Cs2NaLuCl6: Sb3+, Tb3+, Sm3+ phosphors for high quality tunable white light application

Lead-free double perovskites (LFDPs) have attracted considerable attention in recent years owing to their distinctive optical characteristics. While multi-component phosphor blends dominate commercial white light-emitting diode (WLED), the pursuit of efficient white light generation from a single crystalline lattice has yet to overcome critical bottlenecks in emission harmonization. In this study, we present a triple-doped rare-earth double perovskite, Cs 2 NaLuCl 6 : Sb 3+ , Tb 3+ , Sm 3+ . We pioneer a competitive energy transfer engineering strategy in this material, in which orchestrated energy routing from Sb 3+ to Tb 3+ and Sm 3+ enables precise spectral harmonization. This overcomes the long-standing efficiency-color quality trade-off in single-matrix WLEDs, which can be precisely controlled via dopant ratio optimization. Both steady-state and time-resolved photoluminescence (PL) spectroscopy were used to investigate the synthesis and luminescence behavior of the triple-doped Cs 2 NaLuCl 6 : Sb 3+ , Tb 3+ , Sm 3+ . Analysis of the PL spectra reveals three key energy transfer mechanisms: (i) Sb 3+ → Tb 3+ , (ii) Sb 3+ → Sm 3+ , and (iii) Tb 3+ → Sm 3+ . Temperature-dependent PL spectra demonstrate exceptional thermal stability, and the luminous intensity decreases by only 8.8 % at high temperatures of 473 K. By fine-tuning the dopant concentrations, precise control over the CIE coordinates within the white-light region is achieved, driven by competitive energy transfer dynamics. In addition, the photoluminescence quantum yield (PLQY) reaches 38.29 % in a Cs 2 NaLuCl 6 Single Crystal (SC) co-doped with 0.5 % Sb 3+ , 60 % Tb 3+ , and 25 % Sm 3+ . When incorporated into WLED devices, these phosphors deliver a color rendering index (CRI) of 94.7, a correlated color temperature (CCT) of 5018 K, and a near-ideal white light emission with CIE coordinates of (0.344, 0.338). This work provides a high-performance single-matrix white light emitter for WLEDs and a practical energy transfer design strategy for rare-earth-doped LFDPs, promising to advance lead-free perovskite applications in solid-state lighting.