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Phosphor‐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. [ABSTRACT FROM AUTHOR]

High‐brightness phosphor‐converted solid‐state light (SSL) sources based on blue light‐emitting diodes (LEDs) or laser diodes (LDs) will enable versatile optical applications other than general illumination. However, luminescence ceramics/crystals are too expensive for widespread use, while phosphor‐in‐glass converters suffer from low conversion efficiency at high‐power‐density excitation and poor chemical and thermal stabilities of low‐melting glasses. Herein, an ultrathin interface (<50 nm) is reported in Lu3Al5O12:Ce3+ phosphor‐in‐silica‐glass (LuAG:Ce‐PiSG) despite being sintered at 1250 °C, endowing them with high internal quantum efficiency (>95%) and excellent stabilities. Combined experimental results and first‐principles calculations reveal that the large formation energy of SiAl point defects makes the undesired interfacial reaction between aluminate garnets and silica glass intrinsically suppressed. Phosphor‐converted LEDs/LDs fabricated by LuAG:Ce‐PiSG exhibit high luminous efficiency (195 lm W−1 @ 20 mA) and high brightness (1914 lm @ 13.4 W mm−2), approaching the performances of their ceramic counterparts. The results not only provide a way to balance the brightness and the price for SSL sources but also unleash the potential of silica glass as an inorganic matrix for emerging optical applications. [ABSTRACT FROM AUTHOR]

With the implementation of the Minamata Convention on Mercury, there is an urgent need to find a new way to generate ultraviolet‐C (UVC) light to replace mercury lamp. Upconversion phosphors have the potential to generate UVC light as they are able to convert low energy photons into high energy emissions. Here a new Sr2SiO4:Pr3+ phosphor is reported that could emit UVC light under excitation of a commonly used 450 nm laser diode, a cheap blue light‐emitting diode (LED) with central emitting wavelength at 450 nm, and even sunlight. Moreover, the potential applications of the UVC light of Sr2SiO4:Pr3+ phosphor upon excitation at 450 nm are demonstrated in several different situations, including static marking and dynamic tracking. Demonstration of the unique advantage of photon‐upconverted UVC emission of Sr2SiO4:Pr3+ in the application of sterilization is mainly focused, especially when the deep ultraviolet (DUV) LED cannot work adequately. This work opens a new route for generating UVC light and expands the applications of photon‐upconverted UVC emission, which is expected to be an indispensable supplement to the deep ultraviolet LED. [ABSTRACT FROM AUTHOR]

Broadband near‐infrared (NIR) phosphor‐converted light‐emitting diodes (pc‐LEDs) are recently regarded as the next‐generation smart light sources for miniaturized optical applications. However, their way to practical applications is largely obstructed by the lack of efficient NIR phosphors with photoluminescence (PL) spectrum covering the whole range of 700–1100 nm. Here, an ultra‐broadband NIR phosphor is designed by rationally constructing a Cr3+ → Yb3+ energy transfer system in a garnet crystal Lu2CaMg2Ge3O12 (LCMG). The disordering of the neighboring cations of LCMG is exploited for removing the inversion symmetry of octahedrally coordinated Cr3+ to promote its parity‐forbidden d–d transition probability; meanwhile, efficient Cr3+Yb3+ energy transfer is leveraged not only to enrich the short‐wave NIR PL in 950–1100 nm, but also to greatly improve the internal quantum efficiency (QE) (from 57.8% to 84.2%) as well as thermal stability. The resulting high external QE (35.6%) enables the demonstration of ultra‐broadband NIR pc‐LED with a record NIR output power of 93.2 mW (350 mA), which promises better performance of pc‐LEDs in non‐visible optical applications. This work provides a possible paradigm for developing ultra‐broadband NIR phosphors activated by transition metal ions. [ABSTRACT FROM AUTHOR]

