绝缘层LiF/Al电极对提高P-PPV发光器件发光性能的研究

为了提高聚合物电致发光器件中Ba（Ca）／Al阴极的稳定性,在该阴极与聚合物发光材料poly（2-（4-ethylexyl）phenyl-1,4-phenylene vinylene）（P-PPV）层之间插入一层7nm的LiF绝缘层,发光器件的发光性能在多项参数（发光器件的电压．电流特性、发光强度及外量子效率,以及电流效率等发光性能指标）上能够与工作性能优良但稳定性较差的Ba（Ca）／Al电极结构PLEDs器件的发光特性具有可比性。这对于研制高效率、高稳定的聚合物电致发光器件并最终将其用于商业目的,具有重大现实意义。     

电极修饰层PEO/LiF对聚合物发光二极管发光性能的提高

在以聚合物发光材料poly(2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylene vinylene)(MEH-PPV)为发光层的聚合物发光二极管(PLEDs)的金属阴极与聚合物发光层之间插入一层绝缘的聚合物poly(ethylene oxide)(PEO),发光器件的发光性能有所提高,尤其是PEO/LiF共同对Al电极修饰时发光器件的开启电压、发光强度、电流效率等性能显著提高。初步分析表明修饰层的插入造成了发光聚合物层与金属电极界面形成势垒,通过空穴堆积抑制空穴的注入,增加电子的注入,并且PEO层可以有效抑制激子在阴极的猝灭。     

CsF/Al阴极对提高芴基饱和红光器件性能的研究

从聚合物/电极界面修饰的角度对基于饱和红光聚合物PFO-SeBT(9,9-二辛基芴与4,7-二硒吩-2,1,3-苯并噻二唑的无规共聚物)的发光二极管的性能进行了改进，通过采用CsF/Al阴极并优化CsF的厚度以及在PFO-SeBT1/阳极界面插入聚乙烯基咔唑(PVK)层，使器件的最大电致发光外量子效率达到1.79%，比采用低功函数的金属Ba/Al阴极器件的效率提高了两倍多.器件的性能得以改善的原因是CsF/Al阴极能有效提高电子注入能力以及PVK层对电子的阻挡作用. 关键词： 聚合物发光二极管 聚合物/电极界面 CsF/Al阴极 电子注入     

无机厚膜发光器件绝缘层的研究

采用丝网印刷技术,在Al2O3陶瓷基板上印刷、高温烧结内电极及绝缘层,制备出陶瓷厚膜基板,进而制备了新型厚膜电致发光显示器(TDEL)。整个器件结构为陶瓷基板/内电极/厚膜绝缘层/发光层/薄膜绝缘层/ITO透明电极。研究不同结构的无机厚膜发光器件对器件性能的影响,并对器件的亮度—电压、亮度—频率进行测量。结果显示绝缘层在无机发光器件中不是单纯的保护作用,它对器件的性能有十分重要的影响。主要是对注入电子的加速作用,从而提高发光亮度。绝缘层本身对无机厚膜发光器件的发光机理没有关系。     

CBP有机薄膜对MEH-PPV聚合物发光二极管性能的影响

以聚合物发光材料MEH-PPV为发光层的聚合物发光二极管的ITO阳极与发光层之间,加入一层溶解于氯仿中的有机小分子CBP,能显著改善发光器件的电流特性。在电压较低的时候能提高电流,在电压较高的时候能抑制电流,从而增加工作电压范围。此外,器件的电流效率也能得到显著的提高。实验结果表明,加入CBP层后,在低电压时,CBP层能够减缓空穴注入到发光层中,将其限制在CBP层,从而在器件中形成一个内电场,有助于电子的传输,降低开启电压,提高发光亮度。在电压较高时,CBP作为电子阻挡层,能阻挡电子漏泄到阳极,从而使在复合区的空穴与少数载流子电子的复合效率提高,改善器件的性能。     

