Phosphor-converted Light-emitting Diodes Research Articles

Achievement of high photoluminescence quantum yield orange-red phosphors by designing Eu2+ reduction environment for multi applications

The high photoluminescence quantum yield (PLQY) orange-red phosphor, which is of great significance for the application of phosphor-converted light-emitting diode (LED). Herein, the novel BaSrLu4O8:Eu2+ orange-red phosphor was synthesized, and the PLQY is enhanced from 30 % to 91 % by Al2O3 assisted sintering. Combined with the trap energy level analysis, it is considered that the addition of Al2O3 introduces new vacancies, which release electrons during high temperature sintering, creating a more favorable environment for the reduction of Eu3+, increasing the Eu2+ luminescence center in the matrix and improving the PLQY. The white LED device prepared with BaSrLu4O8:Eu2+ and Y3(Al,Ga)5O12:Ce3+ has a color rendering index of 84.4 at a low correlated color temperature of 4295 K. Meanwhile, the luminous brightness of the orange LED prepared by BaSrLu4O8:Eu2+ can maintain 89 % of the original light intensity in the simulated foggy day illumination experiment, which proves its excellent lighting prospect as an automobile steering lamp in foggy and smog extreme conditions. The results indicate that this work provides a new strategy for the reduction of Eu2+ while realizing the multi-application of phosphors.

Barbier Polymerization-Induced Emission towards Fully Substituted Polyethylene Analogues with Non-Traditional Intrinsic Luminescence.

The properties of polyethylene are highly dependent on the variety and quantity of substitutions. Generally, polyethylene can only be fully substituted with fluorine atoms, mainly e. g., polytetrafluoroethylene and nafion, because atomic radius of fluorine atom is small enough. The preparation of fully substituted polyethylene analogues (FSPEA) and their non-traditional intrinsic luminescence (NTIL) are attractive, especially for substitutions with relatively larger atomic radii than a fluorine atom. Here, Barbier polymerization-induced emission (PIE) is demonstrated as a universal method for the molecular design of NTIL type FSPEAs with intriguing aggregation-induced emission (AIE) behaviors. Through Barbier polymerization of diphenyldichloromethane and different peroxyesters in the presence of Mg in one pot, a series of FSPEAs, including polytriphenylethanol (PTPE), polydiphenylfurylethanol (PDPFE), polydiphenylthiophenylethanol (PDPTE) and polydiphenylnaphthylethanol (PDPNE) have been successfully prepared. Further potential applications for explosive detection, artificial light-harvesting system and white phosphor-converted light-emitting diode are investigated. Therefore, this work opens up a new approach for the molecular design of FSPEA with non-conjugated luminescence, which may cause inspirations to different research fields like polyolefin and luminescent materials.

Thermally stable broadband near-infrared emitting pyrochlore oxide phosphors codoped with Cr3+ and Yb3+ ions

The advance of portable and smart near-infrared (NIR) light sources has sparked significant interest. However, achieving high-performance NIR emission at longer wavelengths remains a formidable challenge. In this study, we prepared broadband NIR phosphors by codoping pyrochlore oxide Y2GaSbO7 (YGSO) with Cr3+ and Yb3+ ions using a conventional high-temperature solid-state reaction. Upon excitation by blue light, YGSO: 0.03Cr3+ exhibited a broadband NIR emission centered at 765 nm with a full width at half maximum (FWHM) of 160 nm. The purposeful incorporation of Yb3+ ions facilitated efficient energy transfer from Cr3+ to Yb3+, resulting in a newly observed NIR emission peak at 970 nm. Notably, the addition of Yb3+ improved the overall thermal quenching resistance owing to its inherent thermal stability. Furthermore, we encapsulated the as-obtained phosphors with commercial blue LED chips to create prototype phosphor-converted light-emitting diodes (pc-LEDs). The Cr3+ and Cr3+-Yb3+ codoped pc-LEDs achieved output powers of 120 mW@660 mA with a photoelectric conversion efficiency of 12.66%@30 mA, and 131.7 mW@1020 mA with a photoelectric conversion efficiency of 13.93%@30 mA, respectively. These broadband NIR pc-LEDs hold promise for optical imaging applications.

