Broadband Short-Wave Infrared Light-Emitting Diodes Based on Cr³⁺-Doped LiScGeO₄ Phosphor

Abstract

Short-wave infrared (SWIR) spectroscopy has recently emerged as an important technology across a wide range of areas, whether industrial, biomedical, or environmental. Nevertheless, it is still a longstanding challenge to develop robust SWIR light sources. The SWIR phosphor-convert light emitting diodes (LEDs) by coating blue LED chips with desirable SWIR-emitting phosphors are becoming an ideal alternative for solid-state SWIR light sources due to its compactness, low-cost, and long operating lifetime, as does the commercial white LEDs. Herein, we report a blue-pumped Cr 3+ -doped LiScGeO 4 SWIR phosphor as a luminescent converter for phosphor-convert SWIR LEDs. This phosphor shows an intense SWIR emission band with a peak wavelength at ∼1120 nm owing to the 4 T 2 → 4 A 2 electron transition of Cr 3+ when exciting with blue light. The full width at half-maximum (fwhm) of the phosphor is ∼300 nm and the absolute quantum efficiency is determined to be ∼26%. SWIR LED prototypes are constructed by combining the optimized phosphor materials with commercial blue InGaN LED chips, which can generate a commendable emission band in the SWIR region over 800−1600 nm and achieve a maximum output power of ∼4.78 mW at 60 mA with the photoconversion efficiency of 4.4%. The current exploration of Cr 3+ -doped SWIR-emitting phosphors will lay the foundation to engineer phosphor-convert SWIR LEDs for applications in night-vision surveillance and SWIR spectroscopy technology. These blue-light-excitable SWIR-emitting phosphors can serve as an important complement to the spectral gap of the current Cr 3+ -doped phosphors in the SWIR region and will pave the way toward cost-effective phosphor-converted solid-state SWIR light sources.

A simple and generic post-treatment strategy for highly efficient Cr3+-activated broadband NIR emitting phosphors for high-power NIR light sources

“…Moreover, the heavily overlapped sub-bands between the Cr 6+ and Cr 3+ ions means that the competitive absorption between Cr 6+ and Cr 3+ ions inevitably happens. Additionally, we cannot find any extra absorption band beyond 1000 nm, which covered the absorption band of Cr 4+ , 33 so the existence of Cr 4+ in LiInO 2 :Cr 3+ can preliminarily be ruled out. Therefore, the key to attaining high-efficiency luminescence of the LiInO 2 :Cr 3+ phosphor is to remove Cr 6+ in the samples.…”

A non-rare earth ion doped broadband emission phosphor located in NIR-II for ethanol concentration detection

“…S4† shows the fluorescence decay curves of Ca 2 GeO 4 : x Cr phosphors at different Cr contents by monitoring the emission at 1270 nm under 489 nm and 628 nm radiation excitation; all the decay curves can be well fitted using a second-order exponential equation as follows: I ( t ) = A 1 exp(− t / τ 1 ) + A 2 exp(− t / τ 2 )where A 1 and A 2 are constants, τ denotes the decay lifetime, I ( t ) is the luminescence intensity at time t , and τ 1 and τ 2 are the rapid and slow components of the lifetime, respectively. 21 The average lifetimes of Ca 2 GeO 4 : x Cr under 489 nm excitation were thus calculated to be 16.77, 14.75, 13.91, and 12.02 μs, respectively, and 15.81, 14.62, 14.05, and 12.37 μs, respectively, under 628 nm excitation (Table S1†). It was noted that with the increase of the Cr doping concentration, the Ca 2 GeO 4 : x Cr phosphor lifetime decreases, which can be attributed to the increased chance of the non-radiative transition of the Ca 2 GeO 4 : x Cr phosphor at higher Cr doping concentrations.…”

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

“…[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. [8][9][10][11] Although the AlGaAs NIR LEDs have the merits of efficiency, compactness and durability, their intrinsic narrowband emission (full width at half maximum (FWHM o 50 nm)) and huge production costs make them difficult for use in diverse applications.…”