白光LED用高效荧光粉的制备研究进展

制备具有球形度高、结构均匀、光学性能优异及发射光谱可控的YAG粉体是实现高性能白光LED的关键. 本文综述了目前国内外白光LED用高效荧光材料的主要研究成果,并对其主要制备技术的优缺点进行了较详细的分析;在分析总结相关研究的基础上,对目前白光LED用高效荧光粉的研究现状及存在的问题做了简要的概括,最后对其发展前景进行了展望,指出稀土元素的均匀掺杂及颗粒形貌的有效控制是解决白光LED显色性差、发光效率低等问题的有效措施,并提出等离子体方法有可能成为解决上述问题的有效途径之一.     

金属氧化物/聚合物异质结构电致发光

异质结构聚合物电致发光（HyLEDs）是近几年来聚合物电致发光研究的热点,其典型结构是将金属氧化物半导体材料用作聚合物电致发光器件（PLEDs）的载流子传输和注入层。本文概述了HyLEDs相对传统PLEDs的优势,分别从金属氧化物在PLEDs的阳极和阴极两个方面的应用对HyLEDs的研究进展进行了回顾,探讨了HyLEDs的工作机理,并对它的应用前景作出展望。     

Transparent Conducting Electrodes for Quantum Dots Light Emitting Diodes

In this review, we briefly describe a recent research development of transparent conducting electrodes (TCEs) for next‐generation quantum dot‐based light‐emitting diodes (QDLEDs). Although sputtered Sn‐doped In₂O₃ (ITO) and chemically grown F‐doped SnO₂ (FTO) electrodes have mainly been employed as transparent electrodes for QDLEDs, there have been great advances in TCE materials and fabrication processes. This review presents important characteristics of various TCE and applications in QDLEDs as a transparent cathode or anode. In particular, we will focus on characteristics of metal grids, metal nanowire, carbon nanotube, graphene, and hybrid electrodes for QDLEDs as promising alternatives to typical ITO and FTO electrodes. In addition, we discuss the current status of transparent conducting oxide‐based QDLEDs. By comparing the performances of QDLED with different TCEs, we suggest promising alternatives ITO or FTO electrodes.     

白光LED用荧光粉的研究进展

白光LED被誉为第四代照明光源,有着显著的节能前景和庞大的应用市场,荧光粉光转换型是未来白光LED发展的主流方向。本文重点介绍了蓝光芯片激发的黄色,绿色和红色荧光粉以及紫光芯片激发的红色,绿色荧光粉的研究进展,和该领域存在的问题及其发展趋势。     

Synthesis of Benzothiadiazole-Based Liquid Crystalline Polyacrylates for Polarized Light Emitting Diodes

Two benzothiadiazole-based liquid crystalline polyacrylates were synthesized. These polymers revealed a nematic liquid crystal phase and exhibited photoluminescence as well as polarized electroluminescence when incorporated into light-emitting diode applications. The polymers showed dichroic ratios of about 8.3–8.8 in UV-vis absorption and photoluminescence emission. The polymer with vinylene linkages (P2) showed better electroluminescence device performance than that with acetylene linkages (P1). The P2 device emitted red light at 604 nm with a turn-on voltage at 6 V, and a maximum polarized luminance of 235 cd/m² at 12 V, with an efficiency of 0.09 cd/A and a polarization ratio of 6.5.     

白光LED用新型荧光粉的探索

白光LED具有效率高、寿命长、响应快、安全、环保等优点,被誉为继白炽灯、荧光灯和高强度气体放电灯后的“第四代照明光源”.白光LED用荧光材料的制备及其发光性能的研究已成为半导体照明领域的一个热点.本文主要从蓝光芯片激发和近紫外光芯片激发的角度分别介绍了钼酸盐红色荧光粉和单一基质白光荧光粉的研究概况.     

Recent Advances in Encapsulation Materials for Light Emitting Diodes: a Review

Silicon - Light emitting diodes (LEDs) as the emerging green light sources are of great significance to achieve the energy saving and emission reduction. The encapsulation materials as the key...     

