Radiation resistant chalcopyrite CIGS solar cells: proton damage shielding with Cs treatment and defect healing via heat-light soaking

Abstract

Cu(In, Ga)Se₂ (CIGS) solar cells are recognized as next-generation space technology due to their flexibility, lightweight nature, and excellent environmental stability. However, assessing their radiation durability remains challenging, necessitating thorough exploration for space viability. We conduct proton irradiation field tests with varying dosages at 380 keV. Both irradiated control and Cs-treated CIGS solar cells demonstrate impressive efficiency recovery after undergoing heat-light soaking (HLS), exceeding 97% and 100%, respectively. Interestingly, Cs-treated CIGS exhibits higher radiative emission intensity even under high fluence irradiation, indicating a shielding effect within the Cs-compound that protects the inner CIGS grains. Leveraging the knowledge gained from power-dependence, temperature-dependence PL, and time-resolved photoluminescence (TRPL), valuable insights into radiation damage, such as potential fluctuations and transitions involving donor–acceptor pairs, are obtained. X-ray absorption near-edge spectroscopy (XANES) and extended X-ray absorption fine structure (EXAFS) spectra further verify the formation of Frenkel defect pairs within the CIGS during irradiation. Remarkably, following HLS treatment, the K-edge shifts back to its initial state, implying a reversible defect healing mechanism. The harsh proton irradiation is first conducted on CIGS solar cells that have a power conversion efficiency exceeding 17%. This accomplishment firmly establishes CIGS thin-film solar cells as the iconic choice for space applications.