Light-Induced Charge Transfer to Achieve Deep-Red Emission in SrSc2O4:Bi toward Multiple Optical Applications

Bismuth (Bi) is used for luminescent materials due to its unique optical performance, but deep-red light from Bi-doped materials is rarely reported. In particular, establishing a design principle for Bi-doped red materials is considered to be a significant challenge. Herein, using a deep-red SrSc2O4:Bi material featuring Bi–Bi pair emission, light-induced charge-transfer from BiSc3+–BiSr3+ to BiSc4+–BiSr2+ enables the realization of Bi2+2P3/2(1) → 2S1/2 deep-red emission. Intriguingly, SrSc2O4:Bi displays an excellent zero-thermal-quenching performance from 298 to 423 K, with a peak intensity that retains 98% of the intensity at 298 K and an integrated intensity at 423 K that even reaches 110% of the initial intensity. The intriguing spectroscopic characteristics of SrSc2O4:Bi make it a promising candidate in the agricultural field, night-vision security, and the medical treatment area. This work advances the understanding of red luminescence in Bi-activated luminescent materials and thus can initiate more exploitation of red materials for emerging applications.