摘要:Bloch surface wave (BSW) is an electromagnetic mode in which the light field is localized in the surface layer and propagates along the surface layer of the photonic crystal. In this paper, a PS∶C545T organic luminescence layer was prepared on a one-dimensional photonic crystal, and the fluorescence of the exciton of organic C545T molecules coupled into the BSW mode was observed. By studying the performance of the output light emission of the sample through the hemispherical lens coupling, different characteristics of the conventional luminescence and the BSW mode luminescence of C545T are analyzed and compared. The results show that the coupled BSW mode outputs a ring light spot, which has the characteristics of narrow spatial distribution, linear polarization and adjustable spectral with angle, and is obviously separated from the light spot of the conventional radiation mode. The radiation transition rate of luminous films on one-dimensional photonic crystals is anisotropic, and the BSW mode fluorescence has a faster radiation transition rate. The above luminescence characteristics of BSW mode can be utilized to develop polarized light-emitting devices with certain directivity.
摘要:Transparent display is one of the development directions for future displays, with huge application potential in fields such as smart windows, wearable electronic products, virtual reality technology, and touch screens. With the emergence of new luminescent materials such as organic, quantum dots, and perovskites, the brightness, efficiency, and stability of light-emitting diodes have rapidly developed. However, achieving high-performance transparent light-emitting diodes with symmetrical luminescence on both sides remains a challenging task. This article starts from three new luminescent materials, namely organics, quantum dots, and perovskites, and summarizes specific schemes for achieving transparency using different transparent electrodes. It summarizes the characteristics, advantages, and disadvantages of various transparent electrodes, and finally prospects the development of transparent displays.
摘要:One-dimensional photonic crystals (1DPCs) are artificially constructed periodic optical dielectric structures. 1DPCs can modulate the luminescent material mainly by defect mode modulation and band-edge mode modulation. 1DPC band-edge mode with a large density of photonic states can effectively modulate the luminescent properties of the luminescent material. In this paper, the fluorescence emission of colloidal quantum dot (CQD) materials coated on the surface of 1DPC is studied. By using different QD materials, different surface film thicknesses, and different angles for fluorescence detection, luminescence characteristics of the samples have been investigated. The results show that 1DPC band edge mode can effectively regulate the luminescence characteristics of CQD films located in the surface layer, effectively enhance the fluorescence emission intensity and narrow the emission linewidth. CQD materials controlled by 1DPC band edge mode have faster fluorescence radiation transition rate. The influence of 1DPC on the luminescent properties of CQD materials is helpful to optimize the design of the device structure, so as to greatly improve the performance of the luminescent devices.
摘要:Improving the upconversion luminescence efficiency is the key to promoting the practical application of upconversion luminescent materials. In the NaErF4@NaYF4 system, the inert NaYF4 shell can inhibit the concentration quenching under high Er3+ doping, and the upconversion luminescence is mainly from the energy transfer upconversion of Er3+-Er3+. In this paper, Er3+ and Yb3+ partition doped NaErF4@NaYbF4@NaYF4 core-shell nanoparticles were prepared by the coprecipitation method, and the energy transfer and back energy transfer processes between Er3+-Yb3+-Er3+ was studied. Since the 808 nm can only excite Er3+ but not Yb3+, under 808 nm excitation, Er3+ harvests the pumping energy and transfers it to Yb3+ and subsequently back to Er3+ due to the protection offered by NaYF4 inert outer shell, which finally enhances the upconversion luminescence of Er3+. When the doping concentration of Yb3+ in the intermediate layer is 100%, the maximum enhancement multiple is 24.9 and 9.79 for green and red upconversion, respectively.
关键词:rare earth nanoparticles;upconversion luminescence;back energy transfer;β-NaErF4
摘要:Owing to its excellent stability and wide self-trapped excitons(STEs)emission induced by the special three-dimensional(3D)crystal structure, all inorganic cadmium-based metal halide perovskite CsCdCl3 has attracted broad attention in the field of solid-state lighting. However, the luminescence efficiency through radiative recombination of STEs is not high. Herein, a serious of Mn2+-doped hexagonal CsCdCl3∶x%Mn microcrystals were prepared by a facial room-temperature solution method. Under 254 nm UV excitation, CsCdCl3 microcrystals after Mn2+ doping show bright orange-yellowish emission peaking at about 598 nm with a full width at half-maximum of 75 nm and the photoluminescence quantum yield of 99.1%. Steady-state and transient photoluminescence results suggest that the broad emission is originating from the matrix STEs and the Mn2+ dopant. Meanwhile, the as-synthesized materials also display excellent air, heat, and water stability. Two white light-emitting diodes(LEDs)were further fabricated by integrating a mixture of CsCdCl3∶5%Mn and commercial phosphors on a deep UV LED and a blue LED, which demonstrate bright white light with CIE coordinates of (0.36, 0.35) and (0.40, 0.36), high color rendering indices of 91 and 83, respectively. The synthesized Mn2+-doped CsCdCl3 phosphor holds great promise for new-generation luminescent materials in the field of lighting.
