Development of a high efficiency mechanically stacked multi-junction solar cell

Abstract

An affinity for high performance solar cells in the space market, as well as the development of new engineered substrate technology, has warranted a re-consideration of mechanically stacked solar cell technologies. Mechanically stacked approaches result in a wider materials and interconnectivity design space compared to monolithic approaches. We are investigating the Smart-cut technology to produce InP/Si engineered substrates. Successful transfer of InP films to a silicon substrate has been demonstrated, and the resulting structure is mechanically stable after MOCVD growth. The electrical resistivity of the bonded interface is low, despite the presence of a very thin interfacial oxide. Work continues in regard to producing an epi-ready surface for the subsequent growth of high quality MOCVD layers. Tandem cell interconnectivity approaches are being investigated which can result in minimal parasitic loss and are also simple to process. Bottom tandem prototype cells have been fabricated on InP, with encouraging results. New AR coatings have also been designed to improve the optical coupling to these extremely wide-band solar cells.