Luminescence in Zinc Selenide Doped with Sn and (Sn,Dy) Phosphors

Zinc selenide doped with Sn and (Sn, Dy) phosphors has been prepared by firing the samples in an atmosphere of nitrogen gas. The voltage and frequency dependence of electrolyte brightness has been studied. Voltage dependence of electroluminescence (EL) brightness reveals an acceleration collision mechanism in the Schottky barrier at the metal–semiconductor interfaces. EL and photoluminescence (PL) spectra and thermoluminescence (TL) glow curves of these phosphors have also been recorded to understand the nature and mechanism involved in the luminescence process. The trapping parameters are calculated for the glow curves of these phosphors.     

Voltage-tunable Electroluminescence of Porous Silicon

The voltage-tunable EL was obtained upon cathodic bias of n-type PS in contact with aqueous solution containing the persulphate ion. The EL behavior as a function of the external voltage and time was investigated. The results suggest that the mechanisms of voltage-tunable EL of n-typt PS cannot easily be attributed to quantum confinement effect.     

聚(2-甲氧基-5-丁氧基)对苯乙炔的合成、表征及光性能研究

１９９０年,Ｂｕｒｏｕｇｈｅｓ等［１］发现聚对苯乙炔（ＰＰＶ）类衍生物不仅是导电高分子材料,而且也是性能优良的发光材料．随后,许多科学家立即将注意力集中于这类共轭聚合物的合成及光性能的研究上,并取得了可喜的研究成果［２］．目前,对ＰＰＶ衍生物的合成,...     

多孔硅表面钝化对其发光性能的影响

报道多孔硅（PS）的表面钝化对其光致发光（PL）和电致发光（EL）的影响。PL和EL谱表明,经钝化处理的PS的PL和EL强度明显增强,且发光峰位较大蓝移;存放实验表明,经钝化处理的PS的PL和EL发光强度和发光峰位具有较好的稳定性;I～V曲线显示,经钝化处理的PS发光器件具有较低的启动电压。这些结果表明：用钝化处理的方法是提高PS的PL和EL强度和稳定性及改善其器件性能的有效途径。     

Electroluminescent method for determining hydrogen peroxide and peroxydisulphate ions in aqueous solution using TiO(2) film electrodes

An electrochemical optical sensor system with luminescence response was proposed for the continuous determination of hydrogen peroxide or peroxydisulphate concentration in aqueous solutions. The electroluminescence (EL) of TiO(2) film electrodes, which arises under conditions of the cathodic polarization as a result of the hole injection into the TiO(2) from high-energy OH or SO(4)(2-) radicals produced by the electroreduction of H(2)O(2) or S(2)O(8)(2-) ions on the electrode surface, was used as the analytical signal. The EL response is linearly related, in a logarithmic scale, to the hydrogen peroxide or peroxydisulphate concentration ranging from 10(-3) to 10(-1) M H(2)O(2) and from 5 x 10(-4) to 1 M Na(2)S(2)O(8). It was shown that a substantial increase in the quantum efficiency of the EL and, as a consequence, in the sensitivity of the sensor system can be achieved by doping TiO(2) films with chromium. The potential dependence of the EL spectrum for TiO(2) electrodes in S(2)O(8)(2-) solutions differs essentially from that in H(2)O(2) solutions which allows measurement of the concentration of S(2)O(8)(2-) ions when they coexist with H(2)O(2) in solution.     

