Broadband Near-infrared Emission Research Articles

Broadband near-infrared emission in barium gallo-germanate glasses co-doped with bismuth, chromium and erbium ions

This work presents barium gallo-germanate glasses co-doped with Bi+/Er3+ and Cr3+/Er3+ ions for NIR luminescence. The addition of Al2O3 content in the glass matrix made it possible to obtain luminescence corresponding to the 3P1→3P0 transition of Bi+ ions. Co-doping with the Bi+/Er3+ system resulted in a broad luminescence spectrum of 1.0-1.6 µm and Cr3+/Er3+ co-doping in selected glass matrix resulted in luminescence in 0.9-1.6 µm band. However, the luminescence of the Cr3+ ions is much lower than that of Er3+ ions. Full Text: PDF References T. Suzuki, G.S. Murugan, and Y. Ohishi, 'Optical properties of transparent Li2O-Ga2O3-SiO2 glass-ceramics embedding Ni-doped nanocrystals', Appl. Phys. Lett., 86(13), 131903 (2005). CrossRef N.V. Golubev et al., 'Pre-crystallization heat treatment and infrared luminescence enhancement in Ni2+-doped transparent glass-ceramics', J. Non-Cryst. Solids, 515, 42 (2019) CrossRef Z. Xu, W. Feng, T. Chen, X. Liu, and J. Qiu, 'Tuning optical properties in PbSe quantum dot-doped borosilicate glass fiber by modulation of network topology', Opt. Laser Technol., 158, 108910 (2023). CrossRef M.A. Hughes, T. Suzuki, and Y. Ohishi, 'Spectroscopy of bismuth-doped lead-aluminum-germanate glass and yttrium-aluminum-silicate glass', J. Non-Cryst. Solids, 356(44), 2302 (2010). CrossRef J. Song, Z. Zhou, B. Zhong, M. Zhang, J. Huang, and L. Han, 'Ultra-broadband near-infrared Cr3+-doped multi-phase glass-ceramics realized by the selective enrichment strategy for near-infrared spectroscopy applications', J. Alloys Compd., 968, 172126 (2023). CrossRef M.A.U. Martines, M.R. Davolos, M.J. Júnior, D.F. de Souza, and L.A.O. Nunes, 'Cr3+ and Cr4+ luminescence in glass ceramic silica', J. Lumin., 128(11), 1787 (2008). CrossRef S. Zhou, H. Dong, H. Zeng, J. Hao, J. Chen, and J. Qiu, 'Infrared luminescence and amplification properties of Bi-doped GeO2−Ga2O3−Al2O3 glasses', J. Appl. Phys., 103(10), 103532 (2008). CrossRef T. Suzuki and Y. Ohishi, 'Ultrabroadband near-infrared emission from Bi-doped Li2O-Al2O3-SiO2 glass', Appl. Phys. Lett., 88(19), 191912 (2006). CrossRef T. Minh Hau et al., 'Super broadband near-infrared emission and energy transfer in Bi-Er co-doped lanthanum aluminosilicate glasses', Opt. Mater., 35(3), 487 (2013). CrossRef H.K. Dan et al., 'Effects of Y3+on the enhancement NIR emission of Bi+-Er3+ co-doped in transparent silicate glass-ceramics for Erbium-doped fiber amplifier (EDFA)', J. Lumin., 219, 116942 (2020). CrossRef E.M. Dianov, 'Bismuth-doped optical fibers: a challenging active medium for near-IR lasers and optical amplifiers', Light Sci. Appl., 1(5) (2012). CrossRef L. Wang, L. Tan, Y. Yue, M. Peng, and J. Qiu, 'Efficient Enhancement of Bismuth NIR Luminescence by Aluminum and Its Mechanism in Bismuth‐Doped Germanate Laser Glass', J. Am. Ceram. Soc., 99(6), 2071 (2016). CrossRef Z. Jiang et al., 'Effects of Al2O3 composition on the near-infrared emission in Bi-doped and Yb-Bi-codoped silicate glasses for broadband optical amplification', J. Non-Cryst. Solids, 383, 196 (2014). CrossRef

