Achieving Thermally Stable YAl<sub>3–<i>x</i></sub>Ga<sub><i>x</i></sub>(BO<sub>3</sub>)<sub>4</sub>:Cr<sup>3+</sup> Near-Infrared Emitting Phosphors via Chemical Substitution for Plant Growth LEDs
Jin Yang, Jianhao Zha, Qinan Mao, Heyi Yang, Lang Pei, Jiasong Zhong
Abstract
Indoor plant cultivation has been receiving increased attention due to concerns about sustainable agricultural production. Phosphor-converted light-emitting diodes (pc-LEDs) offer substantial promise as lighting solutions for regulating plant growth. However, the quest for high-performance phosphors with precise responsiveness to far-red phytochromes poses a challenge. Our study proposes a chemical substitution strategy to develop near-infrared (NIR) phosphors, YAl 3– x Ga x (BO 3 ) 4:Cr 3+ . Benefiting from Ga 3+ replacement of Al 3+, a red shift in the NIR emission of YAl 3– x Ga x (BO 3 ) 4:Cr 3+ is realized to attain a good alignment with far-red phytochrome absorption centering at 730 nm. The optimized YAl 2.5 Ga 0.5 (BO 3 ) 4:Cr 3+ exhibits a favorable quantum yield of 71.8% and robust thermal stability of 101.0%@423 K, owing to local structural distortion and thermal repopulation caused by Ga 3+ incorporation. The fabricated pc-LED combined with the phosphor yields an NIR output power of 40.9 mW and a photoelectric conversion efficiency of 15.4% at 100 mA. Plant growth experiments demonstrate that under NIR illumination from the devices, the average lengths of pea roots and stems gain 127 and 225% promotion, respectively, further highlighting the potential of YAl 2.5 Ga 0.5 (BO 3 ) 4:Cr 3+ phosphors for applications in plant cultivation.