Ga0.47In0.53As photovoltaic booster cells for tandem solar energy conversion

Abstract

Abstract Ga0.47In0.53As photovoltaic structures are grown lattice matched on InP[100] substrates. The cells that are fabricated from these structures are intended to convert the part of the solar spectrum that is lost by transparency of GaAs cells (i.e. photons with energy of less than 1.43 eV). An average collection efficiency of 60% in the 0.75-1.43 eV range is measured without antireflection coating (ARC). A double-layer ARC is expected to improve the collection efficiency to about 90% in this small band of the solar spectrum. In this work, particular attention has been paid to conversion efficiency measurements under concentration. The projected Ga0.47In0.53As cell contribution to the GaAs/(Ga,In)As stacked tandem conversion reaches 6% with concentration ratio C = 170 (AM 1), including grid obscuration and optical losses due to GaAs spectrum filtering. Recent efficiency values of GaAs under concentration (28%, C = 500 , AM 1), measured by Sandia Laboratories, suggest that a GaAs/Ga0.47In0.53As tandem photovoltaic structure might have a combined efficiency as high as 34% under concentration ( C = 500 ).