摘要:A series of CsLa(WO4)2 phosphors with different doping concentrations of Pr3+ were prepared by the high temperature solid-state method. X-ray diffraction (XRD), diffuse reflectance spectra, excitation spectra, emission spectra and fluorescence decay curves were analyzed. The concentration and temperature-dependent luminescent properties were investigated. The fluorescence temperature sensing parameters were calculated based on the fluorescence intensity ratio (FIR) technique. The optimal doping concentrations of Pr3+ for the emissions from 3P0 and 1D2 levels in CsLa(WO4)2 were found to be 0.03 and 0.01, respectively, and it was confirmed that concentration quenching was caused by the dipole-dipole interactions. The emission trends of 3P0 and 1D2 levels were different with temperature, mainly due to the effects of the cross-over process to Pr3+-W6+ intervalence charge transfer (IVCT) state, cross relaxation process and multiphonon relaxation process. The different concentration and temperature-dependent characteristics of the emissions from 3P0 and 1D2 levels enabled tunable color emissions. According to the fluorescence intensity ratio (FIR) of 3P1→3H5/3P0→3H4 thermally coupled energy levels and 1D2→3H4/3P0→3H4 non-thermally coupled energy levels, the calculated relative sensitivities were 586.01/T2·K-1 and 1 071.78/T2·K-1, respectively, indicating the potential application of this material in temperature sensing.
关键词:Pr3+;CsLa(WO4)2;photoluminescence;temperature sensing;fluorescence intensity ratio (FIR)
摘要:Efficient and thermally robust glass ceramic phosphors combined both the merits of phosphors and matrix have received growing interests in the white-LED and laser driven lighting. Here, the YAG∶Ce glass ceramics were prepared by an energy saving and fast selective laser sintering with suitable parameters (laser power: 24 W, scanning speed: 135 mm/s, scanning intervals: 9 μm). The results show that selective laser sintered YAG∶Ce glass ceramic after heat treatment (630 ℃, 1 h) exhibits the typical Ce3+ 4f→5d broadband excitations centered at 340 nm and 455 nm and 5d→4f emission centered at 570 nm and its photoluminescence quantum yield is up to 82%. Moreover, combining with a 450 nm LED chip (3.11 V, 0.30 A) directly, the obtained performances including the luminous flux (92 lm), luminous efficiency (98 lm/W), color rendering index (69), correlated color temperature (5 001 K), and chromaticity coordinates (0.34, 0.35) are close to other YAG∶Ce glass ceramic reported. All of those validate the suitability of selective laser sintering for preparation of glass ceramics.
摘要:Organic red emitters have attracted significant research attention owing to their promising applications in panchromatic display, biological imaging, and fluorescent probes. Herein, a fluorescent compound DBPAP was developed by introducing electron-donating group diphenylamine derivative at the positions of 3 and 6, and electron-withdrawing group pyridine at the positions of 11 and 12 of dibenzophenazine core. Its chemical structure was characterized and confirmed by elemental analysis, nuclear magnetic resonance spectroscopy and mass spectroscopy. Spectroscopic results showed that the addition of the poor solvent water to the tetrahydrofuran solution of DBPAP caused obvious aggregation-induced emission (AIE) phenomenon. Based on its efficient red emission in solid state, LED devices based on DBPAP doped PMMA were fabricated. The devices exhibited a red emission at 644 nm with Commission Internationale de L’Éclairage coordinates of (0.58, 0.35), and a maximum brightness of 1 616 cd·m-2 at a 3.8 V work voltage. This work provides a promising strategy for developing solid-state red emissive organics.
