Cr3+-Doped Broadband NIR Garnet Phosphor with Enhanced Luminescence and its Application in NIR Spectroscopy

Broadband near-infrared (NIR) phosphor-converted light emitting diode (pc-LED) is demanded for wearable biosensing devices, but it suffers from low efficiency and low radiance. This study reports a broadband NIR Ca3-xLuxHf2Al2+xSi1-xO12:Cr3+ garnet phosphor with emission intensity enhanced by 81.5 times. Chemical unit co-substitution of [Lu3+-Al3+] for [Ca2+-Si4+] is responsible for the luminescence enhancement and further alters the crystal structure and electronic properties of the garnet. Using the optimized phosphor, a NIR pc-LED with photoelectric efficiencies of 21.28%@10 mA, 15.75%@100 mA and NIR output powers of 46.09 mW@100 mA, 54.29 mW@130 mA is fabricated. The high power NIR light is observed to penetrate upper arms (approximate to 8 cm). For application in NIR spectroscopy, the NIR pc-LED is used as light source to measure transmission spectra of water, alcohol, and bovine hemoglobin solution. These results indicate the NIR garnet phosphor to be a promising candidate for NIR pc-LED.