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

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 Sb3+-Ln(3+)-codoped Cs2NaYCl6 single crystals (SCs) is reported. Particularly, bright white-light emission with a high photoluminescence quantum yield of 80.5% is yielded in 0.5%Sb3+-2%Tb3+-2%Sm3+-codoped Cs2NaYCl6 SCs. Steady-state photoluminescence (PL) and time-resolved PL spectra are employed to reveal the energy transfer from Sb3+-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%Sb3+-2%Tb3+-2%Sm3+-codoped Cs2NaYCl6 SCs delivers a higher average color rendering index of 87 than 0.5%Sb3+-0.8%Tb3+-2.5%Ho3+-codoped Cs2NaYCl6 (74.6). The outstanding white-light-emission performance together with the high temperature dependence of the fluorescence spectra confers Sb3+-Ln(3+)-codoped Cs2NaYCl6 with huge application potential in solid-state lighting and ratiometric optical thermometry.