Near‐infrared (NIR) phosphor‐converted light‐emitting diodes (pc‐LEDs) are newly emergent broadband light sources for miniaturizing optical systems like spectrometers. However, traditional converters with NIR phosphors encapsulated by organic resins suffer from low external quantum efficiency (EQE), strong thermal quenching as well as low thermal conductivity, thus limiting the device efficiency and output power. Through pressureless crystallization from the designed aluminosilicate glasses, here broadband Near‐infrared (NIR) emitting translucent ceramics are developed with high EQE (59.5%) and excellent thermal stability (<10% intensity loss and negligible variation of emission profile at 150 °C) to serve as all‐inorganic visible‐to‐NIR converters. A high‐performance NIR phosphor‐converted light emitting diodes is further demonstrated with a record NIR photoelectric efficiency (output power) of 21.2% (62.6 mW) at 100 mA and a luminescence saturation threshold up to 184 W cm−2. The results can substantially expand the applications of pc‐LEDs, and may open up new opportunity to design efficient broadband emitting materials. [ABSTRACT FROM AUTHOR]

Laser‐driven (LD) lighting is emerging as the next‐generation high‐power solid‐state lighting technology. All‐inorganic color converters with high quantum efficiency (QE), small thermal quenching, high thermal conductivity, and high thermal and chemical stabilities are crucial to coping with the enormous heat generated in LD lighting. Although luminescent translucent ceramics are the most promising class of color converters, only green/yellow‐emitting ones with satisfactory performance are developed before. Here, a far‐red‐emitting composite ceramics Y3Al5O12 (YAG)–Al2O3:Cr3+ with near‐unity internal QE and zero‐thermal quenching are prepared via pressureless glass crystallization, where the inside light scattering is finely tuned by simply manipulating the temperature to induce controllable grain growth. The commonly used inert matrix Al2O3 here becomes an optically active component as YAG, thus alleviating the undesired concentration quenching while maintaining strong light absorption. Therefore, a high‐power LD far‐red lighting source with luminescence saturation threshold up to 21.4 W mm−2 is demonstrated, which may find broad applications in plant growth lighting, solar simulators, and phototherapy. [ABSTRACT FROM AUTHOR]

Phosphor‐converted light‐emitting diodes (pc‐LEDs) with broadband near‐infrared (NIR) emission have emerged as compact light sources for portable NIR spectroscopy. However, the associated broadband NIR phosphors suffer from low quantum efficiency (QE) and severe thermal quenching. Here the realization of highly efficient (internal QE ≈ 90%) and nearly zero‐thermal‐quenching broad NIR emission in Cr3+ and Yb3+ codoped Gd3Sc1.5Al0.5Ga3O12 (GSGG) via efficient energy transfer from Cr3+ to Yb3+ is reported, whereby a high‐performance NIR pc‐LED is obtained that can generate ultra‐broad‐band NIR emission covering the whole range of 700−1100 nm with high output power (50 mW at a current of 100 mA) and high photoelectric efficiency (24% at a current of 10 mA). The results not only demonstrate that Cr3+ and Yb3+ codoped GSGG has great potential for compact NIR light sources, but also indicate that the strategy of energy transfer can be exploited for developing new NIR phosphors with both high QE and thermal stability. [ABSTRACT FROM AUTHOR]

Compact near‐infrared (NIR) light sources with broad emission band are essential to enable NIR spectroscopy compatible with portable devices, and phosphor‐converted light emitting diodes (pc‐LEDs) are efficient, low‐cost, and compact light sources. However, it is more challenging to develop highly efficient and thermally stable broadband NIR phosphors than conventional phosphors for white LEDs. Here, a series of solid solution phosphors with broadband NIR emission designed by cationic substitution in Cr3+ activated garnet Gd3Sc2Ga3O12 are reported. The internal quantum efficiency of Cr3+ emission can be significantly improved to nearly 100% via the substitution of ScO6 with smaller AlO6 octahedrons, which is attributed to the reduction of antisite defects. Moreover, the phosphor with optimized composition shows highly thermally stable emission, which renders the as‐fabricated pc‐LED with high‐power (750.8 mW) NIR emission covering the wavelength range of 700–1000 nm. The results could advance the development of NIR pc‐LEDs as high‐performance light sources for miniature NIR spectrometers. [ABSTRACT FROM AUTHOR]

