烷氧链链长对吐昔烯电荷传输性质的影响

吐昔烯衍生物的盘状液晶分子,在有机电子材料领域被用作光导材料和载流子传输材料。使用电子转移的Marcus模型,在B3LYP/6-31G**水平上研究了5个含三条烷氧链(n=1,3,5,8,10)的吐昔烯衍生物分子的电荷转移性质。计算表明,电荷转移矩阵元t是影响分子电荷转移的主要因素。5个分子中,随烷氧链长度(n)增大,空穴、电子传输重组能的变化范围分别为16~19 kJ/mol和26~ 30 kJ/mol。空穴传输矩阵元t+减小超过4倍,空穴传输载流子迁移率μ+减小超过3个数量级。电子传输矩阵元t-增大幅度不大,电子传输载流子迁移率μ-增大2倍,表明烷氧链增长不利于空穴传输,有利于电子传输。     

烷氧链链长对吐昔烯电荷传输性质的影响

吐昔烯衍生物的盘状液晶分子,在有机电子材料领域被用作光导材料和载流子传输材料。使用电子转移的Marcus模型,在B3LYP/6-31G**水平上研究了5个含三条烷氧链(n=1,3,5,8,10)的吐昔烯衍生物分子的电荷转移性质。计算表明,电荷转移矩阵元t是影响分子电荷转移的主要因素。5个分子中,随烷氧链长度(n)增大,空穴、电子传输重组能的变化范围分别为16~19 kJ/mol和26~ 30 kJ/mol。空穴传输矩阵元t+减小超过4倍,空穴传输载流子迁移率μ+减小超过3个数量级。电子传输矩阵元t-增大幅度不大,电子传输载流子迁移率μ-增大2倍,表明烷氧链增长不利于空穴传输,有利于电子传输。     

采用Li3Nn型掺杂层作为电子注入层的OLED器件研究

相对于传统的无机半导体材料,有机半导体材料特别是有机电子传输材料的载流子浓度和迁移率较低,从而影响了有机发光器件的亮度、效率等性能.为了提高有机发光器件器件性能必须增强电子注入和传输能力,对有机电子传输材料进行n型电学掺杂能够有效地提高电子的注入和传输能力.本文利用Li3N作为n型掺杂剂,以掺杂层Alq3:Li3N作为...     

P-MBE制备氮掺杂p型ZnO中空穴的散射机制

利用等离子体辅助的分子束外延(P-MBE)技术,在蓝宝石衬底上制备了氮掺杂的p型ZnO薄膜。通过变温霍尔测量研究了空穴浓度和迁移率随温度的变化特性。对载流子浓度拟合的结果表明氮受主具有75meV的能级深度。通过对各种散射机制下迁移率的讨论,发现由晶粒及其晶界组成的这种结构极大地降低了p型ZnO中载流子的迁移率。     

碘化铟晶体本征缺陷的第一性原理研究

采用基于密度泛函理论的第一性原理方法,对正交碘化铟（InI）晶体可能存在的6种本征点缺陷（碘空位、铟空位、碘占铟位、铟占碘位、碘间隙、铟间隙）结构进行优化. 通过缺陷形成能的计算,得出各缺陷在生长过程中形成的难易程度;通过态密度的计算,分析出各种缺陷能级位置及其对载流子传输的影响. 结果表明：最主要的低能缺陷铟间隙会引入复合中心和深空穴陷阱,前者降低少数载流子的寿命,后者俘获价带的空穴而降低空穴的迁移率-寿命积. 计算结果为实验中提高InI 晶体载流子的迁移率-寿命积提供理论指导,对获得性能优异的InI核辐射探测材料有重要帮助. 关键词： 碘化铟 形成能 缺陷能级 深空穴陷阱     

载流子迁移率对单层有机发光二极管复合效率的影响

建立了在单层有机发光二极管中电场强度不太大(E≤104Vcm)的情况下,载流子注入、传输和复合的理论模型.通过求解非线性Painleve方程得出了电场强度随坐标变化的解析函数关系式以及电流密度随电压变化关系,给出了电流密度以及器件的复合效率在不同的载流子迁移率情况下随电压变化关系图像.结果表明,复合效率受载流子迁移率影响较大,在器件中多数载流子应具有较低的迁移率,而少数载流子应具有较高的迁移率,这样有利于载流子的注入和传输,从而可提高发光效率.并且得出当空穴迁移率大于电子迁移率时,复合区域偏向阴极,反之亦 关键词： 单层有机发光二极管 复合效率 迁移率     

