Efficient Phosphor Research Articles

Highly efficient green phosphor Ca4La(PO4)3O:Eu2+,Tb3+ for white LEDs.

Although the green light emission of Tb3+ ions can be effectively improved by utilizing energy transfer from Eu2+ to Tb3+ ions, obtaining phosphors with high quantum efficiency remains a major problem. Here, we have achieved a novel apatite-type structure Ca4La(PO4)3O (CLPO) containing Eu2+ and Tb3+ ions. The CLPO:Eu2+ is capable of being effectively excited by near-ultraviolet light and emits blue light at about 460 nm. Energy transfer from the Eu2+ to Tb3+ ions in CLPO:Eu2+,Tb3+ can be readily constructed by utilizing the energy transfer from Eu2+ to Tb3+ ions. The optimized phosphor CLPO:0.02Eu2+,0.7Tb3+ has a high internal quantum efficiency of 96.6% and an external quantum efficiency of 64.7%. CLPO:0.02Eu2+,0.7Tb3+ and commercially available blue and red phosphors were coupled with a 365 nm chip package to form WLEDs, which presented a good Ra value (89.9) and correlated color temperature (3808 K). Our work provides an avenue to realize novel and efficient green phosphors by selecting suitable hosts and constructing efficient energy transfer.

Synergetic Contributions of High Quenching Concentration and Tuned Square Antiprism Geometry Boosting Far-Red Emission of Eu3+ with Near-Unit Efficiency.

Far-red phosphors have emerged as a desirable research hotspot owing to their critical role in promoting plant growth. Especially, Eu3+ ions typically present the 5D0→7FJ (J = 0, 1, 2, 3, 4) transitions, which overlap with the far-red light required for plant photosynthesis. However, achieving high-efficiency far-red emission of Eu3+ remains challenging due to weak 5D0→7F4 transition and concentration quenching. The study constructs two anomalously efficient far-red garnet phosphors A3Sc2C3O12 (A = Y3+, Gd3+. C = Al3+, Ga3+):Eu3+. A high-resolution STEM measurement equipped with an aberration corrector provides the direct proofs for both the [EuO8] configuration-dependent strong 5D0→7F4 and the origin of high quenching concentration. Excitedly, a two-component substitution (replacing Y3+-Al3+ with Gd3+-Ga3+) triggers a near-unity internal quantum efficiency (IQE = 99.01%) and high external quantum efficiency (EQE = 38.73%) in Gd3Sc2Ga3O12:60%Eu3+, resulting from the effective modulation of 5D0→7F4/7F2 transitions. A far-red LEDs device based on Gd3Sc2Ga3O12:60%Eu3+ exhibits an output power of 113mW at 300mA. Subsequently, practical applications for promoting plant growth underscore the significance of these findings. This work opens a new path for the development of highly efficient far-red phosphors via the synergistic effect of Eu3+ square antiprism configuration and high quenching concentration.

Highly efficient and thermally stable cyan-emitting ZnS/ZnO phosphors for full-visible-spectrum LED lighting.

Near-ultraviolet (NUV)-pumped white light-emitting-diodes (WLEDs) often suffer from poor color rendering in the 480-520 nm range, highlighting the need for an efficient cyan phosphor with strong absorption at 370-420 nm. This study presents the successful synthesis of cyan-emitting ZnS/ZnO phosphors using a high-energy planetary ball milling method followed by post-annealing. The fabricated phosphors, with particle sizes ranging from 1 to 3 μm, exhibit strong cyan emission with CIE chromaticity coordinates of (0.2302, 0.3759) and excellent thermal stability with an activation energy of 0.26 eV. A prototype near-ultraviolet (NUV)-pumped cyan LED was developed, achieving chromatic coordinates of (0.2769, 0.4380) and a quantum efficiency of 77% by coating an NUV chip at 370 nm with the synthesized phosphor. These results demonstrate the potential of ZnS/ZnO-based materials as efficient, non-toxic alternatives to rare-earth phosphors, paving the way for advancements in full-spectrum white LEDs for solid-state lighting.

Efficient narrow-band green phosphors for mini-LED displays using dual strategies of high concentration quenching and energy transfer

Narrow-band green phosphor have been realized by high doping concentration and energy transfer in GMAO. The luminous color has achieved a wide range of adjustability. GMAO:Eu2+,Mn2+ is valuable for applications in Mini-LED displays.