The development of high-power white light-emitting diodes demands highly efficient and stable all-inorganic color converters. In this respect, phosphor-glass/ceramic composites show great promise as they could combine the merits of high quantum efficiency of phosphors and high chemical and thermal stabilities of glass/ceramic matrices. However, strong interfacial reaction between phosphors and matrices at high temperature results in quantum efficiency loss of the embedded phosphors, and traditional solutions rely on high-pressure consolidation techniques. Here we report the intrinsic inhibition of interfacial reaction by using silica glass rather than multicomponent glasses as the matrix. The embedment of phosphors is achieved via a pressureless sintering method, rendering these color-tunable phosphor-glass composites not only accessible to three-dimensional printing technique, but also highly efficient (internal quantum efficiency >90.0%), thermally stable at 1200 °C and hydrothermally stable at 200 °C. Our results provide a facile and general strategy for developing all-inorganic functional composites. Phosphor-glass/ceramic composites are attractive for high-power white light-emitting diodes, but interfacial reaction leads to loss of quantum efficiency. Here the authors report a reduction sintering method for embedment of phosphors into silica glass with limited interfacial reaction. [ABSTRACT FROM AUTHOR]

Rational design and fabrication of multicolor fluorescent sources represent one of the significant challenges in the development of high‐performance solid‐state lighting, tunable coherent lasing, and full‐color display technologies. However, generation of simultaneous multicolor emission, especially white light generation with a wide color gamut is usually beyond the ability of a single material. Heterogeneous structures made by combinations of red, green, and blue emission building blocks are bulky, inefficient, complicated, and costly. Here reported is a bottom‐up strategy to generate simultaneous multicolor emission with continuous tunability in a single monolithic material based on the "nanocrystals‐in‐glass composite" (NGC) architecture. In this approach, a self‐sustained low‐temperature solution combustion process enables homogeneous solvent dispersion and eventually stable immobilization of multiple nanocrystals in transparent matrix. With transparency of up to 80%, further demonstrated is drawing of fiber from the melt of these combustion‐processed NGC materials. The optical spectra of the as‐drawn glass fiber can be precisely tuned and clustering is effectively suppressed. Moreover, the NGC materials exhibit remarkable anti‐thermal quenching behavior at temperatures of up to 200 °C. The bottom‐up strategy for NGC provides a versatile platform for the fabrication of high‐performance multifunctional fiber‐based devices for advanced applications in lasers, illumination, displaying, and biophotonics. [ABSTRACT FROM AUTHOR]

PbS quantum dot (QD)‐doped glasses were fabricated through melt‐quenching method. After heat treatment schedule, uniform QDs were precipitated in the glasses and near‐infrared emission covering 900‐1700 nm was obtained under excitation. From photoluminescence (PL) spectra and lifetime decay curves, the whole emission band of QD‐doped glasses consisted of emission from the 1S‐1S state and the trap state. While using excitation with higher energy, the full width at half maximum (FWHM) of QD‐doped glasses broadened because smaller QDs were excited. Energy transfer process among QDs was revealed by measuring the lifetime of different emission bands in PL spectrum and the energy transferred from smaller QDs with broader bandgap to bigger QDs with narrow bandgap. Temperature‐dependent PL and the corresponding lifetime decay curves of PbS QD‐doped glasses were analyzed. Temperature‐dependent bandgap structure of PbS QDs was obtained by using density functional theory (DFT) calculations. The results here give deep insight into optical properties of PbS QD‐doped glasses and it is beneficial to design and develop high‐performance QD‐based optoelectronic devices in theory. [ABSTRACT FROM AUTHOR]

Alkaline earth orthosilicates M2SiO4 (M = Ba, Sr and Ca) phosphors doped with Mn5+ ions have been prepared by the conventional solid-state reaction method. The crystal structures were verified by X-ray diffraction. By varying the host composition from Ba to Ca, the position shifting of photoluminescence emission bands corresponding to the 1E → 3A2 transition are induced by the increasing angular distortion and covalence. The nonradiative energy transfer becomes a dominant role in the photoluminescence process with substituting Ba2+ sites for smaller cations. The structural evolution and relevant luminescence mechanisms in (Ba1−xCax)2SiO4 phosphors also have been investigated in detail. It reveals that the chemical composition modification and structural variation can be an efficient approach to optimize the photoluminescence behaviors. [ABSTRACT FROM AUTHOR]