Strategies to Realize Efficient and Stable Broadband NIR Emission in Germinate Oxides

AbstractPhosphor‐converted light‐emitting diodes (pc‐LEDs) are efficient and cost‐effective ultrabroadband light sources for miniaturizing various optical systems, but they exhibit poor optical performance due to the lack of efficient near‐infrared (NIR) phosphors with a wide spectral coverage of 700−1100 nm. Although germanate oxides are a promising class of host materials for Cr3+ to generate broadband NIR light, the preferred formation of [CrO4]4− and the high vapor pressure of Ge element cause these Cr3+ activated phosphors to suffer from low internal quantum efficiency (IQE) and poor thermal stability. Here, highly efficient (IQE > 90%) and thermally stable broadband NIR emission of Cr3+ in the germinate garnet Ca2LuMgScGe3O12 (CLMSG) are obtained by exploiting a two‐step sintering method to achieve full reduction of Cr4+ to Cr3+. Further, efficient energy transfer from Cr3+ to Yb3+ is leveraged to significantly improve the emission intensity of CLMSG:Cr3+ in the shortwave infrared range of 900−1100 nm. Finally, an ultrabroadband NIR pc‐LED with a high NIR conversion efficiency (21.5%@10 mA) and high NIR power (116.4 mW@350 mA) is demonstrated to verify the strong capability of CLMSG:Cr3+, Yb3+ in blue‐to‐NIR light conversion. The results open up new ways to realize efficient ultrabroadband NIR‐emitting materials.

Efficient Near‐Infrared Emitting Halide Scintillators with Mitigating External Light Crosstalk for Portable X‐Ray Imaging

AbstractPortable X‐ray imaging technology plays a crucial role in enabling prompt diagnosis and treatment outdoors. Nevertheless, the persistent challenge of external optical signal crosstalk poses a significant bottleneck to its advancement. Herein, a solution utilizing near‐infrared (NIR) light to effectively mitigate optical crosstalk is proposed, thereby demonstrating the feasibility of portable X‐ray imaging even under ambient light. A series of rare earth ions doped Cs2AgxNa1‐xInyBi1‐yCl6 halide scintillators is reported, which possess bright broadband visible and NIR emissions. Taking Cs2Ag0.6Na0.4In0.95Bi0.05Cl6: 5%Tm as an example, it shows decent thermal quenching resistance, high PLQY up to 76.3%, and compelling light yield up to 33500 photons MeV−1. The highly efficient NIR emission is attributed to the energy transfer from the optimized host to lanthanide ions. A flexible scintillation film is prepared by mixing poly(dimethyl‐siloxane) with Cs2Ag0.6Na0.4In0.95Bi0.05Cl6: 5%Tm powder, realizing a low X‐ray detection limit of 55.2 nGyair/s and a high spatial resolution of 11.2 lp mm−1. Due to the efficient NIR emission, the scintillation film enables clear X‐ray imaging under bright LED illumination with the simple addition of filters, avoiding the necessity of a complex imaging apparatus. This work sheds light on NIR emissive scintillator for rapid outdoor response and portable X‐ray imaging.

Trivalent chromium ion doping garnet phosphor with broadband near-infrared emission for night-vision applications

Trivalent chromium ion doping garnet phosphor with broadband near-infrared emission for night-vision applications

Antimony doping in A2ZnCl4 (A= Rb, Cs) metal halides enabling tunable near-infrared emission

Lead-free metal halides with stable and tunable emission have shown great promise for broad application prospects in the visible light range. However, it remains a fundamental challenge to realize tunable near-infrared (NIR) luminescence in these metal halide materials. Herein, a cation regulation strategy in zero-dimension organic metal halides A2ZnCl4:Sb3+ (A = Rb, Cs) to achieve tunable NIR luminescence is reported. The prepared A2ZnCl4:Sb3+ (A = Rb, Cs) halides exhibited efficient broadband NIR emission, which originates from self-trapped excitons of the [SbCl4]− polyhedron. Based on the regulation of cation, the [SbCl4]− tetrahedral distortion capacity changes, exciton–phonon coupling is enhanced, leading to a red shift of the emission wavelength. The results provide inspiration for the regulation of the self-trapped excitons luminescence of halides and demonstrate potential as a non-visible light source for night vision.

