Phosphor layers are of vital importance for the development of advanced phosphor-converted light-emitting diodes (LEDs). However, owing to the fixed ratio of red-green-blue (RGB) phosphors, it has been difficult for the RGB phosphor layers with conventional structure to tune light emission colours. Herein, we have experimentally fabricated nine types of phosphor layers with patterned RGB pixel array, which consist of tuneable RGB ratio in a planar configuration. Moreover, we carried out optical simulation based on Monte-Carlo theory to assist in adjusting the light-emission colours and the corresponding chromaticity coordinates. The simulations were further verified by the experimental results via samples fabricated by the stencil printing technique. In accordance with the nine types of phosphor layers with patterned pixel arrays in various RGB ratios, we have finally obtained corresponding nine light-emission colours for the applications of LED light emission decoration. These designed advanced pixel-array phosphor layers demonstrate great potential for applications in decorated light emission and display devices with significant implications for industrial improvement in these research areas.

A new scintillation material including CaF2: Eu nanocrystals contained in SiO2–Al2O3–CaO–CaF2–LiF system was successfully prepared via melting method with additional heat treatment. Structural and luminescence properties were investigated by characterization techniques including XRD, SEM, photoluminescence (PL) excitation and emission spectra and absorption profile. The emission intensity of the glass ceramics containing CaF2: Eu nanocrystals under illumination at 356 nm were significantly more than the as-made glass and enhanced with increasing the temperature and duration of the heat treatment. Spectral analysis of gamma rays showed a full-energy peak in comparison with the similar chemical compositions that do not show such a response. Also an energy continuum with specific reaction-product peak was detected for thermal neutrons. The scintillation efficiency was enhanced with increasing crystallization. The fabricated Eu-doped transparent CaF2 glass ceramics has the potential to be a desired composite scintillator for detection of low energy gamma rays and thermal neutrons.

Organic room temperature phosphorescence (RTP) molecules have attracted significant attention recently due to their promising application in security, bioimaging, sensing and organic light emitting diodes (OLEDs). Nevertheless, limited RTP molecules were reported until now and most of RTP phenomena were observed in crystal. Moreover, the underlying mechanisms of RTP still remain ambiguous. In this paper, excited-state properties of CZs-CN with RTP features in three crystals are theoretically studied using the combined quantum mechanics and molecular mechanics (QM/MM) method. Moreover, the photophysical properties of CZs-CN in solvent are also investigated by polarizable continuum model (PCM). The mechanism of aggregation induced RTP is revealed which is mainly contributed by the enhanced phosphorescence rates in aggregation, rather than the traditional restricted intramolecular motion mechanisms which usually bring decreased non-radiative decay rates. In addition, different crystal structures could induce different phosphorescence properties, and the emission spectra of the molecule in three crystals and THF are explained reasonable. Furthermore, dimers are confirmed to be involved in the emission when the intermolecular interaction is strong enough in aggregation. Our theoretical results provide inner perspective for aggregation induced RTP mechanism and could help one to better understand the different light-emitting properties in aggregation and solvent.

A series of Ca2La8(SiO4)6O2:Eu3+ (CLSO:Eu3+) and Ca4La6(SiO4)4(PO4)2O2:Eu3+ (CLSPO:Eu3+) oxyapatite phosphors have been prepared via traditional solid-state reaction processes. The phase compositions of phosphors were analyzed by X-ray powder diffraction (XRD), and the morphologies were displayed by scanning electron microscopy (SEM). The characteristic photoluminescence properties were studied by photoluminescence excitation (PLE) and emission (PL) spectra. In addition, the luminescence decay times and emission-temperature relationship were also characterized. The results indicated that the phosphors could be efficiently excited by the near ultraviolet (NUV) light and blue light, and exhibited red light emission. Meanwhile, the average particle sizes of CLSO and CLSPO hosts are about 2–3 μm. Moreover, a low symmetry C3 or Cs sites supplied by the CLSO:Eu3+ and CLSPO:Eu3+ hosts for Eu3+ is benefit to 5D0 → 7F2 electric dipole transition, which leads to the R/O values of CLSO:yEu3+ keep greater than that of CLSPO:yEu3+. All the obtained results suggested that the prepared phosphors possess potential application in white light emitting diodes (WLEDs).

All-inorganic lead halide perovskite nanocrystals (NCs) as new emerging semiconducting luminescent materials have attracted tremendous attention for designing optoelectronic devices. We have synthesized high quality of the CsPbX3 NCs with tunable entire visible spectral region by a modified lower temperature method, featured with facile, low-cost and easily operating in an open environment without vacuumization or glovebox system. Besides, we have investigated the incorporation of Ni and K ions into CsPbX3 NCs by adjusting all kinds of composition concentration from halogen salts, based on above mentioned preparation method. The absolute photoluminescence quantum yields (PLQYs) of doped CsPbX3 NCs with different dopant (Ni or K ions) concentration were discussed. It is found that a certain amount of doping is beneficial for suppressing the defects and improving the lattice structure of nanocrystals, whereas an excessive dopant may induce quenching centers of the emission. In addition, a glorious absolute PLQYs of doped CsPbX3 NCs can be obtained by our method, especially for CsPbBr3 and CsPbI3 NCs, and nearly reach 80%.

Zn-doped Ga2O3 nanostructures were synthesized by thermal evaporation. SEM results show that there are plenty of nanorods in the samples. The EDS analysis of the samples demonstrate that the nanostructures are mainly composed of Ga and O elements, and a small amount of Zn element is also observed. The Raman spectra indicate that the samples still keep the monoclinic structure consistent with the pure Ga2O3 crystal structure. A broad-band blue-green luminescence centered around at 2.3 eV was observed at room temperature. The luminescence intensity of the PL spectra of the Zn-doped Ga2O3 nanostructures varied with the amount of Zn doping. Besides, the PL spectra of the Zn-doped Ga2O3 nanostructures have a red-shift compared to that of the pure Ga2O3 nanostructures. The analysis of the PL spectrum of Zn-doped Ga2O3 nanostructures with a mass ratio of Ga2O3 powder to zinc powder of 10:1 indicates that the broad-band blue-green luminescence of the Zn-doped Ga2O3 nanostructures is composed of one blue luminescence (2.8 eV, 450 nm) band, one green luminescence (2.3 eV, 533 nm) band, one yellow luminescence (2.1 eV, 592 nm) band, and one red luminescence (1.9 eV, 638 nm) band, respectively. Further, their luminescence mechanisms will be discussed.