Abstract: A novel non‐rare‐earth doped phosphor La2MgGeO6:Mn4+ (LMG:Mn4+) with near‐infrared (NIR) long persistent luminescence (LPL) was successfully synthesized by solid‐state reaction. The phosphors can be effectively excited using ultraviolet light, followed by a sharp deep‐red emission peaking at 708 nm, which is originated from 2Eg → 4A2g transition of Mn4+ ions. The luminescent performance was analyzed by photoluminescence (PL) and photoluminescence excitation (PLE) spectra. The crystal field parameters were calculated to describe the environment of Mn4+ in LMG host. The LPL behaviors as well as the mechanisms were systematically discussed. This study suggests that the phosphors will broaden new horizons in designing and fabricating novel NIR long phosphorescent materials. [ABSTRACT FROM AUTHOR]

There are many reports on long persistent phosphors (LPPs) applied in bioimaging. However, there are few reports on LPPs applied in photothermal therapy (PTT), and an integrated system with multiple functions of diagnosis and therapy. In this work, we fabricate effective multifunctional phosphors Zn3Ga2SnO8: Cr3+, Nd3+, Gd3+ with NIR persistent phosphorescence, photothermal response and magnetism. Such featured materials can act as NIR optical biolabels and magnetic resonance imaging (MRI) contrast agents for tracking the early cancer cells, but also as photothermal therapeutic agent for killing the cancer cells. This new multifunctional biomaterial is expected to open a new possibility of setting up an advanced imaging-guided therapy system featuring a high resolution for bioimaging and low side effects for the photothermal ablation of tumors. [ABSTRACT FROM AUTHOR]

Owing to the unique mechanism of photoelectron storage and release, long persistent phosphorescence, also called long persistent luminescence or long lasting afterglow/phosphorescence, plays a pivotal role in the areas of spectroscopy, photochemistry, photonics and materials science. In recent years, more research has focused on the manipulation of the morphology, operational wavebands and persistent duration of long persistent phosphors (LPPs). These desired achievements stimulated the growing interest in designing bio-labels, photocatalysts, optical sensors, detectors and photonic devices. In this review, we present multidisciplinary research on synthetic methods, afterglow mechanisms, characterization techniques, materials system, and applications of LPPs. First, we introduce the recent developments in LPPs for the synthesis of nanoparticles from the aspects of particle sizes, monodispersity and homogeneity based on the urgent application of bio-imaging. In the later sections, we present the possible mechanisms, which involve the variation of trap distribution during the trapping and de-trapping process, complicated photo-ionization reaction of trap site levels and impurity centers together with their corresponding migration kinetics of carriers. Meanwhile, we emphasize the characterization techniques of defects, used to qualitatively or quantitatively describe the types, concentrations and depths of the traps. This review article also highlights the recent advances in suggested LPPs materials with a focus on the LPPs' hosts and optically active centers as well as their control, tuning and intrinsic links. We further discuss the classification of LPPs based on the different emission and excitation wavebands from the ultraviolet to the near-infrared region along with an overview of the activation mode of afterglow. Afterwards, we provide an exhibition of new products towards diverse application fields, including solar energy utilization, bio-imaging, diagnosis, and photocatalysts. Finally, we summarize the current achievements, discuss the problems and provide suggestions for potential future directions in the aforementioned parts. [ABSTRACT FROM AUTHOR]

Transfer of energy occurs endlessly in our universe by means of radiation. Compared to energy transfer (ET) in free space, in solid state materials the transfer of energy occurs in a rather confined manner, which is usually mediated by real or virtual particles, including not only photons, but also electrons, phonons, and excitons. In the present review, we discuss the recent advances in optical ET by resonance mediated with photons in solid materials as well as their nanoscale counterparts, with focus on the photoluminescence behavior pertaining to ET between optically active centers, such as rare earth (RE) ions. This review begins with a brief discussion on the classification of optical ET together with an overview of the theoretical formulations and experimental method for the examination of ET. We will then present a comprehensive discussion on the ET in practical systems in which normal photoluminescence, upconversion and quantum cutting resulted from ET involving metal ions, QDs, organic species, 2D materials and plasmonic nanostructures. Diverse ET systems are therefore simply categorized into cases of ion–ion interactions and non-ion interactions. Special attention has been paid to the progress in the manipulation of spatially confined ET in nanostructured systems including core–shell structures, as well as the ET in multiple exciton generation found in QDs and organic molecules, which behave quite similarly to resonance ET between metal ion centers. Afterwards, we will discuss the broad spectrum of applications of ET in the aforementioned systems, including solid state lighting, solar energy utilization, bio-imaging and diagnosis, and sensing. In the closing part, along with a short summary, we discuss further research focus regarding the problems and possible future directions of optical ET in solids. [ABSTRACT FROM AUTHOR]

