Enabling narrowband cyan photoluminescence and long-lasting ultraviolet-A persistent luminescence in Bi3+ single-doped Sr3Sc2Ge3O12 phosphors by selective site occupation

Abstract

Trivalent bismuth (Bi³⁺) has been regarded as a favorable emitting center since it can give off light of different wavelengths from ultraviolet (UV) to red in different host materials. These Bi³⁺ single-doped phosphors have been of great interest for applications in white light-emitting diodes (LEDs), optical information storage and anti-counterfeiting. However, it still remains a challenge to achieve multimodal luminescence in Bi³⁺ activated single-component inorganic luminescent materials for multifunctional applications. Here, Bi³⁺ single-doped Sr₃Sc₂Ge₃O₁₂ phosphors with dual-mode luminescence, emitting narrowband cyan photoluminescence and long-lasting ultraviolet-A (UVA) persistent luminescence, are reported for the first time by selective site occupation of a Bi³⁺ emitter. Intense cyan photoluminescence peaking at 487 nm when excited at 386 nm is assigned to the Bi³⁺ in the Sr²⁺ site, which shows very good luminescence thermal stability. Moreover, after UV excitation at 254 nm or under sunlight irradiation, UVA persistent luminescence with a peak maximum at 333 nm and a long persistence time of more than 12 h is achieved, which can be attributed to the Bi³⁺ in the Sc³⁺ site. The dual-mode luminescence in a Bi³⁺ single-doped Sr₃Sc₂Ge₃O₁₂ garnet not only provides a directional solution for constructing warm white LEDs, but also holds great promise for optical information write-in and read-out applications.