Polymer Light Emitting Diodes: Materials,Technology and Device

Polymer Light Emitting Diodes (PLEDs), the most promising name in the field of display technology has received tremendous attention from various research groups. The research on light emitting polymers are an interdisciplinary zone which has challenging investigates on materials science and engineering, physics of device architecture and technology. This review addresses the wide range of tailored polymers, evolution of LED device structure for high performance, single and multicolor polymer based LEDs. Though, polymers are possessing better efficiency and easy fabrication processes, it has very low stability and short life. This study also reviews, device degradation during device fabrication and operation.     

Photoluminescence of Sr2P2O7:Sm3+ Phosphor as Reddish Orange Emission for White Light‐Emitting Diodes

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.     

新型有机红色发光材料的设计、合成及在有机电致发光器件中的应用

有机电致发光器件（Organic Light—Emitting Diodes，OLEDs）具有直流电压驱动、主动发光、体积小、无视角限制、响应快，以及色彩全、制作工艺简单等优点，作为新型显示技术倍受瞩目．     

Orderly‐Layered Tetravalent Manganese‐Doped Strontium Aluminate Sr4Al14O25:Mn4+: An Efficient Red Phosphor for Warm White Light Emitting Diodes

Searching for an efficient non rare earth‐based oxide red phosphor, particularly excitable by light in the wavelength from 380 to 480 nm and unexcitable by green light, is essential for the development of warm white light emitting diodes (WLEDs). Here, we report a promising and orderly‐layered candidate: Sr₄Al₁₄O₂₅:Mn⁴⁺ with CIE color coordinates (0.722, 0.278). It has higher luminescence efficiency particularly upon blue excitation and is much cheaper than the commercial red phosphor 3.5MgO·0.5MgF₂·GeO₂:Mn⁴⁺ (MMG:Mn⁴⁺). In sharp contrast to Eu²⁺‐doped (oxy)nitrides, the phosphor can be synthesized by a standard solid‐state reaction at 1200°C in air. The effects of flux boron content, environment, and preparation temperature, sintering dwelling time as well as Mn concentration have been systematically investigated for establishing the optimal synthesis conditions. The low temperature emission spectra reveal that there are at least three types of Mn⁴⁺ ions in Sr₄Al₁₄O₂₅:Mn⁴⁺ due to the substitution for the distorted octahedral Al³⁺ sites. The AlO₆ layers where Mn⁴⁺ prefers to reside are well separated from one another by AlO₄ tetrahedra in one dimension parallel to axis a. This scenario can efficiently isolate Mn⁴⁺ ions from local perturbations, thereby enabling the high efficiency of luminescence. The energy transfer rates and mechanism are discussed.     

Antimicrobial Combined Action of Graphene Oxide and Light Emitting Diodes for Chronic Wound Management

Innovative non-antibiotic compounds such as graphene oxide (GO) and light-emitting diodes (LEDs) may represent a valid strategy for managing chronic wound infections related to resistant pathogens. This study aimed to evaluate 630 nm LED and 880 nm LED ability to enhance the GO antimicrobial activity against Staphylococcus aureus- and Pseudomonas aeruginosa-resistant strains in a dual-species biofilm in the Lubbock chronic wound biofilm (LCWB) model. The effect of a 630 nm LED, alone or plus 5-aminolevulinic acid (ALAD)-mediated photodynamic therapy (PDT) (ALAD-PDT), or an 880 nm LED on the GO (50 mg/l) action was evaluated by determining the CFU/mg reductions, live/dead analysis, scanning electron microscope observation, and reactive oxygen species assay. Among the LCWBs, the best effect was obtained with GO irradiated with ALAD-PDT, with percentages of CFU/mg reduction up to 78.96% ± 0.21 and 95.17% ± 2.56 for S. aureus and P. aeruginosa, respectively. The microscope images showed a reduction in the cell number and viability when treated with GO + ALAD-PDT. In addition, increased ROS production was detected. No differences were recorded when GO was irradiated with an 880 nm LED versus GO alone. The obtained results suggest that treatment with GO irradiated with ALAD-PDT represents a valid, sustainable strategy to counteract the polymicrobial colonization of chronic wounds.     

