Emerging Fe³⁺ Doped Broad NIR-Emitting Phosphor Ca_2.5Hf_2.5(Ga, Al)₃O₁₂: Fe³⁺ for LWUV Pumped NIR LED

Fe3+ is a promising dopant for designing near-infrared (NIR) phosphors due to its broadband emitting, non-toxic, and inexpensive properties. However, the( 4)E (D-4) and E-4 + (4)A(1) ((4)G) levels of Fe3+ ions are independent of the crystal-field parameter, and the spectral regulation has become a huge challenge. Herein, a broadband NIR-emitting phosphor Ca2.5Hf2.5(Ga, Al)(3)O-12: Fe3+ is successfully developed toward long-wave ultraviolet (LWUV) light-pumped NIR phosphor-converted LED (pc-LED). Significantly, the excited transition reverse of Ca2.5Hf2.5(Ga, Al)(3)O-12: Fe3+ can be realized by simply adjusting Fe3+ concentration, which results in the largely enhanced excitation around 410 nm and matches well with the commercial LWUV LED. Moreover, Ca2.5Hf2.5(Ga, Al)(3)O-12: Fe3+ can exhibit a broadband NIR emission centered at 770 nm with optimized doping content at 0.01 mol%, which are demonstrated to ascribe to Fe3+ occupying both octahedral Hf (4+) and tetrahedral Ga3+ sites. Further, a simple cation modulation strategy is proposed to successfully break the lattice symmetry around Fe3+ ions and largely enhance the NIR-emission intensity to 200% as much as before. Finally, a NIR pc-LED is fabricated by employing Ca2.5Hf2.5(Ga, Al)(3)O-12: Fe3+, Al3+ coating on a 410 nm LED chip, which shows great potential in non-destructive inspection applications.