. In parallel, the project contributed to improving the acceptance of PV installations, particularly by working on strategies aimed at minimising space usage and by improving efficiencies and promoting building integration on the basis of aesthetic solutions.

Relevance for research

The scientific concepts that emerged from the project had a major impact on the global research community, as highlighted by numerous invitations to present the research findings at international scientific conferences, or the high number of citations of publications associated with the project.

Relevance for practice

The project took the concept of high-efficiency perovskite/c-Si and /CIGS solar cells from an idea at the start of the project to fully functional devices that exhibit a clear efficiency gain compared to single-junctions. These results provide valuable feedback for industrial companies aiming to upgrade their c-Si or CIGS process lines with a perovskite top cell. Although several challenges still need to be tackled, high-efficiency perovskite-based solar cells have high industrial potential, as highlighted by the emergence of several companies dedicated to this subject. The façade elements designed in the project also have wide-ranging practical implications as they add another functionality to structural elements.

PV2050: Novel PV technologies for optimum space usage and efficient electricity production

The joint project consists of six research projects

PV2050: Novel materials and interfaces for advanced photovoltaic devices

• Prof. Frank Nüesch, Departement Moderne Materialien, ihre Oberfläche und Grenzflächen, EMPA Dübendorf; Prof. Christophe Ballif, Prof. Michael Grätzel, Prof. Ayodhya Tiwari

PV2050: Building blocks for Next Generation Multi-Junction Solar Cells

• Prof. Christophe Ballif, Institut de Microtechnique, EPFL Neuchâtel; Prof. Michael Gätzel, Prof. Ayodhya Tiwari

PV2050: Novel Generation Perovskite Devices

• Prof. Michael Grätzel, Laboratoire de photonique et interfaces, EPF Lausanne; Dr. Jun-Ho Yum, Prof. Ullrich Steiner

PV2050: Photovoltaics into the built environment: from semi-transparent PV glazing to high efficiency roof integrated solutions

• Dr. Laure-Emmanuelle Perret-Aebi, Centre Suisse d'Electronique et de Microtechnique SA, Neuchâtel; Prof. Emmanuel Rey

PV2050: Simulation and characterization: from cells to systems

• Dr. Matthias Schmid, Institute for Computational Physics, ZHAW Winterthur; Dr. Mohammed Zakeeruddin Shaik, Prof. Christophe Ballif, Prof. Ayodhya Tiwari

PV2050: Sustainability, market deployment and interaction to the grid – the impacts of advanced photovoltaic solutions

• Prof. Bettina Furrer, Institut für Nachhaltige Entwicklung, ZHAW Winterthur; Prof. Martina Hirayama-Bumm