Carrier recombination effects on the performance of InGaAs/GaAs quantum dot intermediate band solar cell: A drift–diffusion study

Abstract

In this paper, we employ the drift–diffusion model to investigate the carrier recombination lifetime effects on the performance of the InGaAs/GaAs quantum dot intermediate band solar cells. In our model, we use experimentally achieved material parameters such as the absorption coefficients, carrier mobilities, quantum dot concentration, etc. for quantum dots and host material. Proper operation of the QD-IBSC would require that no charge carriers are allowed to be extracted from the quantum dot confined levels or intermediate bands. This would reduce the power output of the IBSC and thus the conversion efficiency. But carrier recombination in intermediate band and carrier transition between intermediate bands are an important parameter in the operation of QD-IBSC. In this study, we propose a model that by using the possible values of carrier recombination lifetimes, the effective recombination rate and photocurrent processes in active region of the cell can be calculated. By using the three values of the recombination life time, Voc, jsc and efficiency of the cell have been calculated and it was shown that higher value of recombination lifetime leads to the higher efficiency due to increase the jsc, but not significant increase occurred in Voc. This paper indicates that in experimental design and fabrication of InGaAs/GaAs based QD-IBSC, the recombination lifetime of carriers should be controlled, which if the value of recombination lifetimes in fabricated cell is too low, then performance of the cell will be lower than reference cell without QDs.