Air Induced Formation of Cs3Bi2Br9/Cs3BiBr6 Bulk Heterojunction and Its Dual‐band Photodetection Abilities for Light Communication

Abstract Metal‐halide perovskites have long carrier diffusion lengths, low trap densities, and high carrier mobilities, and are therefore of value in the development of photodetectors (PDs). However, the research on dual‐band lead‐free perovskite bulk heterojunction has not been well developed. Here, a novel air induced formation of Cs 3 Bi 2 Br 9 /Cs 3 BiBr 6 bulk heterojunction, reaching a high‐performance dual‐band photodetecting performance with an ultra‐violet main band (360 nm) peak responsivity of 5.6 mA W −1 and a blue sub‐band (450 nm) peak responsivity of 0.6 mA W −1 at 2 V, is reported. The bulk heterojunction exhibits superior photodetecting performance than that of lateral heterojunction. Furthermore, the PD exhibits a fast response speed (rise time 1.4 µs and decay time 2.0 µs) and good cyclic stability. Theoretical and experimental characterizations suggest Cs 3 Bi 2 Br 9 exhibits a more stable structure in air than that of Cs 3 BiBr 6 . The dual‐band photodetection abilities of Cs 3 Bi 2 Br 9 /Cs 3 BiBr 6 bulk‐heterojunction demonstrate great application prospects in light communication. These state‐of‐the‐art findings shed light on the fabrication of novel dual‐band high‐performance PDs based on lead‐free perovskite bulk‐heterojunction.