Structural Confinement Engineering of Cr 3+ in Nanocrystalline Spinel Glass‐Ceramics for Efficient and Thermally Robust Deep‐Red Plant‐Growth LEDs

Abstract

ABSTRACT Sustainable high‐yield agriculture in controlled environments demands lighting with spectral precision and thermal robustness. Deep‐red light at 680–690 nm aligns with photosynthetic pigment absorption maxima, enhancing efficiency and regulating plant photomorphogenesis. However, emitters combining spectral precision, high quantum efficiency, and thermal stability within this narrow band remain challenging. Here, we investigate Cr 3+ ‐doped ZnGa 2 O 4 glass‐ceramics, where structural confinement regulates the local coordination environment of Cr 3+ ions. Multi‐scale molecular dynamics and density functional theory calculations indicate preferential confinement of Cr 3+ to strong‐field [GaO 6 ] octahedral sites within ZnGa 2 O 4 nanocrystals embedded in a Na 2 O‐Al 2 O 3 ‐SiO 2 glass matrix. The resulting glass‐ceramics exhibit a photoluminescence quantum yield of 87.5% and retain 96.9% of the emission intensity at 393 K. The emission centered at 688 nm yields a high photosynthetic‐action‐weighted photoluminescence quantum yield ( Φ PAW ) of 61.7%, representing an 81% increase in photosynthetic effectiveness over conventional longer‐wavelength Cr 3+ ‐based emitters. This metric links quantum efficiency to plant photosynthetic response, thereby allowing fairer comparison of materials intended for agricultural use. A prototype LED device achieves simultaneous enhancement in plant biomass and nutritional quality. This work demonstrates structural confinement as a viable approach to address the trade‐off among spectral precision, efficiency, and thermal stability in luminescent materials for advanced agricultural lighting.