Facet‐Dependent, Fast Response, and Broadband Photodetector Based on Highly Stable All‐Inorganic CsCu2I3 Single Crystal with 1D Electronic Structure

Abstract Low‐dimensional metal halides at molecular level, which feature strong quantum confinement effects from intrinsic structure, are emerging as ideal candidates in optoelectronic fields. However, developing stable and nontoxic metal halides still remains a great challenge. Herein, for the first time, high‐crystalline and highly stable CsCu 2 I 3 single crystal, which is acquired by a low‐cost antisolvent vapor assisted method, is successfully developed to construct high‐speed (t rise / t decay = 0. 19 ms/14. 7 ms) and UV‐to‐visible broadband (300–700 nm) photodetector, outperforming most reported photodetectors based on individual all‐inorganic lead‐free metal halides. Intriguingly, facet‐dependent photoresponse is observed for CsCu 2 I 3 single crystal, whose morphology consists of 010, 110, and 021 crystal planes. The on–off ratio of 010 crystal plane is higher than that of 110 crystal plane, mainly owing to lower dark current. Furthermore, photogenerated electrons are localized in twofold chains created by CuI 4 tetrahedra, leading to relatively small effective mass and fast transport mobility along the 1D transport pathway. Anisotropic carrier transport characteristic is related to stronger confinement and higher electron density for 110 crystal planes. This work not only demonstrates the great potential of CsCu 2 I 3 single crystal in high‐performance optoelectronics, but also gives insights into 1D electronic structure associated with fast photoresponse and high anisotropy.