Unraveling the Defect‐Induced Spectral Tuning in a Ce‐Doped Garnet Solid‐Solution Phosphor

The increasing demand for white light‐emitting diode (WLED) has prompted the development of phosphors, in which Ce 3+ ‐activated garnet has been representative and widely investigated. The optimization and improvement of performance have long been a focus in the phosphor area. However, the trade‐off of phosphor performance always exists and is difficult to satisfy simultaneously, thereby necessitating a better understanding of the design principles that tune spectra performance comprehensively. Herein, the defect‐induced spectral tuning mechanism in a Ce‐doped garnet solid‐solution phosphor Ca 1.5‐ x Y 1.5+ x Al 3.5+ x Si 1.5‐ x O 12 :Ce 3+ (CYAS:Ce 3+ ) is promoted. The enhancement of luminescence intensity and thermal stability together with red‐shift of emission can be achieved by chemical unit co‐substitution of [Y 3+ ‐Al 3+ ] for [Ca 2+ ‐Si 4+ ], which originated from the increasing anti‐site vacancy. The related mechanism is fully elucidated by combining structural and spectral analysis with density functional theory (DFT) calculations. This study provides a subtle control for the performance‐tuning of phosphors, which can deepen the understanding of the design principle inside‐out and the subsequent development and exploration of novel optoelectronic functional materials.