Efficiency Enhancement of Single Junction GAAS Solar Cells using Strain-Balanced Quantum Well Structures Under Concentration

GaAs based strain-balanced quantum well solar cells (SB-QWSCs) have been shown to enhance efficiency compared to a bulk control cell, if the overall photocurrent increase is not offset by the reduction in open-circuit voltage. Here we demonstrate the performance of QWSC in light fluxes of up to 400 suns equivalent. The QWSC maintains additivity (the total current is the sum of dark current and the photocurrent) at these concentration levels and we demonstrate an efficiency of 27.0% at 328 suns for a SB-QWSC under the low aerosol optical density spectrum (AOD). The SB-QWSC is a p-i-n structure with 50 In_0.1Ga_0.9As wells in the i-region and a 20 period staircase distributed Bragg reflector (DBR) optimized to reflect light in the stop-band range of (880-930) nm. The entire device is grown monolithically in a robot-loading 7times2 Thomas Swan Shower-Head Reactor recently commissioned at the University of Sheffield