Breaking Spin-Forbidden Transition by an Antisite Defect Strategy for Enhancing Far-Red Emission of Cr(3+)-Activated Phosphors.

Cr-activated phosphors have recently attracted significant research interest because their excellent luminescence properties are comparable to those of lanthanides, enabling diverse applications in modern optical devices. However, Cr ions often encounter a spin-forbidden EA transition in a strong crystal field, such as ABO-type spinel oxides, causing a significant limited far-red-emitting performance. Herein, we adopted an effective antisite defect strategy for reducing the local lattice symmetry and breaking the forbidden transition of Cr by constructing antisite defects based on ingenious Al-by-Zn substitution within the ZnAlO matrix, thus converting harmful lattice defects into beneficial luminescence elevations. As a result, the emissive intensity of the Cr-activated phosphors was increased by 2.5-fold, while the internal quantum efficiency (IQE) increased from 46.40% to 73.74%. Moreover, rational ion doping of nonmetallic B, rare earth-based Y, and Lu further reinforced the absorption and luminescence of phosphors by intensifying lattice distortion, which actualized diverse applications of plant lighting devices, light-converted films, and night vision. This antisite defect strategy provides a fresh perspective for an in-depth understanding of intrinsic structure-property relationships and the design of high-performance phosphors.