As an indispensable component of full-color luminescence, the development of reddish orange light emitting materials cannot be ignored. Here, we prepared a novel Eu3+-doped P2O5–SrO–BaO–ZnO glasses with distinctive fluorescence properties. The effects of Eu2O3 content on the structure and properties of glasses were studied, aiming to provide a key guidance for the preparation of reddish orange light emitting glass. The prepared glasses consisted predominantly of metaphosphate units along with minor contribution from pyrophosphate and orthophosphate units. Three intensity parameters (Ω2,4,6) were estimated by Judd-Ofelt theory, which followed the trend as Ω2 > Ω4 > Ω6. Particularly, the intensity of 5D0 →7F4 transition was much greater than that of 5D0→7F2 transition as the Eu2O3 content exceeded 0.50 mol.%. Under excitation by 397 nm xenon lamp, the fluorescence lifetimes of glasses that emit reddish orange light were 2.49, 2.52, 2.61, 2.54 and 2.48 ms with increase in Eu2O3 content. Considering the common experimental errors, there was no significant change in the fluorescence lifetimes. The distinctive fluorescence properties indicate that this novel glass has potential applications in display devices.

Alkali-alumino-telluroborate glasses with the different network modifier elements were prepared by melt–quenching method. Absorption, excitation, luminescence spectra as well as decay curves of 5D4 level were measured at room temperature. A phonon side band of 7F6 → 5D4 transition has been obtained from the excitation spectra of Tb3+ ion. The role of modifier ion radius in luminescence enhancement from 5D4 level of Tb3+ ion was discussed in detail. In prepared glasses, multiphonon relaxation rate from 5D3 level to 5D4 is enhanced in the host glasses containing modifier ions with large radius. This is main reason leading to the enhancement of luminescence from 5D4 level of Tb3+ ion in alkali-alumino-telluroborate glasses under excitation at 350 nm. Additionally, the Judd-Ofelt theory was used to estimate the features of ligand field and radiative properties of Tb3+ ion. The calculated results have shown that the 5D4→7F5 transition has potential applications for laser action and optical amplifier.

The upconversion of near-infrared (NIR) fluorescence, with a high tissue penetration depth, possesses a distinct advantage in biological temperature detection but is limited by the lack of rare earth-doped nanophosphors with intense and selective NIR UC emission. Here, we show that high-efficiency NIR temperature sensing can be achieved by appropriately doping Tm3+ activators into a polarized layered host, utilizing the high environmental sensitivity of the 3H4→3H6 electric dipole transition (808 nm) of Tm3+. To confirm this concept, Yb3+/Tm3+ codoped Bi7F11O5 upconverting nanosheets were synthesized and characterized. Furthermore, the thermometric performance of the samples was analyzed based on the temperature-dependent fluorescence intensity ratio from the thermally coupled levels (3F3/3H4) of Tm3+. The results showed that, under 980 nm diode laser excitation, the prepared samples can produce a high NIR-to-visible UC emission ratio (I800nm/I475nm) of over 2000 for Tm3+. The maximum sensitivity Sa/Sr was 1.4% K−1/0.577 K−1 at 303 K based on the 3F3 and 3H4 levels, and the material exhibited a wide functional temperature range of 303–573 K. The results of our work not only improve the understanding of the optical properties of RE3+ ions in layered materials but also show a potential application for physiological temperature sensing in biological tissues and cells.

Optical thermometry has drawn great attention due to its sensitive and noncontact properties. Herein, Yb3+/Er3+ codoped Bi4Ti3O12 phosphor microcrystals have been synthesized by solid phase reaction for optical temperature sensing. The phase, microscopic structure and morphology of the prepared sample have been studied by the X-ray diffraction, transmission electron microscopy, etc. The process of upconversion emission has been researched with different environmental temperature and excitation power under 980 nm laser excitation. Meanwhile, the temperature sensing nature of the as-prepared microcrystals has been investigated based on the luminescence intensity ratio of two thermally coupled energy levels (Er3+:2H11/2, 4S3/2). The excitation laser power density is 3.95 mW/mm2, and the absolute sensitivity reaches 0.0046 K-1. The result demonstrates potential of the Bi4Ti3O12:Yb3+/Er3+ microcrystals in making optical sensing device under low excitation power density.

The La1-0.03-yGdyAlO3: 0.03Eu (y = 0.2–0.8) phosphors are prepared via solid phase method. The normal thermal quenching of Eu2+ ion and abnormal thermal quenching of Eu3+ ion in La1-0.03-yGdyAlO3: 0.03Eu (y = 0.2–0.8) phosphors are explained by the configuration coordinate system and energy transfer process. Considering the fluorescence intensity ratio temperature measurement technology, the temperature sensitivity values of the phosphors increase with the increase of Gd3+ ion concentration. When Gd3+ ion concentration is 0.8, the maximal Sa and Sr can even reach 0.084 K-1 and 3.233% K−1. Moreover, the excellent separation of emission peaks of Eu2+ and Eu3+ ions also provides good signal discriminability for temperature measurement. These results indicate that the La1-0.03-yGdyAlO3: 0.03Eu phosphors can be used as the superior non-contact optical thermometry materials.