Utilization of photons with subband-gap energy, mostly near-infrared (NIR) photons, is highly desirable for photovoltaic cells; which can be achieved by adding an upconversion layer at the rear face of photovoltaic cells. Here, we study the upconversion luminescence properties of BaCl2:Er3+ phosphors and hexagonal NaYF4:Er3+ phosphors upon excitation of incoherent NIR sunlight with wavelength λ > 800 nm. Higher efficacious upconversion emissions of BaCl2:Er3+ phosphors have been observed in comparison with the well-known hexagonal NaYF4:Er3+ phosphors. We demonstrate that the photocurrent response from the thin-film-hydrogenated amorphous silicon solar cell attached with the BaCl2:Er3+ phosphor is notably enhanced under irradiation of incoherent NIR sunlight with wavelength λ > 800 nm. This judicious design may be envisioned to shorten the distance for the remarkable improvement of the power conversion efficiency of the next-generation photovoltaic cells and suggests a promising application for other NIR photoresponsive devices. [ABSTRACT FROM AUTHOR]

A reddish orange emission Sr2P2O7:Sm3+ phosphor is prepared by the solid-state reaction method in air, and the crystal structure and luminescence properties of phosphors are investigated. Sr2P2O7:Sm3+ phosphor shows Commission International de I'Eclairage (CIE) chromaticity coordinates (x = 0.5753, y = 0.4147). White light-emitting diodes (W-LEDs) fabricated using Sr2P2O7:Sm3+ phosphor etc. show CIE chromaticity coordinates (x = 0.3471, y = 0.3124). These results indicate that Sr2P2O7:Sm3+ phosphor could be a potential suitable reddish orange emitting phosphor candidate for W-LEDs with excitation of a ~400 nm n-UV LED chip. [ABSTRACT FROM AUTHOR]

Phosphors with an efficient yellow-emitting color play a crucial role in phosphor-converted white LEDs (pc-WLEDs), but popular yellow phosphors such as YAG:Ce or Eu2+-doped (oxy)nitrides cannot smoothly meet this seemingly simple requirement due to their strong absorptions in the visible range. Herein, we report a novel yellow-emitting LuVO4:Bi3+ phosphor that can solve this shortcoming. The emission from LuVO4:Bi3+ shows a peak at 576 nm with a quantum efficiency (QE) of up to 68 %, good resistance to thermal quenching ( T50 %=573 K), and no severe thermal degradation after heating-cooling cycles upon UV excitation. The yellow emission, as verified by X-ray photoelectron spectra (XPS), originates from the (3P0,3P1)→1S0 transitions of Bi3+. Increasing the temperature from 10 to 300 K produces a temperature-dependent energy-transfer process between VO43− groups and Bi3+, and further heating of the samples to 573 K intensifies the emission. However, it subsequently weakens, accompanied by blueshifts of the emission peaks. This abnormal anti-thermal quenching can be ascribed to temperature-dependent energy transfer from VO43− groups to Bi3+, a population redistribution between the excited states of 3P0 and 3P1 upon thermal stimulation, and discharge of electrons trapped in defects with a trap depth of 359 K. Device fabrication with the as-prepared phosphor LuVO4:Bi3+ has proved that it can act as a good yellow phosphor for pc-WLEDs. [ABSTRACT FROM AUTHOR]

