Efficient Yellow Self-Trapped Exciton Emission in Sb³⁺-Doped RbCdCl₃ Metal Halides

Metal halide perovskites have flexible crystal and electronic structures and adjustable emission characteristics, which have very broad applications in the optoelectronic field. Among them, all-inorganic perovskites have attracted more attention than others in recent years because of their characteristics of large diffusion length, high luminescence efficiency, and good stability. In this work, Sb³⁺-doped RbCdCl₃ crystalline powder was synthesized by a simple hydrothermal method, and its luminescence properties were studied, which showed a broad emission band with a large Stokes shift and efficient yellow light emission at about 596 nm at room temperature with a photoluminescence quantum yield of 91.7%. The emission came from the transition of the self-trapped exciton 1 (STE1) out of ³P (n = 0, 1, and 2) to S₀ due to strong electron-phonon coupling, which scaled with increasing temperature. Moreover, its emission color became white at low temperatures due to the occurrence of transition of other self-trapped exciton 0 (STE0) state emission out of the ¹S states of Sb ions to S₀ in the lattice. These emission color changes may be used for temperature sensing, and this Sb³⁺-doped RbCdCl₃ material expands the knowledge of the efficient luminescent inorganic material family for further applications of all-inorganic perovskites.