In this letter, high Q factor microsphere resonators with excellent stability and high damage threshold are fabricated from Tm3+ doped fluorosilicate glasses using the traditional melt-quenching and fiber heating techniques. Intense 1.88 μm photoluminescence and single mode laser emission are obtained under the excitation of an 808 nm laser. The Q factor of the microsphere resonator is measured to be as high as 1.4 × 106. Models for photoluminescence and lasing are proposed using spectroscopic data from the absorption and emission spectra. The excellent resistance to humidity and temperature are characterized from the transmittance spectra under different environmental conditions. Differential thermal analysis (DTA), measured in four different glass samples proves the high damage threshold. The proposed glass microsphere resonator laser can find application in optical sensors and micro lasers, especially in complex environments.

Li-doped SnO2 nanobelts have been fabricated by thermal evaporation based on vapor-solid (VS) growth mechanism. The three feature-peaks of Raman scattering spectra at 475 cm −1 (Eg), 634 cm −1 (A1g), and 776 cm −1 (B2g) at room temperature indicate that the samples still keep the rutile structure. One new mode at 591 cm−1 is observed, which is due to a slight distortion of the tin oxide lattice. The low-temperature (less than 90 K) photoluminescence properties of the samples show that there is an intensive broadband blue light emission centered at 480 nm (2.583 eV). When the temperature is larger than 90 K, one yellow light emission centered at 580 nm (2.138 eV) will dominate and the blue light emission peak at 480 nm will vanish. The analyzed results indicate that the 90 K is served as a transitional temperature. The temperature has a much larger influence on the intensity of the emission band of the Li-doped SnO2 nanostructures.

The red oxide phosphors activated by Mn4+ have become a research hotspot because of their excellent physical/chemical stability, which can be applied in the field of light-emitting diodes (LED) plant growth lighting. Here, a new type of Sr9Gd2W4O24 (SGWO):Mn4+ red phosphor was prepared by traditional high temperature solid state reaction method. The phase compositions and morphologies of powders were analyzed by X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM). The luminescent properties of the samples with varying Mn4+ concentrations were investigated, and the photoluminescence excitation (PLE) spectra illustrate that samples can be effectively excited by near-ultraviolet/blue light. Furthermore, typical concentration quenching occurs when the doping concentration of Mn4+ exceeds 0.4 mol%. In addition, the thermal activation energy of the sample was calculated to be 0.3641 eV. Importantly, under the excitation of near-UV light at 365 nm, SGWO:0.004Mn4+ phosphor can emit bright far-red light. All the results indicated that SGWO:Mn4+ phosphors have potential application value in indoor plant cultivation.

Near-infrared emitting persistent luminescent materials have potential applications in night-vision surveillance and medical imaging. Rational designing of the phosphor composition is of great importance for achieving sufficiently strong and long-lasting persistent luminescence. Herein, a series of MgGa2O4:Cr3+ phosphors with variable concentrations of Cr3+ were prepared via solid state reaction. MgGa2O4:Cr3+ exhibits strong emission in the range from 650 to 800 nm and three excitation bands centered at 275, 420 and 576 nm. With appropriate selection of codopant M (M = Al3+, Si4+, Ge4+ or Sn4+), the MgGa2O4:Cr3+, M phosphor presents remarkably enhanced persistent luminescence. Moreover, the trap distributions were tuned and the number of traps was greatly increased via codoping. In particular, MgGa2O4:Cr3+, Si4+ shows more than 7 h of persistent near-infrared light emission before the intensity drops to 5 × 10−4 mWsr−1m−2. Codoping with appropriate ions provides a good example in optimization and development of persistent luminescent phosphors for potential bioimaging applications.

By co-doping Yb3+/Er3+ into ordinary material In2O3, the up-conversion glow behavior will be triggered up. On this basis, the luminescence intensity can be significantly improved by tri-doping Zn2+ ions. Compared with In2O3:Yb3+/Er3+, the luminescence intensity of In2O3:Yb3+/Er3+/Zn2+ is significantly enhanced and the emitting light changes from faint red to bright green. This can be attributed to the reduction of site symmetry of the luminescence center and the promotion of crystallinity because of lattice distortion caused by Zn2+ ions. The up-conversion luminescence of the In2O3:Yb3+/Er3+/Zn2+ in the red and green light regions are two-photon excitation process, and the quantum yield (QY) is calculated to be 0.1%. The luminescence at the 524 nm emission peak corresponds to the transition Er3+:2H11/2 → 4I15/2. Other two emission peaks in green area (550 nm, 564 nm) correspond to the transition Er3+:4S3/2 → 4I15/2. And the emission peaks in red area (659 nm, 683 nm) root in the transition Er3+:4F9/2 → 4I15/2.

Owing to the superior performance of lead-halide perovskites in various optoelectronic devices, their low-dimensional counterparts of quantum-confined nanocrystals (NCs) have started drawing intensive research attention. Here we report a systematic study on the optical properties of single FAPbBr3 NCs, which demonstrate high-purity single-photon emission, large absorption cross-section and narrow photoluminescence linewidth. Interestingly, linearly-polarized emission can be partially observed in single FAPbBr3 NCs at the room temperature, the degree of which is significantly enhanced at the cryogenic temperature. The above polarization phenomenon is attributed to the large energy-level splitting of the bright-exciton states, leading to efficient exciton recombination from the lowest state with a 1D dipole moment. This unique feature of linear polarization in the optical emission of single FAPbBr3 NCs has not only provided a deep understanding of their exciton energy-level structures, but also suggested potential polarization-oriented applications such as in photo-detectors, light-emitting diodes and lasers.