The trivalent green element of bismuth, when doped into different compounds, can produce multiple emissions in ultraviolet, blue, green or even yellow spectral regimes. The emission adjustability comes from the susceptibility of bismuth naked 6s electrons to the crystal field particularly surrounding Bi3+. However, this has never been observed in a single compound. In this work, we report that broadly tunable bismuth emission indeed occurs even within the same host (CaMoO4) when the local microenvironment around Bi3+ is modified by intentional introduction of alkali ions. As the radius of the selected alkali ion decreases, the emission regularly blue-shifts from 586 to 554 nm, and its intensity is enhanced greatly. For instance, the integrated intensity for the Li+ and Bi3+ codoped sample is 4.46 times stronger than the Bi3+ single-doped sample upon excitation at 300 nm. Low-temperature photoluminescence spectra surprisingly reveal that energy transfer can partially take place from the MoO42- group to Bi3+ at lower temperature when excited into the charge transfer state of the MoO42- group, however, this does not occur at higher temperature. The mechanism needs further study. Dynamic luminescence analysis between 10 and 300 K implies a population dependence of the excited states 3P0 and 3P1 on temperature that is responsible for the evolution of the Bi3+ emission lifetime with temperature. [ABSTRACT FROM AUTHOR]

Cr3+-doped LiInSiO4 phosphors were prepared by a solid-state reaction method. X-ray diffraction measurement was carried out for crystalline phase identification. Absorption, photoluminescence, excitation, and time-resolved spectra were measured to investigate the optical properties of the phosphors. Two broadband near-infrared emissions centered at 920 and 1172 nm were observed. Time-resolved spectra show that the emission at 1172 nm decays more quickly than the emission at 920 nm. The electron spin resonance spectra exhibit a broad resonance signal at g = 1.96 because of exchange-coupled Cr3+ pairs. The value of Dq/B for low and intermediate crystal fields was evaluated. We suggest that Cr3+ incorporated into different octahedral sites of the crystal is responsible for the different near-infrared luminescence. [ABSTRACT FROM AUTHOR]

Recent observations suggest that continuum white light generation driven by a near infrared (NIR) laser is not limited to rare earth (RE) doped phosphors, but is rather a general photophysical process of light–matter interaction as long as the NIR laser energy is efficiently absorbed. Since the proposed explanations seem to be material‐dependent, a comparative investigation on the white light generation in graphene, and its mixture with a typical RE‐doped oxide phosphor is reported here for a general understanding of this process. In contrast to the steady increase of white light intensity in graphene, the white light generated from the oxide phosphor and their mixtures with graphene exhibits a stepwise growth of intensity with laser power. By using the temperature‐dependent upconversion luminescence as ratiometric temperature sensing, it is observed that this emission is closely correlated with the jumps in temperature with the rise of excitation power. Since the black body temperatures are much higher than the temperatures derived by the ratiometric method, it is suggested that this process can be understood by a general thermally assisted direct photon‐to‐photon conversion process, rather than by pure thermal radiation. The results of this work may have important implication for the understanding and design of efficient continuum white light sources. [ABSTRACT FROM AUTHOR]

Trivalent terbium (Tb3+)‐activated luminescence materials usually show highly efficient green emission with the full width at half maximum of merely 10 nm, but suffer from the unsatisfactory excitable wavelength (<380 nm) as well as the inefficient light absorption. Here, the realization of efficient visible light excitation of Tb3+ is demonstrated in terbium‐concentrated garnet Ca2TbHf2Al3O12 (CTHA) by introducing Ce3+ as the sensitizer. Owing to highly efficient energy transfer from Ce3+ to Tb3+, CTHA:Ce3+ combines advantages of the extra narrow green emission of Tb3+ peaking at 544 nm and the efficient broad excitation of Ce3+ covering the short‐wavelength visible light from 380 to 450 nm. The color gamut of the prototype white light‐emitting diode (LED) by using CTHA:Ce3+ as the green emitter can reach 95% (coverage ratio) of National Television Standards Committee (NTSC) space in Commission Internationale de L'Eclairage (CIE) 1931, indicating its great potential for LED (or laser diode)‐based applications. [ABSTRACT FROM AUTHOR]

