Emerging Fe3+ Doped Broad NIR‐Emitting Phosphor Ca2.5Hf2.5(Ga, Al)3O12: Fe3+ for LWUV Pumped NIR LED

Abstract Fe 3+ is a promising dopant for designing near‐infrared (NIR) phosphors due to its broadband emitting, non‐toxic, and inexpensive properties. However, the 4 E ( 4 D) and 4 E + 4 A 1 ( 4 G) levels of Fe 3+ ions are independent of the crystal‐field parameter, and the spectral regulation has become a huge challenge. Herein, a broadband NIR‐emitting phosphor Ca 2.5 Hf 2.5 (Ga, Al) 3 O 12 : Fe 3+ is successfully developed toward long‐wave ultraviolet (LWUV) light‐pumped NIR phosphor‐converted LED (pc‐LED). Significantly, the excited transition reverse of Ca 2.5 Hf 2.5 Ga 3 O 12 : Fe 3+ can be realized by simply adjusting Fe 3+ concentration, which results in the largely enhanced excitation around 410 nm and matches well with the commercial LWUV LED. Moreover, Ca 2.5 Hf 2.5 Ga 3 O 12 : Fe 3+ can exhibit a broadband NIR emission centered at 770 nm with optimized doping content at 0.01 mol%, which are demonstrated to ascribe to Fe 3+ occupying both octahedral Hf 4+ and tetrahedral Ga 3+ sites. Further, a simple cation modulation strategy is proposed to successfully break the lattice symmetry around Fe 3+ ions and largely enhance the NIR‐emission intensity to 200% as much as before. Finally, a NIR pc‐LED is fabricated by employing Ca 2.5 Hf 2.5 Ga 3 O 12 : Fe 3+ , Al 3+ coating on a 410 nm LED chip, which shows great potential in non‐destructive inspection applications.