关键词:Organic red emitters;dibenzophenazine;donor-acceptor;aggregation-induced emission;red LED
摘要:In this paper, scintillator Ba2LuNbO6∶Tb3+(x = 0.01, 0.02, 0.05, 0.10, 0.20) phosphors with double perovskite structure were synthesized by the traditional high temperature solid state method. The crystal structure, morphology, and optical properties of the as-obtained Ba2LuNbO6∶Tb3+ phosphors were investigated in detail. Under X-ray excitation, the radiation luminescence (RL) spectra of Ba2LuNbO6∶0.1Tb3+ phosphor exhibit the characteristic emissions of Tb3+ ions, and the strongest emission peak is dominantly located at 545 nm. The RL intensity gradually increases with the increased concentration of Tb3+ ions, and achieves the optimized intensity when x = 0.1. In addition, the thermoluminescence (TL) curve of Ba2LuNbO6∶0.1Tb3+ phosphors after X-ray irradiation for 5 min, manifest that there are two deep traps, located at T1(377 K) and T2(460 K), respectively. The corresponding trap depths are respectively calculated to be 0.754 eV and 0.920 eV, which indicates that the as-explored sample performs a potential optical storage performance. Moreover, the captured carriers captured by deep traps could be released induced by thermal stimulus and the 980 nm laser, and then resulting in bright photo-stimulated luminescence (PSL) and thermal-stimulated luminescence (TSL) behaviors, respectively. Furthermore, the flexible scintillator film encapsulated with Ba2LuNbO6∶Tb3+ phosphor and PDMS shows high X-ray imaging resolution(12.5 lp/mm) and time-delay imaging characteristics at low radiation dose, demonstrating that the as-fabricated Ba2LuNbO6∶0.1Tb3+ phosphors exhibit potential application prospect in X-ray detection and X-ray information storage.
摘要:As one of the most important schemes to realize the stretchable displays, the stretchable light-emitting device array based on the island-bridge structure has attracted much attention. In this paper, we introduce the research progress of stretchable light-emitting device array based on island-bridge structure in the past ten years, and summarize the performance and characteristics of each device. Focusing on the key issues such as stretchability, mechanical stability and display quality of the device, the shape design and material selection scheme of the stretchable wires (interconnect bridge) between luminous units are introduced. The common optimization strategy of high-density pixel integration, tensile strain distribution and the solution for decreased pixel density due to the increase of stretchability are summarized. At present, the research of the stretchable luminescent display array based on island-bridge structure is still in its initial stage. The design, fabrication and realization of high-performance devices still face many challenges. This review aims to make some contribution to advancing the development of stretchable displays by summarizing current research.
摘要:Superluminescent diode (SLD) has optical characteristics such as high power, wide spectrum and low coherence, and has high application value in the fields of optical fiber communication, industrial defense, biological imaging and trace gas detection. This paper focuses on the output power and spectral bandwidth characteristics of SLD, and comprehensively reviews the research progress of quantum well, quantum dot near-infrared SLD and quantum cascade mid-infrared SLD. Among them, the novel active structure of InP based quantum dash, hybrid quantum well/ quantum dots and hybrid quantum well-dots, as well as quantum dot doping and selective area intermixing are introduced in detail. Finally, the application prospects of SLD are outlined, and the potential research directions and technological application trends of SLD are discussed.
摘要:Passivation of the lower surface (buried interface) of perovskite using organic small molecules is an effective strategy to suppress carrier recombination. This work focuses on passivation of the buried interface of perovskite by pre-coating the passivation material of phenylethylamine (PEA) before depositing the perovskite film. After passivation treatment, the grain size and morphology of the perovskite crystalline film did not change. After passivation, there is a slight red-shift in the absorption edge and emission wavelength of perovskite, and a slight increase in the energy level of highest occupied molecular orbital. “Pb” binding energy moves to a higher level, while “N” binding energy moves to a lower level. These results confirm that the “N” atoms on PEA molecules can interact with the dangling “Pb” at the buried interface of perovskite. The results showed a significant reduction of residual PbI2 in perovskite, indicating that PEA molecules reacted with PbI2 to form a certain complex. Furthermore, the solar cells were fabricated to investigate the passivation effect and the results showed that the open-circuit voltage (Voc), short-circuit current density(Jsc), fill factor(FF) and power conversion Efficiency(PCE) of the control perovskite solar cells were 1.041 V, 21.29 mA/cm2, 74.09%, and 16.41%, which for PEA-passivated perovskite solar cells, increased to 1.102 V, 22.44 mA/cm2, 79.28%, and 19.6%, respectively. The significant improvement of device performance induced by passivation of perovskite buried-interface defects is mainly due to the reduction of carrier recombination which mainly attributed to passivation of the defects caused by unsaturated-coordination “Pb”, passivation of the defects caused by the complex phases of PbI2 microcrystals, and improvement of the charge transfer rate between perovskite and the hole-transporting layer. The stability of passivated perovskite solar cells is significantly enhanced. This simple and effective buried-interface passivation strategy can be applied to the fabrication of large-scale perovskite solar cells in the future.