Near infrared to visible up-conversion luminescence in Er 3+ single doped BaCl 2 , BaF 2 and NaYF 4 phosphors were compared. Intense blue emission at 410 nm due to 2 H 9/2 → 4 I 15/2 transition and greenish-blue emission at 496 nm due to 4 F 7/2 → 4 I 15/2 transition were only observed in BaCl 2 :Er 3+ when excited by 808 nm and 976 nm laser diodes, respectively. The phenomena can be ascribed to the direct two-step excitation processes which occur in the chlorides where multiphonon relaxation is rapidly suppressed. In addition, the intensity of upconversion emission in BaCl 2 :Er 3+ is greatly enhanced upon broadband near-infrared excitation. [ABSTRACT FROM AUTHOR]

Highlights: [•] Phosphors are synthesized by solid-state reaction method in air. [•] Phosphors contain SrMgAl10O17 and Al2O3 phases. [•] Emission of phosphor is greatly enhanced due to multiple scattering and absorption of excitation light. [•] White-LED has been demonstrated by blend composition phosphors pumped with a 397nm near UV LED chip. [ABSTRACT FROM AUTHOR]

A novel single-phased tunable emitting phosphor Ba 9 Lu 2 Si 6 O 24 :Bi 3+ ,Eu 3+ (BLSO:Bi 3+ ,Eu 3+ ) was successfully prepared via a simple solid-state approach. The main excitation peaks range from 320 to 400 nm of BLSO:Bi 3+ were identified by photoluminescence characterization, indicating BLSO:Bi 3+ viable for ultraviolet (UV) excitation. Emission spectra show that Bi 3+ occupies at least two nonequivalent sites in BLSO host, and display broad emission peaks at 410 and 490 nm when excited by UV light, respectively. As red emitting center Eu 3+ was introduced into BLSO:Bi 3+ , significant energy transfer (ET) occurs from Bi 3+ to Eu 3+ through a dipole-dipole mechanism. The ET efficiency reaches 97.57%. By varying the doped ratio of Bi 3+ and Eu 3+ , tunable light and white emission can be easily realized. Results indicate that BLSO:Bi 3+ ,Eu 3+ is a potential tunable emission phosphor in UV excited W-LEDs. [ABSTRACT FROM AUTHOR]

Abstract: A novel non‐rare‐earth doped phosphor La2MgGeO6:Mn4+ (LMG:Mn4+) with near‐infrared (NIR) long persistent luminescence (LPL) was successfully synthesized by solid‐state reaction. The phosphors can be effectively excited using ultraviolet light, followed by a sharp deep‐red emission peaking at 708 nm, which is originated from 2Eg → 4A2g transition of Mn4+ ions. The luminescent performance was analyzed by photoluminescence (PL) and photoluminescence excitation (PLE) spectra. The crystal field parameters were calculated to describe the environment of Mn4+ in LMG host. The LPL behaviors as well as the mechanisms were systematically discussed. This study suggests that the phosphors will broaden new horizons in designing and fabricating novel NIR long phosphorescent materials. [ABSTRACT FROM AUTHOR]

Review: multidisciplinary research on synthetic methods, afterglow mechanisms, characterization techniques, material kinds, and applications of long persistent phosphors; 318 refs. [ABSTRACT FROM AUTHOR]

We report a simple approach to activate the near-infrared (NIR) long persistent phosphorescence via redox reaction. NIR long persistent phosphorescence is observed in a Cr-doped non-gallate phosphor, i.e. CaTiO 3 : Cr with perovskite structure through heat treatment in reducing atmosphere, while no such phenomenon is observed in the sample with same composition and heat treated in air. The mechanism for activation of Cr-related long persistent phosphorescence is discussed. The designed phosphors successfully break the monopoly of the ordinary Cr 3+ -activated gallate phosphors with the spinel structure and provides a new route for design of long persistent phosphors. [ABSTRACT FROM AUTHOR]