Cooperative cationic substitution strategy triggers high blue-light absorptance and near-infrared emission with high quantum efficiency in Cr3+-activated pyroxene-type assembly

Near-infrared phosphor-converted light-emitting diodes (NIR pc-LEDs) assembled with the broadband NIR-emitting phosphors has been a promising light source for application in agricultural plant lighting, night vision, food analysis and medical diagnosis. But it suffers from a low photoelectric efficiency (<30 %) due to deficiency of phosphors with high internal quantum efficiency (IQE) and strong absorption capacity in the blue spectral region. Herein, a broadband NIR-emitting luminescent material capable of efficient blue to NIR light conversion with still high IQE was developed via the chemical-composition engineering of CaMgGe2O6:Cr3+ using cooperative cationic substitution of Ca2+-Mg2+ by Na + -Ga3+. The emission profiles evolved a red-shift from 839 to 859 nm with the full width at half-maximum (FWHM) extending from 161 nm to 177 nm as the increase of [Na+-Ga3+] pairs. In addition, the IQE can be finely adjusted. Importantly, the blue-light absorption efficiency can be greatly improved to 34.8 % upon pumping by the constant excitation energy. The increased local structural distortion induced by introducing [Na+-Ga3+] pairs has been verified for the main factor causing these desirable optical properties change. Benefiting from the improvement of blue-light absorptance, the fabricated NIR pc-LED device via coating the developed phosphor on a blue LED chip achieved the larger photoelectric efficiency 31.2 %@10 mA compared to the previously reported value of 27.2 %@10 mA. The excellent performance of biomedical imaging and night vision surveillance represented by the assembled NIR pc-LED was demonstrated.

Realization of Broadband Near-Infrared Emission with High Thermal Stability in YGa3(BO3)4: Cr3+ Borate Phosphor.

As a key material for phosphor-converted light-emitting diodes (pc-LEDs) applications, broadband near-infrared (NIR) phosphors currently face poor thermal stability issues. In this work, we synthesized a broadband near-infrared phosphor YGa3(BO3)4: Cr3+ (YGBO: Cr3+) with a high thermal stability. The YGBO: Cr3+ sample exhibits a broadband near-infrared emission centered at 770 nm with a full width at half-maximum (fwhm) of 2130 cm-1 under blue light excitation. Benefiting from the borate host crystal's strong structural rigidity, wide optical band gap, and weak electron-phonon coupling strength, YGBO: Cr3+ demonstrates strong luminescence thermal stability, and the corresponding luminescence intensity can maintain 80% at 150 °C compared to room temperature. Furthermore, we fabricated a pc-LED device using a blue light chip and YGBO: Cr3+ phosphor, and confirmed its application potential as a near-infrared light source in the spectral analysis of fruit freshness.

Tunable broadband near-infrared photoluminescence of Mg2LaTaO6:Cr3+ phosphors for light-emitting diodes

Near-infrared phosphor-converted light-emitting diodes (NIR pc-LED) prepared with near-infrared (NIR) phosphors have potential applications in various aspects. In this paper, Cr3+-activated Mg2LaTaO6 (MLTO: Cr3+) phosphors were prepared by the conventional high-temperature solid-phase method. The structure, morphology, and photoluminescence (PL) spectra of MLTO: Cr3+ phosphor were investigated. There is broadband NIR emission and the emission peak is red-shifted with the increase of doping concentration. The crystal field strengths of the samples were calculated and the relationship between the emission peak positions of the samples and the crystal field strengths was investigated. In addition, the concentration quenching mechanism of the samples was discussed, which is mainly attributed to dipole-dipole interactions. The internal quantum efficiency (IQE) of the MLTO: 0.4 mol% Cr3+ sample was measured with an IQE value of 76.48 %. NIR pc-LED devices were fabricated by combining the prepared MLTO: Cr3+ phosphor and blue-emitting LED chips, which are capable of emitting NIR light.