磷酸酯聚芴阴极界面修饰层对聚合物电致发光性能的影响

发展了基于稳定金属电极的阴极界面材料,对促进聚合物电致发光器件的产业化进程具有重要意义。侧链含磷酸酯功能基团的聚芴衍生物（PF-EP）是一种极性聚合物中性材料,能溶于乙醇等醇类溶剂,非常适合制备多层溶液加工型发光器件。除此之外,它结合稳定的金属Al电极能实现有效电子注入。本文以PF-EP在绿光聚芴发光器件中的应用为例,详细对比分析了两种基于PF-EP的阴极电极结构（PF-EP/LiF/Al和PF-EP/Al）的器件EL性能。结果显示,PF-EP/LiF/Al阴极结构具有更优异的电子注入能力。基于单电子器件和X射线光电子能谱,本文对这一高效电子注入结构的注入能力和注入机理进行了探讨。     

倒置器件结构及局域等离子体效应对CdSe量子点LED发光性能的改进

研究了倒置器件结构以及CdSe量子点发光材料与金属纳米粒子之间的相互作用对量子点的电致发光性能的影响。利用TiO₂作为电子传输/注入层,成功地制备了倒置结构的量子点电致发光器件。通过对单载流子器件电压-电流特性的分析,证明了ITO作为阴极到TiO₂的电子注入特性与Al作为阴极时的效果几乎相同。观察到金属纳米粒子产生的局域等离子体效应提高了器件的效率,使得效率随电流增大而降低的速度明显减小。在电流密度为200 mA/cm²时,电致发光器件的效率大约提高了42%。     

以硫氰酸亚铜作为空穴注入层的钙钛矿发光器件

同有机电荷注入材料相比,无机电荷注入材料具有许多优良的性质,包括高载流子迁移率、良好的稳定性、制备简单和成本低廉等,其在光电器件中的应用备受瞩目。本文采用硫氰酸亚铜(CuSCN)作为有机金属卤化物钙钛矿发光器件的空穴注入层,研究了在其上涂敷钙钛矿薄膜的形貌、晶体结构和光物理性质,并与在普遍采用的导电聚合物空穴注入层上制备钙钛矿薄膜的特性进行了比较。实验结果表明,CuSCN对钙钛矿发光具有显著的猝灭作用,在CuSCN与钙钛矿层之间加入有机间隔层能够明显提高钙钛矿薄膜的发光强度。在此基础上制备了以CuSCN作为空穴注入层的发光器件,器件的最大发光效率为11.7 cd/A,较采用导电聚合物作为空穴注入层器件的效率提高了近3倍,并且器件驱动稳定性也有一定程度的提高。     

Li_2CO_3电子注入层改善有机发光二极管性能的研究

常规有机发光二极管发光层中载流子浓度的不平衡,导致器件发光亮度、效率等性能不能达到最优.为了改善电子的注入和传输,采用Li_2CO_3作为电子注入层,并将其掺入4,7-二苯基-1,10菲啰啉(Bphen)电子传输材料中,研究电子注入和传输能力的变化及其对器件发光性能的影响.结果表明:Li_2CO_3作为有效的电子注入层,使器件的驱动电压降低1.0V,发光亮度提高3倍,电流效率提高1倍.Li_2CO_3掺杂Bphen能进一步改善电子传输性能,提高发光层中的电子浓度,进而改善发光亮度和效率.     

高效率的有机电致发光器件

有机电致发光器件 (OL EDs)的发光机理包括电子和空穴从电极的注入、激子的形成及复合发光 ,其中 ,空穴和电子的注入平衡是非常重要的。为了平衡载流子的注入以得到高效率和稳定性好的器件 ,人们不仅使用了电子注入更为有效的 L i F/ Al[1] 和 Cs F/ Al[2 ] 等复合电极 ,同时也使用了空穴缓冲层 ,如 S.A.Van Slyke等 [3]在ITO和 NPB之间使用 Cu Pc,使得器件的稳定性得到了明显的提高 ;A.Gyoutoku等[4 ] 用碳膜使器件的半寿命超过 3 5 0 0小时 ;最近 ,Y.Kurosaka等 [5]和 Z.B.Deng[6 ]分别在 ITO和空穴传输层之间插入一薄层 Al…     

Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide

Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs.     

