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

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.