Efficient near-infrared luminescence in a Na2CaTi2Ge3O12:Cr3+ garnet for light-emitting-diode applications

Near-infrared phosphor-converted light-emitting diodes (NIR pc-LEDs) have emerged as ideal light sources for a variety of advanced spectroscopy applications, demonstrating the importance of developing efficient NIR phosphors. In this work, a Ti4+-containing garnet, Na2CaTi2Ge3O12, was selected as the host material to minimize the ionic size mismatch after Cr3+ substitution. Interestingly, this substitution generates charge self-balance, enabling excellent efficiency of the developed material. Under 465 nm excitation, it exhibits broadband emission covering the first NIR window (λem,max = 790 nm) with a full width at half maximum (FWHM) of 120 nm. The optimized sample achieved a photoluminescence quantum yield (PLQY) of 75%. Moreover, a NIR pc-LED device was fabricated by combining the optimized phosphor with a blue (λem = 455 nm) InGaN chip. Upon application of a driving current of 100 mA, the device demonstrated a NIR output power of 18.24 mW and a corresponding NIR photoelectronic conversion efficiency of 6.49% and exhibited excellent performance in biological tissue imaging and non-destructive testing. Therefore, this work provides an efficient NIR phosphor, which has promising potential in spectroscopy applications.