Luminescence Properties and Energy‐Transfer Behavior of a Novel and Color‐Tunable LaMgAl11O19:Tm3+, Dy3+ Phosphor for White Light‐Emitting Diodes

Novel LaMgAl₁₁O₁₉:Tm³⁺, Dy³⁺ phosphors were prepared utilizing a high‐temperature solid‐state reaction method. The phase formation, luminescence properties, energy‐transfer mechanism from the Tm³⁺ to the Dy³⁺ ions, the thermal stability, and CIE coordinates were investigated. When excited at 359 nm, the LaMgAl₁₁O₁₉: xTm³⁺ phosphors exhibit strong blue emission bands at 455 nm. After codoping with Dy³⁺ and excitation at 359 nm, the LaMgAl₁₁O₁₉:0.03Tm³⁺, yDy³⁺ phosphors emitted white light consisting of the characteristic emission peaks of Tm³⁺ and Dy³⁺. The Dy³⁺ emission intensity increased with the Dy³⁺ concentration due to the energy transfer from Tm³⁺ to Dy³⁺, and concentration quenching due to the high Dy³⁺ doping concentration (y = 0.1 mol) did not occur. The calculation of the CIE coordinates of the LaMgAl₁₁O₁₉:Tm³⁺, yDy³⁺ phosphors revealed the tunability of the emission color from blue to bluish‐white and to white by changing the excitation wavelength and the doping concentration. An energy transfer from Tm³⁺ to Dy³⁺ by dipole–dipole interaction was confirmed by the decay curve, lifetime, and energy‐transfer efficiency measurements. When excited at 359 nm, the LaMgAl₁₁O₁₉:Tm³⁺, Dy³⁺ phosphor also showed good thermal stability, suggesting that it can be used in white LEDs excited by a GaN‐based ultraviolet LED.     

Structure and Photoluminescence of A Blue‐Green‐Emitting Phosphor for Near‐UV White LEDs

A series of phosphors Ca_12(0.97?x)Al₁₄O₃₂F₂: 0.03Ce³⁺, xTb³⁺ have been prepared by a hightemperature solid‐state reaction using boric acid as flux. These oxyfluorides crystallize in cubic structure, space group. Under the near ultraviolet excitation within wavelength range 310–390 nm, Ca_12(0.97?x)Al₁₄O₃₂F₂: 0.03Ce³⁺, xTb³⁺ phosphors exhibit an intense emission covering a broad band of 370–500 nm derived from the 5d→4f transitions of Ce³⁺ and a characteristic emission at 544 nm of Tb³⁺. The emission can be tuned from blue to green by altering the relative ratio of Ce³⁺ to Tb³⁺ in the composition. The energy‐transfer mechanism from Ce³⁺ to Tb³⁺ is investigated based on the site occupancy of the luminescence center in the crystal structure of the Ca₁₂Al₁₄O₃₂F₂ host. More importantly, when a certain amount of boric acid is added as flux in the synthesis, the fluorescence intensity of the phosphors increases about 65%. Because of its broad excitation and efficiently tunable blue to green luminescence, the Ca_12(0.97?x)Al₁₄O₃₂F₂: 0.03Ce³⁺, xTb³⁺ phosphors may find promising application as a near UV‐convertible phosphor for white‐light‐emitting diodes.     

Effect of Particle Size on the Optical Properties of Yellow Silicate Phosphor in Light‐Emitting Diodes

Understanding the effect of particle size on the optical properties of phosphor is important to increase packaging efficiency in white light‐emitting diodes (LEDs). We have investigated the effect of particle size (10–20 μm, 20–25 μm, 25–32 μm) on the optical properties of a yellow silicate phosphor adopted in white LEDs. X‐ray diffraction results show negligible modification in crystallinity as the particle size of the yellow silicate phosphor varies, whereas the photoluminescence excitation intensity and quantum yield are enhanced as the particle size increased. LED packages fabricated using phosphors with different mean particle sizes, and their optical properties were analyzed. The radiant flux improved with increasing particle size, whereas the luminous flux increased with decreasing particle size. The effect of immersion on the optical properties of the LED light source has been also measured, and the details are discussed.     

