Room-Temperature Crystallization of Ultralong (≈3.5 mm) CsCu2I3 Microbelt to Suppress Carrier Recombination for High-Performance UV Heterojunction Photodetector

Lead-free ternary copper iodide perovskite analogues demonstrate great potential in photodetector, due to their nontoxity and excellent photophysical properties. However, the fast carrier recombination limits the photoelectric conversion efficiency. Herein, a room-temperature growth strategy with the selected raw ratio is adopted to enhance carrier dynamics. The optimized-grown CsCu 2 I 3 single crystal exhibits longer carrier lifetime of 157 ns, and its switch ratio and response time are enhanced by 20 000% and 600% compared with those of stoichiometric-grown single crystal, respectively. Furthermore, space-confined method is introduced to prepare ultralong single-crystalline CsCu 2 I 3 microbelt, with the aspect ratio up to 600. The sensitivity and self-powered performance of the UV photodetector are improved through constructing heterojunction with p-CuI and asymmetric electrodes. The enhanced performance is ascribed to superior type-II band alignment between CsCu 2 I 3 and CuI, which effectively promotes the separation of photogenerated carriers. This work not only provides an efficient way to boost the photoresponse in low-dimensional metal halide perovskite analogue, but also displays 1D anisotropic growth for potential application in large-area vapor-assisted patterned devices.