Copper Chalcopyrites for Solar Energy Applications

Abstract

Solar photovoltaic (PV) technology is a reliable and environmental friendly alternative for electricity generation. There are a number of solar PV technologies at different maturity levels, ranging from well-established and commercialized silicon PV to still in conceptual and R&D phase quantum dot and organic/polymer solar cells. Chalcopyrite solar cells, named so because of the thin absorber layer of Cu-based chalcopyrite materials used in these cells, are one of the frontrunners in thin-film PV technology owing to their tunable direct bandgap, large absorption coefficient and long-term stability. Among all Cu-chalcopyrite materials, copper indium selenide (CISe) and copper indium gallium selenide (CIGSe) are most suitable for use as light-absorbing layer. Although CISe and CIGSe absorber-based PV modules are being produced commercially for several years now, the technology is yet to mature fully as there is still scope for improvement in efficiency, manufacturability and cost reduction. The present article discusses the status of CISe-/CIGSe-based thin-film PV technology while primarily focusing on the absorber material. Different vacuum and non-vacuum methods for fabricating these materials are reviewed along with their merits/demerits and suitability to large-scale production. Current status of commercial maturity for CIGSe PV is discussed while providing general process details of selected industrial manufacturers. Existing bottlenecks for this technology are deliberated, and future directions for improvement in laboratory-scale efficiency and manufacturability are outlined.