迁移率对单层有机发光器件中电场与载流子分布的影响

有机发光器件的宏观特性与有机层中的电场和载流子浓度分布密切相关。建立的有机电致发光器件模型是由两个金属电极中间夹一层有机发光薄膜材料组成的单层器件,金属与有机发光层之间为欧姆接触。模型以载流子运动的扩散-漂移理论为基础,利用数值方法研究了有机发光层中双极载流子注入时的电势、电场、载流子浓度和复合密度分布。分析结果表明:当两种载流子的迁移率相同时,电场强度、载流子浓度、复合密度的分布呈对称形式。而当电子和空穴的迁移率μn和μp相差比较大时,高迁移率的载流子不仅仅分布在注入端附近而且还有一小部分能够传输到另一端,而低迁移率的载流子只分布在其注入端附近;当μn、μp的大小相差不大时,载流子传输情况就介于两者之间。当μn/μp的比值变化时,电场强度的极大值向载流子迁移率小的注入端偏移。     

OLED电子传输材料研究进展

有机电致发光（OLED）是目前最有竞争力的显示技术,市场占有量逐年攀升。高效、稳定的OLED,特别是深蓝光器件,性能仍需提升,其关键问题是高性能的电子传输材料的研发。这是由于有机分子难以获得较高电子迁移率,器件中的复合区域通常靠近电子传输层一侧,这就要求电子传输材料需要具有较高三线态能级来限域激子,尤其是高能量的蓝光激子。而高三线态（弱共轭）和高迁移率（强共轭）一直是有机分子设计中难以调和的矛盾,此外更宽的带隙也会导致较差的热稳定性,这些难题始终限制着OLED电子传输材料的发展。本文分类介绍了高性能的电子传输材料所需要具备的几点特性,包括热稳定性、光化学稳定性、电子迁移率、前线轨道能级和三重态能级等,并且综述了21世纪以来OLED小分子电子传输材料的重要研究进展,以期对未来开发理想的电子传输材料提供参考。     

Alq3和CdSeS量子点掺杂体系的载流子输运性质的研究

利用飞行时间法(time-of-flight)测定了有机小分子发光材料8-羟基喹啉铝(Alq3)与CdseS量子点掺杂体系的载流子迁移率.研究了Alq3和CdSeS混合薄膜的载流子迁移率与外加电场强度和量子点浓度的变化关系.研究结果表明,CdSeS量子点的掺杂浓度的增加会引起薄膜样品位置无序的增加.除此之外,Alq3和CdSeS量子点界面之间的电荷转移作用,以及在量子点之间进行跳跃传输的电子数量都会改变样品的载流子迁移率.     

PbS纳米晶修饰的ZnO/PVP复合电双稳器件阻变机制

采用简单旋涂工艺制备了具有ITO/PVP/ZnO NCs/PbS NCs/PVP/Al 夹心结构的有机/无机复合电双稳存储器件,与没有PbS纳米晶修饰层的器件ITO/PVP/ZnO NCs/PVP/Al相比,PbS纳米晶的引入使目标器件的开关比提高了2个数量级。结合器件的I-V曲线和能级结构分析了PbS 纳米晶修饰层对器件阻变和载流子传输的影响。结果显示,PbS纳米晶层的加入不仅优化了器件能级结构,有利于载流子的俘获和释放,还修饰了ZnO纳米晶的表面缺陷,降低了器件载流子的复合损耗。     

Self-organization of five species in a cyclic competition game

Cyclic competition game models, particularly the “rock–paper–scissors” model, play important roles in exploring the problem of multi-species coexistence in spatially ecological systems. We propose an extended “rock–paper–scissors” game to model cyclic interactions among five species, and find that two of the five can coexistent when biodiversity disappears, which is different from the “rock–paper–scissors” game. As the number of fingers is five, we named the new model the “fingers” game, where the thumb, forefinger, middle finger, ring finger, and little finger cyclically dominate their subsequent species and are dominated by their former species. We investigate the “fingers” model in two ways: direct simulations and nonlinear partial differential equations. An important finding is that the number of species in a cyclic competition game has an influence on the emergence of biodiversity. To be specific, the “rock–paper–scissors” model is in favor of maintaining biodiversity in comparison with the “fingers” model when the variables (population size, reproduction rate, selection rate, and migration rate) are the same. It is also shown that the mobility and reproduction rate can promote or jeopardize biodiversity.     

