Tandem InGaP/GaAs-quantum well solar cells and their potential improvement through phosphorus carry-over management in multiple quantum well structures

InGaP/GaAs/Ge multijunction solar cell (MJSC) efficiency can be increased through improved current matching among the subcells with multiple quantum wells (MQWs) being promising for this purpose. In this study we show that InGaAs/GaAsP QWs utilizing high phosphorus composition barriers can be successfully incorporated into the GaAs subcell of an InGaP/GaAs tandem solar cell. This InGaP/GaAs-MQW device has an enhanced short circuit current density when compared to that of a standard InGaP/GaAs tandem device with minimal impact on either GaAs or InGaP subcell open circuit voltage. Additionally, phosphorus carry-over in the MQW structure is investigated through the use of photoluminescence (PL). It is demonstrated that the phosphorus carry-over can be overcome through the utilization of thick GaAs transition layers at the GaAsP→InGaAs interfaces, resulting in a MQW with an extended absorption edge.