Antimony Doping Enabled Photoluminescence Quantum Yield Enhancement in 0D Inorganic Bismuth Halide Crystals

Owing to the exterior self-trapped excitons (STEs) with adjustable fluorescence beams, low-dimensional ns²-metal halides have recently received considerable attention in solid-state light-emitting applications. However, the photoluminescence (PL) mechanism in metal halides remains a major challenge in achieving high efficiency and controllable PL properties because the excited-state energy of ns² conformational ions varies inhomogeneously with their coordination environments. Here, a novel zero-dimensional (0D) lead-free bismuth-based Rb₃BiCl₆·0.5H₂O crystal was reported as a pristine crystal to modulate the optical properties. By doping Sb³⁺ ions with 5s² electrons into Rb₃BiCl₆·0.5H₂O crystals, bright orange emission at room temperature was obtained with a photoluminescence quantum yield of 39.7%. Optical characterizations and theoretical studies show that the Sb³⁺ doping can suppress the strong exciton-phonon coupling, optimize the electronic energy band structure, improve the thermal activation energy, soften the structural lattice of the host crystals, deepen the STE states, and ultimately lead to strong photoluminescence. This work manifests a fruitful manipulation in ripening bismuth-based halides with high-efficiency PL properties, and the PL enhancement mechanisms will guide future research in the exploration of emerging luminescent materials.