γ-Ray-Induced Degradation in the Triple-Cation Perovskite Solar Cells

We report on the impact of gamma radiation (0-500 Gy) on triple-cation Cs(0.15)MA(0.10)FA(0.75)Pb(Br0.17I0.83)(3) perovskite solar cells. A set of experiments was designed to reveal the individual contributions of the hole-collecting bottom electrode, perovskite absorber, and electron transport layer (ETL) to the overall solar cell degradation under radiation exposure. We show that the glass/ITO/PEDOT:PSS hole-collecting electrode withstands a 500 Gy dose without any losses in the solar cell performance. In contrast, the perovskite absorber films and PC61BM ETL are very sensitive to gamma rays, as can be concluded from the radiation-induced decay of the solar cell efficiency by similar to 32-41%. Red shift of the perovskite emission bands and strong enhancement of the photoluminescence suggest that gamma rays induce phase segregation of iodine-rich and bromine-rich domains, which represents the first reported example of the radiation-induced halide phase separation in perovskite films. The degradation pathway revealed here emphasizes the need for developing a new generation of metal halide absorbers and ETL materials with improved radiation stability to enable potential space applications of perovskite photovoltaics.