Comprehensive first-principles studies on phase stability of copper-based halide perovskite derivatives AlCumXn (A = Rb and Cs; X = Cl, Br, and I)

Abstract Recently, inorganic copper-based halide perovskites and their derivatives (CHPs) with chemical formulas A l Cu m X n (A = Rb and Cs; X = Cl, Br and I; l , m , and n are integers.), have received increasing attention in the photoluminescence field, due to their lead-free, cost-effective, earth-abundant and low electronic dimensionality. Ascribed to flexible valence charge of Cu (Cu 1+ and Cu 2+ ) and complex competing phases, the crystal structures and phase stabilities of CHPs are complicated and ambiguous, which limits their experimental applications. Via comprehensive first-principles calculations, we have investigated thermodynamic stabilities of possible crystal phases for A l Cu m X n by considering all the possible secondary phases existing in inorganic crystal structure database (ICSD). Our results are in agreement with existing experiments and further predicted the existence of 10 stable CHPs, i.e. Rb 3 Cu 2 Br 5 , Rb 3 Cu 2 I 5 , RbCu 2 Cl 3 , Rb 2 CuI 3 , Rb 2 CuBr 4 , RbCuBr 3 , Rb 3 Cu 2 Br 7 , Cs 3 Cu 2 Br 7 , Cs 3 Cu 2 Cl 7 and Cs 4 Cu 5 Cl 9 , which have not yet been reported in experiments. This work provides a phase and compositional map that may guide experiments to synthesize more novel inorganic CHPs with diverse properties for potential functional applications.