Open-Circuit Voltage Improvement of InAs/GaAs Quantum-Dot Solar Cells Using Reduced InAs Coverage

Ten-, 20-, and 40-layer InAs/GaAs quantum-dot (QD)-embedded superlattice solar cells were compared with a baseline GaAs p-i-n solar cell. Proper strain balancing and a reduction of InAs coverage value in the superlattice region of the QD embedded devices enabled the systematic increase in short-circuit current density with QD layers (0.02-mA/cm(2)/QD layer) with minimal open-circuit voltage loss (similar to 50 mV). The improvement in voltage was found to be due to a reduced nonradiative recombination resulting from a reduced density of larger defective QDs and effective strain management. The 40-layer device exceeded the baseline GaAs cell by 0.5% absolute efficiency improving efficiency relative to the baseline by 3.6%.