Influence of built-in charge on photogeneration and recombination processes in InAs/GaAs quantum dot solar cells

Selective doping of quantum dots is often used to improve efficiency of intermediate band solar cells (IBSC) due to IR harvesting and built-in-dot charge. To investigate the effects of the built-in-dot charge on recombination processes and device performance InAs/GaAs quantum dot IBSCs with direct Si doping in the quantum dots are fabricated, and the I-V characteristics and transients of the open circuit voltage and short circuit current are measured. The decay times of both the open circuit voltage and the short circuit current increase as the concentration of n-type doping increases in the quantum dots. The observed increase in the charge carrier lifetime is attributed to suppressed recombination of electron-hole pairs through the states of quantum dots and shrinking the depletion layer. This is supported by measurements of both photovoltage and photoluminescence spectra.