Development of a high performance laminated transparent top-electrode for emerging thin-film photovoltaics

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Photovoltaic (PV) devices convert sunlight directly into electricity and so are set to play a major role in the global renewable energy landscape in the coming decades as humanity transitions to a low carbon future. Today's PVs are based on conventional semiconductors which are relatively energy-intensive to produce and largely restricted to rigid flat plate designs. Consequently, PVs that can be fabricated by printing at low temperature onto flexible substrates are attractive for a broad range of applications in buildings and transportation, where flexibility, colour-tuneability, light-weight and low cost are essential requirements. Two emerging PV technologies that have strong potential to meet these requirements are organic PVs and perovskite PVs. It is however widely recognised that these classes of PV can only fulfill their full cost-advantage and functional advantages over conventional thin film PVs if a suitable transparent, flexible electrode is forthcoming. Indium-tin oxide (ITO) is currently the dominant transparent conductor used in opto-electronics, including PVs. However, its fragile ceramic nature makes it poorly compatible with flexible substrates and indium has been identified as a 'critical raw material' for the European economic area, due to the high risk of supply shortages expected in the next 10 years. Consequently there is a need to develop a viable alternative to ITO and conducting oxide electrodes in general, particularly for utility in PVs where large quantities will be needed in the coming decades to help address the threat posed by global warming. This proposal seeks to address this challenge by developing a high performance transparent electrode based on a copper grid that can be integrated with the rest of the PV device by simple lamination. This approach avoids the inevitable compromises in electrode transparency and conductivity that arise when using the conventional approach of fabricating the transparent electrode directly on top of the rest of device. Two unconventional approaches to fabricating this electrode using low cost sustainable materials and processes will be explored. The outputs have the potential to be transformative for the advancement of OPV and PPV, as well numerous other optoelectronic devices requiring a transparent top-electrode. The UK is a global leader in the development of materials and processes for next generation PVs and so the outputs of the proposed research has strong potential to directly increase the economic competitiveness of the UK in this increasingly important sector and will help to address the now time critical challenge of climate change due to global warming.