Defect analysis of 1-MeV electron irradiated flexible InGaAs solar cells by deep-level transient spectroscopy and photoluminescence

1-MeV electron irradiated InGaAs flexible solar cells were investigated based on solar cell I-V characteristics, external quantum efficiency, photoluminescence, and deep-level transient spectra (DLTS) mesurements. The electrical parameters of the solar cells, including Rs and Rsh, were extracted from the I-V curves. With an increase in irradiation fluence, the electrical and optical characteristics of the solar cells continuously degraded. The Voc, Isc, and Pmax values decreased to 83.16%, 81.96%, and 68.88% of their initial values, respectively, when the irradiation fluence was increased to 2 x 1015 e/cm2. Photoluminescence (PL) emission peak intensity decreased to 0.54% of its original value, and the minority carrier lifetimes derived from fitting PL emission spectra were reduced to 1.25%. DLTS technique was used to analyse the irradiation-induced defect properties. Similar fitting values for the minority carrier lifetimes were obtained from the PL and DLTS measurements.