Large-scale irrigation of Cr3+ into different octahedra of zinc aluminate toward continual broadband near-infrared emission

Broadband near-infrared (NIR) phosphors, as key materials in NIR phosphor-converted light-emitting diodes (pc-LEDs) for emerging applications, have recently attracted considerable attention. Herein, by selecting a comprehensive engineering strategy of co-substituting [Al3+-Al3+] with [Mg2+-Ge4+] units and increasing Cr3+ concentration, a novel Cr3+-doped ZnAl1.16Mg0.4Ge0.4O4 (ZA(MG)0.4:2 at.%Cr3+) phosphor with continual broadband NIR emission was synthesized. The site occupation of Mg2+/Ge4+ in ZnAl2O4 is unraveled by Rietveld structure refinement and density functional theory (DFT) calculations. According to the photoluminescence behaviors, the formed defect clusters of ZnAl’-Cr3+-GeAl· and MgAl’-Cr3+-GeAl· can not only introduce shallow defects to serve as new traps to obtain long-persistent luminescence but can also enhance the emission intensity at ∼689 nm and ∼694 nm. The quantity and scale of Cr3+-Cr3+ pairs and Cr3+ in distorted sites, which can improve the thermal quenching resistance and emission intensity in the range of 700–800 nm, can be accurately regulated by varying the concentration of Cr3+. Under 387 nm excitation, the designed material exhibits intensive NIR emission from 685 to 750 nm with a wide full-width at half maximum (FWHM) of 95 nm. The electroluminescence spectrum and potential applications of the NIR pc-LED prepared using ZA(MG)0.4:2 at.%Cr3+ phosphor are also reported. The results promise a feasible strategy to develop NIR phosphors as NIR pc-LEDs lighting sources for applications in non-destructive detection and anti-counterfeiting.

Enhancing quantum efficiency of Mn4+-doped fluoride phosphors through reverse doping strategy toward potential biological detection

Mn4+-doped fluoride red-emitting materials are renowned for their distinct characteristics, including fixed emission peaks and narrow spectral emission, rendering them highly favored in photoluminescent light-emitting diodes (LEDs). However, achieving ultra-high-concentration Mn4+ doping in fluoride phosphors is imperative to enhance quantum efficiency. Nevertheless, attaining such doping levels in metastable compound systems poses considerable challenges. In this study, we introduce an innovative reverse doping strategy, leading to the synthesis of Mn4+-doped cubic K2SiF6 phosphor (11.38 mol %) from hexagonal K2MnF6. Remarkably, this approach significantly improves the external quantum efficiency (EQE) to 66.7 % upon 450 nm excitation. Through systematic comparisons with conventional co-precipitation and ion exchange methods, our findings unequivocally demonstrate the superior efficacy of this approach in achieving high-concentration Mn4+ ion doping within relatively insoluble matrices. The successful application of our optimized phosphor enabled the fabrication of a red light-emitting diode (LED) that exhibits an exceptional photoelectric efficiency of 31.67 % at 350 mA, surpassing the performance of a commercial red LED chip. Furthermore, the stable red-light emission from the phosphor-converted LED (pc-LED) proves instrumental in rapid-response vascular imaging, showcasing the potential of our findings in advancing light sources for biological detection applications. This research provides valuable insights into enhancing red emission efficiency in slightly-soluble fluoride phosphors via novel synthetic strategy, unlocking possibilities for the development of highly efficient light sources in biological detection and imaging applications.

Broadband La2LiSbO6: Cr3+ Phosphors with Double Luminescent Centers for NIR pc-LEDs.