In this work, we explore emission properties of Pr3+ ion doped aluminosilicate glasses at visible wavelengths where alkaline earth oxide modifiers (Mg2+, Ca2+, Sr2+, Ba2+) are introduced for enhancement of the Stark splitting of Pr3+ in the silicate matrix. The Pr3+ ion doped aluminosilicate glasses present strong absorption at visible wavelengths between 440 and 500 nm which gives rise to intense emission in the visible spectrum from 570 to 660 nm. The visible luminescence spectra under excitation at different pump wavelengths and the lifetime of spontaneous emission are investigated as functions of Pr3+ doping concentration. We report a longest lifetime of 115 μs measured at 3P0 level in Pr3+ implying Pr3+ doped aluminosilicate glass may be a promising candidate for efficient visible fiber laser operated at 610 and 640 nm wavelength. The concentration-induced quenching and various energy transfer processes are also investigated.

In linear the modulation (LM) technique of optically stimulated luminescence (OSL), the stimulation power changes with a linear ramping rate, while the signal intensity starts to increase from background level and continues by forming peaks. In some cases as in the present study, the LM-OSL curve has a non-conventional shape with a strongly decaying signal at the beginning of the stimulation. In order to deal with this dominant decaying component, two different deconvolution approaches were used by adding, besides the conventional LM-OSL components, (a) a phosphorescence (PH) decaying component and (b) a continuous wave (CW) - OSL decaying component to the initial part of the LM-OSL curves. The fitting results showed that temperature dependences of the fitting parameters (τ and σ) contradict standard OSL theory, so the non-conventional dominant decay component is not another CW-OSL. This non-conventional component could be attributed to an intense optically stimulated phosphorescence (OSP) component, due to the experimentally verified stimulated temperature dependence of the decay coefficient λ. This signal is intense at stimulation temperatures 125 °C and below, with various arguments suggesting that at these temperatures the signal originates from the 110 °C TL trap.

Fluorescence resonance energy transfer (FRET) nanoprobes based on aggregated induced emission (AIE) molecules are promising for the monitoring of biomolecules in living cells, but this nanoprobe for reactive oxygen species (ROS) has rarely been reported. Here, a novel AIE-based FRET nanoparticles (NPs) is developed for ratiometric detection and imaging of hypochlorite in live cells. Different to common FRET-based nanosensors, the NPs is prepared via facile co-assembly strategy in water using amphiphilic tetraphenylethene (TPE1, energy donor) and thienyl-diketopyrrolopyrrole (NDPP, energy acceptor). This hybrid NPs are uniform spherical, with size of approximately 120 nm. NDPP maintains bright fluorescence inside the hybrid NPs and acts as the reactive unit for hypochlorite in this FRET nanosystem. As a ratiometric fluorescent nanoprobe, the hybrid NPs shows high selectivity to hypochlorite with a detection limit calculated to be 105 nM, thanks to its stable particle size in hypochlorite sensing. Furthermore, the successful ratiometric fluorescent imaging of ClO− in HeLa cells demonstrates that our NPs can effectively pass through the cell membrane and recognize the ClO− in living cells.

Multiple facile synthetic strategies for all inorganic perovskite CsPbBr3 nanocrystals (NCs) have been established and developed, profiting from their excellent performance and great potential applied in the field of photonic and optoelectronic. Here, CsPbBr3 NCs were synthesized by both hot injection method (method 1) and conversion method (method 2), and the discrepancy of their photophysical properties is elucidated via the complementary studies between time-resolved photoluminescence (TRPL) and transient-absorption (TA) spectroscopy. We found that CsPbBr3 NCs prepared by conversion method exhibited lower PL quantum yield (QY), which was ascribed to the larger partition of the NCs being passivated from the quenchers from the deep trap states. On the other hand, we also observed different radiative recombination rates between two samples which should be due to various trapping/detrapping times prior to the radiative recombination of the charge carriers in two samples. These results provide better guidance for the development and improvement of synthesis methodology for perovskite NCs.

Sb-doped ZnO nanowires with hexagonal wurtzite structures have been synthesized via chemical vapor deposition method, and the main charge state of Sb dopants is Sb5+. The photoluminescence spectra demonstrate the existence of shallow acceptors, SbZn-2VZn complexes in all probability. On the other hand, Sb doping caused more native and impurity donors in Sb-doped ZnO nanowires. Then, field effect transistors of single Sb-doped ZnO nanowire were fabricated and the transport properties shows n-type conductivity. The competition between shallow acceptors and donors, and the influence of Sb valency need to be investigated further to obtain stable Sb-doped p-type ZnO. At last, we have shown the potential application of Sb-doped ZnO nanowires for nanoscale UV photodetector.

White organic light emitting diodes (WOLEDs) incorporating gold (Au) nanoparticles (NPs) beneath PEDOT:PSS hole injection layer (HIL) and employing neat blue DMAC-DPS(B) and green 4CzIPN(G) thermally activated delayed fluorescence (TADF) emission layer (EML) together with sandwiched ultrathin red phosphorescence Ir(piq)2(acac)(R) EML have been fabricated and the effects of the localized surface plasmon resonance (LSPR) of Au NPs and EML thickness on the electroluminescence (EL) performance are investigated. It is found that EML thickness imposes vital influence on the EL performance of the WOLEDs and the WOLEDs with the embedded Au NPs and simple EML structure with optimal thickness of G(15 nm)/R(0.3 nm)/B(15 nm) demonstrate maximum power efficiency (PE), external quantum efficiency (EQE) and color rendering index (CRI) around 11.73 lm/w, 10.51% and 94, indicating the achievement of balance between EL efficiency and CRI by carefully adjustment of EML thickness with the presence of Au NPs. Furthermore, the LSPR effects from the Au NPs on the EL efficiency and CRI have been clearly demonstrated. Especially the green and red light emission is dramatically enhanced leading to enormous improvement of CRI, which can be ascribed to the remarkable enhancement of energy transferring inside G(15 nm)/R(0.3 nm)/B(15 nm) EML proved by the much shortened decaying lifetime at 475 and 550 nm from transient photoluminescence(PL) decaying testing. Almost double enhancement of the total fluorescence efficiency (including prompt fluorescence (PF) and delayed fluorescence (DF)) at 550 nm can be obtained with the assistance of LSPR from Au NPs, which increase from 23.85% to 49.82% and 15.22%–28.86% for respective EML of G(15 nm)/B(15 nm) and G(15 nm)/R(0.3 nm)/B(15 nm). The decaying dynamics including the DF, PF, phosphorescence (PH) and energy transferring inside G(15 nm)/R(0.3 nm)/B(15 nm) EML with and without embedded Au NPs is discussed in details. The study provides an easy way to utilize the LSPR of Au NPs together with simple neat TADF and phosphorescent EML to develop high quality WOLEDs.

