Thin film synthesis and violet-light emission of widegap Cu₂ZnI₄

Abstract

Cu₂ZnI₄ (CZI) is a non-perovskite-type iodide that has a zincblende-derived layered structure. Since the identification of CZI in the late 1980s, the thin film synthesis and optoelectronic properties of this compound have not ever been reported. We expect CZI to be a potential optoelectronic material because several Cu-based halides are excellent optoelectronic semiconductors. In this study, we synthesized CZI thin films and investigated their optical properties. Single-phase CZI polycrystalline films were obtained for the first time using vacuum evaporation. These films were highly transparent in the visible region, and optical absorption analysis revealed CZI to be a widegap compound with the bandgap of 3.1 eV. Furthermore, the CZI films exhibited violet-light photoluminescence originating from excitonic transitions even at room temperature. Our findings suggest that CZI is a potential candidate for a light-emitting material.