Degradation behavior of electrical properties of inverted metamorphic tri-junction solar cells under 1 MeV electron irradiation

Abstract

In this study, the degradation effects of inverted metamorphic tri-junction (IMM3J) solar cells were investigated after 1MeV electron irradiation using spectral response and photoluminescence (PL) signal amplitude analysis, as well as electrical property measurements. The results show that, similar to traditional tri-junction (TJ) GaInP/GaAs/Ge solar cells, the electrical properties (such as Isc, Voc, and Pmax) degrade as a function of logφ, where φ represents the electron fluence. In particular, the degradation of Voc is more serious than that of Isc because of the sum rule for Voc and the limit rule for Isc in IMM3J cells. Analysis of the spectral response curves indicates that, unlike traditional TJ cells, the bottom In0.3Ga0.7As (1.0eV) sub-cell exhibits the most severe damage in the irradiated IMM3J cells. Meanwhile, the PL amplitude measurements qualitatively confirm that the degradation in the effective minority carrier lifetime τeff of single junction (SJ) In0.3Ga0.7As cells is more drastic than that of SJ GaAs cells after irradiation. Thus, the output current of the In0.3Ga0.7As sub-cell should be the rate-limiting cell in the irradiated IMM3J cells.