(Invited) Applications of Mn4+ and Cr3+ Ions for Lighting and Optical Thermometry

Transition metal ions with the 3d3 electron configuration (Cr3+ and Mn4+, in particular) are widely used for the lighting (red and deep red emission) and non-contact optical thermometry. This is due to their specific energy level scheme and favorable relative position of the spin-quartet state 4T2 and spin-doublet state 2E. Complicated interplay of electronic properties of impurity ions and host materials (covalent bonding between dopants and ligands) is the main reason for wide tunability of emission wavelength of such phosphors. The main goal of this presentation is to review the fundamental spectroscopic properties of Mn4+ and Cr3+ ions to illustrate the fundamental role of the “structure-optical property” relationships and to illustrate how such studies can have applied importance as useful guides facilitating search for new efficient phosphors [1-9].

Influence of Alkaline-Metals Co-Doping on Luminescence Intensity of Er-Doped Up-Conversion Oxide Phosphors

Up-conversion (UC) phosphors, which can convert lower energy photons to higher energy ones, have been widely investigated owing to a wide range of applications, including bioimaging to visualize information in living organisms [1], solar cells to improve power conversion efficiency [2], and security inks to prevent counterfeiting [3]. However, in device applications, there are two big problems to overcome, those are 1) UC efficiency and 2) lifetime for long term use. Currently materials containing fluoride are often used for UC phosphors, but several types of oxides with rare-earth ions such as Y2O3:Er, Yb [4] and CaWO4:Er [5] have been reported as efficient UC phosphors with long lifetime. UC phosphors using organic solvents have also been reported to improve emission intensity, but they are difficult to apply to devices and are virtually unusable. To improve UC efficiency, it was reported that UC luminescence intensity can be enhanced by a co-doping of alkaline-metals in CaTiO3:Er [6].In this study, we have investigated the influence of alkaline-metal co-dopings on UC luminescence intensity of various types of oxides doped with Er ions. All the samples were prepared by a conventional solid state reaction method. The systematic analysis were carried out for the synthesized samples, i.e., the crystal structures and the phase analysis were examined by X-ray diffraction, the elemental analysis by X-ray fluorescence, energy levels and electronic structure analysis by diffuse reflectance with UV-vis spectrometer equipped with integration sphere, surface morphology and grain size observation by scanning electron microscope. In addition to such experimental analysis, first-principles calculations within a density functional theory have also been conducted to interpret the influence of alkaline metal co-dopings on the geometrical and electronic structures.As an example of our current UC measurements, UC luminescence spectra of CaMoO4:Er with and without alkaline-metal co-dopings are shown in Fig. 1, in which significant enhancement of UC luminescence has been achieved by alkaline-metal co-dopings in CaMoO4:Er.

Structure-Photoluminescence Relationship in Ce3+-Doped K5Y(P2O7)2 and Its Sensitization to Dy3+ with Enhanced White Light Emission.

From a fundamental point of view, the structure-photoluminescence relationship is vitally important for developing efficient phosphors and rationally improving their performances. In this work, Rietveld refinements on high-resolution powder X-ray diffraction (XRD) data were conducted to verify the Ce3+ distribution in K5Y(P2O7)2 (KYPO). Ce3+ ions are located at both M1 and M2 sites, with occupation factors of 0.31(2) and 0.19(2), respectively. Importantly, the crystal field strength (CFS) is stronger at the former site due to the larger bond valence sum. Correspondingly, the Ce3+ emission can be deconvoluted into four Gaussian-type bands centered at ∼353, ∼383, ∼343, and ∼369 nm, where the former two belong to Ce3+ at the M1 site and the latter two are assigned to Ce3+ at the M2 site. Ce3+ in KYPO is a highly efficient activator, with optimal internal and external quantum efficiencies of 98.9 and 74.6%, respectively, and was thus utilized to sensitize the Dy3+ emission. Indeed, energy transfer from Ce3+ to Dy3+ was confirmed by fluorescent decay curves for Ce3+/Dy3+ codoped KYPO, and the mechanism was supposed to be dominated by dipole-dipole interactions. Indeed, it can be pumped by a 310 nm LED chip and emits a bright white light. Ce3+ photoluminescence exhibits high resistance to thermal quenching, and it can be further enhanced by codoping Dy3+, i.e. the emission intensity remains 96.3% at 423 K.

