Ultrafast Synthesis of a Highly Luminescent Zero-Dimensional Hybrid Perovskite TEA_<b>2</b>HfCl_<b>6</b>:Sb^<b>3+</b> for Optical Encryption and Healthy Lighting

Organic-inorganic hybrid metal halides have attracted considerable attention due to their facile synthesis, low cost, and high thermal and chemical stability. However, developing environmentally benign, readily synthesized, high-performance, and spectrally tunable broadband-emitting materials remains challenging. Herein, this study reports a zero-dimensional perovskite material, TEA₂HfCl₆:Sb³⁺, using a room-temperature coprecipitation method. This material exhibits low toxicity and excitation-wavelength-dependent modulation of singlet and triplet emission ratios, enabling broadband emission ranging from warm white to deep red. Notably, TEA₂HfCl₆:11%Sb³⁺ achieves a high photoluminescence quantum yield of up to 93.1%. Steady-state and time-resolved spectroscopic analyses reveal that these emissions arise from Sb³⁺-induced radiative transitions of singlet and triplet self-trapped excitons. Furthermore, leveraging its scalable synthesis process and favorable emission characteristics, the material shows potential for applications in large-area optical anticounterfeiting paper and full-spectrum, eye-friendly white-light-emitting diode (WLED). These findings highlight the dual functionality of TEA₂HfCl₆:Sb³⁺ in secure optical encryption and solid-state lighting, providing a promising platform for the development of multifunctional luminescent materials.