Contrastive analysis on tone between Putonghua and Taiwan Mandarin

The differences of the pitch and duration of Chinese syllables between Putonghua （PTH） and Taiwan Mandarin （TM） were studied. The speech materials to be used are not only isolated syllables, but also sentences. The results reveal that： For the isolated syllables, T1 and T2 in TM are influenced by Minnan dialect, therefore their pitch are lower than those in PTH. T3 is fall-rise in PTH, while it is fall in TM. Moreover, the syllable duration sequence for different tone is T3〉T2〉T1〉T4 in PTH, while it is T1〉T2〉T3〉T4 in TM. For the syllables in sentences, T2 is mid-rise in PTH, while it is mid-level in TM. And the T3 is longer than T4 but shorter than T1 or T2 in PTH, while it is the shortest in TM. Furthermore the effects of prosodic phrase boundary on duration for different tones are almost the same in PTH, but the lengthening part of T1 or T2 is longer than that of T3 or T4 in TM.     

Experimental study on downstep in Chinese intonation

Downstep in pitch contour of Chinese Putonghua is examined using subtly designed sentences by controlling tone combinations. The results show both automatic and nonautomatic downstep phenomena exist in Chinese. In non-automatic downstep, low tones compress downwards the pitch range of the following syllables. and the main influence of downstep is on topline. Low tone not only lower the topline behind it, but also raise the high tones before it, the effects are compatible with each other. In automatic downstep, the topline of pitch contour in intonational phrase is presented as a linear downtrend, but it differs among speakers due to the effect of personal stress practice. In comparison with downstep phenomenon in other tone or non-tone languages, the downstep ratio in Chinese is not constant, and the domain of downstep is not limited within the adjacent tones.     

Abelian-Higgs phase of SU(2) QCD and glueball energy

It is shown that SU(2) QCD admits an dual Abelian-Higgs phase, with a Higgs vacuum of a type-Ⅱ superconductor. This is done by using a connection decomposition for the gluon field and the random-direction approximation. Using a bag picture with soft wall, we presented a calculational procedure for the glueball energy based on the recent proof for wall-vortices [Nucl. Phys. B 741(2006)1].     

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.     

Signal generation in an isotropic medium in scanning electron acoustic microscope

Based on the research in Ref. [5][Materials Science and Engineering, 1989; A122： 57 63], an improved model of heat source is set up, the different modes of Lamb wave in an isotropic sample generated by a chopped electron beam at frequency f are obtained with integral transform and normal function expansion method, and the output signal of PZT coupled at the back surface of the sample is found out. The generation mechanism of SEAM （Scanning Electron Acoustic Microscopy） signal is discussed. It shows that the SEAM is a near field imaging technique with high spatial resolution and its best lateral spatial resolution is about 2√2α （α is the radius of the focused electron beam）. Some of experimental results of SEAM images are presented in the paper and it shows that the spatial resolution of SEAM is better than 0.5 μm and smaller than the thermal diffusion length of the sample. Therefore the character of near field imaging in SEAM is also proved experimentally.     

High efficiency filtering using two-dimensional photonic crystal coupled cavity structures

Transmission spectra of coupled cavity structures (CCSs) in two-dimensional (2D) photonic crystals (PCs) are investigated using a coupled mode theory, and an optical filter based on CCS is proposed. The performance of the filter is investigated using finite-difference time-domain (FDTD) method, and the results show that within a very short coupling distance of about 3λ, where λ is the wavelength of signal in vacuum, the incident signals with different frequencies are separated into different channels with a contrast ratio of 20 dB. The advantages of this kind of filter are small size and easily tunable operation frequencies.