Defect-Enabled Superior Negative Thermal Quenching in Palmierite Ba9La(VO4)7:Eu3+ for WLED In Situ Temperature Measuring.

Negative thermal quenching (NTQ) of the phosphors is critically important for both scientific research and practical applications, but the design of efficient NTQ phosphors is still a challenging task. Herein, we report a new strategy for developing NTQ materials by cation-vacancy engineering. Specifically, a new color-tunable Ba9La1-x(VO4):xEu3+ (BLVO:xEu3+) phosphor with abundant intrinsic cation vacancy was developed, exhibiting superior NTQ behavior under 365 nm excitation. The NTQ performance can be modulated via adjusting Eu3+ doping levels, and the emission intensity of Eu3+ ions in the BLVO:0.20Eu3+ phosphor increased by 275% at 473 K compared to room temperature. Furthermore, the reported material emitting bright white light under 365 nm excitation was well-suited for use in white light-emitting diode (WLED) phosphor and fluorescent temperature sensors, exhibiting outstanding color-rendering index (90.1) in lighting and high sensitivity (Sa = 11.83% K-1, Sr = 2.33% K-1) in temperature detecting. Lastly, the operating temperature of WLED at different currents can be monitored and displayed in real time through emission spectroscopy. All of the results demonstrated that the designed NTQ BLVO:xEu3+ can be used as a single-phase white phosphor and optical thermometry. This work provides a fresh perspective for designing high-efficient NTQ phosphors and expands the application of phosphors in WLED in situ temperature detection.

Sodium fluoride and rare earth trifluorides systems. Review

NaF–RF3 systems, which are composed of sodium fluorides and rare earth trifluorides, are sources of many functional materials. Data on phase formation and phase equilibria in these systems were analyzed. The polymorphism and morphotropy of rare earth fluorides were considered taking into account the influence of pyrohydrolysis. A summary series of NaF–RF3 phase diagrams are presented and the coordinates of invariant equilibria are tabulated. The data of research by Thoma et al., performed in the sixties of the twentieth century, are now only of historical interest. In these systems, a-Na0.5–xR0.5+xF2+2x (cubic, R = Pr-Lu, Y) and b-Na3xR2–xF6 (hexagonal, R = La–Lu,Y) phases of variable composition with fluorite and gagarinite structures, respectively, are formed. In addition, solid solutions based on rare earth trifluorides with the LaF3–tysonite (R = La–Gd) structure and the berthollide phase of such a structure in the system with TbF3 were identified. Data was presented on the concentration dependence of the lattice parameters of fluorite phases. High temperature a-phases with maxima on the melting curves allow growing single crystals from the melt. A complex pattern of ordering of these phases with decreasing temperature was observed. Low-temperature syntheses of intermediate phases in these systems led, in accordance with the Ostwald’s step rule, to the initial formation of nonequilibrium phases of a fluorite structure, usually designated as “a-NaRF4”, which were then replaced by equilibrium low-temperature hexagonal phases of “b-NaRF4”. The hexagonal phase in the NaF–YF3 system, doped with ytterbium and erbium (“b-NaYF4:Yb,Er”), is one of the most well-known, efficient up-conversion phosphors

Fluorescent Tetraphenylethylene-Based Cerium Metal-Organic Frameworks for White-Light-Emitting Diodes.

Discovery of highly efficient and thermal stable phosphors is the focus of the studies in phosphor-converted white light-emitting diodes (LEDs). Herein, a tetraphenylethylene-based cerium metal-organic framework (SYNU-2) was synthesized and characterized. The intricate architecture of SYNU-2 shows an overall 3D → 3D 2-fold interpenetration framework. SYNU-2 exhibited good luminescence properties, and its latent fingerprint developer was prepared, which showed good fluorescence and stability under ultraviolet (UV) radiation. It is worth noting that a prototype WLED device can be designed using SYNU-2 and red phosphors (Ca,Sr)AlSiN3:Eu2+ with CIE coordinates of (0.33, 0.33) at an applied 3 V bias.

