Zero-dimensional Sb<sup>3+</sup> doped Rb<sub>7</sub>Bi<sub>3</sub>Cl<sub>16</sub> metal halides with triplet self-trapped exciton emission

Low-dimensional metal halides have attracted extensive attention due to their excellent optical properties, especially zero-dimensional metal halides, which can improve the radiation recombination probability due to the characteristics of their isolated octahedral structures. In this paper, we report a zero-dimensional metal halide Sb³⁺ doped Rb₇Bi₃Cl₁₆ with a broadband orange-yellow emission at 613 nm. When the Sb³⁺ doping concentration is 30%, the highest photoluminescence quantum yield of the system reaches 30.7%. This high-efficiency luminescence is derived from the self-trapped excitons generated by the strong interaction between electrons and the crystal lattice. The specific physical mechanism and energy transfer process of self-trapped exciton luminescence are further studied through characterizing the optical performances. The electronic states in the singlet ¹P₁level are relaxed to the triplet ³P₁via an intersystem crossing process, and the strong orange-yellow emission comes from the triplet state ³P₁→¹S₀ radiation recombination process. In addition, Sb³⁺ doped Rb₇Bi₃Cl₁₆ has satisfactory environmental stability, the Sb³⁺:Rb₇Bi₃Cl₁₆-based light-emitting diodes (LED) are fabricated here in this work, and the color coordinates and correlated color temperature of the LED are (0.4886, 0.4534) and 2641 K, respectively. The highly efficient and stable Sb³⁺ doped Rb₇Bi₃Cl₁₆ is expected to be used in solid-state lighting and display fields.