Novel Cr3+-Doped Garnet Phosphor with Broadband Efficient Far-Red Emission for Photochrome Matching Plant-Lighting

Cr³⁺-doped phosphors are highly recognized in various fields for their remarkable luminous efficiency and spectral flexibility, including modern agriculture and horticulture. However, the shortage of suitable Cr³⁺-doped phosphors for far-red LED devices has inhibited their popularization in plant lighting. Herein, an innovative Cr³⁺-doped phosphor Ca₂YAl₃Ge₂O₁₂:Cr³⁺ (CYAG:Cr³⁺), achieving a broad far-red emission at 770 nm upon 450 nm blue light excitation is designed. The optimal CYAG:Cr³⁺ phosphor exhibits a high internal quantum yield of 78.2% and low thermal-quenching behavior of 85%@373 K. Thus, the fabricated phosphor-converted LEDs (pc-LEDs) for plant far-red lighting have a high output power of 33.3 mW and photovoltaic conversion efficiency of 11.5% at 100 mA. The potential of CYAG:Cr³⁺ in plant lighting is assessed by supplementing the far-red lighting of Italian lettuce with fabricated pc-LEDs, and the biomass of Italian lettuce is significantly increased by 33%. The successful development of CYAG:Cr³⁺ phosphors provides a high-quality option for plant far-red light devices and further stimulates the development of new Cr³⁺-doped plant-lighting phosphors.