Improved synthetic method for the color-tunable LiYGeO4:Tb3+ persistent phosphor toward information storage

Efficient and stable persistent phosphors play a crucial role in the fields of energy storage, anti-counterfeiting, and biomedical fields. Here, we present an improved synthetic method for preparing a series of color-tunable LiYGeO4:Tb3+ persistent phosphor. The increased Tb3+ concentration in the improved method enhances the persistent luminescent intensity at 20 s by ∼2.96 times. This enhancement is due to the dual roles of Tb3+ as both emitters and trap centers within LiYGeO4. By simply increasing the doping concentrations, the persistent color can be adjusted from blue to green. LiYGeO4:Tb3+ exhibits no loss of persistent luminescent intensity even after exposure to water at 80 °C for 72 h, surpassing the commercial green persistent phosphor. Furthermore, information storage was successful demonstrated by using LiYGeO4:Tb3+ with various doping concentrations. This study represents a significant advancement in optimizing the properties of persistent luminescent materials, where dopants simultaneously serve as emitters and trap centers.

Realizing Tunable Long Persistent Luminescent in Novel Cu2+‐Doped NaGaO2 for Multi‐Level Information Storage and Encryption

AbstractAnti‐counterfeiting and encryption are key technologies for information transmission in modern society. However, most optical materials offer only a single fixed response mode, limiting their security level in advanced anti‐counterfeiting applications. Exploring efficient and tunable long persistent luminescent (LPL) phosphors is urgently demanded and highly meaningful. In this work, a dual‐site occupancy strategy is innovatively reported via Li+ doped NaGaO2: Cu2+ (NGO: Cu2+/Li+) phosphors for enhancing LPL properties. To be specific, Cu2+ initially occupies both Na and Ga sites in NaGaO2, producing orange–yellow LPL at 585 nm and near‐infrared (NIR) emission at 712 nm, respectively. Furthermore, the introduction of Li+ will occupy the Na+ sites, attenuating the NIR emission and increasing the defect density of the oxygen‐deficient states, which results in enhanced LPL intensity and prolonged afterglow time. Significantly, the obtained NGO:Cu2+/Li+ exhibits multi‐emission modes with dynamic change of LPL time (10–20 min). More importantly, the NGO: Cu2+/Li+ has great potential applications in multi‐level information storage and encryption.

Developing an efficient garnet-type near-infrared phosphor Na1.5Gd1.5Sc2Ge3O12:Cr3+ with relatively long-wavelength emission.

Developing efficient near-infrared (NIR) phosphor with an emission peak wavelength over 850 nm is crucial to realize multi-functional spectroscopy applications, while this remains a significant challenge. Herein, a garnet-type Na1.5Gd1.5Sc2Ge3O12:Cr3+ phosphor with an emission peak located at 882 nm was created from NaδGdδCa3-2δSc2Ge3O12:Cr3+ (0 ≤ δ ≤ 1.5) solid solutions basing on the effect of cationic disorder. The maximum internal quantum efficiency (IQE) of Na1.5Gd1.5Sc2-xGe3O12:xCr3+ reached 84.6% when x = 0.01. The maximum external quantum efficiency (EQE) can be optimized to 20.6%. Using this material, a prototype NIR phosphor-converted light-emitting diodes (pc-LEDs) device was fabricated, which demonstrates an excellent prospect in spectroscopy applications.

Suppressed concentration quenching and tunable photoluminescence in Eu2+-activated Rb3Y(PO4)2 phosphors for full-spectrum lighting

Highly efficient inorganic phosphors are desirable for lighting-emitting diode light sources, and increasing the doping concentration of activators is a common approach for enhancing the photoluminescence quantum yield (PLQY). However, the constraint of concentration quenching poses a great challenge for improving the PLQY. Herein, we propose a fundamental design principle by separating activators and prolonging their distance in Eu2+-activated Rb3Y(PO4)2 phosphors to inhibit concentration quenching, in which different quenching rates are controlled by the Eu distribution at various crystallographic sites. The blue-violet-emitting Rb3Y(PO4)2:xEu (x = 0.1%–15%) phosphors, with the occupation of Rb1, Rb2 and Y sites by Eu2+, exhibit rapid luminescence quenching with optimum external PLQY of 10% due to multi-channel energy migration. Interestingly, as the Eu concentration increases above 20%, Eu2+ prefer to occupy the Rb1 and Y sites with separated polyhedra and large interionic distances, resulting in green emission with suppressed concentration quenching, achieving an improved external PLQY of 41%. Our study provides a unique design perspective for elevating the efficiency of Eu2+-activated phosphors toward high-performance inorganic luminescent materials for full-spectrum lighting.