Red-emitting ceramic phosphors are significant for warm white light emitting diodes (WLEDs) with high color rendering index (CRI). In this work, Mn doped spinel ceramic phosphors were prepared via high temperature solid-state reaction sintering. The photoluminescence properties of the as-prepared ceramic phosphors were elaborately discussed. The Mn4+ doped spinel ceramics were successfully obtained by incorporating excessive Mg2+ as the charge compensator. They showed red emission peaking at 652 nm under 450 nm excitation. Furthermore, it's exciting to find that the red-emitting ceramic phosphors showed high thermal stability. As operated at 450 K, the emission intensity remained about 66% of the initial intensity operated at room temperature. The results indicate that the Mn4+ doped spinel ceramic phosphors are promising red color converters for warm-WLEDs.

The features of IR luminescence of colloidal Ag2S QDs passivated with thioglycolic acid (Ag2S/TGA) under the formation of Ag2S/ZnS/TGA core/shell QDs are considered. A 4.5-fold increase in the quantum yield of recombination IR luminescence within the band with a peak at 960 nm (1.29 eV), full width at half maximum of 250 nm (0.34 eV), and the Stokes shift with respect to the exciton absorption of 0.6 eV was found. The increase in the IR luminescence intensity of Ag2S/ZnS/TGA QDs is accompanied by an increase in the average luminescence lifetime from 2.9 ns to 14.3 ns, which is explained as “healing” of surface trap states during the formation of the ZnS shell. For the first time, the enhancement of the luminescence intensity photodegradation (hereinafter referred to as fatigue) was found during the formation of the Ag2S/ZnS/TGA core/shell QDs. The luminescence fatigue is irreversible. We conclude that the initial stage of photolysis of the Ag2S core QDs under laser irradiation plays a key role. Low-atomic photolytic clusters of silver formed on the Ag2S core QDs act as luminescence quenching centers and do not reveal structural transformations into Ag2S, provided that the clusters are not in contact with TGA.

In this paper, Dy3+ doped SrCO3–WO3–SiO2 glass ceramics are successfully prepared by melt-quenching method. The microscopic morphology, structure and luminescence properties of Dy3+ doped glass ceramics are investigated through XRD, DSC, SEM, photoluminescence spectra and decay curves etc. It can be determined that the crystalline phase is SrWO4 after comparing with PDF normal card by XRD. Also, combining with the transmission curves, the optimum heat treatment temperature and time are 740 °C/1.5 h. In the emission spectrum, there are three obvious emission peaks at 484 nm, 575 nm and 665 nm, respectively. The optimum concentration of Dy3+ is found to be 1.6 mol, and electric multipole interaction is the main reason for the concentration quenching. The maximum fluorescence lifetime is 796.5 μs.

In this paper, we report an improved luminous efficiency of a direct-current-driven electroluminescent (EL) device using ZnS powder by controlling electron and hole injection barriers. The emission layer was fabricated by screen-printing of an EL paste using Cu-coated ZnS particles on a transparent conductive indium–tin-oxide electrode. The device was completed by stacking an Al thin film on the emission layer by thermal evaporation. We applied various forming voltages to investigate the current–voltage–luminescence characteristics of the device. An abrupt change in current during the forming process was caused by variation of the electron-blocking barrier toward the anode. The hole-injection barrier from the anode to the emission layer increased with the forming voltage. The obtained results indicated that the hole-injection barrier to the emission layer can be lowered by inserting materials with a low highest-occupied-molecular-orbital (HOMO) energy level between the anode and emission layer. We achieved a brightness enhancement of 29% by employing a thin film of poly-N-vinyl carbazole with a HOMO level of −5.6 eV as a hole-injection layer on the anode. We believe that the presented results will guide further studies for efficiency improvement of EL devices using powder particles applicable to next-generation lighting and displays.

In this work, we have reported on enhanced emission in Ho3+-doped sol-gel high silica glasses by doped Y2O3. Effects of Y2O3/Al2O3 ratio on the structural and optical properties of Ho3+-doped glasses were investigated. According to the analysis of Si 2p3/2 XPS, 27Al NMR, FTIR, it can be concluded that the Y2O3 has greatly changed the structure of the high silica glass. The 27Al NMR spectra showed that the population of Ho3+ ions in the vicinity of Al3+ decreased with an increase in the Y2O3/Al2O3 ratio. Judd–Ofelt parameters have been evaluated from absorption spectrum of Ho3+-doped glass and predicted the high asymmetric coordination environment around Ho3+ when incorporating Y3+ into the glass network. The 2.0-μm fluorescence intensity, fluorescence lifetime and σems × τrad of Ho3+-doped glasses steadily increase with the increase in the ratio of Y2O3/Al2O3. These results suggest that Y2O3 has a good dispersion homogeneity for Ho3+ ions in high silica glass.

