Efficient, Stable, and Tunable Cold/Warm White Light from Lead‐Free Halide Double Perovskites Cs2Zr1‐xTexCl6

Abstract Single‐component materials with efficient, stable, and tunable cold/warm white‐light emission are ideal candidates for lighting applications, which can overcome the problems of different deterioration rates and reabsorption effect in conventional mixed‐phosphors strategy. Efficient white phosphors based on double halide perovskite have been reported via manipulating the parity transitions recently. However, the emission wavelength is nonadjustable. Herein, a lead‐free double perovskite Cs 2 Zr 1− x Te x Cl 6 that exhibits efficient and stable white‐light emission is reported. The introduction of Te 4+ results in bright self‐trapped exciton (STE) emission, which endows Cs 2 ZrCl 6 matrix with multiple luminescent centers. Efficient white luminescence with tunable color temperature and high photoluminescence quantum yield (PLQY) of 61.5% (under 254 nm, CCT = 4039 K) and 96.1% (under 365 nm, CCT = 3313 K) is achieved. Efficient energy transfer between multiple luminescent centers and appropriate doping concentrations are the key points to achieve such highly efficient and tunable white emission. The as‐synthesized Cs 2 Zr 1− x Te x Cl 6 composites exhibit a robust stability against heat, ultraviolet light, and environmental oxygen/moisture, which show little spectra variation with less than ≈ 20% efficiency loss after 980 h testing even under high temperature and UV light. These results indicate Cs 2 Zr 1− x Te x Cl 6 are promising single‐component white‐light‐emitting phosphors for next‐generation lighting and display technologies.