Broadband Near-infrared Luminescence Research Articles

Fe3+-doped broadband near-infrared phosphor with high quantum efficiency toward multifunctional pc-LEDs applications

A broadband near-infrared (NIR) luminescence that is comparable to chromium ions activated materials is fulfilled in Li3Sc2(PO4)3:Fe3+ phosphor, which is highly desired for environmental and biomedical applications due to the non-toxicity of Fe3+ ions. Structural and spectral analysis reveal that the broadband NIR emission peaked at 805 nm with a full width at half-maximum of 130 nm is derived from the non-selective two-site occupation of Fe3+ in the Sc3+ sites. A high internal/external quantum efficiency of 53 %/38.7 % is achieved via relaxing the selection rule for the forbidden 4T1(4G) → 6A1(6S) transitions of Fe3+ by larger lattice distortion. The influence of Fe3+ concentration and environment temperature on the broadband NIR luminescence properties of the as-prepared phosphors are also investigated. Finally, a NIR pc-LED prototype is fabricated and its electro-optical performance has guaranteed the applications in non-destructive detection and night vision. All the results have validated Li3Sc2(PO4)3 as a novel matrix system for access to highly efficient broadband NIR Fe3+-doping phosphor materials.

Broadband near-infrared luminescence in spinel Zn4InSbO8:Cr3+ phosphor for light-emitting diodes application

Near-infrared (NIR) phosphor-converted light-emitting diode (pc-LED) has been considered as a smart light source for NIR spectroscopy applications, leading to a growing need of developing broadband NIR phosphors. Herein, a new composition Zn4InSbO8:Cr3+ phosphor with classical spinel-type structure was synthesized, which emits a broadband NIR light covering a region of 700–1200 nm with a peak centered at 860 nm under 460 nm excitation. The sample with an optimized Cr3+ concentration possesses a full width at half maximum (FWHM) as broad as 180 nm mainly ascribing to multi crystallographic sites occupation. Moreover, the absorption efficiency (AE), internal quantum efficiency (IQE) and thermal stability were investigated to estimate the practicality. The relatively long-wavelength NIR emission produced by Cr3+ in this spinel make it suitable for multi-functional applications. Finally, the asprepared phosphor combining with blue LED chip is used to fabricate a prototype NIR pc-LED, giving a NIR output power of 4.8 mW under 100 mA forward bias current with a photoelectric efficiency of 1.63%, showcasing the potential use of this material as a luminescent converter in the application of NIR pc-LEDs.

Unraveling Broadband Near-Infrared Luminescence in Cr3+-Doped Ca3Y2Ge3O12 Garnets: Insights from First-Principles Analysis.

In this study, we conducted an extensive investigation into broadband near-infrared luminescence of Cr3+-doped Ca3Y2Ge3O12 garnet, employing first-principles calculations within the density functional theory framework. Our initial focus involved determining the site occupancy of Cr3+ activator ions, which revealed a pronounced preference for the Y3+ sites over the Ca2+ and Ge4+ sites, as evidenced by the formation energy calculations. Subsequently, the geometric structures of the excited states 2E and 4T2, along with their optical transition energies relative to the ground state 4A2 in Ca3Y2Ge3O12:Cr3+, were successfully modeled using the ΔSCF method. Calculation convergence challenges were effectively addressed through the proposed fractional particle occupancy schemes. The constructed host-referred binding energy diagram provided a clear description of the luminescence kinetics process in the garnet, which explained the high quantum efficiency of emission. Furthermore, the accurate prediction of thermal excitation energy yielded insights into the thermal stability of the compound, as illustrated in the calculated configuration coordinate diagram. More importantly, all calculated data were consistently aligned with the experimental results. This research not only advances our understanding of the intricate interplay between geometric and electronic structures, optical properties, and thermal behavior in Cr3+-doped garnets but also lays the groundwork for future breakthroughs in the high-throughput design and optimization of luminescent performance and thermal stability in Cr3+-doped phosphors.

