Diagnosis of GaInAs/GaAsP Multiple Quantum Well Solar Cells With Bragg Reflectors via Absolute Electroluminescence

By using absolute electroluminescence measurement, we characterized current-dependent external radiative efficiency of GaInAs/GaAsP multiple quantum well (MQW) single-junction solar cells with and without a back distributed Bragg reflector (DBR). Internal radiative efficiency (η
_int
) under illuminated condition was quantified for analyzing their difference in photovoltaic performances. It was revealed that MQWs showed an advantage of improved η
_int
compared with a bulk layer, and that a back DBR indeed improved conversion efficiency via double-pass absorption of sun light, but improvement via reduction of rear radiative emission loss toward substrate was small. Efficiency add-on via improved material quality, or ηρ, in the same structures was predicted.