  Near-infrared phosphor-converted light-emitting diodes (NIR pc-LEDs) are
compact light sources of great interest for NIR spectroscopy applications.
Beyond typical Cr3+-activated NIR-emitting phosphors, there exists a strong
demand for Cr3+-free alternatives with high efficiency and broadband emission
to rich the landscape of NIR luminescent materials and extend their range of
application fields. Here, we report a series of Fe3+-activated Ca3Ga2Sn3O12
garnet-type phosphors exhibiting broadband NIR emission in the 650-1000 nm
range attributed to 4T1(G)-->6A1(S) transition, with a maximum at 754 nm and a
FWHM of 89 nm upon UV excitation. The spectroscopic results were analyzed
according to the Tanabe-Sugano theory from which the crystal field parameter Dq
and Racah parameters B and C were obtained for the octahedrally coordinated
Fe3+ ion. Notably, the NIR persistent luminescence lasting over 1 h was
detected following UV or X-ray irradiation. The possible mechanism involving
electron traps was proposed to explain the observed persistent luminescence.
Furthermore, a NIR pc-LED was fabricated by coating synthesized phosphor on a
UV chip, and its performance was evaluated to assess its potential suitability
as a NIR light source. Our discovery of novel type of nontoxic Fe3+-activated
broadband NIR luminescence phosphors with efficient NIR persistent luminescence
paves the way for discovering Cr3+-free multifunctional NIR luminescence
materials, thereby expanding their application possibilities.
