Photovoltaic characteristics of InAs/InGaAs/GaAs QD heterostructures

In this work, preliminary photovoltaic results of the 10-layer InAs/InGaAs/GaAs quantum dot (QD) heterostructures were presented. As demonstrated, enhancement in the sub-GaAs bandgap spectral response was observed, especially at the 1.0-1.2 eV energy range. This implies that the incorporation of InAs QDs in existing InGaP/GaAs/Ge multijunction solar cells is beneficial for increasing the spectral utilization between Ge (0.67 eV) and GaAs bandgaps (1.42 eV). The open-circuit voltage (V_OC) and fill factor (FF) of the device are 0.4 V and 0.51, respectively. The obtained values are smaller than that reported by GaAs solar cells (V_OC=1.04 eV and FF=0.85), and the degradation is believed to be due to the accumulated strain from the 10-layer QDs. We believe that, upon optimization, incorporation of the InAs/InGaAs/GaAs QDs into existing InGaP/GaAs/Ge solar cells will result in solar cells with higher efficiency and render solar energy more cost competitive.