Multifunctional Applications Enabled by Tunable Multi-Emission and Ultra-Broadband VIS-NIR Luminescence via Energy Transfer in Sn²⁺/Mn²⁺-Doped Lead-Free Zn-Based Metal Halides

Metal halides are widely applied in solid-state lighting (SSL), optoelectronic devices, information encryption, and near-infrared (NIR) detection due to their superior photoelectric properties and tunable emission. However, single-component phosphors that can be efficiently excited by light-emitting diode (LED) chips and cover both the visible (VIS) and NIR emission regions are still very rare. To address this issue, (TPA)2ZnBr4:Sn2+/Mn2+ (TPA = [(CH3CH2CH2)4N]+) phosphors were synthesized by using the solvent evaporation method. The Sn2+ doping significantly enhances the luminescence of (TPA)2ZnBr4, and shifts the weak emission of blue light to efficient emissions in the red and NIR zones. Spectroscopic studies and density functional theory (DFT) calculations reveal that the emissions are attributed to the different levels of 3P1-1S0 in the [SnBr4]2- tetrahedron caused by Jahn-Teller distortion. More importantly, energy transfer from Mn2+ to Sn2+ enables ultra-broadband VIS-NIR emission across the 400-1000 nm range, with excitation-dependent tunable emission characteristics. These properties suggest that (TPA)2ZnBr4:Sn2+/Mn2+ has great potential as a high-performance, single-component luminescent material for applications in general lighting, NIR light source, and anti-counterfeiting labels.