Exploring the Intrinsic Point Defects in Cesium Copper Halides

Cesium copper halides Cs3Cu2X5 (X = Cl, Br, and I) have attracted much attention for optoelectronic applications because of their self-trap excitons and high photoluminescence quantum yield. Intrinsic point defects play a critical role in the optoelectronic performance of these materials by affecting fundamental properties, such as carrier mobility, lifetime, and recombination rate. In this work, we have calculated, by means of quantum mechanical calculations, formation energies and transition levels of all possible intrinsic point defects in Cs3Cu2X5. We have found that only Xi and XCs defects show simultaneously, deep transition energy levels and negative formation energies. Interestingly, the dominant defect under halide-rich growth conditions exhibits much higher concentration than that under halide-poor conditions. Thus, avoiding the halide-rich conditions could help in reducing the defect concentration.