Broadband near-infrared luminescence properties of fluoride phosphor K3AlF6:Cr3+

Broadband near-infrared luminescence properties of fluoride phosphor K3AlF6:Cr3+

Achieving broadband near-infrared luminescence in Cr3+-Activated Y2Mg2Al2Si2O12 phosphors via multi-site occupancy

Cr3+-activated near-infrared (NIR) phosphors are key for NIR phosphor-converted light emitting diodes (NIR pc-LED). While, the site occupancy of Cr3+ is one of the debates that have plagued researchers. Herein, Y2Mg2Al2Si2O12 (YMAS) with multiple cationic sites is chosen as host of Cr3+ to synthesize YMAS: xCr3+ phosphors. In YMAS, Cr3+ ions occupy simultaneously Al/SiO4 tetrahedral, Mg/AlO6 octahedral, and Y/MgO8 dodecahedral sites which form three luminescent centers named as Cr1, Cr2, and Cr3, respectively. Cr1 and Cr2 relate to an intermediate crystal field, with transitions of 2E→4A2 and 4T2→4A2 occurring simultaneously. As Cr3+ concentration increases, the 4T2→4A2 transition becomes more pronounced in Cr1 and Cr2, resulting in a red-shift and broadband emission. Cr3 consistently behaves a weak crystal field and exhibits the broad and long-wavelength emission. Wide-range NIR emission centering at 745 ​nm is realized in YMAS: 0.03Cr3+ phosphor. This phosphor has high internal quantum efficiency (IQE ​= ​86%) and satisfying luminescence thermal stability (I423 K ​= ​70.2%). Using this phosphor, NIR pc-LEDs with 56.6 ​mW@320 ​mA optical output power is packaged and applied. Present study not only demonstrates the Cr3+ multi-site occupancy in a certain oxide but also provides a reliable approach via choosing a host with diverse cationic sites and local environments for Cr3+ to achieve broadband NIR phosphors.

Near-Infrared Light Emitting Metal Halides: Materials, Mechanisms, and Applications.

Near-Infrared (NIR) light emitting metal halides are emerging as a new generation of optical materials owing to their appealing features, which include low-cost synthesis, solution processability, and adjustable optical properties. NIR-emitting perovskite-based light-emitting diodes (LEDs) have reached an external quantum efficiency (EQE) of over 20% and a device stability of over 10,000 h. Such results have sparked an interest in exploring new NIR metal halide emitters. In this review, several different types of NIR-emitting metal halides, including lead/tin bromide/iodide perovskites, lanthanide ions doped/based metal halides, double perovskites, low dimensional hybrid and Bi3+/Sb3+/Cr3+ doped metal halides, are summarized, and their recent advancement is assessed. The characteristics and mechanisms of narrow-band or broadband NIR luminescence in all these materials are discussed in detail. Also, the various applications of NIR-emitting metal halides are highlighted and an outlook for the field is provided.

Highly efficient broadband near-infrared luminescence phosphors Ca3MgSn0.5Zr0.5Ge3O12:Pr3+,Cr3+ for multifunctional applications in pc-LEDs field

Exploring high-performance broadband near-infrared (NIR) emitting materials is crucial for the development of NIR devices. In this study, Ca3MgSn0.5Zr0.5Ge3O12:Cr3+ and rare earth ion Pr3+ co-doped Ca3MgSn0.5Zr0.5Ge3O12:Pr3+,Cr3+ phosphors were successfully synthesized. By utilizing time-resolved emission spectroscopy (TRES), photoluminescence (PL) spectra, and fluorescence decay curve, the Ca3MgSn0.5Zr0.5Ge3O12:Cr3+ phosphor is determined to exhibit a broadband emission (650–1150 nm) with a peak at 795 nm due to Cr3+ occupying multiple cationic sites. Ca3MgSn0.5Zr0.5Ge3O12:0.1Cr3+ has excellent thermal stability (86%@425 K), and co-doping Pr3+ ions into Ca3MgSn0.5Zr0.5Ge3O12:0.1Cr3+ obtains highly efficient NIR emission. The Ca3MgSn0.5Zr0.5Ge3O12:0.01Pr3+,0.1Cr3+ phosphor has quantum yield of 89.4% thanks to the energy transfer effect from Pr3+ to Cr3+. The fabricated NIR phosphor-converted light emitting diodes (pc-LEDs) by integrating the blue chip with Ca3MgSn0.5Zr0.5Ge3O12:0.01Pr3+,0.1Cr3+ has diverse applications including night vision, non-destructive testing, and medical imaging.

Sol-gel combustion synthesis and near-infrared luminescence of Ni2+-doped MgAl2O4 spinel phosphor