A Cr3+-Yb3+ co-doped high-efficiency near-infrared luminescent phosphor for NIR-II light source applications

Phosphor conversion light-emitting diode (PC-LED) technology has become a focal point of research for portable near-infrared light sources in recent years. One of the crucial aspects is to develop phosphor materials that can be effectively stimulated by commercial available blue light. Unfortunately, efficient phosphors in the NIR-II that can be excited by commercial blue light are particularly scarce. In this study, Mg4Ta2O9:0.04Cr3+,0.03Yb3+,0.07Li+ (MTO:0.04Cr3+,0.03Yb3+,0.07Li+) phosphor was synthesized using the high temperature solid phase method, and its emission spectrum covered the first and second near-infrared windows (700–1200 nm). The internal quantum efficiency (IQE) and external quantum efficiency (EQE) are 88.7 % and 45.6 %, respectively, due to the synergistic effect of energy transfer and Li-ion modification. Additionally, the doping of Yb3+ ions and Li+ ions enhances the thermal stability of luminescence. The thermal stability of MTO:0.04Cr3+,0.03Yb3+,0.07Li+ and MTO:0.04Cr3+,0.03Yb3+ is 9.81 % and 14.43 % higher, respectively, than that of MTO:0.04Cr3+,0.03Yb3+ and MTO:0.04Cr3+. To evaluate its potential applications, we developed a prototype PC-LED utilizing MTO:0.04Cr3+,0.03Yb3+,0.07Li+ phosphor as an emission emitter which demonstrated advantages in biomedical imaging, night vision, and non-destructive testing.

Designing a high-efficiency broadband cyan phosphor for low-blue full-spectrum LED lighting

Efficient cyan-emitting phosphor plays an important role in the development of solid-state lighting, which is indispensable to filling the cyan gap for full-spectrum warm-white light-emitting diodes (WLEDs) with high color rendering index (CRI). Herein, a novel highly efficient broadband cyan phosphor Ce3+-doped Ca3HfAl2Si2O12 (CHASO: Ce3+) garnet compound was developed by the substitution of Lu3+-Al3+ with Ca2+-Hf4+/Si4+ in Lu3Al5O12. The crystal structure and photoluminescence (PL) properties of CHASO: Ce3+ were investigated in detail. Notably, CHASO: Ce3+ phosphor can be effectively excited by violet light (390 – 430 nm) and exhibited bright cyan emissions around 490 nm with high PL internal quantum yields of 89.2 %. Moreover, the integrated PL intensity of the phosphor at 423 K was 66.3 % of that at room temperature. Finally, by incorporating CHASO: 11 %Ce3+ with commercial blue/yellow/red phosphor onto a violet LED chip (400 nm), the prototype full-spectrum WLEDs device exhibits warm white light with high color rendering index (CRI, Ra and R9 > 90) and low correlated color temperature 3301 K. These results suggest the highly efficient phosphor CHASO: Ce3+ is promising for low-blue full-spectrum healthy lighting.

Enhancing Optical Properties of Zn-Mn Solid Solution Hybrid Halides for Wide Color Gamut Backlight Displays.

Hybrid metal halides display a range of optical properties and hold promise for various applications such as solid-state lighting, anti-counterfeiting measures, backlight displays, and X-ray detection. The incorporation of zinc into (C13H26N)2MnBr4 aims to enhance its structural rigidity and improve its narrow band green light emission properties. The resulting (C13H26N)2ZnBr4 compound exhibits an identical crystal structure to (C13H26N)2MnBr4, indicating the potential for a solid solution of varying Zn and Mn ratios within this structural framework. (C13H26N)2Zn0.2Mn0.8Br4 exhibits significantly enhanced properties, including a photoluminescence quantum yield of 92%, a minimum full width at half maximum of 43nm, and 85% retention of room temperature emission at 420K. Additionally, crystals of (C13H26N)2ZnCl4 and (C7H18N)2ZnX4 (X = Br, I) are synthesized, with (C7H18N)2ZnBr4 displaying luminescent color changes dependent on excitation. (C7H18N)2Zn0.2Mn0.8Br4 demonstrates reversible phase transitions and alterations in optical properties. A white light-emitting diode utilizing (C13H26N)2Zn0.2Mn0.8Br4 and commercial phosphors exhibited a color gamut of 112.2% of the National Television Standards Committee 1931 Standard. This investigation introduces a stable and highly efficient narrow-band green phosphor suitable for displays.

