Ultrastable Lead-Free Double Perovskite Warm-White Light-Emitting Devices with a Lifetime above 1000 Hours

Recently, white light-emitting devices (WLEDs) based on halide perovskites has been extensively studied. However, the lead toxicity and poor stability of conventional lead halide perovskites severely hinder their commercial applications. In this study, lead-free double perovskite Cs₂AgInCl₆ with a broadband emission was fabricated by a heat-assisted solution evaporation method, in which a compositional engineering by sodium (Na⁺) alloying and bismuth (Bi³⁺) doping was performed. The photoluminescence quantum yield was promoted from ∼1.1 to 46.4% and then to 87.2% by Na⁺ alloying and subsequent Bi³⁺ doping. In addition, the theory calculation reveals that the diffusion barrier of Cl^- vacancy in Cs₂AgInCl₆ can be increased by Na⁺ alloying, which would contribute to the stability of the material. Experimentally, the resulting Cs₂Ag_0.7Na_0.3InCl₆:Bi products demonstrate a remarkable stability under heat, ultraviolet light, and moisture conditions. The above advantages make it possible for this material to be used as solid-state phosphors for WLED applications, and the Commission International de I'Eclairage color coordinates at (0.38, 0.44), correlated color temperature of 4347 K, and high color rendering index of 87.8 were achieved. More importantly, the WLED demonstrates a remarkable operation stability in air ambient, and only 4.5% emission decay occurs after a long working time for 1000 h, the longest lifetime for perovskite-based WLEDs as far as we know.