LAUSR

Perovskite materials are third‐generation optoelectronic materials and require a lot of research work to improve their stability. Recently, lead‐free double perovskite materials have attracted significant attention due to their environmental friendliness, stability, and tunable optoelectronic properties. However, a limited number of double perovskite materials have been reported for optoelectronics applications. Therefore an effort is needed to explore more lead‐free double perovskites and alter the properties for their further applications. In this manuscript, we report lead‐free bismuth and bismuth/antimony‐based perovskite materials [Cs2AgBiBr6, Cs2AgBi0.6Sb0.4Br6, and Cs2AgBi0.6Sb0.4(Br0.278I0.722)6] nanocrystals (NCs) synthesized using the hot injection method and benzoyl bromide has been used as a precursor and trimethyl‐silyl iodide (TMSI) as the iodine source for anion‐exchange (from Br to Br/I). The formation of NC has been confirmed using X‐ray diffraction and X‐ray fluorescence spectrometer studies for phase and elemental analysis of synthesized NCs. The transmission electron microscopy of Cs2AgBiBr6 and Cs2AgBi0.6Sb0.4Br6‐based perovskite revealed cubic‐shaped NCs with size 15.0 ± 4.5 nm and 14.0 ± 5.3 nm, respectively, which changed to hexagonal (Cs2AgBi0.6Sb0.4(Br0.278 I0.722)6 NCs) shaped NCs with size 30 to 70 nm (after anion exchange). The successful bismuth replacement by bismuth/antimony is carried out. The time‐correlated single‐photon counting measurements on Cs2AgBi0.6Sb0.4Br6 NCs is carried out. The calculated average lifetimes of toluene (T)‐Cs2AgBi0.6Sb0.4Br6 and dichlorobenzene D‐ Cs2AgBi0.6Sb0.4Br6 NCs are 4.70 ns and 8.67 ns, respectively. After the anion exchange, the average lifetime value for T‐Cs2AgBi0.6Sb0.4(Br0.278I0.722)6 and D‐ Cs2AgBi0.6Sb0.4(Br0.278 I0.722)6 NCs are 8.73 and 9.78 ns, respectively. Additionally, the effect of light on the current density‐voltage characteristics of the Cs2AgBi0.6Sb0.4Br6 NCs device has been studied to ascertain its utility in solar cells. The device is fabricated using nickel oxide and PCBM as interface layers with power conversion efficiency 0.09%.