摘要:This paper proposes a strategy to successfully realize ultra-thin transparent conductive Ag thin films with excellent surface, optical, and electrical properties by introducing a silver oxide seed layer onto the surface of a glass substrate. Firstly, a 1-nm-thick Ag film is evaporated onto a glass substrate by thermal deposition and then treated with oxygen plasma to generate a silver oxide seed layer. The seed layer can alleviate the random migration of Ag atoms and improve the nucleation density of the subsequently deposited Ag atoms, thus promoting the film formation of Ag atoms. An efficient phosphorescent organic light-emitting device was fabricated using the realized ultra-thin transparent silver oxide/silver film as an anode. The device's maximum current efficiency and power efficiency are 60.4 cd·A-1 and 63.2 lm·W-1, respectively, 1.45 and 1.60 times higher than those of the conventional ITO-based devices. The results show that the ultra-thin transparent Ag thin film with silver oxide as a seed layer is a highly promising transparent conductive electrode.
摘要:The new perovskite solar cells based on ABX3 crystal structure material have the advantages of high photoelectric conversion efficiency, solution processability, and low temperature process compatibility. At the same time, semitransparent perovskite solar cells prepared by using the advantages of simple synthesis methods, adjustable band gap and controllable film thickness and transmittance of perovskite materials have brought new opportunities for the development of thin film photovoltaics. Semitransparent solar cells have broad application prospects in building-integrated photovoltaics and tandem photovoltaics. Developing efficient and highly stable semitransparent perovskite solar cells has become a research focus in the photovoltaic field. This article systematically reviews the technical strategies for selecting functional layer (perovskite photoactive layer, charge transport layer and electrode) materials, regulating optical properties, optimizing electrical properties, and regulating the preparation processes of semitransparent perovskite solar cells. At the same time, some prospects for the future development of semitransparent perovskite solar cells are presented.
关键词:semitransparent;building photovoltaic integration;tandem;perovskite solar cells
摘要:Based on the reduction of photon reflection, scattering and spontaneous fluorescence, NIR-Ⅱ window enables high resolution and signal-to-noise ratio biofluorescence imaging, which plays an important role in a variety of biomedical applications. The construction of donor-acceptor-donor structure is an effective method for the design of NIR-Ⅱ small organic molecules. NIR-Ⅱ small organic molecules based on benzothiadiazole structure can not only realize optical imaging, but also realize phototherapeutics by utilizing the light-activated excited state energy conversion. This review summarizes the research advances of NIR-Ⅱ small organic molecules based on benzobisthiadiazole (BBT) and [1,2,5]thiadiazolo[3,4-g]quinoxaline (TQ) in bioimaging and image-guided therapy, and prospects of the design and application of NIR-Ⅱ small organic molecules in the future are presented.
摘要:Lanthanide Eu3+-doped metal-organic backbone material Eu/ZIF-67 was prepared by a one-step hydrothermal method with a novel pleated sphere structure. A dual-emission fluorescent hybrid material Eu/ZIF-67@ZnO QDs with a zeolite imidazolium ester backbone was obtained by loading ZnO quantum dots onto the surface of Eu/ZIF-67 via coordination bonding. The structure, morphology and fluorescence sensing properties of the material were characterized in detail. Furthermore, the fluorescent material was found to display the dual fluorescence emission of ZnO quantum dots and lanthanide red europium ions. The fluorescence sensing performance of Eu/ZIF-67@ZnO QDs to tannic acid was further investigated, and the results indicated that tannic acid can effectively burst the characteristic fluorescence emission of Eu/ZIF-67@ZnO QDs at ZnO QDs with a detection limit of 0.029 9 µmol/L. Meanwhile, Eu/ZIF-67@ZnO QDs have the fluorescence response to tannic acid with anti-interference ability, which can be used as a cost-effective fluorescence sensor to specifically identify tannic acid.
摘要:Eu(DBM)3Phen was firstly encapsulated into carboxylated polystyrene microspheres by the encapsulation method, and then the lanthanide luminescence center Tb3+ was introduced by coordination to obtain the fluorescent polystyrene microsphere hybrid probe Tb-PS@Eu(DBM)3Phen with dual emission centers. The results indicated that Tb-PS@Eu(DBM)3Phen has excellent stability, dispersibility and fluorescence properties. In addition, by further investigating the fluorescence sensing properties of the probe molecule on 2,6-pyridinedicarboxylic acid (DPA), it was found that Tb-PS@Eu(DBM)3Phen could produce a significant enhancement with the present of DPA, which might be due to the coordination of terbium ions on the surface of DPA and polystyrene microspheres, which in turn affected the energy transfer process between the ligand-rare earths, resulting in Tb-PS@Eu-(DBM)3Phen's fluorescence enhancement. Meanwhile, Tb-PS@Eu(DBM)3Phen has strong selectivity and anti-interference ability for DPA, which is expected to be used as a potential fluorescent probe for the recognition of DPA.