Broadband near-infrared (NIR)-emitting phosphors are key for next-generation smart NIR light sources based on blue LEDs. To achieve excellent NIR phosphors, we propose a strategy of enhancing the crystallinity, modifying the micromorphology, and maintaining the valence state of Cr3+ in Ca3Sc2Si3O12 garnet (CSSG). By adding fluxes and sintering in a reducing atmosphere, the internal quantum efficiency (IQE) is greatly enhanced to 92.3%. The optimized CSSG:6%Cr3+ exhibits excellent thermal stability. At 150 °C, 97.4% of the NIR emission at room temperature can be maintained. The fabricated NIR-LED device emits a high optical power of 109.9 mW at 520 mA. The performances of both the achieved phosphor and the NIR-LED are almost the best results until now. The mechanism for the optimization is investigated. An application of the NIR-LED light source is demonstrated. A near-infrared light-emitting (NIR-LED) diode that emits high-power light could pave the way for the development of next-generation monitoring and detecting devices. Although solid-state NIR-LEDs are used in such devices, their narrow emission band limits their range of applications. Broadband NIR-emitting phosphor-converted LEDs offer the best solution. However, creating NIR phosphors that are sufficiently excited by blue light is challenging. Now, a team of Chinese and American researchers, led by Yongfu Liu from the Chinese Academy of Sciences, has created a NIR-LED that emits light in the 700–900 nm with an output of 109.9 mW at 520 mA after excitation with blue light. The device has the highest recorded power rating to date and could be used in applications from bioimaging and night-vision technologies, to monitoring food and medicines.

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Strategies to approach high performance in Cr 3+ -doped phosphors for high-power NIR-LED light sources.

Near-infrared (NIR) phosphors have received increasing attention for designing novel solid-state light sources with broadband NIR output. In this work, a novel NIR phosphor LiScP2O7:Cr3+ (LSP:Cr3+)...

Enhancing Near-Infrared Photoluminescence Intensity and Spectral Properties in Yb3+ Codoped LiScP2O7:Cr3+

The development of phosphor materials with outstanding photoluminescence properties is critical for next-generation high-quality solid-state white lighting. As there is a blue-green cavity existing in the emission spectra of the traditional phosphor-converted white-light-emitting diodes (w-LEDs), the cyan-emitting phosphor serves as an important function in compensating the spectral gap to realize “full-visible-spectrum lighting”. Herein, we reported the discovery of an efficient cyan-emitting Ce3+-doped Ca2YHf2Al3O12 (CYHAO) garnet phosphor with good thermal stability. The as-prepared CYHAO:xCe3+ phosphor exhibited a broad excitation band in the range of 360 to 460 nm with a maximum at 408 nm, making this phosphor compatible with an efficient 400 nm near-ultraviolet (NUV)-emitting LED chip. Under 408 nm excitation, the optimal sample of CYHAO:0.03Ce3+ exhibited bright broadband cyan emission (λem = 493 nm; bandwidth = 100 nm) together with an extra-high internal quantum efficiency (IQE) of 89.5% and external quantum efficiency (EQE) of 69.1%. Notably, the as-prepared CYHAO:0.03Ce3+ phosphor showed good thermal stability (64.2% of emission intensity retained at 423 K) and excellent color stability when working in the temperature range of 303–463 K. Importantly, the constructed w-LED device exhibited bright well-distributed warm white light with a high color rendering index (CRI; Ra = 93.5 and R12 = 90.4) and low correlated color temperature (3700 K) under 60 mA driven current, indicating that the title cyan phosphor can be utilized for the compensation of the blue-green cavity to be applied in full-visible-spectrum lighting. Furthermore, these findings provide new insights into exploring high-performance cyan phosphors for NUV-pumped high-CRI warm w-LEDs.

Full-visible-spectrum lighting enabled by an excellent cyan-emitting garnet phosphor

Searching for high performance and broader applications of inorganic halide perovskites has drawn extensive attention. In this work, a Cr3+-doped halide perovskite, Cs2AgInCl6:Cr3+, which exhibits broadband near-infrared (NIR) emission is first obtained via the traditional high temperature solid-state reaction. A broad emission band ranging from 850 to 1350 nm centered at 1010 nm with a full-width at half-maximum (FWHM) of 180 nm is assigned to the spin-allowed 4T2 → 4A2 transition of octahedrally coordinated Cr3+ ions in a very weak crystal-field environment. The excitation bands centered at 353, 565 and 800 nm can be attributed to the absorption of the Cs2AgInCl6 host, the Cr3+ d–d transitions of 4A2 → 4T1 and 4A2 → 4T2, respectively. Upon 760 nm excitation, the photoluminescence quantum yield (PLQY) of Cs2AgIn0.9Cl6:0.1Cr3+ is about ∼22.03%. Cs2AgInCl6:Cr3+ phosphors with such broadband NIR emission have potential in phosphor converted light emitting diodes (pc-LEDs) which have applications in bioimaging and biomonitoring.