In order to avoid the shortcoming of the luminescence singleness of traditional carbon quantum dots (CQDs), the free regulation of luminous color of CQDs were achieved by doping lanthanide ions in the study. Firstly, Eu3+-doped carbon quantum dots (Eu-CQDs) were synthesized with citric acid-chelated europium ions as the precursor by a hydrothermal method. Doped europium ions existed in the Eu(III) state in Eu-CQDs and the prepared Eu-CQDs showed two parts of the photoluminescence (PL) spectrum, which originated from the blue emission of CQDs and the characteristic photoluminescence of Eu3+ ions, respectively. With an increase in the concentration of Eu3+, the intensity of Eu3+ characteristic emission showed an enhanced trend, but the intensity of the characteristic peaks of CQDs decreased. The CIE coordinate confirmed the continuous regulation of the luminous color of CQDs from blue to red. When the concentration of Eu3+ ions was 6%, the ratio of PL intensity between Eu3+ ions and CQDs was higher, thus generating purple-red light emission. In addition, the dual fluorescent characteristics of Eu-CQDs showed quite different responses to different environment pH values. When pH = 6, the CCT value of Eu(6%)-CQDs was 2156 K, indicating a good red light performance. The white light emission of CQDs could be realized by co-doping 5 mol% Eu3+ and 2 mol% Tb3+ in CQDs and adjusting the environmental pH = 7. The CCT value of doped CQDs was 5115 K, indicating a good neutral white light performance.

GaN nano/micro-structure based light-emitting diodes (LEDs) have drawn much attention owing to their potential applications in display and optoelectronics integration. Here, we have fabricated coaxial semipolar InGaN/GaN multiple quantum wells (MQWs) microwire array LED with superior performances in suppressing efficiency droop. The results show that our as-synthesized microwire has two semipolar planes (1¯101) and (11¯01), and the InGaN/GaN MQWs have superior crystal quality. In addition, the efficiency droop ratio of our device is about 9.7% as the injected current increases from 3 to 100 A/cm2, which is largely declined by 47% compared with that of the conventional polar c-plane LEDs. Meanwhile, the microwire array LED reveals a small wavelength shift (3 nm) as the injected current increases from 3 to 23 A/cm2. The effective advances in the device should be attributed to the weaker quantum-confined stark effect of InGaN/GaN MQWs in semipolar plane. This work proposes a high repeatability method to fabricate microwire array LED for future optoelectronic integrated systems.

Lead halide perovskite semiconductors are promising materials for optical devices due to their excellent optoelectronic properties. In addition to strong light absorption coefficients, which originate from a direct band gap structure, they also exhibit almost no Stokes shift between absorption edge and photoluminescence (PL) peak. Therefore, the effect of PL reabsorption plays an important role for their emission spectra in bulk crystals. In this review, we analyze the PL dynamics in CH3NH3PbX3 (X = I, Br, Cl) single crystals to provide a clear picture of the dynamical effects of PL reabsorption that occur in perovskites. This knowledge is essential for accurate characterization via PL and photon management for optical devices. We also show that the grain size dependence of PL spectra obtained from polycrystalline thin films can be interpreted by PL reabsorption.

We report on the synthesis of composites based on poly(styrene) (PS) and CdSe/ZnS quantum dots (QDs). The reduction of terminal functional group of RAFT polymerized PS to thiol group allows for a partial substitution of low molecular weight ligands at the surface of CdSe/ZnS QDs by a polymer. The combination of TEM and FTIR data results in the model of the composite formation with PS macromolecules wrapped around QDs. The photoluminescence (PL) of QDs in PS-CdSe/ZnS composites decreases with an additional embedding of Au nanoparticles (NPs). The reason of the PL drop observed is analyzed in terms of combined inner filter effects and the influence of dielectric properties of the medium surrounding Au NPs embedded in PS-CdSe/ZnS composites. The calculations of the radial distribution function of QDs regarding the position of Au NPs are carried out and compared with the experimental data.

We report on the photoluminescence properties of Sr4Al14O25:Eu2+,Dy3+ (SAED) phosphors modified by adding Ho3+ in excess and partially substituting Dy3+ with Ho3+ (SAEDHs). Samples were produced using an established solid-state synthesis method known to consistently yield long-persistent afterglow phoshors. Substitutions were performed in stoichiometrically modified host lattices (Al/Sr = 3.2, 3.5, 3.7). Partially substituting Dy3+ with Ho3+ resulted in a remarkable increase in photoluminescence (PL) intensity, Ho3+ co-doping caused a shift in the main emission peaks between 494 and 497 nm and introduced new peaks as well. Important from the security application point of view, the PL intensity was significantly improved under both purple (400 nm) and blue (445 nm) illumination. Color shift of the powders from green to a yellowish and pale pink shade resulted from the Ho3+ addition. Afterglow (AG) properties and thermoluminescence (TL) response decreased non-gradually as Dy3+ was substituted by Ho3+, due to possible charge transfer effects caused by Ho3+. AG and TL properties remained more intact in the presence of Ho3+ when the Al/Sr ratio differed from the ideal 3.5 ratio. Rearrangements of trap energy levels, and energy transfer induced by Ho3+ co-doping were analysed by TL. Dy3+/Ho3+ co-dopants and Al/Sr stoichiometric ratios asymmetrically influenced the trapping/detrapping and energy transfer processes of the SAEDH phosphors. The developed new materials meet the general characteristics of long-persistent phosphors: charging by sunlight, efficient light conversion, chemical stability, all-night afterglow observable by the human eye.

The Near-infrared (NIR) nanothermometer has a novel application in medical treatment and biological sensing. Well dispersed β-NaYF4: Er3+ nanoparticles were synthesized and investigated for application of NIR optical temperature sensing. The fluorescence intensities of 837 nm and 980 nm with function of temperature were measured from 113 K to 443 K under 517 nm excitation. As the temperature rises, opposite change trend of these two emissions was observed and confirmed theoretically. The fluorescence intensity ratios of 980 nm and 837 nm in different temperatures were studied to investigate the NIR temperature sensing performance. High temperature sensitivity S (0.1914 K−1 at 443 K) and relative temperature sensitivity Sr (2.1% K−1 at 290 K) were obtained. Moreover, in the biological temperature sensing range from 270 K to 320 K, the value of Sr is greater than 2.0%. The result indicates that β-NaYF4: Er3+ NPs presents great NIR temperature sensing performance, and has potential application in biological temperature sensing.