Near-infrared phosphor converted light-emitting diode (NIR pc-LED) has many advantages over traditional NIR light sources, and has broad application prospects in night vision surveillance, non-destructive testing, bioimaging, and other fields. Phosphors are typically synthesized by the high-temperature solid-phase method as chunks or large granules, which need to be ground to small particles for practical application. This process introduces surface defects and reduces the luminous efficiency of phosphors. In this work, near-infrared phosphors composed of spinel MgAl2O4:Ni2+ with particle size less than 100 nm was synthesized in high-purity by sol-gel combustion method using nitrate salts with citric acid were used as raw materials. Under 365 nm excitation, MgAl2O4:Ni2+ phosphors emit broadband near-infrared luminescence of 1000–1600 nm with a width at half maximum of 237 nm. The optimal Ni2+ doping concentration was determined to be 1.5 mol% and the optimal sintering temperature was 1200 °C. The thermal activation energy of this phosphor was found to be 0.409 eV and the phosphor had good luminescence thermal stability. An NIR pc-LED device was assembled from the phosphor and commercially available near-ultraviolet LED, which showed a current-dependent increased of NIR luminescence up to 160 mA and an efficiency drop appeared with further increase of the current, suggesting a thermal dependent quenching may have occurred. On the other hand, the output of NIR luminescence increased nearly linearly with the increased of current when a 360 nm laser diode was used as the excitation light source, indicating the NIR phosphor has a very high fluorescence saturation threshold. Our study provides the utility for the sol-gel method in the preparation and the potential application of the nanoscale NIR-II phosphor materials.

Broadband near-infrared luminescence in a cubic pyrophosphate Al0.5Ta0.5P2O7:Cr3+ phosphor for multi-functional applications.

Near-infrared phosphor-converted light-emitting diodes (NIR pc-LEDs) are considered as next-generation of NIR light sources for spectroscopy. However, it is still a challenge to develop an inexpensive broadband NIR phosphor with relatively long-wavelength (λem > 800 nm) emission. In this work, an octahedral Al3+-containing pyrophosphate Al0.5Ta0.5P2O7 with a cubic structure was chosen as a host for Cr3+. Synthesizing this material indicates that this phosphor exhibits a broadband NIR emission peaking at 850 nm with a full width at half maximum (FWHM) of 155 nm under 465 nm excitation. The crystal structure, morphology, local structure, and photoluminescence properties of this material were investigated in detail. The results revealed a full understanding of this new material. A NIR pc-LED device fabricated by using this material combined with a 450 nm LED chip generates a NIR output power of 10.7 mW and a NIR photoelectric conversion efficiency of 3.4% under a 100 mA driving current, which shows the possibility of this material to be utilized in NIR pc-LED applications. Moreover, this material exhibits a linear relationship between emission intensity, decay time and temperature in a wide temperature range, implying that excellent multi-model temperature sensing applications can be expected.

Energy Transfer Induced Blue-Light Excited Broadband Near-infrared Luminescence in Fluoride Na3AlF6:Mn4+,Fe3+

Energy Transfer Induced Blue-Light Excited Broadband Near-infrared Luminescence in Fluoride Na3AlF6:Mn4+,Fe3+

Tunable broadband near-infrared luminescence from Cr3+-doped gallium oxide-based phosphors for advanced sensing and LED applications

A series of Cr3+-activated near-infrared luminescent materials were successfully prepared by using [Zn2+-Ge4+] and [Ga3+-Ga3+] co-unit substitutions, with the peak luminescence tuned from 713 to 767 nm and the FWHM extended from 92 to 155 nm.

Chromium Cluster Luminescence: Advancing Near‐Infrared Light‐Emitting Diode Design for Next‐Generation Broadband Compact Light Sources

AbstractIn modern technology devices, an energy‐saving miniature near‐infrared (NIR) light source plays a critical role in non‐destructive, non‐invasive sensing applications and further advancement of technology. This paper reports the broadband NIR luminescence of Cr3+ clusters for designing phosphor‐converted NIR light‐emitting diodes as an alternative to typical isolated Cr3+ centers and Cr3+ ion pairs. Here, Cr3+ clusters form in the intermediate spinel structure of MgGa2O4 by utilizing the long‐chain edge‐shared octahedral dimers with the shortest bond distance between Cr3+ cations. Electron paramagnetic and magnetometry measurements confirm the isolated Cr3+ and Cr3+ clusters, resulting in NIR luminescence with three distinct emission centers. The formation of Cr3+ clusters in MgGa2O4 ensures stable internal quantum efficiency (≈94%), full‐width‐half‐maximum (248 nm), thermal stability (87%), and a radiant flux of ≈17.66 mW. This work offers a promising approach to NIR phosphor design and enhances the understanding of luminescence mechanisms in spinel and related structures.