Double perovskite Cs2AgInCl6:Cr3+: broadband and near-infrared luminescent materials

Broadband Near-Infrared Garnet Phosphors with Near-Unity Internal Quantum Efficiency

The near-infrared phosphor-converted light-emitting diodes (NIR pc-LEDs) have great potential in food industry and medical fields. For applications based on NIR spectroscopy, the next generation of...

Two-Site Occupation for Exploring Ultra-Broadband Near-Infrared Phosphor—Double-Perovskite La2MgZrO6:Cr3+

The rapid development of portable spectrometers has evoked a large demand for minimized light sources; meanwhile, NIR phosphor-converted light-emitting diodes (NIR pc-LEDs) are an optimal choice due to their compactness and low cost. The phosphors used in NIR spectroscopy (NIRS) are required to have broadband emission and high quantum efficiency (QE) for a wider detection range and efficient photo-to-electricity conversion. Inspired by the structural tunability of Y3Al5O12 (YAG), we proposed to achieve broadband emission by crystal field engineering, i.e., indirectly regulating the crystal field strength of Cr3+via the co-substitution of Y3+–Al3+ by Ca2+–Si4+ in YAG. The crystal field strength experienced on Cr3+ decreased as the octahedron was distorted and enlarged by the co-substitution. A broadband NIR emission with a large full width at half maximum (FWHM) of 160 nm and a high internal quantum efficiency (IQE) of ∼75.9% was realized in Y3−xCaxAl5−xSixO12:0.6% Cr (x = 1). The suitability of the investigated NIR phosphor was demonstrated by fabricating an NIR pc-LED prototype, and the detection resolution was improved by 30% compared to that of a traditional white pc-LED. These results indicate the great potential of the Y2CaAl4SiO12:Cr phosphors for use in highly precise and sensitive NIR pc-LEDs.

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Broadband near-infrared (NIR) emission realized by the crystal-field engineering of Y3−xCaxAl5−xSixO12:Cr3+ (x = 0–2.0) garnet phosphors

To investigate the luminance saturation in high-power blue-laser-driven solid state lighting, the Y3Al5O12: Ce (YAG)-based PiG films was co-fired with a high thermally conductive sapphire substrate. When the PtG ratio or the thickness of the PiG film increases, the luminance saturation becomes worse and both of the luminous flux and luminous efficacy decrease. With an additional sapphire substrate coated with an anti-reflection layer on one side and a blue-pass filter on another side attached to the PiG film, the film shows an improvement in luminous flux and efficacy, and produces the white light with a luminous flux of 1709 lm, a luminous efficacy of 211 lm W−1 and a correlated color temperature of 6602 K under the maximum (10.3 W mm−2) blue laser light excitation. It indicates that the PiG film could be applied in high power laser-driven solid state lighting when its microstructure is carefully tailored.

On the luminance saturation of phosphor-in-glass (PiG) films for blue-laser-driven white lighting: Effects of the phosphor content and the film thickness

The invention belongs to the technical field of luminous materials, and particularly relates to a broad-band near-infrared-emission luminous material, in particular to a material capable of emitting red rays and near-infrared rays within 650nm to 1,600nm under excitation of ultraviolet, violet, blue and red rays, and further discloses a preparation method of the luminous material and a luminous device comprising the luminous material. The broad-band near-infrared-emission luminous material is prepared from an inorganic compound with the molecular formula of AaDbMcOe:xCr, has a strictly occupied ordered structure, and has a broader excitation wavelength (250-700 nm); the material is a single substance which takes Cr as an optically active center, and can well absorb the ultraviolet rays, the blue rays and the red rays; under the excitation of the ultraviolet rays, the violet rays or the blue rays, the broad-band red rays and the near-infrared rays can be emitted within the range of 650nm to 1,600 nm.

Broad-band near-infrared-emission luminous material and luminous device comprising luminous material

Belonging to the technical field of luminescent materials, the invention in particular relates to a broad-band near-infrared emission luminescent substance, in particular to a material capable of generating red light and near-infrared emission in a range of 700nm-1600nm under the excitation of ultraviolet, purple light, blue light and red light, and further discloses a preparation method of the material and a luminescent device containing the luminescent material. The broad-band near-infrared emission luminescent substance includes an inorganic compound with a molecular formula of AaDbMcEdOe:xCr. The luminescent substance has a strictly occupied ordered structure, and the material is a single substance, adopts Cr as the optical active center, can well absorb ultraviolet light, blue light and red light, and under the excitation of ultraviolet or purple light or blue light, can realize broad-band red light and near-infrared emission in the range of 700nm-1600nm, and has shorter fluorescence lifetime.

Zeng Huatao

Papers

Two-Site Occupation for Exploring Ultra-Broadband Near-Infrared Phosphor—Double-Perovskite La2MgZrO6:Cr3+

Broadband near-infrared (NIR) emission realized by the crystal-field engineering of Y3−xCaxAl5−xSixO12:Cr3+ (x = 0–2.0) garnet phosphors

On the luminance saturation of phosphor-in-glass (PiG) films for blue-laser-driven white lighting: Effects of the phosphor content and the film thickness

Broad-band near-infrared-emission luminous material and luminous device comprising luminous material

Broad-band near-infrared emission luminescent substance and luminescent device containing the same