Material Design and Optoelectronic Properties of Three-Dimensional Quadruple Perovskite Halides

The discovery of new halide perovskite-type structures could favor the exploration of optoelectronic materials, as in the case of double perovskites applied in solar cells, light-emitting diodes, and X-ray detectors. In this work, we propose a strategy for designing quadruple perovskites by heterovalent cation transmutation from double perovskites. Two stable quadruple perovskite halides, i.e., Cs₄CdSb₂Cl₁₂ and Cs₄CdBi₂Cl₁₂, with a vacancy-ordered three-dimensional (3D) crystal structure were predicted through symmetry analysis and density functional theory (DFT) calculations. The title perovskite halides are also electronically 3D with direct forbidden bandgaps. Following the indication provided by the DFT results, Cs₄CdSb₂Cl₁₂ and Cs₄CdBi₂Cl₁₂ as unique quadruple perovskites were successfully synthesized by a solvothermal method. The steady-state photoluminescence (PL) shows wide emission, while the transient PL exhibits carrier recombination lifetime on the order of microseconds at low temperature. The quadruple perovskite halides provide an alternative platform for promising optoelectronic material design in addition to simple and double perovskites.