Effect of Glass Refractive Index on Light Extraction Efficiency of Light‐Emitting Diodes

Light‐emitting‐diode (LED) encapsulants, such as epoxy and silicone resin, have a lower refractive index than YAG:Ce phosphor, and this is usually one of the major causes of LED inefficiency. To improve LED performance, a glass encapsulant is considered. In this study, the SiO₂–B₂O₃–ZnO glass system containing La₂O₃ and WO₃ was investigated as an encapsulant to minimize total internal reflection and to increase the light extraction efficiency of LED packages. The characterization of glass encapsulants was performed using a differential scanning calorimeter, a pycnometer, a prism coupler, X‐ray photoelectron spectroscopy, and integrating spheres. The refractive index increased linearly with increasing molar volume of glass because La₂O₃ and WO₃ act as modifiers in the glass, creating more nonbridging oxygen. The refractive index of glass increases with the content of La₂O₃ and WO₃, which is attributed to the increase in polarizability of oxide ions in the glass. When the refractive index between glass and phosphor matched, light extraction efficiency was maximized because total internal reflection decreased.     

一类掺杂稀土离子的红光与蓝光荧光体

采用高温固相反应在空气中成功合成了MBPO5:0.04Pr3+(M=Ca,Sr,Ba)荧光体,测定了样品的晶体结构和发射光谱,在发射光谱中可观察到Pr3+的发光,深入讨论了光谱特征及影响因素,这一研究结果为寻找新的稀土发光材料提供了依据。     

Yellow‐Emitting Y3Si6N11: Ce3+ Phosphors for White Light–Emitting Diodes (LEDs)

A novel Y_3?xSi₆N₁₁: xCe³⁺ yellow phosphor was synthesized using the carbothermal reduction and nitridition method at 1550°C for 16 h in this letter. Photoluminescence spectra indicated that the phosphor showed broad excitation spectrum and had strong absorption in range of 350–450 nm. It also gave a broad emission band (Full width at half maximum = 153 nm) centered at 575 nm under 425‐nm excitation. With increasing Ce³⁺ concentration, the strongest emission intensity was obtained at 5 mol% Ce³⁺ doping amount and a systematic redshift was observed as the Ce³⁺ concentration increased. The results indicate that this novel yellow phosphor is a promising candidate for using in blue‐chip‐excited white light–emitting diodes (LEDs).     

Far‐Red‐Emitting BiOCl:Eu3+ Phosphor with Excellent Broadband NUV‐Excitation for White‐Light‐Emitting Diodes

Rare‐earth ion‐doped semiconducting phosphor has attracted extensive attention due to the ability to achieve efficient luminescence through the host sensitization. Here, we present a new type red‐emitting Eu³⁺ ‐doped BiOCl phosphors possessing a broad excitation band in the near‐ultraviolet (NUV) region. Experimental measurements and theoretical calculations confirm that Eu³⁺ ion dopants result in forming impurity energy level near valence band, and the excellent broadband NUV‐exciting ability of Eu³⁺ ion is due to the electronic transitions of BiOCl band gap. Moreover, the highest emission intensity of the phosphors is from the ⁵D₀ → ⁷F₄ transition of Eu³⁺ around 699 nm (far‐red) through whether host excitation or direct Eu³⁺ ions excitation, which lie in the particular structure of BiOCl crystals. Our results indicate that the Eu³⁺ ‐doped BiOCl crystals show great potential as red phosphors for white‐light‐emitting diodes.     

白光发光二极管用单体白色荧光粉的研究进展

近年来,单体白色荧光粉,尤其是基于能量传递原理构建的白色荧光粉成为发光领域的研究热点。简要评述了近5年紫外一近紫外基白光LEDs用单体白色荧光粉的研究进展。重点阐述了单掺杂体系,以及基于能量传递原理构建的双掺杂及三掺杂等单体白色荧光粉的研究结果与最新进展;同时,分析和预测了该类材料的研究前景及发展方向。