Evidence for enhanced carrier escape from multiple stepped quantum well (MSQW) and its impact on photovoltaic performance

A multiple stepped quantum wells (MSQWs) solar cell, in which GaAs stepped-potential layers are sandwiched between strain-balanced InGaAs wells and GaAsP barriers, has been proposed. The bias-dependent photoluminescence has been studied to estimate the radiative recombination velocity, in comparison between the MSQW and the normal multiple quantum well (MQW) structures. Thermalized energy distribution from the wells was examined in terms of temperature-dependent PL and higher average carrier temperature was observed for MSQWs than for MQWs. Such enhanced carrier escape in the case of MSQWs allowed us to obtain increased short-circuit current density 25 mA/cm
²
which is approximately 14% higher than that of a normal MQWs solar cell.