Sb3+ Dopant and Halogen Substitution Triggered Highly Efficient and Tunable Emission in Lead-Free Metal Halide Single Crystals

Rational doping and compositional control remain significant challenges in designing luminescent metal halides to achieve highly efficient and tunable emission. Here, the air-stable lead-free Cs2InCl5·H2O crystal with a zero-dimensional structure was investigated as a pristine compound to design new luminescence materials. Sb3+-doping in Cs2InCl5·H2O:Sb3+ enabled broadband yellow emission with a photoluminescence quantum yield up to 95.5%. The emission colors can be expanded into the orange-red region by halogen compositional substitution for Cs2InX5·H2O:Sb3+ (X = Cl/Br/I). The optical characterizations along with the theoretical calculations demonstrate that the characteristic singlet and triplet self-trapped exciton emissions of ns2-metal-halide centers account for the tunable luminescence. Moreover, the admirable stability against air and heat pave way for its further applications in white light-emitting diodes and high-resolution fluorescent signs in anticounterfeiting technology. Our achievement in the case of Sb3+-doped Cs2InCl5·H2O represents a successful strategy for developing stable lead-free metal halides with highly efficient emission for versatile optical applications.