Characterizations of radiation damages in multi-junction solar cells focused on subcell internal luminescence quantum yields via absolute electroluminescence measurements

Via absolute electroluminescence (EL) measurements, we characterized degradations of internal luminescence quantum yields in respective subcells in GaInP/GaAs/Ge triple-junction solar cells after radiation damages by proton irradiations with different energy and fluence. Compared with typical open-circuit-voltage characterizations, the internal luminescence quantum yield turned out to be a sensitive, high-dynamic-range, quantitative, and fair indicator of radiation damage, since it purely represents material-quality change due to radiation damage, independently from small differences in band-gap energy due to alloy composition fluctuations and in other cell structures.