Composition optimization of lead-free double perovskite Cs2AgIn1-xBixCl6 for efficient and stable photoluminescence

Recently, lead-free double perovskites is increasingly focused in view of the nontoxicity and stability compared to lead-halide perovskites. In this study, we optimized the composition of lead-free double perovskite Cs2AgIn1-xBixCl6 nanocrystals (NCs) via an antisolvent recrystallization method at room-temperature. The pure Cs2AgInCl6 NCs show a low emission at 520 nm with a low photoluminescence quantum yield (PLQY) of 1.2%, which was assigned as the parity-forbidden direct band transition. By alloying 20%mol Bi3+ with In3+, broad-band orange emission peaking at 575 nm with the PLQY of 28.9% was obtained. The increasing of PL efficiency was considered mainly come from the breaking of the parity-forbidden direct band transition and improved crystal quality, which enhances the radiative recombination probability and decreases the defects density of the NCs. To further understand the exciton recombination dynamics, time-resolved PL and femtosecond TA technique were performed. And, a detailed photo-induced charge carrier dynamics process, especially the charge carrier trapping, recombination, and transition were confirmed and plotted. Moreover, the resulting Cs2AgIn0.8Bi0.2Cl6 products demonstrate a remarkable stability against heat, ultraviolet light irradiation, and moisture. The results suggest that the lead-free double perovskite Cs2AgIn0.8Bi0.2Cl6 is potentially an attractive candidate for solid-state lighting application.