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

Cr 3+ -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 3+ ions often encounter a spin-forbidden 2 E → 4 A 2 transition in a strong crystal field, such as AB 2 O 4 -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 3+ by constructing antisite defects based on ingenious Al-by-Zn substitution within the ZnAl 2 O 4 matrix, thus converting harmful lattice defects into beneficial luminescence elevations. As a result, the emissive intensity of the Cr 3+ -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 3+, rare earth-based Y 3+, and Lu 3+ 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.