The La2LiSbO6: xCr3+ phosphors were synthesized by means of a high-temperature solid-phase method. Based on the differences in ionic radius, valence state, and formation energy, the substitution sites of Cr3+ ions are discussed in detail. The optimized doping concentration of Cr3+ is determined to be 0.01. Under 517 nm excitation, the La2LiSbO6: 0.01Cr3+ phosphor presents a wide emission band (from 700 to 1350 nm) with a peak centered at 952 nm. Additionally, its corresponding full width at half-maximum is 155 nm, and the internal quantum efficiency reaches 62.4%. Meanwhile, the emission intensity of the La2LiSbO6: 0.01Cr3+ phosphor at 373 K is about 63.7% of that at room temperature, exhibiting good thermal stability. Aiming to fabricate a near-infrared phosphor-converted light-emitting diode device, the La2LiSbO6: 0.01Cr3+ phosphor is mixed with epoxy adhesive and cured on a green light-emitting diode chip. Under the irradiation of the fabricated light-emitting diode device, fruits and writing in the dark environment can be captured by a near-infrared camera. Hence, the La2LiSbO6: 0.01Cr3+ phosphor is promising for night vision.

Valence conversion and site reconstruction in near-infrared-emitting chromium-activated garnet for simultaneous enhancement of quantum efficiency and thermal stability

Achievement of high photoluminescence quantum efficiency and thermal stability is challenging for near-infrared (NIR)-emitting phosphors. Here, we designed a “kill two birds with one stone” strategy to simultaneously improve quantum efficiency and thermal stability of the NIR-emitting Ca3Y2-2x(ZnZr)xGe3O12:Cr garnet system by chemical unit cosubstitution, and revealed universal structure-property relationship and the luminescence optimization mechanism. The cosubstitution of [Zn2+–Zr4+] for [Y3+–Y3+] played a critical role as reductant to promote the valence transformation from Cr4+ to Cr3+, resulting from the reconstruction of octahedral sites for Cr3+. The introduction of [Zn2+–Zr4+] unit also contributed to a rigid crystal structure. These two aspects together realized the high internal quantum efficiency of 96% and excellent thermal stability of 89%@423 K. Moreover, information encryption with “burning after reading” was achieved based on different chemical resistance of the phosphors to acid. The developed NIR-emitting phosphor-converted light-emitting diode demonstrated promising applications in bio-tissue imaging and night vision. This work provides a new perspective for developing high-performance NIR-emitting phosphor materials.

Improved spectral mismatch and performance of a phosphor-converted light-emitting diode solar simulator

&lt;span lang="EN-US"&gt;A phosphor-converted light-emitting diode (LED) solar simulator is an illuminance device that produced irradiance intensity and spectral close to the sunlight. It is determined as spectral mismatch, non-uniformity of irradiance, and temporal instability. This paper has improved the LED solar simulator (LSS) system to have a spectral distribution consistent with the AM1.5G spectrum at 100%. It was developed as a new prototype to have the AAA class spectral characteristics, time instability, and inconsistency according to IEC 60904-9. The results showed that an optimal approach was to use phosphor-converted natural white LED (pc-nWLED), combining a monochromatic near-infrared (NIR) (730, 800, 850, 940, and 1,000 nm) as well as the proposed LSS system capable of generating 1,000 W/m&lt;sup&gt;2&lt;/sup&gt; irradiation over the test plane of 125×125 mm and operated continuously in a constant temperature LED state for at least 2 hours, therefore suitable for demonstration of solar cell features under standard test condition (STC) in the laboratory.&lt;/span&gt;

High-Efficiency Narrow-Band Green-Emitting Manganese(II) Halide for Multifunctional Applications.