Broadband NIR emission from Te doped silicate glass as gc-LED light source for biological detection

Near-infrared (NIR) glass-converted light-emitting diodes (gc-LEDs) are newly emergent broadband light sources for miniaturizing optical systems like spectrometers. While lots of effort has been spent on materials doped with rare-earth and transition-metal ions, the achievement of these materials with broadband NIR emission and desired wavelength region remains a long-standing challenge, especially operating in the spectral region between 700 and 1100 nm. Herein, a broadband NIR LEDs based on Te cluster-doped silicate glass is developed. Through adjustment of melting atmosphere and network topology of the glass matrix, active NIR Te cluster centers can be generated and stabilized in silicate glass and show a broad emission at 980 nm with a full width at half maximum (FWHM) of 300 nm under blue light excitation. The photoluminescence of the glass matches well with the absorption of several primary chemical bonds in food and biological tissue. In demonstration experiments, the NIR absorption of different biological tissue by NIR light from our glass is measured, suggesting that the super-broad NIR luminescence of Te-doped silicate glass has potential applications as light sources for nondestructive analysis.

Net gain in C+L band from LED pumped broadband emission in Er3+-doped oxyhalide tellurite glass

Expanding gain bandwidth into the L-band for erbium-doped fiber amplifiers (EDFAs) is a crucial strategy to overcome limitations in prevalent C-band focused commercial silica-based EDFAs, significantly boosting optical network transmission capacity. Herein, we synthesized Er3+-doped broadband near-infrared emission tellurite glasses utilizing the melt quenching process, systematically exploring the impact of ZnCl2 on the glass structure and optical properties. The 82TeO2–3Nb2O5–15ZnCl2–3Er2O3 (TNZ15) glass emerged as a standout candidate for broadband amplifiers around wavelength at 1.55 μm. With escalating ZnCl2 concentration, a discernible red shift in the emission peak wave lines was observed, accompanied by an expansion of the full width at half maximum (FWHM) from 98 nm to 106 nm. Noteworthy characteristics of all samples included exceptional thermal stability and elevated near-infrared (NIR) transmittance. Application of the Judd-Ofelt (J-O) theory facilitated the calculation of J-O parameter intensity, providing deeper insights into the optical behavior of the materials. Finally, the evaluation of TNZ15 planar optical waveguides, employing the vertical top pumping mode of two 980 nm LEDs, encompassed both the C-band (1530–1565 nm) and the L-band (1565–1625 nm). The results underscore the potential of TNZ15 glass as a promising gain material for broadband optical amplifiers and lasers, offering valuable insights into the development of next-generation optical amplification technologies.

Directly Identifying Multiple Cr3+ Emitting Centers for Broad Near‐Infrared Emission in an Efficient and Near‐Zero Thermal Quenching Garnet‐Type Phosphor

AbstractCr3+ doped garnet‐type (A3B2C3O12) near‐infrared (NIR) phosphors is a desirable research hotspot due to their prospective night vision, bioimaging, and plant growth utilizations. Meanwhile, the origin of multisite broad emission is yet a controversial topic. To resolve the trouble, verifying accurately the multiple Cr3+ occupancy sites is a key. Furthermore, it is an urgent need for improving the external quantum efficiency and luminescent thermostability. Herein, in Y3Sc2Al3O12 (YSAO), advanced electron microscopy technique is employed to directly confirm that the obtained broadband NIR emission originates from Cr3+ in [ScO6] octahedral and [YO8] dodecahedral sites. The optimal YSAO:5%Cr3+ sample exhibits high quantum efficiency (IQE/EQE = 74/31%) and near‐zero thermal quenching (97%@423 K and 92%@473 K). The theoretical calculations and experimental proofs reveal that YSAO possesses high structural rigidity and wide bandgap, which is responsible for the extremely thermostable luminescence. The high‐power YSAO:5%Cr3+‐converted NIR LED device shows promising multifunctional applications. This work not only provides an efficient NIR broadband phosphor with near‐zero thermal quenching, but also provides an effective determination method for the multiple emitting centers of phosphor materials.

