All Inorganic Sb3+–Ln3+‐Codoped Cs2NaYCl6 for Highly Efficient Single‐Source White‐Light Emission and Ratiometric Optical Thermometer Applications

Abstract Single‐source white‐light emitters are highlighted with stable color and excellent color rendering ability, which can largely simplify the white‐light‐emitting‐diode (WLED) structure. All‐inorganic and lead‐free double perovskites have attracted extensive research interest and provide versatile doping sites to accommodate the extrinsic multi‐valent ions. Herein, the synthesis and tunable emission of Sb 3+ –Ln 3+ ‐codoped Cs 2 NaYCl 6 single crystals (SCs) is reported. Particularly, bright white‐light emission with a high photoluminescence quantum yield of 80.5% is yielded in 0.5%Sb 3+ –2%Tb 3+ –2%Sm 3+ ‐codoped Cs 2 NaYCl 6 SCs. Steady‐state photoluminescence (PL) and time‐resolved PL spectra are employed to reveal the energy transfer from Sb 3+ ‐induced self‐trapped excitons to Ln 3+ ions. Temperature‐dependent PL spectra further demonstrate that the fluorescence intensity ratio of band 657 to band 590 nm is highly dependent on the temperature, and the relative sensitivity reaches a maximum of up to 1.59% K −1 at 260 K. Moreover, the WLED based on 0.5%Sb 3+ ‐2%Tb 3+ ‐2%Sm 3+ ‐codoped Cs 2 NaYCl 6 SCs delivers a higher average color rendering index of 87 than 0.5%Sb 3+ ‐0.8%Tb 3+ ‐2.5%Ho 3+ ‐codoped Cs 2 NaYCl 6 (74.6). The outstanding white‐light‐emission performance together with the high temperature dependence of the fluorescence spectra confers Sb 3+ –Ln 3+ ‐codoped Cs 2 NaYCl 6 with huge application potential in solid‐state lighting and ratiometric optical thermometry.