Lead-Free CsCu₂I₃ Halides with 1D Crystal Structure for UV Photodetection

Copper halide semiconductors are attracting extensive attention due to their nontoxic composition and excellent optoelectronic properties. Most so far are prepared via solution methods; however, grain boundaries and defects existing in those products hinder their further practical applications in solid-state devices. In this work, CsCu2I3 halides with 1D crystal structure are initially prepared by a vapor phase deposition method. The large Stokes shift coupling with a long photoluminescence decay time (112 ns) suggests the existence of a self-trapped exciton process in these CsCu2I3 nanowires, responsible for the yellow light emission emerging at 570 nm. UV photodetectors based on individual CsCu2I3 nanowires that are constructed via an etching-free dry transfer route reveal a responsivity of 122 mA W-1 and rise/decay times of 203/223 ms (310 nm, 5 V bias), comparable to or better than those congeneric UV sensors made of other lead-free halides. These CsCu2I3 nanowire-based photodetectors also reveal good stability in the atmosphere (RH = 60-70%, 17 ?), benefitting from their fourfold coordination environment of Cu(I) atoms in the 1D crystal structure. These results imply the technical potential of manufacturing low-dimensional lead-free halide semiconductors for next-generation green optoelectronics.