Chromium Ion Pair Luminescence: A Strategy in Broadband Near-Infrared Light-Emitting Diode Design

Abstract

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 Cr 3+ ion centers, and it is challenging to design broadband NIR phosphors based on Cr 3+ −Cr 3+ pairs. Here, we explore the solidsolution series SrAl 11.88−x Ga x O 19 :0.12Cr 3+ (x = 0, 2, 4, 6, 8, 10, and 12) as phosphors featuring Cr 3+ −Cr 3+ 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 Cr 3+ −Cr 3+ ion pair proximity. Electron paramagnetic measurements reveal the presence of both isolated Cr 3+ and Cr 3+ − Cr 3+ 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 Cr 3+ −Cr 3+ ion pair. We demonstrate the application of the SrAl 5.88 Ga 6 O 19 :0.12Cr 3+ 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.

Disorder–Order Conversion‐Induced Enhancement of Thermal Stability of Pyroxene Near‐Infrared Phosphors for Light‐Emitting Diodes

“…CaMgSi 2 O 6 : Cr 3+ afforded excellent thermal stability, with a narrow FWHM and a small Stokes shift due to its weak thermal quenching effect induced by weak electron‐phonon coupling [10, 25] . Intensity of the x =0.800 sample increased from 25 °C to 50 °C, which is considered to be a result of increased absorption probability of the 4 A 2 → 4 T 1 transition [26] . The Huang–Rhys parameter ( S ) represents the degree of electron‐phonon coupling: S <1 represents weak coupling, 1< S <5 indicates intermediate coupling, and S >5 implies strong coupling.…”

Highly efficient and thermally stable broadband near-infrared emitting fluoride Cs2KGaF6:Cr3+ for multiple LED applications

“…Near-infrared (NIR) radiation plays an important role in night vision safety testing, non-destructive testing, intelligent recognition, biomedical imaging and other fields because of its strong penetration ability, and because it is non-destructive and invisible to the naked eye. [1][2][3][4] At present, traditional NIR radiation sources mainly include incandescent lamps, halogen lamps, supercontinuum lasers and NIR light-emitting diodes (LEDs), but they all have irreparable shortcomings. [5][6][7] Incandescent lamps, halogen lamps and supercontinuum lasers are extensively used NIR broadband radiation sources, but the large volume and low efficiency restrict their practical applications.…”

High-Pressure Photoluminescence Properties of Cr3+-Doped LaGaO3Perovskites Modulated by Pressure-Induced Phase Transition

“…It is known that the Cr 3+ -doped LaGaO 3 perovskite shows deep red luminescence at around 730 nm due to 2 E → 4 A 2 . In addition, the Cr 3+ –Cr 3+ pair luminescence ( N -line) in the longer-wavelength region than R -line has been reported in the highly Cr 3+ -doped compounds such as Al 2 O 3 and MgAl 2 O 4 , ZnGa 2 O 4 , ZnAl 2 O 4 , SrAl 12– x Ga x O 19 , and so on. − For instance, the Cr 3+ –Cr 3+ pair in the face-sharing octahedral sites of α-Al 2 O 3 shows the antiferromagnetically coupled pair luminescence. On the other hand, the oxide perovskite compounds (YAlO 3 and LaAlO 3 ) with Cr 3+ –Cr 3+ pair in the corner-sharing octahedral sites also show strong luminescence with the antiferromagnetic interaction because of the superexchange interaction from the almost linear Cr–O–Cr angle. − Thus, it is expected that LaGaO 3 :Cr 3+ also shows strong Cr 3+ –Cr 3+ pair luminescence and its optical properties can be elucidated by changing the Cr 3+ –Cr 3+ distance and the Cr–O–Cr angle by pressure.…”