Cr3+↔Fe3+ Energy Transfer Offset Enabling Anti‐Thermal Quenching Near‐Infrared Emission for Coded Wireless‐Communication Applications

AbstractBroadband near‐infrared (NIR) emission phosphors are crucial for the construction of next‐generation smart lighting sources; however, the thermal quenching (TQ) issue poses a significant challenge to their applications. In this study, anti‐TQ NIR emission is demonstrated in hexafluoride phosphors, using a facile Cr3+/Fe3+ co‐doping strategy. Owing to the controlled forward resonance energy transfer (ET) from Cr3+ to Fe3+ and one‐phonon‐assisted back ET from Fe3+ to Cr3+, the thermally enhanced broadband NIR luminescence is realised in series of fluoride such as Na3FeF6:Cr3+, Na3GaF6:Cr3+, Fe3+, K2NaScF6:Cr3+, Fe3+, etc. By varying the chemical composition of the phosphor, the anti‐TQ emission is achieved even upon raising the temperature to ≈423 K. The anti‐TQ luminescence mechanism is investigated, and the ET offset effect on luminescence TQ is demonstrated. More importantly, by combining these phosphors with blue InGaN chip, anti‐/zero‐TQ NIR light emitting diodes with a high photoelectric conversion efficiency even up to 19.13%@20 mA are further fabricated to realize the emerging coded optical wireless‐communication applications. These findings can initiate the exploration of NIR phosphors with anti‐TQ luminescence properties for advanced optoelectronic applications.

Effect of ZrO2 and TiO2 on the micro-structure and NIR luminescence of mullite type Cr:Al4B2O9 glass ceramics

Boron-mullites are potential candidate crystal phases for broadband near-infrared (NIR) luminescence in the mullite series due to their higher complexity in crystal structure and abundant [AlO6] units for accommodating transition metal ions as luminescence activators. In this work, the effect of ZrO2 and TiO2 on the microstructure and NIR luminescent properties of mullite type Cr3+:Al4B2O9 glass ceramics were analyzed in detail. Through characterizations including XRD, SEM, TEM and NMR, the oriented growth of strip-shaped grains in ZrO2 doped glass ceramic samples has been verified. The proportion of [AlO6] units is strongly correlated with NIR spectra, suggesting that the strategy for modulation the NIR luminescence through oriented growth can be generalized as a universal method for manipulation of the optical properties for transition metal ion activated crystals with the mullite type structure.

Boroaluminosilicate glass-ceramics containing mullite-type Cr3+:Al4B2O9 nanocrystals with broadband near-infrared luminescence

Multi-component silicate glass is an ideal matrix for fabricating glass-ceramics because of its excellent physical-chemical stability and high optical transmittance. In this paper, a series of Cr3+ doped multi-component silicate glasses were designed for the preparation of glass-ceramics that crystalizes mullite-type Cr3+:Al4B2O9 nanocrystals. When excited at 450 nm, the obtained GCs exhibit a broadband NIR luminescence band covering a spectral region from 650 to 1200 nm. Two different crystallographic sites of Cr3+ in Al4B2O9 nanocrystal are considered to account for the observed broadband luminescence. Due to the controllable size and uniformly dispersion of precipitated nanoparticles, this boroaluminosilicate glass-ceramic could find potential applications as monolithic near-infrared light sources in solid-state light emitting devices.

Multiple lattice sites occupied AlTaO4:Cr3+ phosphor for luminescence ratiometric thermometry and NIR light source

Cr3+-doped near infrared (NIR) phosphors have promising applications in NIR light sources and optical temperature detection. The development of materials with high relative sensitivity and efficient broadband NIR luminescence is the key. In this paper, we report a new multifunctional NIR phosphor AlTaO4:Cr3+, which contains both narrow-band emission associated with 2Eg→4A2 g transition and broadband emission induced by the 4T2 g→4A2 g transition owing to Cr3+ occupies both AlO6 and TaO6 lattice sites. The R-line (2Eg→4A2 g) emission and its anti-Stokes phonon sideband emission follow the Boltzmann distribution, and the thermometer constructed accordingly reaches a maximum Sr of 1% K−1 at 110 K. Under 425 nm excitation, the broad emission band (FWHM = 200 nm) reaches maximum at 880 nm with an internal quantum efficiency of 62.8%. The NIR LEDs prepared with AlTaO4:Cr3+ confirm the application value in NIR light sources.

Broadband near-infrared luminescence in the novel Li3Cs2Sr2B3P6O24:Cr3+ phosphor for NIR pc-LED

Broadband phosphors materials with near-infrared emission have recently gained significant attention for their applications in bio-medication and bio-imaging, phototherapy, night vision, non-destructive diagnostic solution, and quality/risk control of food. This study introduces a novel phosphor material with a broad NIR emission spanning 700–1100 nm. Under 450 nm excitation, this material features a wide full width at half maximum (FWHM) of 170 nm. This broad-spectrum emission results from Cr3+ ion occupancy at Sr2+ sites. A promising quantum yield (PLQY) of 34.7 % was measured. The emission intensity at 423 K maintains 31.3 % of that at 298 K, which needs to be improved. Moreover, successful fabrication of packaged near-infrared phosphor-converted LEDs (pc-LEDs) displaying a broad emission centered on 890 nm further underscores the exceptional potential of Li3Cs2Sr2B3P6O24:Cr3+ phosphors in the realm of broadband NIR pc-LED applications.

