Excitation-Wavelength-Dependent Emission Behavior in (NH 4 ) 2 SnCl 6 via Sb 3+ 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 Sb ³⁺ ions into the lead-free perovskites derivative (NH ₄ ) ₂ SnCl ₆ 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 Sb ³⁺ 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 SbCl ₅ , 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.