Large-scale irrigation of Cr3+ into different octahedra of zinc aluminate toward continual broadband near-infrared emission

Broadband near-infrared (NIR) phosphors, as key materials in NIR phosphor-converted light-emitting diodes (pc-LEDs) for emerging applications, have recently attracted considerable attention. Herein, by selecting a comprehensive engineering strategy of co-substituting [Al 3+ -Al 3+ ] with [Mg 2+ -Ge 4+ ] units and increasing Cr 3+ concentration, a novel Cr 3+ -doped ZnAl 1.16 Mg 0.4 Ge 0.4 O 4 (ZA(MG) 0.4 :2 at.%Cr 3+ ) phosphor with continual broadband NIR emission was synthesized. The site occupation of Mg 2+ /Ge 4+ in ZnAl 2 O 4 is unraveled by Rietveld structure refinement and density functional theory (DFT) calculations. According to the photoluminescence behaviors, the formed defect clusters of Zn Al ’ -Cr 3+ -Ge Al · and Mg Al ’ -Cr 3+ -Ge Al · can not only introduce shallow defects to serve as new traps to obtain long-persistent luminescence but can also enhance the emission intensity at ∼689 nm and ∼694 nm. The quantity and scale of Cr 3+ -Cr 3+ pairs and Cr 3+ in distorted sites, which can improve the thermal quenching resistance and emission intensity in the range of 700–800 nm, can be accurately regulated by varying the concentration of Cr 3+ . Under 387 nm excitation, the designed material exhibits intensive NIR emission from 685 to 750 nm with a wide full-width at half maximum (FWHM) of 95 nm. The electroluminescence spectrum and potential applications of the NIR pc-LED prepared using ZA(MG) 0.4 :2 at.%Cr 3+ phosphor are also reported. The results promise a feasible strategy to develop NIR phosphors as NIR pc-LEDs lighting sources for applications in non-destructive detection and anti-counterfeiting.