Ni2+ in Distorted Octahedral Geometry toward High‐Efficiency NIR‐II/III emitter

Abstract Ni 2+ activated phosphor has attracted wide attention because it can be radiated in near‐infrared (NIR) II–III region; however, the low external quantum yield (EQY) hinders its further application (most are below 8 %). In this work, distortion of crystallographic site strategy is proposed to enhance EQY. LaTiTaO 6 : 0.004Ni 2+ exhibits an NIR emitting spectrum centered at 1450 nm with an EQY of ~9.00 %, which has been the highest EQY of reported Ni 2+ single‐doped phosphor. Distortion degrees of the octahedral geometry in LaTiTaO 6 and LaTiTaO 6 : 0.004Ni 2+ changing from 0.038 to 0.047 result in the absorption efficiency of 38.6 % due to the breaking of parity forbidden of the d‐d transition, further improving the EQY. Besides, LaTiTaO 6 : 0.004Ni 2+ mixed with LaTiTaO 6 : 0.04Cr 3+ phosphors have demonstrated their application for spectral analysis. This work provides a new idea for constructing efficient NIR‐II to NIR‐III phosphors.