Zero-dimensional (0D) Mn2+-based metal halides used as luminescent materials and scintillators have become a research hotspot in the field of photoelectric materials and devices due to their unique composition, structure, and fluorescence properties. It is of great value to explore new Mn2+-based metal halides to achieve multifunctional applications. Herein, the novel 0D Mn2+-based metal halide single crystal (BPTP)2MnBr4 is synthesized by a simple solvent-antisolvent recrystallization method. Under excitation at 468 nm, the (BPTP)2MnBr4 single crystal shows a pronounced narrow-band green luminescence centered at 515 nm derived from the d-d transition of the Mn2+ ion. This emission has a relatively narrow full width at half maximum of 43 nm and a high photoluminescence quantum yield (PLQY) of 82%. In addition, (BPTP)2MnBr4 exhibits good thermal stability at 393 K with a retention of 79% of the initial photoluminescence intensity at 298 K. Benefiting from its strong blue light excitation, high PLQY, and good thermal stability, we manufacture an ideal white light-emitting diode (LED) device using a 460 nm blue LED chip, green-emitting (BPTP)2MnBr4, and commercial K2SiF6:Mn4+ red phosphor. Under 20 mA drive current, the LED shows a high luminous efficiency of 112 lm/W and a wide color gamut of 110.8%, according to the National Television System Committee standard. In addition, (BPTP)2MnBr4 crystals show a strong X-ray absorption. Based on the commercial Lu3Al5O12:Ce3+ scintillator, the calculated light yield of (BPTP)2MnBr4 reaches up to about 136,000 photons/MeV and the detection limit reaches 0.282 μGyair s-1. Additionally, a melt quenching approach is used to construct a (BPTP)2MnBr4 clear glass scintillation screen, realizing a spatial resolution of 10.1 lp/mm. The proper performances of (BPTP)2MnBr4 as phosphor-converted LED materials and the X-ray scintillator with the addition of eco-friendly, low-cost solution processability make 0D Mn2+-based metal halides potential luminescent materials for multifunctional applications.

Structure modulation induced luminescence improvement in Gd3-xYxGa5O12:Cr3+ deep-red phosphors for dragon fruit cultivation

Deep-red phosphor-converted light-emitting diodes (pc-LEDs) have kept booming for the application in plant cultivation, but it suffers from low efficiency and low thermal quenching temperature. Here we report a series of Gd3-xYxGa5O12:Cr3+ garnet deep-red phosphors with high efficiency and excellent thermal stability. Y3+ ions with the same valence state and smaller radius were adopted to substitute Gd3+ to modulate the structure and further enhance the luminescence properties. Structure variation and microstructure of this garnet were carried out to verify the successful doping of Y3+. These phosphors show a broad excitation band from 400 nm to 650 nm and match well with blue chips. By modulating the structure, the crystal field was enhanced and the peak position shifted toward the blue direction. Representative Gd2.5Y0.5Ga5O12:Cr3+ exhibited excellent thermal stability and kept 93% emission at 423 K than that at room temperature. The internal quantum efficiency and external quantum efficiency of Gd0.5Y2.5Ga5O12:Cr3+ are 71.77% and 11.86%, respectively. As the temperature increased, the emission spectra were broadened and matched better with phytochrome PR and PFR. LED devices were fabricated by combining blue chip with this deep-red phosphor and applied to the cultivation of dragon fruit. The reducing sugar content was improved from 98.28 g/L to 111.85 g/L of the dragon fruit juice, verifying this thermally stable garnet deep-red phosphor exhibited huge potential in plant cultivation.

Suppressed Concentration Quenching Brightens Short-Wave Infrared Emitters.

The brightness of doped luminescent materials is usually limited by the ubiquitous concentration quenching phenomenon resulting in an intractable tradeoff between internal quantum efficiency and excitation efficiency. Here, an intrinsic suppression of concentration quenching in sensitized luminescent systems, by exploiting the competitive relationship between light emitters and quenchers in trapping excitation energies from sensitizers, is reported. Although Cr3+ sensitizers and trivalent lanthanide (Ln3+ , Ln = Yb, Nd, and Er) emitters themselves are highly susceptible to concentration quenching, the unprecedentedly high-brightness luminescence of Cr3+ -Ln3+ systems is demonstrated in the short-wave infrared (SWIR) range employing high concentrations of Cr3+ , whereby a record photoelectric efficiency of 23% is achieved for SWIR phosphor-converted light-emitting diodes, which is about twice as high as those previously reported. The results underscore the beneficial role of emitters in terminating excitation energies, opening up a new dimension for developing efficient sensitized luminescent materials.

