Orientation Regulation of One-Dimensional CsCu 2 I 3 Perovskites for Visible-Blind Ultraviolet Photodetectors.

Ternary copper halides with a formula of CsCu 2 X 3 (X = Cl, Br, I) have been considered as prospective materials for ultraviolet (UV) photodetectors, due to their suitable band gaps, environmental stability, eco-friendliness, and low cost. However, the crystal orientation of one-dimensional (1D) CsCu 2 X 3 perovskites significantly affects the exciton/carrier transport in the films and thus the photodetector performance. Here, we tune the crystal orientation and exciton/charge transport of 1D CsCu 2 I 3 perovskite films by using antisolvents during the film formation process. Compared to the randomly oriented film treated by ethyl acetate, the CsCu 2 I 3 film using toluene as antisolvent exhibits preferential (221)-oriented growth, which induces enhanced vertical exciton diffusion/charge transport and suppressed nonradiative recombination. On the basis of this strategy, we demonstrate a self-powered, stable, and visible-blind UV photodetector with significantly enhanced response speed and detectivity. Our work clarifies that tuning the crystal orientation of 1D CsCu 2 X 3 perovskites is the key to achieve efficient exciton diffusion/charge transport and thus high-performance lead-free perovskite optoelectronic devices.