Achieving a tunable and ultra-broadband near-infrared emission in the Ga2−2xZnxGexO3:Cr3+ phosphor

Abstract

Near-infrared (NIR) spectroscopy (700–1100 nm) based on a phosphor-converted light-emitting diode (pc-LED) has multi-functional applications in bio-imaging, night-vision, and food quality analysis, simulating the development of efficient and ultra-broadband NIR phosphors. Herein, a series of tunable and ultra-broadband NIR phosphor Ga_2−2xZn_xGe_xO₃:Cr³⁺ was successfully produced by a [Zn²⁺–Ge⁴⁺] unit co-substituting a [Ga³⁺–Ga³⁺] unit in Ga₂O₃:Cr³⁺. With the increasing amount of [Zn²⁺–Ge⁴⁺] incorporation, the emission peak can be tuned from 726 to 808 nm, and the maximum FWHM can be extended from 126 to 190 nm. However, the excitation peak position remained nearly unchanged in the blue light region, enabling this material to perfectly match the InGaN blue LED chip. Although the gradually enhanced electron–lattice coupling and low energy barrier for thermal quenching caused by this co-substitution lead to a decrease in the photoluminescence quantum yield (PLQY) and thermal stability, respectively, the absolute values of these two criteria can be well maintained. Finally, to evaluate the practical applications, prototype NIR pc-LEDs were fabricated using these materials combined with 450 nm LED chips. Under the same conditions, the NIR output power and photoelectronic conversion efficiency of these devices are superior to those fabricated using the well-known ScBO₃:Cr³⁺ phosphor. These results demonstrate that this series of materials with tunable and ultra-broadband NIR emissions has great potential for NIR pc-LED applications.