A variety of materials sintered in different atmosphere have been well investigated, but there are few reports on the long-persistent phosphorescent materials, especially the near-infrared long-persistent phosphorescent materials sintered in various atmosphere. Changing the surrounding atmosphere is an effective method to improve the afterglow properties of the materials. In this work, we fabricate a typical kind of near-infrared long-persistent phosphorescent materials of Zn 3 Ga 2 Ge 2 O 10 : 0.5% Cr 3+ in neutral, oxidizing, and reducing atmosphere. By analyzing the XRD patterns, afterglow spectra, decay and thermo-luminescence curves, we discuss the great effects on the structure, long persistent properties and trap properties of the phosphor. This work of obtaining the Zn 3 Ga 2 Ge 2 O 10 : 0.5% Cr 3+ is of great potential in the applications in night-vision surveillance and in vivo bio-imaging. [ABSTRACT FROM AUTHOR]

Recently, long persistent phosphors (LPPs) have been considered to be the most prominent candidates for biomedical applications. However, the LPPs suffer from a dramatic decrease in luminescence intensity after incorporation into the tissue. Therefore, it is very necessary to develop the more competitive LPPs and acquire the reproducible tissue imaging. Here, we propose and experimentally demonstrate an effective bifunctional La 3 Ga 5 GeO 14 : Cr 3+ , Nd 3+ phosphor with the interesting characteristic of near-infrared long persistent phosphorescence and NIR-to-NIR Stokes luminescence. Cr 3+ and Nd 3+ ions are simultaneously selected as the emission centers in order to take advantage of the remarkable phosphorescence properties of Cr 3+ , and the appropriate energy level characteristic of NIR-excitation band (808 nm) and NIR-emission (1064 nm), and the ability as the brilliant auxiliary to create more efficient defects of Nd 3+ . The efficient dual-modal emission is, accordingly utilized to realize the convenient, high-resolution global detection and local imaging. [ABSTRACT FROM AUTHOR]

Highlights: [•] A blue-white long persistent phosphor. [•] Zn imperfections as emitting centers without any rare-earth doping. [•] An energy transfer and remission process is proposed. [Copyright &y& Elsevier]

Highlights: [•] Ba3(PO4)2:Mn5+ phosphor shows NIR emission in NIR-II region. [•] The emission band peak is at ∼1191nm. [•] The quantum yield is above 40%. [•] The fluorescence lifetime is ∼550μs. [Copyright &y& Elsevier]

A series of LuAG: 5 mol%Yb3+/x mol%Tm3+ (x = 0.1, 0.3, 0.5, 1, 2) poly-crystals have been prepared through floating zone method with CO 2 laser. The up-conversion luminescence spectra of the samples were recorded under 980 nm excitation. The results tell us that the optimal concentration of Tm3+ ions is around 0.3 mol%. Moreover, the optical temperature sensing properties of the LuAG: 5 mol%Yb3+/0.3 mol%Tm3+ have been investigated by using fluorescence intensity ratio (FIR) method. The FIR data obtained agree well with the fitting curve from 298 K to 1023 K. The absolute and relative sensitivities reach the highest values of 5.55 × 10−3 K−1 at 1023 K and 7.17 × 10−3 K−1 at 555 K, respectively. The results indicate that the Tm3+/Yb3+:LuAG poly-crystalline phosphor is a promising candidate for wide-range and highly sensitive temperature sensor. • Tm3+/Yb3+: LuAG poly-crystal has been prepared by zone melting method. • Optical temperature sensing behavior of Tm3+/Yb3+: LuAG was investigated. • The proposed optical temperature sensor has a range from 298 to 1023 K. [ABSTRACT FROM AUTHOR]

Multifunctional phosphors Zn3Ga2SnO6:Cr3+, Nd3+, Gd3+ with near-IR long persistent phosphorescence, photothermal response, and magnetism are prepared by solid state reaction of stoichiometric amounts of ZnO, Ga2O3, SnO2, Cr2O3, Gd2O3, and Nd2O3 (1350 °C, 4 h). [ABSTRACT FROM AUTHOR]

SrSnO3:Bi2+ is prepared by a two-step calcination of stoichiometric amounts of Bi2O3, SnO2, and SrCO3 in air (1. [ABSTRACT FROM AUTHOR]

Unusual concentration induced antithermal quenching of divalent bismuth ions occurs in heavily Bi2+-doped Sr2P2O7 phosphors along with a blueshift of the emission peak at higher temperature. [ABSTRACT FROM AUTHOR]