Crystal-Phase-Engineered Rashba Indirect Exciton Emission in CsPbBr₃ Single Crystals

All-inorganic metal halide perovskites are promising candidates for light-emitting devices due to their stability, spectral tunability, and high quantum efficiency. However, dual-peak emission has been widely reported in these all-inorganic metal halide perovskites, which influences the monochromaticity and the quantum efficiency of light-emitting devices. To this end, it is important to reveal the underlying mechanism of the dual-peak emission and to further control the dual-peak emission. Here, we report on crystal phase engineered dual-peak emission in cubic and monoclinic CsPbBr₃ single crystals. The presence of the dual-peak emission would affect the absolute emission quantum yield and can be attributed to the occurrence of the Rashba effect induced by the surface effect and the thermally assisted structural distortion. Especially, the crystal phase-dependent emission profile might originate from the different effective phonon energy and carrier-phonon interaction strength as well as the intrinsic band structure and transition matrix difference between the cubic and monoclinic CsPbBr₃. Our studies establish a relationship among the crystal phase, the Rashba effect, and the emission properties of the CsPbBr₃ and provide insights for controlling the Rashba effect and designing the materials for applications in light-emitting and light-harvesting optoelectronics.