Measuring Photovoltages of III–V Multijunction Solar Cells by Electroluminescence Imaging

A technique is presented that allows the determination of the photovoltages of subcells in an InGaP/InGaAs/Ge triple-junction solar cell utilizing electroluminescence (EL) imaging. The EL intensity of a subcell was found to be quenched when the others' subcells were illuminated by an extra laser. From analysis of the EL intensity under variable spectral illumination conditions, we estimated the photovoltages of the individual subcells. The measured photovoltages were successfully reproduced using the Simulation Program with Integrated Circuit Emphasis (SPICE) in an equivalent electric network.