Emerging Fe3+ Doped Broad NIR‐Emitting Phosphor Ca2.5Hf2.5(Ga, Al)3O12: Fe3+ for LWUV Pumped NIR LED

AbstractFe3+ is a promising dopant for designing near‐infrared (NIR) phosphors due to its broadband emitting, non‐toxic, and inexpensive properties. However, the 4E (4D) and 4E + 4A1 (4G) levels of Fe3+ ions are independent of the crystal‐field parameter, and the spectral regulation has become a huge challenge. Herein, a broadband NIR‐emitting phosphor Ca2.5Hf2.5(Ga, Al)3O12: Fe3+ is successfully developed toward long‐wave ultraviolet (LWUV) light‐pumped NIR phosphor‐converted LED (pc‐LED). Significantly, the excited transition reverse of Ca2.5Hf2.5Ga3O12: Fe3+ can be realized by simply adjusting Fe3+ concentration, which results in the largely enhanced excitation around 410 nm and matches well with the commercial LWUV LED. Moreover, Ca2.5Hf2.5Ga3O12: Fe3+ can exhibit a broadband NIR emission centered at 770 nm with optimized doping content at 0.01 mol%, which are demonstrated to ascribe to Fe3+ occupying both octahedral Hf 4+ and tetrahedral Ga3+ sites. Further, a simple cation modulation strategy is proposed to successfully break the lattice symmetry around Fe3+ ions and largely enhance the NIR‐emission intensity to 200% as much as before. Finally, a NIR pc‐LED is fabricated by employing Ca2.5Hf2.5Ga3O12: Fe3+, Al3+ coating on a 410 nm LED chip, which shows great potential in non‐destructive inspection applications.

Tunable broadband near-infrared emission from environmentally friendly Fe3+-activated lead-free perovskites for spectral analysis and rapid nighttime recognition

With the increasing role of near-infrared (NIR) light sources in many fields such as food and industry, NIR emitting phosphors have flourished in recent years. In addition to the widely reported Cr3+-activated NIR phosphors, environmentally friendly Fe3+ can also produce tunable broadband NIR spectra, which are expected to enrich the next generation of intelligent NIR light sources. In this work, a series of Fe3+-activated perovskite-type Sr2ScSbO6 (SSSO) NIR phosphors were successfully prepared and an emission wavelength of 900 nm with a full width at half maximum (FWHM) of 110 nm was obtained. Through the crystal field engineering strategy, the lattice site of Sr2+ was completely replaced by Ba2+ and Ca2+ to obtain Ba2ScSbO6 (BSSO) and Ca2ScSbO6 (CSSO), and the emission peak was continuously adjusted from 840 nm to 950 nm. When the temperature increased from 300 K to 400 K, BSSO:Fe3+, SSSO:Fe3+ and CSSO:Fe3+ could maintain 69 %, 82 % and 67 % of the original luminescence intensity, respectively. The opposite crystal field dependence between Fe3+ and Cr3+ was shown in double-layer perovskite-type antimonate materials, which could guide us to develop Fe3+-activated long-wavelength emission NIR phosphors. Benefiting from the long-wavelength emission of BSSO:Fe3+, SSSO:Fe3+, and CSSO:Fe3+, their application potential in the field of spectral analysis and rapid nighttime recognition were successfully demonstrated.

