Breaking the Absorption‐Efficiency Paradigm: 270% EQE Gain in Cr 3+ ‐Doped Phosphors via Crystal Field Engineering

ABSTRACT Near‐infrared (NIR) phosphor‐converted LEDs (pc‐LEDs) are critical for smart agriculture and night vision, but their efficiency is limited by low external quantum efficiency (EQE) of phosphors. Herein, the introduction of Al 3+ ions via chemical substitution increased the EQE of the GdGa 2.85 (BO 3 ) 4 :0.15Cr 3+ NIR phosphor from 8.3% to 30.7% (a relative increase of 270%). Importantly, an “absorption‐efficiency decoupling” paradigm is identified: while the Al 3+ substitution reduces the absorbance, confirmed by Density Functional Theory, diffuse reflectance spectra, and X‐ray photoelectron spectroscopy, the quantum efficiency is significantly increased. Theoretical analyses and spectroscopic evidence suggest that the superior EQE gain stems from Al 3+ ‐induced crystal field enhancement and subsequent energy level remodeling. This remodeling optimizes the Cr 3+ excited state dynamics by suppressing the non‐radiative transitions pathway and increasing the radiative transitions, thus overcoming the detrimental effects of absorption reduction. The optimized phosphor, combined with a blue LED chip, produced an NIR pc‐LED achieving 41.7 mW output power and 15.7% photoelectric efficiency at 100 mA. The device successfully demonstrated potential for precision agriculture and night vision. This work provides novel insight into “absorption‐efficiency decoupling” and offers a new design strategy for efficient Cr 3+ ‐doped NIR phosphors.