多孔硅制备条件对其电致发光特性的影响

应用蒸镀-阳极氧化法制备结构为ITO/PS/p-S i/A l的多孔硅电致发光器件,在7.5V电压下实现了数小时连续电致发光.实验表明,多孔硅电致发光峰位会随着阳极氧化电流密度的增大、腐蚀时间的延长以及HF酸浓度的降低而蓝移.欲制备工作电压较低、发光时间较长、发光效率较高的电致发光样品,则多孔硅制备时的阳极氧化应使用较低电流密度和较短的腐蚀时间.     

n型多孔硅的电发光性能及其XPS和LIMA表征

ｎ型多孔硅的电发光性能及其ＸＰＳ和ＬＩＭＡ表征①李国铮＊张承乾张强（山东大学化学系，济南２５０１００）（厦门大学化学系，厦门３６１００５）多孔硅（ＰＳ）的发光性能与其化学组成和结构的关系已为人们所关注．曾有人认为，发光是由于纳米级多孔硅的量子限制效应...     

Blue light-emitting and electron-transporting materials based on dialkyl-functionlized anthracene imidazophenanthrolines

Two novel blue light-emitting materials based on bis(tert-butyl)anthracenyl-imidazophenanthrolines (BAIPs) have been synthesized and extensively characterized. Both materials exhibited a non-aggregate feature with high fluorescent quantum efficiency and excellent thermal stability. They can serve both as emissive and electron-transporting materials used in electroluminescence (EL) device for blue emission with high luminescence and external quantum efficiency. This study demonstrates that they are potentially useful for a wide range of applications in EL technology.     

Cathodic electroluminescence at the terbium(III)-doped oxide-covered tantalum electrode and its feasibility for the determination of hydrogen peroxide

Anodization of the tantalum electrode with a symmetric double-step potential, (i.e., sequential positive and negative potential pulses with intermittent zero potential pulses), but not with a conventional DC potential, in an electrolyte containing traces of terbium (III) produces a terbium (III)-doped oxide film on the electrode surface. The pulsed cathodic polarization of this doped electrode in the presence of hydrogen peroxide or peroxodisulfate generates sub-bandgap electroluminescence where the oxide-bound terbium (III) is the radiative recombination center. The detailed mechanism for this terbium(III)-based sub-bandgap electroluminescence is discussed, as is the possibility of using the electroluminescence for the determination of trace hydrogen peroxide in aqueous solution.     

Dependence of Performance of Organic Light-emitting Devices on Sheet Resistance of Indium-tin-oxide Anodes

IntroductionIndium-tin-oxide(ITO) has been widely used asthe anode material in organic light-emitting devices(OLEDs) because of its high transmittance in the visi-ble region and low electrical resistivity. In the pastyears, many investigations focused on …     

多孔硅-导电聚酯材料复合发光器的光学特性研究

poly-4-dicyanomethylene-4H-cyclopenta\[2,1-b:3,4-b'\]dithiophene monolayer (PCDM)是一种导电、低导带聚酯材料.如果在多孔硅纳米结构中附上一层以自组方式生成的PCDM单分子层,就可以制成能够产生稳定电致发光的器件.发光器的结构是金/PCDM/多孔硅/硅/铝.发光器的电致发光,在白天可用肉眼观察到.有很宽的发光波长,几乎覆盖了整个可见光区域且峰值位于650 nm.发光器的面积为1 cm2,启动正向电压在14～30 V,电流约300 mA.经长时间测试,发光器的稳定性很好,在空气中放置3个月,在输入功率不变的情况下,发光强度也不发生变化.当施以反向电压时,样品仍可以发光而且稳定性较高,在250 h内I～V未发生明显变化.扫描电镜图像显示PCDM覆盖的表面要比多孔硅表面平整,而PCDM分子有可能进入到多孔硅纳米孔径当中去,起到了提高发光器稳定性和延长其寿命的作用.     