Zero thermal quenching and suppressed concentration quenching in a highly efficient structure‐confined fluoride near-infrared phosphor

The development of thermally stable and efficient broadband near-infrared (NIR) phosphors suffers from severe hindrance. Herein, a unique anti-fluorescence quenching is realized in a novel Cs2NaGaF6: Cr3+ NIR fluoride phosphor with a strategy of integrating the structural confinement effect with weak electron-phonon coupling effect. Upon blue light excitation, this phosphor exhibits a wide emission band with a peak wavelength of ∼789 nm and a full width at half maximum (FWHM) of 117 nm. Thanks to the structural confinement effect, a large quenching content of 20 mol% and a high internal quantum efficiency (IQE) of 87.4% are achieved, showing a suppressed concentration quenching behavior. Significantly, Cs2NaGaF6: 0.20Cr3+ phosphor possesses an abnormal zero thermal quenching, which could be related with the weaker electron-phonon coupling effect. The emission intensity of Cs2NaGaF6: 0.20Cr3+ at 423 K can maintain up to 101.96% of that at 298 K. A fabricated NIR phosphor-converted light-emitting diode (pc-LED) exhibits an output power of 57.71 mW and a photoelectric conversion efficiency as high as 19.24% at 100 mA. Finally, utilizing a high-power NIR LED as the illuminant for traffic surveillance, significant information can be captured even in low-visibility environments. As a result, Cs2NaGaF6: Cr3+ possesses tremendous prospects in high-power NIR LEDs.

Efficient near-infrared luminescence in LiInO2:Cr3+ phosphor for light-emitting-diodes

Broadband near-infrared (NIR) spectroscopy produced by efficient and miniaturized NIR phosphor-converted light-emitting diodes (pc-LEDs) has been utilized in portable and mobile devices to realize a variety of applications such as bio-imaging, food-quality analysis, and night-vision. However, developing blue-light excitable NIR phosphor material with efficient emission around 900 nm remains a great challenge. Herein, an efficient LiInO2:Cr3+ phosphors with an emission peak of 897 nm and a full width at half maximum (FWHM) of 129 nm excited by 468 nm were successfully synthesized under a protective atmosphere. The optimized sample shows a particularly high absorption efficiency (AE = 57.8%) and an excellent internal quantum efficiency (IQE = 42.4%), resulting in a relatively high external quantum efficiency (EQE = 24.5%) compared to the developed phosphors with emission peak around 900 nm. Disappointingly, the emission intensity at 373 K of this material retains only 29.6% of that at room temperature, and the strong electron-phonon-coupling (EPC) effect should be responsible for the relatively poor thermal stability. Thus, this work demonstrated an attempt to develop efficient broadband NIR phosphors for spectroscopy applications, and also performed a comprehensive investigation to understand this material.

Achieving an ultra-high absorption efficiency in a monoclinic LiAlP2O7:Cr3+ near-infrared phosphor

Near-infrared phosphor-converted light-emitting diode (NIR pc-LED) is becoming a smart light source for portable multifunctional devices, utilizing in fields like bio-imaging, night-vision, and food-quality analysis. However, developing broadband, inexpensive, and efficient NIR phosphors are still in great challenges. Herein, we report a phosphate LiAlP2O7:Cr3+ phosphor by choosing highly distorted and inexpensive octahedral Al3+-containing compound as host. This material generates a broadband NIR emission with peak located at 844 nm and a full width at half maximum (FWHM) of 163 nm under 450 nm excitation. Amazingly, the absorption efficiency (AE) was measured to be as high as 64%, being higher than most of Cr3+-activated polycrystalline materials. Unfortunately, the internal quantum efficiency (IQE) was only 26.7%, and the emission intensity at 373 K kept only 56% of that at room temperature. The detailed reasons for these undesired properties are systematically investigated. Moreover, a prototype NIR pc-LED fabricated by using this material combining with 450 nm LED chip demonstrates a NIR output power of 9.7 mW and NIR photoelectronic conversion efficiency of 3.3% under 100 mA driving current, indicating the feasibility of this material to be applied in NIR pc-LEDs.

Achieving Broadband NIR-I to NIR-II Emission in an All-Inorganic Halide Double-Perovskite Cs2NaYCl6:Cr3+ Phosphor for Night Vision Imaging.

