Simultaneous Absorption and Near‐Infrared Emission Enhancement of Cr3+ Ions in MgGa2O4 Spinel Oxide via Anionic F‐Substitution

Near‐infrared (NIR) phosphor‐converted light‐emitting diodes (pc‐LEDs) are newly emerging broadband NIR light sources. However, the lack of high‐performance NIR‐emitting materials limits their popularization. Herein, an anionic F‐substitution strategy is presented to regulate the light absorption and emission of MgGa2O4:Cr3+ phosphors. Accordingly, absorption enhancement as well as emission redshift and broadening are achieved for F‐substituted MgGa2O4:Cr3+ (MGOF:Cr3+) phosphors, simultaneously with high efficiency and excellent thermal stability. Upon blue light excitation, the MGOF:0.02Cr3+ phosphor exhibits a broadband NIR emission (650–1200 nm) with a peak wavelength (λmax) of 835 nm and a full width at half maximum of ≈250 nm. Furthermore, MGOF:0.02Cr3+ has a near‐unity internal quantum efficiency and its emission intensity at 150 °C maintains 94% of the initial value. A record external quantum efficiency of 60.6% is further achieved for MGOF:0.08Cr3+ with a redshifted λmax of 870 nm. The Cr3+ local structural alteration with F‐substitution is revealed to account for the outstanding NIR luminescence characteristics of MGOF:Cr3+ in view of systematic structural characterization and spectroscopic analysis. A broadband NIR pc‐LED device with good optical performance is fabricated and its application in semiconductor wafer inspection is demonstrated. This study initiates a new way to design high‐performance NIR phosphors. Anionic F‐substitution induces the decrease of the symmetry and crystal field strength of Cr3+ coordination environment. Thus, both absorption enhancement and emission broadening are achieved for F‐substituted MgGa2O4:Cr3+ (MGOF:Cr3+) phosphors. The optimal MGOF:Cr3+ phosphor emits from 650 to 1200 nm (λmax = 835 nm), simultaneously exhibiting an ultrahigh internal quantum efficiency (99.4%) and excellent thermal stability (94% @150 °C).