Broadband near-infrared double-perovskite phosphor Sr2ScTaO6:Cr3+, Yb3+ for NIR pc-LED applications

The broadband near-infrared (NIR) phosphor converted light emitting diode (NIR pc-LED) has garnered unprecedented attention due to its crucial role in NIR applications. However, there remains a scarcity of efficient broadband NIR luminescence materials capable of emitting NIR light with wavelengths greater than 800 nm. This study reports the synthesis, crystal structure and photoluminescence (PL) properties for double perovskite Sr2ScTaO6:Cr3+ phosphors which exhibit a broadband NIR emission in the 650–1250 nm range, peaking at∼815 nm with the full width at half maximum (FWHM) of 161 nm. The observed broadband emission arises from two distinct Cr3+ centers, namely Sc3+ and Ta5+ octahedral sites within the Sr2ScTaO6 structure, as demonstrated by luminescence and decay kinetic analysis. A significant enhancement of the thermal stability and a remarkable broadening of the FWHM (from 161 to 275 nm) are achieved by employing Yb3+ co-doping strategy. The efficient energy transfer from Cr3+ to Yb3+ was confirmed through emission and excitation spectra, as well as luminescence decay measurements. Finally, Sr2ScTaO6:Cr3+-Yb3+ phosphor was integrated with a 470 nm blue LED chip to fabricate a NIR pc-LED device, and its potential application in night vision was evaluated.

Mn2+ doped LiBaF3 fluoride perovskite single crystal with broadband infrared luminescence pumped by blue LED

In this study, Mn2+ ions doped lithium barium fluoride single crystals (LiBaF3: Mn2+) with perovskite structure were successfully prepared by a reformative Bridgman technique. A near-infrared (NIR) emitting broadband of the single crystal with a peak wavelength of 767 nm and a full width half maxima (FWHM) of 77 nm is owing to the 4T1g(4G)→6A1g(6S) transition of the Mn2+ ions in strong crystal field. Mn2+ ions replace the lattices of Li+ ions from the results of Rietveld structure refinements of the crystals performed by General Structure Analysis System (GSAS) program. A high internal quantum efficiency (41.4%) can be obtained in the synthesized single crystal upon excitation of 494 nm, and the emission intensity of this single crystal at 473 K remains at 42.9% of that at 298 K. Therefore, the LiBaF3: Mn2+ single crystal is a promising candidate for NIR solid-state light-emitting material due to its effective broadband NIR emission. This work offers a novel route to rational design of efficient broadband NIR luminescence and provides a new insight into Mn2+ luminescence and its applications.

Stable Polyhedron-Cluster-Based Rigid Fluoride Framework toward Zero-Thermal-Quenching Near-Infrared Emission for Prolonged LED Applications.

Development of highly thermally stable broadband near-infrared (NIR) luminescence materials is crucial for advancing the prolonged stable application of smart NIR light sources. In this study, a zero-thermal-quenching and reversible temperature-dependent broadband NIR-emitting Cs2NaAl3F12:Cr3+ phosphor is demonstrated, benefiting from its stable polyhedron-cluster-building rigid structure. The excellent thermal stability of Cs2NaAl3F12:Cr3+ is rooted in its stable [Al6Na4F45] cluster building unit, which provides a rigid structure with a weak electron-phonon coupling effect and a wide band gap with a huge thermal activated barrier. Such characteristics are well revealed by multiple studies on crystal structure, electronic structure, Huang-Rhys factor S, configuration coordinate model, and Debye temperature. The incorporation of Li or K instead of Na weakens the luminescence thermal stability, directly proving the importance of the stable [Al6Na4F45] cluster for stable Cr3+ substitution and rigid structure construction. Furthermore, Cs2NaAl3F12:Cr3+ presents much superior thermal stability compared to traditional rigid garnet-type fluorides Na3X2Li3F12:Cr3+ (X = Al, Ga, In). A high-power NIR LED is presented, utilizing the high quantum efficiency (∼71%) and extremely thermally stable broadband NIR emission around 750 nm of Cs2NaAl3F12:Cr3+. It realizes clear vein and cartilage imaging in the human hand, demonstrating its potential in medical diagnosis applications. This result provides important insights for designing new-type rigid crystal structures using stable polyhedron clusters as basic units, advancing the development of highly thermally stable NIR-emitting phosphors.