High-Quality Single-Source White-Light Emission in Double Perovskite Cs<sub>2</sub>NaGdCl<sub>6</sub>: Sb<sup>3+</sup>/Tb<sup>3+</sup>/Mn<sup>2+</sup> for Ratiometric Optical Thermometry and Anti-Counterfeiting Applications
Huangyao Chen, Qi Chen, Xiang Guo, Jun Zhang, Chaoyong Deng, Ruirui Cui
Abstract
In lead-free halide double perovskites, doping and alloying are key strategies for optical performance enhancement. However, achieving stable full-spectrum white emission in single-component phosphors remains challenging. Herein, high-quality single-phase white emission is realized in Cs 2 NaGdCl 6 via Sb 3+ /Tb 3+ /Mn 2+ codoping. Pristine Cs 2 NaGdCl 6 shows a weak sky-blue emission, while Sb 3+ doping significantly enhances the self-trapped exciton (STE) intensity. Density functional theory calculations show that Sb 3+ doping creates new sensitizing states, boosting the STE emission. Under Sb 3+ sensitization, STE energy transfers to Tb 3+ and Mn 2+ . The incorporation of Tb 3+ elevates the photoluminescence quantum yield from 0.66% (pristine) to 68.38% (CNGC: Sb 3+, Tb 3+ ), while the broadband red emission from Mn 2+ plays a critical role in achieving full-spectrum coverage. Tunable white-light emission is achieved via a dopant ratio optimization. Combining the phosphor with a 340 nm commercial light-emitting diode chip produces a white light-emitting diode with a correlated color temperature of 4658 K and a color rendering index of 91.9. Temperature-dependent photoluminescence spectra confirm ratiometric sensing capability, yielding maximum relative sensitivities ( S r ) of 1.06%/K ( I 4 6 3 nm / I 6 0 8 nm ) and 1.12%/K ( I 5 4 8 nm / I 6 0 8 nm ) at 298 K. These results demonstrate that this material exhibits multifunctional application potential in the fields of white-light illumination, optical thermometry, and fluorescent anticounterfeiting.