All-inorganic copper(i)-based ternary metal halides: promising materials toward optoelectronics.

All-inorganic lead halides, including CsPbX (X = Cl, Br, I), have become important candidate materials in the field of optoelectronics. However, the inherent toxicity of metal lead and poor material stability have hindered further applications of traditional metal halides, CsPbX. Therefore, copper(i)-based ternary metal halides are expected to become promising substitutes for traditional metal halides because of their nontoxicity, excellent optical properties and good stability under ambient conditions. This article reviews the recent development of all-inorganic low-dimensional copper(i)-based ternary metal halides by introducing their various synthesis methods, crystal structures, properties and their optoelectronic applications. In addition, the prospects for future challenges and the potential significance of copper(i)-based ternary metal halides in optoelectronic fields are presented.