A highly efficient and broadband near-infrared-emitting garnet phosphor for plant lighting realized by cation co-substitution in lutetium aluminum garnet

Near-infrared phosphor-converted light emitting diodes (NIR pc-LEDs) is developing rapidly in plant cultivation because of its low cost, compact size and high efficiency. The NIR light of 700 ∼ 760 nm is known to be beneficial for seed germination and growth. Therefore, the exploration of NIR phosphors with specific wavelength and high efficiency is essential for the development of high-performance plant cultivation pc-LEDs. In this study, a highly efficient and thermal stable Cr3+ doped Lu2CaAl4SiO12 (LCAS) phosphor with broadband NIR emission covering phytochrome Pfr absorption range was successfully realized via Ca2+-Si4+ co-substitution of Lu3+-Al3+ pairs. The LCAS:0.07 Cr3+ exhibits a major emission peak of 740 nm with a FWHM of 160 nm and its internal/external quantum yield (IQY/EQY) is as high as 80%/30.5%. The integrated emission intensity of LCAS:0.07Cr3+ at 423 K lost only 33.8% of its initial intensity, indicating that it has a good thermal stability. When the LCAS:0.07Cr3+ was packaged into a pc-LED with a driving current of 320 mA, the device output power and photoelectric efficiency reached 90.6 mW and 8.6%, respectively, demonstrating that this phosphor has potential application in plant cultivation lighting.