Thermally Stable NIR Emission from Disordered Ba5La3MgAl3O15:Cr3+ with Peak Wavelength Beyond 900 nm

AbstractBroadband near‐infrared (NIR) emissions in the long wavelength region with simultaneous high efficiency and thermal stability are desirable for NIR phosphor‐converted light‐emitting diodes (NIR pc‐LEDs) light sources. Herein, a novel broadband NIR‐emitting phosphor is reported, Ba5La3MgAl3O15:Cr3+ (BLMAO:Cr3+), which exhibits a NIR emission band spanning 700–1300 nm with maximum peak wavelength (λmax) at 925 nm and full width at half maximum of 160 nm. The optimized phosphor achieves an internal quantum efficiency of 66%, and the integrated emission intensity at 423 K remains 61% of that at room temperature, which surpasses most Cr3+‐activated phosphors emitting in the long‐wavelength NIR region (λmax > 900 nm). The NIR luminescence properties are elucidated on the basis of density functional calculations of the multiple Cr3+ local structures as generated by the Ba/La occupation disorder in the host material. The applications of the NIR phosphor in pc‐LED devices are demonstrated, showing potential in night‐vision and nondestructive examination. The results indicate that BLMAO:Cr3+ is a promising phosphor with highly efficient and thermally stable broadband NIR emission for NIR LED light sources.

Realizing efficient broadband near-infrared emission and multimode photoluminescence switching via coordination structure modulation in Sb3+-doped 0D organic metal chlorides.

Recently, organic Sb(III)-based metal halides have achieved significant results in the visible light region due to their efficient emission. However, realizing efficient broadband near-infrared (NIR) emission in such materials is a great challenge. Herein, we developed three different NIR emitters via a coordination structure modulation strategy in Sb3+-doped zero-dimensional organic metal chlorides of (C20H20P)2MnCl4, (C20H20P)2ZnCl4, and (C20H20P)2CdCl4 with tetrahedral structure. More specifically, after the dopant Sb3+ is inserted into the host lattice, the coordination structures of Sb3+ ions can change from [SbCl5]2- square-pyramidal configuration to [SbCl4]- clusters, which will bring a larger lattice distortion degree to the excited state compared to the ground state, resulting in a larger Stokes shift. Thus, efficient NIR emission with near-unity photoluminescence quantum yield (PLQY) can be obtained in Sb3+-doped compounds under 365 nm excitation. Moreover, Sb3+-doped NIR emitters also show remarkable stabilities, which prompts us to fabricate NIR phosphor conversion light-emitting diodes (pc-LEDs) and demonstrate their application in night vision. More interestingly, the Sb3+-doped (C20H20P)2MnCl4 shows tunable emission characteristics, which can be tuned from green to greenish-yellow, orange, red, and NIR emission under different external stimuli, and thus we can demonstrate the applications of this compound in quintuple-mode fluorescence anti-counterfeiting and information encryption.

Thermal stability and quantum efficiency improvement of Cr3+-activated garnet phosphors via regulating A/B sites for near-infrared LED applications.

The discovery of phosphors with highly efficient broadband near-infrared emission is urgent for constructing NIR sources for various applications. Herein, we synthesized a series of near-infrared emitting garnet-type (A3B2C3O12) Lu2-xCaAl3.99Cr0.01SiO12:xGd/La and Lu2CaAl3.99-yCr0.01SiO12:ySc/Ga phosphors and systematically investigated the effect of A/B-site substitution on the crystal structure and luminescence properties. Structural and optical analyses revealed that the A/B-site substitution weakened the crystal field strength, further enhancing the broadband emission of the allowed 4T2 → 4A2transition and diminishing the narrow-peak emission of the forbidden 2E → 4A2 transition. As expected, NIR phosphors, exemplified by Lu1.7CaAl3.99Cr0.01SiO12:0.3Gd and Lu2CaAl3.49Cr0.01SiO12:0.5Sc, showed outstanding thermal stabilities at 423 K (150 °C) registering values of 103.02% and 94.91%, with high quantum efficiencies of 80.48% and 85.01%, respectively. In addition, pc-LEDs with broadband NIR output and good optoelectronic properties have been realized, demonstrating the great potential of broadband NIR pc-LEDs for applications. This work not only provides a series of high-efficiency phosphors for NIR pc-LED applications, but also provides a systematic idea and an efficient method to improve the luminescence performance of garnet-type phosphors.

