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Fe3+ is a promising dopant for designing near‐infrared (NIR) phosphors due to its broadband emitting, non‐toxic, and inexpensive properties. However, the 4E (4D) and 4E + 4A1 (4G) 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)3O12: Fe3+ is successfully developed toward long‐wave ultraviolet (LWUV) light‐pumped NIR phosphor‐converted LED (pc‐LED). Significantly, the excited transition reverse of Ca2.5Hf2.5Ga3O12: 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, Ca2.5Hf2.5Ga3O12: 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 Ca2.5Hf2.5Ga3O12: Fe3+, Al3+ coating on a 410 nm LED chip, which shows great potential in non‐destructive inspection applications. [ABSTRACT FROM AUTHOR]

Ultra-broadband-emitting phosphors are crucial for achieving high-quality full-spectrum WLEDs. However, it is difficult to achieve ultra-broadband emission by doping a single luminescent center. In this work, we propose a strategy to achieve ultra-broadband orange-red emission through utilizing Eu2+ selective occupation in multi-cation sites whitlockite-type phosphate Sr 8 Mg 2 Na(PO 4) 7. The result indicates that Eu2+ can occupy Sr1Mg1, Sr2Mg2, and Sr3Mg3 sites, and generate an ultra-broadband emission ranging from 400 to 800 nm with dominant emission at 620 nm and a FWHM of 220 nm upon 385 nm excitation. Interestingly, a new emission shoulder at 430 nm is obtained, which is demonstrated to ascribed to Eu2+ occupying the Mg4Na1 site in a weak crystal field. As an ultra-broadband-emitting and red-light abundant phosphor, the full-spectrum WLEDs shows much higher color index than that of YAG: Ce3+. Moreover, an ultraviolet light pumped full-spectrum WLED with a high Ra (∼92) and low CCT (∼4275 K) is fabricated by mixing the Sr 8 Mg 2 Na(PO 4) 7 : Eu2+ and commercial phosphors BAM: Eu2+, Mn2+. In summary, this work deeply investigated the luminescence properties of Eu2+ in whitlockite-type phosphor Sr 8 Mg 2 Na(PO 4) 7 and is expected to guide the design of novel broadband-emitting phosphors with multi cationic sites for emerging full-spectrum WLED applications. • SMNPO was demonstrated to have multi-cation sites for luminescent center to occupy. • Ultra-broadband emission was achieved by doping Eu2+ ions into SMNPO. • The selective occupation of Eu2+ ions in multiple sites was analyzed in detail. • A full-spectrum WLED with high Ra (∼92) and low CCT (∼4275 K) was prepared. [ABSTRACT FROM AUTHOR]

A series of rare-earth free far-red emitting phosphor NaYBa 4 W 2 O 12 : x Mn4+ (≤ x ≤ 0.75%, NYBW: Mn4+) is successfully synthesized for application in near-ultraviolet (n-UV) light pumped plant cultivation light-emitting diodes (LEDs). The phase purity, crystal structure, electronic structure and luminescent properties of NYBW: Mn4+ are investigated in detail. The results indicate that all NYBW: Mn4+ phosphors are well crystallized with a direct band gap of 3.86 eV. Broad excitation band can be found with dominant wavelengths at 365 and 520 nm, indicating NYBW: Mn4+ can be efficiently excited by commercial n-UV or green LED chip. Upon 360 nm excitation, NYBW: Mn4+ shows intense broad-band far-red emission centered at 696 nm, attributed to the 2E g →4A 2g transition of Mn4+. The optimal doping concentration of Mn4+ is determined to be 0.1% and the concentration quenching mechanism is the dipole-quadrupole interaction. The decay time decreases from 0.58 to 0.081 ms with Mn4+ concentration increasing from 0.025 to 0.75%. The temperature quenching behaviour of Mn4+ in NYBW is investigated, with a thermal activation energy estimated to be about 0.375 eV. Finally, a far-red emitting LED device is fabricated by coating NYBW: Mn4+ phosphor on a 365 nm n-UV LED chip. The above results guarantee that the as-prepared far-red emitting phosphor NYBW: Mn4+ has great potential for application in indoor plant cultivation LEDs. • Successful synthesis of a novel NYBW:Mn4+ perovskite phosphor. • Realization of rare-earth free far-red emission under UV excitation. • Investigation on the optical properties of NYBW:Mn4+ phosphor is conducted. • Potential far-red LED application for plant cultivation lighting is studied. [ABSTRACT FROM AUTHOR]