Stable and Highly Efficient Near‐Infrared Emission Achieved in Spinel Blocks

Abstract Developing efficient and stable near‐infrared emitters related to Cr³⁺‐pairs for advanced optoelectronic devices remains a challenge due to concentration quenching effects and unclear luminescence mechanisms. In this study, Cr³⁺ ions are incorporated into a matrix structure consisting of ZnAl₂O₄ spinel units separated by 11.312 Å, effectively restricting energy transfer between luminescent centers and alleviating quenching effects. Computational analysis identifies the lattice positions of isolated Cr³⁺ ions and Cr³⁺‐pairs at different doping levels, providing insights into their spatial distribution and local structural environments. Photoluminescence measurements reveals a Cr³⁺‐concentration‐dependent emission broadening, with a Cr³⁺‐pair emission band peak at 750 nm, while detailed spectral analysis further clarified the energy level structure of Cr³⁺‐pairs for the first time. Enhanced material performance is achieved through flux‐assisted synthesis, reaching a high external quantum efficiency of 58.3%. Consequently, the assembled pc‐LEDs exhibit minimal efficiency roll‐off and achieve a high output of 183 mW at 650 mA, demonstrating their potential in near‐infrared light sources and night vision technology application.