Excitation-Wavelength-Dependent Emission Behavior in (NH₄)₂SnCl₆ via Sb³⁺ Dopant

With high photoluminescence efficiency and a simple solution synthesis method, lead halide perovskites are expected to be a promising material for display and illumination. However, the toxicity and environmental sensitivity of lead hinder its potential applications. Here, we introduced Sb3+ ions into the lead-free perovskites derivative (NH4)2SnCl6 via a doping strategy. For the first time we synthesis the excitation-dependent perovskite with dynamically tunable fluorescence from yellow to near-infrared (NIR) emission by varying the UV excitation from 360 to 390 nm at room temperature. The DFT calculations are highly consistent no matter whether the coordination number of Sb3+ is 5 or 6. In contrasting to the early report of Sb triplet emission in the Sb doped perovskite, this material give a mixed self-trapped exciton (STE) emission. The 590 nm emission band is derived from the STE of SbCl5, and the 734 nm NIR emission band is attributed to the Sb–Sn mixed STE, which is supported by DFT calculations and spectral results. This study provides guidance for the design of perovskite phosphors with high efficiency and excitation-dependent properties.