Origin of the Cr3+ concentration-dependent broadband near-infrared emission in Sc2Si2O7.

The challenge of developing phosphors with tailored near-infrared (NIR) emission ranges to meet the diverse demands of various applications is a paramount concern in the contemporary realm of NIR phosphor research. A strong dependence of NIR emission on Cr3+ concentration has been demonstrated in Sc2-xSi2O7:xCr3+, which exhibits an NIR emission band at 840 nm for low Cr3+ doping concentrations (x = 0.001-0.01) and an anomalous NIR emission band at 1300 nm for high Cr3+ doping concentrations (x = 0.01-0.10). Careful investigation of the crystal structure, excitation and emission spectra, and luminescence decay curves indicates that the two NIR emissions can be attributed to the isolated Cr3+ ions and the Cr3+-Cr3+ pairs, respectively. The strong interaction of exchange-coupled Cr3+-Cr3+ pairs is supported by temperature-dependent emission spectra, luminescence decay curves and electron paramagnetic resonance (EPR) measurements. This work provides a new insight into the study of Cr3+-Cr3+ pairs for broadband NIR emission.

Novel broadband near-infrared emission in Cr3+-activated Sr3ZnGe5O14 phosphor for an electroluminescent stable pc-LED

Near-infrared (NIR) phosphor-converted light-emitting diodes (pc-LEDs) have exhibited tremendous potential in spectroscopic technology, promoting the demand of developing novel NIR materials with excellent properties. In this paper, a series of germanate based NIR phosphors Sr3ZnGe5O14: xCr3+ (0 ≤ x ≤ 0.05) were synthesized by high temperature solid state reaction. The X-ray diffraction (XRD), scanning electron microscopy (SEM), Ultraviolet diffuse reflection, photoluminescence spectra and PL decay were measured to analyze the crystal structure, morphology properties and elements composition, PL emission properties and lifetimes of these NIR phosphors. Results demonstrated that phosphors Sr3ZnGe5O14: xCr3+ (0 ≤ x ≤ 0.05) crystallized in a trigonal with a space group of P321(150) with a broad band gap (Eg) of 4.70–4.59 eV. Sample Sr3ZnGe5O14: 0.03Cr3+ with the best PL emission properties showed a good thermal stability with the PL emission intensity remains 69 % of its initial value at 420 K. It's worth noting that the NIR device based on Sr3ZnGe5O14: 0.03Cr3+ displays an impressive electroluminescent emission stability, for example, the electroluminescent emission intensity is still about 92.3 % of its initial value when the NIR pc-LED light up for 18 h. These research results provided an important guidance for developing novel Cr3+ doped germanate based NIR phosphors with excellent thermal and electroluminescent emission stability.

Lattice dynamics and electron-phonon interaction in lead-free perovskite-inspired materials with unexpected broadband NIR emission

Air-stable and Sb/Bi-based perovskite-inspired materials are attractive substitutes for their Pb-based counterparts in optoelectronic applications. The attractive low-energy broadband luminescence phenomenon has been hotly investigated. However, understanding the physical mechanism behind it is still at an early stage. Herein, high-quality Cs3SbBiI9 crystals were synthesized and accompanied with reference Cs3Sb2I9 and Cs3Bi2I9. The reformed energy band structure can be confirmed by experiment and density functional theory (DFT) calculation. Unexpected broadband near-infrared (NIR) emission has been discovered and is explained by the nonexclusive self-trapped exciton (STE) and defect-induced emission models. Temperature- dependent Raman and PL spectra confirm the diminished Stokes shift and electron-phonon coupling effect in Sb-Bi alloyed crystals driven by the local broken-symmetry. This result provides a basic physical explanation for the controversial photo-physical process in defect-type Bi/Sb alloyed perovskite-inspired family and it will inspire a feasible way to design novel Pb-free perovskites.

