Sunlight Concentration Properties of InAs/InAsSb Ultrahigh-Density Quantum-Dot Solar Cells

InAs/InAsSb ultrahigh-density (UHD)-quantum dots (QDs) with 1.0×10¹² cm^-2 were introduced into the GaAs solar cell with 500-μm-separated comb electrodes. Fill factor (FF) of GaAs cell and InAs/GaAs high-density QD cell drastically decreased with increasing quasi-sunlight concentration (QX). For UHD-QD cell, the degradation of FF was suppressed because of the lateral carrier transport through the UHD-QD layer. Open-circuit voltage increased logarithmically with the sunlight concentration. Power conversion efficiency (PCE) of UHD-QD cell increased with increasing QX and exceeded PCE of GaAs cell for QX of more than 4.