多孔硅于甲酸-甲酸钠溶液阳极偏压下的电致发光研究

用荧光分光光度法现场监测了多孔硅于甲酸-甲酸钠溶液阳极偏压下的电致发光行为。发现该体系的电致发光峰值随着阳极偏压增大而发生蓝移;发光峰能量值与阳极偏压呈良好的线性关系,其斜率与多孔硅在阴极偏压下电致发光的结果一致。扫描探针技术研究表明：多孔硅的表面形貌明显地影响其发光性质。提出了多孔硅在甲酸-甲酸钠溶液中阳极偏压下的电致发光与多孔硅表面的Si-H键的氧化作用有关的发光机理。发现了多孔硅于甲酸-甲酸钠溶液中在阳极偏压下电压调制的可见光发射行为,并用量子限制效应对该现象进行了解释。     

Electroluminescence of Organoaluminum Complexes in the Presence of Silica Gel

It was demonstrated that light-emitting materials can be produced by the photochemical dissolution of aluminum in composites based on a cresol–formaldehyde novolak resin and CBr₄in the presence of triphenylmethane dyes such as aluminon, pyrocatechol violet, and malachite green. The electroluminescence (EL) is due to the formation of organoaluminum complexes. The SnO₂(anode)/novolak resin + pyrocatechol violet/Al (cathode) diodes exhibited the highest EL intensity. Compositions based on aluminon are characterized by weak EL, which increased by a factor of 30 upon the additional introduction of silica gel into the composition. As a result of supporting a PVA film on the diode surface (on the cathode side), the EL increased by a factor of 1.5 and became as high as 10 cd/m². This value is comparable to the EL of pyrocatechol violet–containing diodes. The possible mechanism of the influence of silica gel and the importance of a PVA film for increasing the EL intensity are discussed. In the aluminon-based compositions, the dependence of EL on the diode storage time both with and without an applied voltage was measured.     

Luminescence Study of ZnS Quantum Dots Prepared by Chemical Method

We report synthesis of ZnS quantum dots by chemical method at room temperature. In this technique, ZnS quantum dots are produced by simple chemical reactions where zeolite, acts as matrix, plays the key role in controlling particle growth during synthesis. Quantum dots exhibit luminescence properties such as Zn²⁺ related emission, efficient low voltage electroluminescence, and super linear voltage-brightness EL characteristics. This study demonstrates the technological importance of semiconductor nanosystems prepared by low cost chemical route.     

Micro-gas-discharges as source of cathodic electroluminescence in non-aqueous solutions

The cathodic light emission observed during electrolysis of solutions of simple inorganic salts (e.g. LiClO₄, NaBF₄ and Tb³⁺ salts) in solvents such as dimethylformamide, dimethylsulphoxide, and POCl₃ at potentials higher than 6 V has been analyzed using spectroscopic, microscopic and electroanalytical techniques.Experimental results indicate that insulating (“passive”) layers on the cathode play an essential role in the mechanism of this electroluminescence. High current densities in the pores of these layers heat the solution and finally lead to local vaporization and decomposition of the solvent, thus creating insulating gas-filled cavities in the pores. If the applied voltage is sufficiently high, an electrical breakdown can develop across this cavity producing the observed luminescence phenomena.The luminescence emission spectra are indicative of excited gaseous species. Insulating model-layers obtained by glow-discharge polymerization were deposited on the cathode and used as models for electrodes with passive layers. Light emission was significantly more reproducible at such electrodes and allowed us to obtain reproducible voltage—current—light curves which support the proposed mechanism. The luminescence from Tb³⁺-ions occurs by energy transfer from the gas discharge.     

Fluorophor-enhanced cathodic electroluminescence at an oxide-covered aluminum electrode

Symmetric double-step potential (i.e., positive and negative potential) pulses with intermittent zero potential pulses at the oxide-covered aluminum electrode generates anodic and cathodic electroluminescence in an aqueous environment in the presence of potassium peroxodisulfate. Organic fluorescent compounds generate changes in the cathodic electroluminescence but not in the anodic emission: intensity is greatly enhanced and the spectrum of a fluorophor-enhanced electroluminescence becomes similar to the fluorescence spectrum of the fluorophor. The mechanism of the fluorophor-enhanced peroxodisulfate-induced cathodic electroluminescence is discussed. It is demonstrated by means of salicylic acid as the model fluorophor that this electroluminescence can be exploited to determine trace organic fluorescent compounds.     