The novel orange-red-emitting CaY0·5Ta0·5O3:xSm3+ phosphors (x = 0.01–0.30) with double perovskite structures are prepared by a solid-state reaction. X-ray diffraction (XRD) patterns, photoluminescence, thermal quenching mechanism, and decay curves of the phosphors are discussed. The CaY0·5Ta0·5O3:Sm3+ phosphor shows the orange-red emission (603 nm) under 407 nm excitation. The photoluminescence (PL) spectra of CaY0·5Ta0·5O3:Sm3+ phosphor are ascribed to the 4G5/2 to 6HJ (J = 5/2, 7/2, 9/2, and 11/2). The quenching concentration of CaY0·5Ta0·5O3:Sm3+ phosphor is approximately 2 mol%. The quenching temperature for CaY0·5Ta0·5O3:0.02Sm3+ is estimated more than 500 K, indicating the products have excellent thermal stability. The temperature-dependent luminescence intensity ratio (I650 nm/I603 nm) of CaY0·5Ta0·5O3:0.02Sm3+ phosphor is discussed. The electroluminescence (EL) spectrum of the packaged red LED is similar to the PL spectrum of CaY0·5Ta0·5O3:Sm3+ phosphor. The CIE coordinates of the packaged white LED are (0.307, 0.335), which approach the equal energy white light. Therefore, Sm3+-doped CaY0·5Ta0·5O3 phosphors have a promising application in white light-emitting diodes.

This ‘History” of Upconversion (UC), starts from a critical discussion about the idea of Bloembergen for an Infra Red Quantum Counter (IRQC) with my thesis Director: “it could not be a thesis subject because during the ions lifetimes not enough energy could be stored”. So it has not been my thesis subject which has been “glass lasers at 1,5microns”, but the object of my thoughts at home all the time. It directed me towards energy transfers study and the discovery of accepting ions already in their excited states which are the necessary steps for UC.

The system of Ho3+/Yb3+ co-doped Ge-Te-Ga-Gd glasses has been successfully prepared by traditional melting method. The thermal stability, Raman spectroscopy and mid-infrared luminescence were studied and analyzed systematically. The effectively enhanced thermal stability of the sample was obtained with the increasing introduced Gd2O3, which was confirmed by the positive ΔT values. The improved robustness and structural stability of the glass network were analyzed through Raman spectroscopy. Enhanced 2–3 μm emissions have been obtained by certain content Gd2O3 with an optimal choice of 15 mol% additive amount under 980 nm pumping. Furthermore, luminous parameters including J-O values, absorption, emission and gain cross sections have been presented together with energy transfer mechanism. Hence, this paper presents a new choice of Ho3+/Yb3+ co-doped Ge-Te-Ga-Gd glass as potential mid-infrared laser materials.

In this study, nanocrystalline Gd2O3:Sm, Gd2O2S:Sm and Gd2O2SO4:Sm phosphors were successfully synthesized through the urea homogeneous precipitation method. Nanocrystalline Gd2O2S:Sm phosphors with two different concentrations of sulfur were prepared. In the first procedure, the weight of sulfur was five times more than Gd2O3 weight (was called sample Gd2O2S:Sm(1)) and in the second procedure, it was equal (was called sample Gd2O2S:Sm(2)). The nanocrystalline powders were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, radioluminescence and thermoluminescence. The XRD and FT-IR results confirmed that nanocrystalline Gd2O3:Sm, Gd2O2S:Sm and Gd2O2SO4:Sm powders had the cubic, hexagonal and orthorhombic structure in preparation temperatures of 620 °C and 900 °C. The SEM images showed that nanocrystalline Gd2O3:Sm, Gd2O2S:Sm and Gd2O2SO4:Sm powders had a semi-spherical shape with a uniform mean size of about 30 nm in diameter and confirmed the XRD results. The presence of all elements was confirmed in the synthesized samples using EDX spectroscopy. The results showed that the weight percent of sulfur during the preparation of Gd2O2S had an effect on the size, morphology and the luminescence intensity of nanocrystalline Gd2O2S powder. Under X-ray irradiation (40 kV and 40 mA), the emission spectra of nanocrystalline Gd2O3:Sm, Gd2O2S:Sm and Gd2O2SO4:Sm phosphors were studied. The results showed the orange-red emission peaks which were observed at 605 nm were the strongest emission peak for all nanocrystalline Gd2O3:Sm, Gd2O2S:Sm and Gd2O2SO4:Sm powders. This peak was corresponded to the 4G5/2-7H7/2 energy transition of Sm3+ ion. The TL response of Gd2O3:Sm, Gd2O2S:Sm and Gd2O2SO4:Sm after irradiation with different X-ray time exposure exhibited a peak shifting towards the lower temperatures. The glow curve deconvolution method was used to calculate trapping parameters and the obtained results were investigated in detail.

To optimize luminescence properties of oxonitridosilicate phosphors are extremely necessary for improving lighting quality of white light-emitting diodes (WLEDs). Herein, we designed Ce3+, Eu2+ codoping and P5+↔Si4+ substitution in the presentative Ba3Si6O12N2:Eu2+ green phosphor to realize an enhancement of luminescence efficiency and thermal stability. Rietveld refinement results of Ce3+, Eu2+, P5+-doped Ba3Si6O12N2 (BSON) confirmed the formation of pure trigonal phase (P-3) of Ba3Si6O12N2 and the successful doping of Ce3+, Eu2+, P5+ ions. Ce3+ and Eu2+ ions randomly occupy two Ba crystallographic sites. Interestingly, a near unity energy transfer (ET, ∼100%) from Ce3+ ions to Eu2+ ions is observed. Meanwhile, the doping of P5+ ions into BSON also helps improving the luminescence efficiency and thermal stability, which should be attributed to the charge compensation and the relax of lattice strain. In addition, the white light emitting diodes (WLEDs) fabricated by employing P5+-doped BSON: Eu2+ present a better electroluminescence performance than BSON: Eu2+. This study could serve as a guide in developing optimized oxonitridosilicates phosphors with improved luminescence performances based on complete energy transfer and lattice variations in local coordination environments through cation substitutions, and the as-prepared Ce3+/P5+-codoped Ba3Si6O12N2:Eu2+ could be an excellent green-emitting phosphor for UV-to-Visible LED chips pumped WLEDs.

