Ga 3+ Cation‐Directed Microstructural Engineering of Glass‐Ceramics Unlocks High‐Power NIR LEDs

ABSTRACT Mullite‐type Al 4 B 2 O 9 glass ceramics (GCs) activated by transition metal ions such as Cr 3 + and Ni 2 + represent a promising class of solid‐state photo‐conversion materials for near‐infrared (NIR) luminescence devices. However, their optical efficiency is often limited by a series of quenching defects that are generated during crystallization. Here, we introduce a partial cation substitution engineering by replacing Al 3 + with Ga 3 + to regulate crystallization kinetics and defect formation. Structural and thermodynamic analyses reveal that Ga 3 + incorporation increases the crystallization activation energy, suppressing grain growth rate and promoting dominant Cr 3 + emission from [AlO 6 ] sites. Consequently, the Ga 3+ ‐induced (Al 4 ‐ x Ga x )B 2 O 9 phase evolution yields significantly enhanced NIR intensity, quantum efficiency (EQE = 34%, IQE = 46%), and thermal stability (I 140°C /I 25°C = 69.2%). The NIR LEDs integrated with the GCs deliver a NIR output power of 464 mW with 9.2% photoelectric conversion efficiency. This work establishes a generalizable approach for defect‐controlled crystallization and luminescence engineering in glass ceramics, opening a pathway toward high‐power, thermally robust NIR LEDs for next‐generation photonic and optoelectronic devices.