Water engineering in lead free CsCu2I3 perovskite for high performance planar heterojunction photodetector applications

In this study, lead-free single crystal perovskite CsCu2I3 was synthesized by anti-solvent evaporation-assisted crystallization. Then CsCu2I3/CuI planar heterojunction was prepared by water treatment to form nanostructured CuI film on the surface of CsCu2I3 single crystal. Due to the enhanced light trapping by the porous CuI surface layer, the photodetector performances are significantly improved. The CsCu2I3/CuI lateral photodetector exhibits high sensitivity from violet to deep ultraviolet region, with the typical responsivity of 1.20, 0.59 and 0.84 A/W for 420 nm, 360 nm and 250 nm at 5 V bias, respectively. The typical response times are 119 ms (rise) and 287 ms (fall). Our findings provide a new perspective to engineer the photoelectric properties of inorganic perovskites through surface modification by water treatment.