The fluorescence quenching rate (KQ) of fluorescence dye in continuous-wave stimulated emission depletion (CW-STED) system is experimentally investigated by utilizing a commercial dye (Coumarin 102). With the plotting of a power-dependence curve, it is found that the quenching rate is increasing rather than staying steady with the raising of depletion beam power in CW STED. Moreover, increasing fluorescence dye concentration and excitation power could also result in the increasing of KQ, which gives rise to the negative influence on spatial resolution of CW STED microscope. The results are helpful in understanding the influence of quenching on CW STED, improving the performance of CW STED microscope and developing new STED-compatible fluorescent dye.

Luminescence spectra of RAlO3:Eu3+ (R = Gd, Tb, Lu, Gd0.6Lu0.4, or Y) single crystalline films grown by liquid phase epitaxy were measured under high pressure in a diamond anvil cell. Pressure application leads to lattice constant changes affecting the intensity ratio of 5D0 –> 7F2 to 5D0 –> 7F1 transitions of the Eu3+ ion (the so-called K-value). In all samples, except LuAP, the K-value was found to decrease with increasing pressure. In the LuAP:Eu/YAG epitaxial structure, in addition to Eu emission, a broad luminescence band was observed at ambient pressure. At high pressure another broadband luminescence appeared, the intensity of which was strongly enhanced at increased pressure. We assign the origin of those bands to defects. The pressure dependence of the luminescence intensity of the defect band correlates with the pressure changes in the K-value. It points to mutual interaction of the defects and dopants in this material.

The combination of red quantum dots with YAG phosphors was used to improve color rendering of LEDs and color gamut of LED backlight. To further improve the stability of quantum dots applications, we encapsulate quantum dots with silicon dioxide. Quantum dots have a certain stability enhancement after coating silica. And the quantum dots-based LEDs fabricated using the modified quantum dots have luminous efficiency of up to 114 lm/w under 30 mA. At the same time, we investigated the temperature tolerance, UV stability and thermal characteristics of quantum dots devices. At the high temperature of 150°, the photoluminescence intensity of the silicon-coated quantum dots increases rather than decreases. In contrast, untreated quantum dots are almost ineffective. Under different operating currents and ambient temperatures, the correlation color temperature, luminous flux, color rendering index and coordinates stability of the silica encapsulated quantum dots device is better than the untreated one. After one month of accelerated aging test, the quantum dots devices have nearly stable optical parameters, such as luminous flux and color rendering index, and high reliability. A set of characteristics indicate that silica-coated quantum dots devices are well suited for large-scale industrial production and commercial applications.

The singlet oxygen quantum yield (ΦΔ) represents the ability of a photosensitizer to produce the photodynamic therapy effect. However, the pursuiting of strong phosphorescence properties of metalloporphyrins hindered the fact that they may have high ΦΔ. In this paper, we studied the effect of imidazole, a small organic molecule used as a solvent in the synthesis of multifunctional photosensitizers (PSs), on the ΦΔ of the PS, gadolinium-containing sinoporphyrin sodium (Gd-DVDMS), using a relative method with Rose Bengal as the reference and 1,3-diphenylisobenzofuran as the singlet oxygen trapping reagent. After completely removal of imidazole by dialysis, the ΦΔ value of Gd-DVDMS was obtained to be as high as 0.97. In addition, with an increase in the imidazole concentration, the ΦΔ of Gd-DVDMS gradually decreased, and stabilized at a value of 0.37. To understand the above phenomenon, the ultraviolet–visible absorption and photoluminescence spectra of Gd-DVDMS for different imidazole concentrations were analyzed. The triplet state quantum yield of Gd-DVDMS was constant, while the O2 quenching rate of the triplet state decreased; this indicated that the energy exchange between the PS and O2 was reduced by imidazole. We deduced that decrease in ΦΔ was attributable to the increase in the distance between Gd-DVDMS and O2, owing to imidazole wrapping around Gd-DVDMS. It is speculated that as the wrapping progressed, the effects of the dissolution and attachment of imidazole reached a balance, and hence, the ΦΔ remained constant.

Single crystal of La3Ga5.5Ta0.5O14 (LGT) doped with Dy3+ was fabricated by the Czochralski technique and investigated employing methods of optical spectroscopy. Polarized optical absorption spectra and luminescence spectra were recorded at room temperature. Unpolarized absorption and luminescence spectra were recorded at 10 K. Spectra of blue luminescence related to transitions 4I15/2, 4F9/2 → 6H15/2 were recorded at several temperatures in the 300–773 K region. Dy3+ ions have the same symmetry sites in LGT but their spectra show inhomogeneous broadening due to structural disorder of the host and are markedly anisotropic. Results of the Judd-Ofelt treatment made it possible to assess emission cross sections for the 4F9/2 → 6H15/2 blue luminescence and for the 4F9/2 → 6H13/2 yellow luminescence employing Fuchtbauer-Ladenburg formula and reciprocity method. In particular, a spectral distribution of La3Ga5.5Ta0.5O14: Dy3+ σ-polarized luminescence band with an emission cross section σem = 0.51 ·; 10−20 cm2 at 573.5 nm is favorable for a laser operation in the visible. Interpretation of the effect of temperature on the blue emission spectra leads to the conclusion that La3Ga5.5Ta0.5O14: Dy3+ is promising for application as luminescent thermometer.