Mn²⁺ doping and halide regulation for efficient LED emission in Cs₃CdBr₅

The halide perovskite phosphor Cs₃CdBr₅ exhibited the best stability among Cs₃CdX₅ (X = Cl, Br, I). Mn²⁺ doping in Cs₃CdBr₅ crystals yielded a photoluminescence quantum yield (PLQY) of 93.6% with 523 nm green emission after ultraviolet photoexcitation, which originated from the spin-forbidden d-d transitions with a microsecond-scale lifetime of 308.7 µs, and no defect-related emission was observed. Cs₃Cd_0.78Mn_0.22Br₅ LEDs exhibited high efficiency and operational stability, demonstrating strong potential for efficient, stable solid-state lighting.