Study of the reverse I–V in component subcells of III–V multijunction space solar cells

Abstract

The reverse bias operation of triple-junction solar cells (GaInP/Ga(In)As/Ge), typically used for space photovoltaics, is poorly understood. In this work, we conduct reverse bias stress tests on both isotype subcells (GaInP, Ga(In)As and Ge) as well as in the complete triplejunction solar cell. After each reverse bias step, forward dark and lighted I-Vs are measured and modelled using Shockley and Spirito and Albergamo models to fit the characteristic parameters of each individual subcell and quantify the variations evolution caused by the stress. The changes in these parameters are thoroughly analyzed in order to comprehend the basic physical processes behind the degradation observed after the reverse bias is applied.Finally, we demonstrate that the individual parameters obtained from each subcell can be combined to simulate the final I-V curve of the complete triple junction and understand how it is affected when reverse bias is applied, linking the changes observed to a sudden degradation of the GaInP top subcell at low reverse voltages.