Facile Melting-Crystallization Synthesis of Cs(2)Na(x)Ag(1-x)InCl(6): Bi Double Perovskites for White Light-Emitting Diodes
Résumé
Lead-free double perovskites (DPs) have outstanding luminescent properties, which make them excellent candidates for wide use in optoelectronics. Herein, a solvent-free melting-crystallization technique, which can produce kilogram-scale DP microcrystals (DP-MCs) in one batch, is invented to synthesize the Cs(2)Na(x)Ag(1-x)InCl(6): Bi (x = 0, 0.2, 0.4, 0.6, 0.8, and 1) DP-MCs. The structure and composition analysis confirmed the products are pure Cs(2)Na(x)Ag(1-x)InCl(6) DP-MCs. Affected by Jahn-Teller distortion of AgCl(6) octahedra, self-trapped excitons appear in the excited state, resulting in the broadband emission (400-850 nm) of Cs(2)Ag(1-x)Na(x)InCl(6): Bi DP-MCs. The enhancement of the photoluminescence quantum yield can be realized by introducing Na(+) to break the parity-forbidden transition in the Cs(2)AgInCl(6) DP. Optimized Cs(2)Na(0.4)Ag(0.6)InCl(6): Bi DP-MC phosphors combined with commercial blue and green phosphors were coated on ultraviolet chips (365 nm) to fabricate white light-emitting diodes (WLEDs) from warm white (2930 K) to cold white (6957 K). An ultrahigh color rendering index of 97.1 and a CCT of 5548 K as well as Commission Internationale de l’Eclairage color coordinates of (0.331, 0.339) have been demonstrated. This kilogram-scale synthesis technique could stimulate the industrial development of WLEDs for general lighting based on DP-MC phosphors.
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