Achieving Nearly Quantitative (∼100%) IQE and 42.3% EQE Across NIR‐I and NIR‐II Regions with Cr3+‐doped Cs2NaScCl6 under 300 nm Excitation

AbstractLead‐free rare‐earth‐based perovskites have received widespread attention for their unique optical properties, although achieving efficient broadband near‐infrared (NIR) emission with these materials remains a challenge. Here the synthesis of a rare earth‐based double perovskite (Cs2NaScCl6) by an improved solid phase method is reported. The doping of Cr3+ led to the formation of [CrCl6]3− octahedron, which exhibited a broadband NIR emission peaked at 950 nm and a half‐peak width of 162 nm. It is worth noting that with the same actual Cr3+ content, the luminous intensity of Cs2NaScCl6 synthesized by the improved solid‐phase synthesis is four times higher than the product synthesized by the hydrothermal method. an efficient Cl−‐Cr3+ charge transfer sensitization facilitated by localized electrons in [CrCl6]3− octahedron is the mechanism for the strong NIR emission of Cr3+ is proposed. Calculations based on density functional theory and Bader charge analysis support the notion that electrons in [CrCl6]3− octahedrons are strongly localized in Cs2NaScCl6:Cr3+, which is conducive to the Cl−–Cr3+ charge transfer process, resulting the internal quantum efficiency of 100% and external quantum yield as 42.3%. The highly efficient ultra‐broadband NIR emission with excellent stability offers many opportunities for applications in the field of NIR night vision and bio‐imaging.

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.

Multi-site occupancy high-efficient Mg2LaTaO6:Cr3+ phosphor for application in broadband NIR pc-LEDs

As a new generation of near-infrared (NIR) light source, phosphor-converted NIR light emitting diodes (NIR pc-LEDs) have broad application prospects in biological tissue imaging, night vision and chemical composition analysis. However, most NIR emitting phosphors are still limited to short-wavelength, narrow-band emission and low efficiency. Here, based on the multi-site occupation strategy, the NIR phosphor Mg2LaTaO6:Cr3+ (MLT:Cr3+) achieves an efficient broadband NIR emission with the full width at half maximum (FWHM) of 203 nm in the range of 600–1300 nm under the excitation of 468 nm blue light. The phosphor MLT:0.01Cr3+ not only exhibits an excellent internal quantum efficiency (IQE) of 85.6 %, but also has good thermal stability and remains about 64.2 % photoluminescence (PL) intensity of room temperature at 423 K. Furthermore, the MLT:0.01Cr3+ phosphor was combined with a blue LED chip to fabricate the NIR pc-LED device, and its potential applications were successfully realized in information encryption, bioimaging and the qualitative or quantitative analysis of mixture of ethanol and water.

Broadband near-infrared emission in Bi-Er co-doped germanosilicate glasses

Broadband gain materials have garnered considerable attention on account of their practical utilization in optical amplifiers. Among them, Bi-doped glasses depict tremendous potential due to their unique broadband emission. In this paper, we report a series of Bi-Er co-doped germanosilicate glasses exhibiting broadband and tunable near-infrared (NIR) emission. By the strategy of Bi-Er co-doping, the luminescence bandwidth is effectively expanded in two ways: co-excitation and energy transfer between two active centers. Importantly, broadband luminescence covering O-E-S-C-L bands with full width at half maximum (FWHM) more than 320 nm is realized via the way of energy transfer. In addition, ultrabroadband emission covering C-L-U bands with FWHM of ∼370 nm and relatively flat emission of ∼170 nm is achieved via the way of co-excitation. Furthermore, the mechanism of energy transfer is discussed. These results indicate that Bi-Er co-doped germanosilicate glasses are the promising candidates in the field of optical fiber amplifiers.