Femtosecond Transform-Limited Pulse Generation by Compensating for the Linear Chirp of SPM Spectra in Dispersion Shifted Fibers

A simple technique of pulse compression, based on the linear chirp compensation of self-phase modulation (SPM) spectra in dispersion shifted fibers, is demonstrated. The optimization procedure is carried out, for a short span of a single-mode fiber, using a parabolic law, which describes the behavior of the squared output pulse width versus the pump peak power in the case of Gaussian pulses. The experimental results give a minimum pulse duration of 233 fs, which is in good agreement with the model. Shorter and coherent pulses, down to 90 fs, have been obtained by inserting an interference filter at the optical output.     

Effect ofγ-radiation on the spectral luminescence characteristics of impure cadmium tungstate crystals

Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation (5.5·10⁴ Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure crystals is analyzed (preliminarily). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997.     

Theoretical analysis and simulation of conjugate heights for dual-conjugate AO system in lidar

A multi-conjugate adaptive optics （MCAO） can offer a possibility of widening field of view （FOV） characterized by the isoplanatic angle, and the choose of conjugate height becomes a basic problem for MCAO, which influences the size of iosplanatic angle. Considering the application of lidar, the isoplanatic angle＇s expressions of two deformable mirrors （DMs） MCAO for uplink and downlink are deduced. The effects of conjugate heights for dual-conjugate AO are thoughtfully discussed, and the isoplanatic angles are further analyzed. The results show that the isopanatic angle varies with the conjugate height and reaches the maximum as the conjugate height is at the optimal altitude. Moreover, the optimal conjugate height changes with the propagation distance.     

Quick single-photon detector with many avalanche photo diodes working on the time division

Due to the limit of response speed of the present single-photon detector, the code rate is still too low to come into practical use for the present quantum key distribution (QKD) system.A new idea is put up to design a quick single-photon detector.This quick single-photon detector is composed of a multi-port optic-fiber splitter and many avalanche photo diodes (APDs).Au of the ports with APDs work on the time division and cooperate with a logic discriminating and deciding unit driven by the clock signal.The operation frequency lies on the number N of ports, and can reach N times of the conventional single-photon detector.The single-photon prompt detection can come true for high repetition-rate pulses.The applying of this detector will largely raise the code rate of the QKD, and boost the commercial use.     

Sorting of bending magnets for the SSRF booster

The Shanghai Synchrotron Radiation Facility(SSRF)booster ring,a full energy injector for the storage ring,is deigned to accelerate the electron beam energy from 150MeV to 3.5GeV that demands high extraction efficiency at the extraction energy with low beam loss rate when electrons are ramping.Closed orbit distortion(COD)caused by bending magnet field uniformity errors which affects the machine performance harmfully could be effectively reduced by bending magnet location sorting.Considering the affections of random errors in measurement,both ideal sorting and realistic sorting are studied based on measured bending magnet field uniformity errors and one reasonable combination of bending magnets which can reduce the horizontal COD by a factor of 5is given as the final installation sequence of the booster bending magnets in this paper.     

Improvement of four-wave mixing-based wavelength conversion efficiency in dispersion shifted fiber by 40-GHz clock pumping

40-GHz clock modulated signal as a pump to improve the efficiency of four-wave mixing (FWM)-based wavelength conversion in a 26.5-km dispersion shifted fiber (DSF) is investigated. The experimental results demonstrate that the conjugated FWM component has higher intensity with the clock pumping than that with the continuous-wave (CW) light pumping. The improvement of FWM-based wavelength conversion efficiency is negligible when the pump power is less than Brillouin threshold. But when the pump power is greater than Brillouin threshold, the improvement becomes significant and increases with the increment of pump power. The improvement can increase up to 9 dB if pump power reaches 17 dBm.     

Characterization of PolyA and PolyC mismatches by Raman spectroscopy

A.C mismatches are studied by Raman spectral characterization of PolyA, PolyC, and their equimolar complex in solution of 0.14 mol/L Na ,pH7.0.Experimental results show that A·C mismatches occur to be A/B (mainly A) conformers, and unlike Watson-Crick base pairing, this kind of mismatches is stabilized by only one hydrogen bond involving cytosine N4H2 and adenine N7.The formation of A·C complex makes the base stacking interactions much stronger, and conformation of the backbone more ordered, which leads to obvious Raman hypochromic effect with some shifts in corresponding bands.