III–V-on-silicon solar cells reaching 33% photoconversion efficiency in two-terminal configuration

Romain Cariou, Jan Benick, Frank Feldmann, Oliver Höhn, Hubert Hauser, Paul Beutel, Nasser Razek, Markus Wimplinger, Benedikt Bläsi, David Lackner, Martin Hermle, Gerald Siefer, Stefan W. Glunz, Andreas W. Bett, Frank Dimroth

Index: 10.1038/s41560-018-0125-0

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Abstract

Silicon dominates the photovoltaic industry but the conversion efficiency of silicon single-junction solar cells is intrinsically constrained to 29.4%, and practically limited to around 27%. It is possible to overcome this limit by combining silicon with high-bandgap materials, such as III–V semiconductors, in a multi-junction device. Significant challenges associated with this material combination have hindered the development of highly efficient III–V/Si solar cells. Here, we demonstrate a III–V/Si cell reaching similar performances to standard III–V/Ge triple-junction solar cells. This device is fabricated using wafer bonding to permanently join a GaInP/GaAs top cell with a silicon bottom cell. The key issues of III–V/Si interface recombination and silicon's weak absorption are addressed using poly-silicon/SiOx passivating contacts and a novel rear-side diffraction grating for the silicon bottom cell. With these combined features, we demonstrate a two-terminal GaInP/GaAs//Si solar cell reaching a 1-sun AM1.5G conversion efficiency of 33.3%.