Sunlight‐Excitable K ₃ YSi ₂ O ₇ : Ce ³⁺ Green

ABSTRACT

Persistent luminescence (PersL) materials have been extensively studied owing to their excellent optical properties. However, their practical applications are restricted by the fact that they can only be charged by a single light source. Consequently, materials capable of PersL under natural light irradiation have attracted considerable attention due to their potential for reducing energy consumption. Nevertheless, the design and development of efficient PersL materials activated by sunlight remains a challenging task. To address this issue, a novel K ₃ YSi ₂ O ₇ : Ce ³⁺ phosphor with the P 6 ₃ / mcm space group was successfully synthesized. The results reveal that this material exhibits significant excitation wavelength‐dependent luminescence characteristics. By varying the excitation wavelength, the relative emission efficiencies of the two luminescence centers—the intrinsic host emission and the 5 d ‐4 f transition of Ce ³⁺ —can be effectively modulated, enabling continuous tuning of the emission color from bluish‐white to green. Meanwhile, the material can be efficiently excited by both UV light and sunlight, generating excellent green PersL (with PersL lifetimes exceeding 2 and 1 h, respectively), which is attributed to the trapping and release of charge carriers by oxygen vacancy defects in the lattice. A pc‐WLED fabricated using this phosphor successfully fills the cyan gap and achieves a high R _a of 94.6. Furthermore, the as‐prepared K ₃ YSi ₂ O ₇ : Ce ³⁺ /PDMS composite flexible film further demonstrates the potential application of this material in the field of optical anti‐counterfeiting.