posted on 2021-11-04, 21:14authored byVeeramani Rajendran, Mu-Huai Fang, Wen-Tse Huang, Natalia Majewska, Tadeusz Lesniewski, Sebastian Mahlik, Grzegorz Leniec, Slawomir M. Kaczmarek, Wei Kong Pang, Vanessa K. Peterson, Kuang-Mao Lu, Ho Chang, Ru-Shi Liu
Portable near-infrared (NIR) light
sources are in high demand for
applications in spectroscopy, night vision, bioimaging, and many others.
Typical phosphor designs feature isolated Cr3+ ion centers,
and it is challenging to design broadband NIR phosphors based on Cr3+–Cr3+ pairs. Here, we explore the solid-solution
series SrAl11.88–xGaxO19:0.12Cr3+ (x = 0, 2, 4, 6, 8, 10, and 12) as phosphors featuring Cr3+–Cr3+ pairs and evaluate structure–property
relations within the series. We establish the incorporation of Ga
within the magentoplumbite-type structure at five distinct crystallographic
sites and evaluate the effect of this incorporation on the Cr3+–Cr3+ ion pair proximity. Electron paramagnetic
measurements reveal the presence of both isolated Cr3+ and
Cr3+–Cr3+ pairs, resulting in NIR luminescence
at approximately 650–1050 nm. Unexpectedly, the origin of broadband
NIR luminescence with a peak within the range 740–820 nm is
related to the Cr3+–Cr3+ ion pair. We
demonstrate the application of the SrAl5.88Ga6O19:0.12Cr3+ phosphor, which possesses an internal
quantum efficiency of ∼85%, a radiant flux of ∼95 mW,
and zero thermal quenching up to 500 K. This work provides a further
understanding of spectral shifts in phosphor solid solutions and in
particular the application of the magentoplumbites as promising next-generation
NIR phosphor host systems.