Cross‐Linked Alq3‐Containing Polymers with Improved Electroluminescence Efficiency Used for OLEDs

Summary: Homopolymers and a series of copolymers with tris‐8‐hydroxyquinoline aluminum (Alq₃) as the cross‐links are synthesized. All these polymers show improved electroluminescence (EL) efficiency over their previously reported counterparts. Among them, the copolymers containing Alq₃ and carbazole groups show higher EL efficiency than that of the homopolymers. We also demonstrate the feasibility of generating patterns using the homopolymers via photopolymerization. The cross‐linked nature, selectivity of patterning, high thermal stability, and EL efficiency might render these polymers a promising material in fabricating large‐scaled multilayered sub‐pixellation organic light‐emitting diodes (OLEDs).

Current–voltage and the electroluminescence–voltage curve of two‐layer devices for the Alq₃‐homopolymers and the Alq₃‐copolymers (luminance is shown by the symbols without lines).     

Synthesis and photoelectric properties of new Pr-bonded polymers by coordination of isopropyloxide and bipyridine unit

A series of novel praseodymium(Pr)-bonded polymers were successfully synthesized via the coordination reaction and palladium-catalyzed Suzuki coupling reaction of 2,7-dibromo-9,9'-dioctylfluorene and different amounts of 5,5'-dibromo-2,2'-bipyridine. The resulting polymers were characterized by ~1H-NMR and GPC. The photoluminescence(PL) and electroluminescence(EL) properties of the resulting polymers were studied to explore the effects of the Pr triisopropyloxide. The results showed that the incorporation of Pr into the polymers caused better coplanarity and effective intermolecular or intramolecular interaction, leading to the higher emission intensity at long-wavelength. Further, it was also found that the emission light color could be tuned from blue to green by introduction of a small amount of Pr into the polymer main chain. A single-layer green emitting EL device based on PF(Bipy Pr)6 with 6 mol% Pr content was fabricated. The device had a low turn-on voltage of 6 V, a brightness of 705.3 cd·m~(-2), the maximum luminous efficiency of 1.53 cd·A~(-1) and the maximum power efficiency of 0.69 lm·W~(-1).     

Polymer light‐emitting electrochemical cell based on a block copolymer containing tri(ethyleneoxide) spacers

We presented the optical properties of a novel block copolymer containing chromophores, 2,5‐dimethoxy‐1,4‐di(α‐(2‐naphthalene vinylene)benzene (MDNVB) and spacers, tri(ethylene oxide) (TEO). The intrachain and interchain excitations due to the molecular aggregation are responsible for the significant bathochromic shift in the photoluminescence (PL) spectrum when going from the solution to the thin film. With a certain content of the polymer electrolyte, blue–green light‐emitting electrochemical cell based on this block copolymer was demonstrated with the turn‐on voltage of 2.5 V, the maximum electroluminescence (EL) efficiency of 1.2 cd/A, and the d.c. response time of less than 5 sec, indicating strongly that an improved morphology of the active layer is formed because of the effective TEO‐PEO interaction. Lowering the content of the polymer electrolyte results in a higher turn‐on voltage and smaller injection current; increasing the content leads to a considerable microscopic leaking current and lower EL efficiency of the device. Copyright © 2002 John Wiley & Sons, Ltd.     

一种含铽单体的合成及其电致发光研究

合成了一种具有聚合活性的含铽配合物单体(Tb(acac)~2(AA)phen),并用红外光谱、元素分析等进行表征。研制了结构为ITO/PVK/Tb(acac)~2(AA)phen/Alq^3/Al的电致发光器件并测定了它的电致发光谱、电流-电压特性、亮度-电压曲线等性能。该器件具有良好的整流特性,其电致发光显示了铽离子的绿光特征发射,并具有较好的单色性。同时,探讨了该器件的电致发光机理。