Design and Demonstration of InGaAs/GaAs/GaAsP Stepped Quantum Well Solar Cell

ABSTRACT In the present work, a series of multiple‐stepped quantum well (MSQW) solar cells were demonstrated, with GaAs step layers inserted between strain‐balanced InGaAs wells and GaAsP barriers. We have studied carrier recombination dynamics and carrier escape kinetics from the wells, comparing the MSQW with the normal multiple quantum well (MQW). Carrier recombination rate was examined by time‐resolved photoluminescence (PL), and a longer carrier lifetime was observed for the MSQW. Carrier escape from the wells was also investigated in terms of temperature‐dependent PL, and smaller thermal activation energy was also observed for the MSQW. Carrier radiative recombination loss was investigated by bias‐dependent PL, and it was found to be smaller for the MSQW than for the normal MQW. Such advantages of the MSQW allowed us to stack a sufficient number of quantum wells to increase short‐circuit current without degrading fill factor. The simulation has also been performed in triple‐junction GaInP/GaAs/Ge solar cell devices with InGaAs/GaAs/GaAsP stepped quantum wells. When standard GaInP/GaAs/Ge solar cells had optimal active layer thickness, the conversion efficiency increased from 24.2% to 33.4%. The positive effects of embedded quantum wells are proven to help improve triple‐junction GaInP/GaAs/Ge solar cell performance.