Realization of narrow-band blue emission based on structurally engineering-designed Bi3+-doped phosphors

The exploration of efficient narrowband emission phosphors is crucial for white light-emitting diodes (WLEDs) in high-performance backlighting applications. Up to now, the discovery of narrow-band Bi3+-doped phosphors for emerging applications remains challenging because Bi3+ typically exhibits broadband emission properties. A novel narrow-band blue phosphor (Ca4SnGe3O12:Bi3+) was successfully synthesized, benefiting from the highly symmetric crystal environment and tightly connected rigid structure of the garnet structure. The phosphor demonstrates broad excitation in the near-ultraviolet (n-UV) region and emits narrowband blue light at 442 nm (FWHM = 36 nm) with a color purity of 94.7 %. In this paper, the assignment of different luminescence centers and the use of Zr/Hf to partially replace Sn to enhance luminescence performance are studied. The reasons for the consequent changes in luminescence behavior are explained in detail. The use of narrowband commercial red K2SiF6:Mn4+, green β-Sialon:Eu2+, and synthetic blue luminescent materials as RGB emitters covered 81 % of the National Television System Committee (NTSC) color space, demonstrating great potential for liquid-crystal-display (LCD) backlight use.

Structural, morphological, optical and down-conversion studies of NaLaMgTeO6:Dy3+ single phase phosphor for white light emitting applications and solar spectral converter for photovoltaic applications

Researches on rare earth activated phosphors in solid state lighting and enhancement in efficiency of solar cells pave attention to develop efficient phosphor materials. In the present work, Dy3+ doped NaLaMgTeO6 phosphors are synthesized using solid state reaction method. The structural studies using XRD analysis confirmed the successful formation of the compound. SEM analysis reveals that the particles are closely packed, which in turn exhibit intense luminescence intensity due to low scattering and high packing density. Elemental configuration were analyzed using EDS analysis. FTIR analysis revealed the vibrational bands of the host matrix. Optical energy bandgap was calculated using DRS spectra. The luminescence characteristics of the samples were investigated using excitation and emission spectra. Upon most intense 351 and 388 nm excitation, sharp yellow emission peak at 572 nm dominates blue emission at 478 nm, further reveals that Dy3+ ions occupy low symmetry site in the host lattice. The optimum concentration of Dy3+ in the present host is x = 0.04 mol and concentration quenching is due to dipole-quadrupole interaction of adjacent Dy3+ ions. The thermal quenching phenomenon is studied using temperature dependent photoluminescence analysis. The CIE chromaticity coordinates and CCT values conclude NaLaMgTeO6:Dy3+ phosphors are good candidate for cool near-white light emitting materials for outdoor illumination. The study on solar spectral response and down-conversion property of the synthesized phosphor demonstrate its applicability as solar spectral converters in solar cell applications.

The highly efficient and stable near-infrared phosphor Ca3MgSnGe3O12: Cr3+ for multifunctional application

The investigation of efficient and stable near-infrared (NIR) luminescent materials is crucial for rapidly developing near-infrared spectroscopic techniques. Herein, NIR phosphors Ca3MgSnGe3O12: Cr3+ with ultra thermal stability and high internal quantum yield (IQY) are explored. The emission intensity remained at 91.75 %@423 K of room temperature and the IQY/EQE reaches 91.41 %/34.04 % after doping the H3BO3 flux agent for optimization. Moreover, a single luminescence center was identified by cryogenic photo luminescence spectroscopy (PL) from 4 K to 300 K and lifetime decay curve. Importantly, NIR light can easily removes all kinds of background interference that cannot be easily eliminated by visible light, which is not only widely used in night vision and biological tissue penetration, but also has higher application prospects in NIR fingerprint detection. Moreover, it clearly displays high level of fingerprint details under high temperature conditions and after water immersion, thus it is perfectly suited for using in Automatic Fingerprint Identification System (AFIS) systems. Therefore, Ca3MgSnGe3O12: Cr3+ NIR pc-LEDs have great potential for latent fingerprint detection at actual crime scenes.