Red‐Emitting Perovskite Variant Cs2PtCl6 Phosphor: Material Design, Luminous Mechanism, and Application in High‐Color‐Rendering White Light‐Emitting Diodes

Recently, A(2)BX(6)-type halide perovskite variant phosphors have been applied for white light-emitting diodes (LEDs) due to their superior photoluminescence properties, excellent stability, and low-cost solution-processability. However, the reported white LEDs, particularly the all-A(2)BX(6) white LEDs, exhibit insufficient color rendering due to the shortage of red light. In this work, through a rational material design, a red-emitting perovskite variant Cs2PtCl6 phosphor is developed. The synthesized Cs2PtCl6 powders exhibit a relatively narrow bandgap of 2.91 eV and an intrinsic broadband red emission centered at 670 nm, which is attributed to the triplet self-trapped excitons associated with the Jahn-Teller-distorted [PtCl6](2-) octahedra in the excited state. Using Cs2PtCl6 as the red phosphor component, an all-A(2)BX(6) white LED is constructed, achieving a standard white light with a Commission Internationale de l'Eclairage chromaticity coordinate of (0.33, 0.33), a correlated color temperature of 5318 K, and a record high color rendering index of 90. This work represents a significant step toward the application of A(2)BX(6) perovskite variant phosphors for solid-state lighting.