Effects of forward bias and substrate misorientation on the electroluminescence properties of GaxIn1-xP/GaAs double-junction tandem solar cells

Abstract

Electroluminescence (EL) measurements at room temperature have been conducted as a function of forward bias on two GaxIn1-xP/GaAs double-junction tandem solar cell structures grown with two distinct GaAs substrate orientations. Noticeable redshift of the peak position of the emission from the GaxIn1-xP top cell was observed in both samples with increasing the forward bias. Heating effect caused by the large injection current as well as the quantum-confined Stark effect (QCSE) induced by the enhanced electric field in the emitter layer of the GaxIn1-xP top cell were considered to be responsible for the observed EL peak redshift. In addition, the EL spectral features such as the energy position, lineshape, linewidth and intensity exhibit a strong dependence on the substrate misorientation angle (SMA). Dependence of defects and disorders in GaInP layer on the substrate misorientation was utilized to explain such dependences. These interesting observations can provide referential information on the design and optimization of GaxIn1-xP/GaAs double-junction photovoltaic structure.