Intrinsic Defect Properties in Halide Double Perovskites for Optoelectronic Applications

Lead-free halide double perovskites with the formula of quaternary A2+B+B ' 3+X6- have recently attracted intense interest as alternatives to lead-halide-perovskite-based optoelectronic materials for their nontoxicity and enhanced chemical and thermodynamic stability. However, the understanding of intrinsic defect properties and their effects on carrier transport and Fermi level tuning is still limited. In this paper, we show that, by exploring the phase diagram of a halide double perovskite, one can control the effects of intrinsic defects on carrier trapping and Fermi-level pinning. Furthermore, we reveal the ideal growth conditions to grow p type Cs2AgInCl6 and Cs2AgBiCl6 as well as semi-insulating Cs2AgBiBr6 with low trap density for targeted photovoltaic or visible light/radiation detection application.