Near-infrared phosphor-converted light-emitting diodes (NIR pc-LEDs) offer numerous advantages, including compact size, tunable emission spectra, energy efficiency, and high integration potential. These features make them highly promising for various applications, such as night vision monitoring, food safety inspection, biomedical imaging, and theragnostics. All-inorganic halide double-perovskite materials, known for their large absorption cross section, excellent defect tolerance, and long carrier diffusion radius, serve as unique matrices for constructing near-infrared fluorescent materials. In this study, we successfully prepared the all-inorganic metal halide double-perovskite Cs2NaYCl6:Cr3+ using a grinding-sintering method. A small fraction of the [YCl6] octahedra within the host material's lattice was substituted with Cr3+ ions, resulting in the creation of the Cs2NaYCl6:Cr3+ phosphor. When excited with λ = 310 nm UV light, the phosphor exhibited a broad emission range spanning from 800 to 1400 nm, covering the NIR-I and NIR-II regions. It had a broad bandwidth emission of 185 nm and achieved a fluorescence quantum yield of 20.2%. The unique broadband emission of the phosphor originates from the weak crystal field environment provided by the Cs2NaYCl6 host matrix, which enhances the luminescence properties of the Cr3+ ions. To create NIR pc-LEDs, the phosphor was encapsulated onto a commercially available UV LED chip operating at 310 nm. The potential application of these NIR pc-LEDs in night vision imaging was successfully validated.

Ultra-broadband near-infrared phosphor La2CaTaxZr(1-x)O6:Cr3+ for phosphor-converted light-emitting diodes

Broadband near-infrared (NIR) phosphors are key materials for the preparation of NIR phosphor-converted light-emitting diodes (pc-LEDs). The wider coverage of the NIR spectrum means that more substances can be detected by NIR light and more applications are possible. However, ultra-broadband NIR phosphors with the full-width at half maximum (FWHM) greater than 200 nm still face challenges in terms of thermal stability as well as internal quantum efficiency (IQE). In this work, a series of La2CaTaxZr(1-x)O6(LCTZO): Cr3+ phosphors was successfully synthesized by the high-temperature solid-phase method. The non-equivalent substitution strategy of Ta5+ in place of Zr4+ effectively modulates the crystal field environment of Cr3+ and reduces the number of defects, thus modulating the luminescence properties of the phosphor. Under the 471 nm excitation, the spectrum of La2CaTa0.3Zr0.7O6: 2 % Cr3+ can cover the 700–1400 nm band (FWHM = 201 nm) with IQE of 42.6 %, and the emission intensity can be maintained at 373 K at 74 % of that at room temperature. The prepared NIR pc-LED with ultra-wide spectral coverage shows better potential applications in the fields of night vision and biological tissue penetration.

Creating an efficient and tunable near-infrared emission by using [Mg2+-Sn4+] chemical unit co-substitution in Ga2O3:Cr3+ phosphor

NIR phosphor-converted light-emitting diode (NIR pc-LED) has attracted many attentions for its promising applications in biomedical imaging, night vision, spectroscopy, and many other fields, while the discovery of broadband NIR phosphors with high external quantum efficiency (EQE) remains a challenge. Herein, a series of efficient and tunable broadband NIR-emitting Ga1.97-2xMgxSnxO3:0.03Cr3+ phosphors were synthesized via [Mg2+-Sn4+] substituting [Ga3+-Ga3+] in Ga2O3:Cr3+ system. As increase of substituting ratio x, a significant red-shift in the emission spectra from 726 to 793 nm with a full width at half maximum (FWHM) extended from 121 to 167 nm can be observed. All the samples have an EQE above 40% under 450 nm excitation; and the excitation peak in the blue light region remains unchanged, enabling these materials to be efficiently excited by blue LEDs. Finally, a NIR pc-LED device was fabricated by integrating the optimized Ga1.77Mg0·1Sn0·1O3:0.03Cr3+ phosphor on a blue LED chip, which exhibits a high NIR output power of 33.41 mW with a photoelectric conversion efficiency of 12.01% under a drive current of 100 mA. These results indicate that the obtained NIR phosphors may have potential in NIR pc-LEDs applications.