Controllable donor-acceptor neutral [2]rotaxanes

In pursuit of a neutral bistable [2]rotaxane made up of two tetraarylmethane stoppers--both carrying one isopropyl and two tert-butyl groups located at the para positions on each of three of the four aryl rings--known to permit the slippage of the pi-electron-donating 1,5-dinaphtho[38]crown-10 (1/5DNP38C10) at the thermodynamic instigation of pi-electron-accepting recognition sites, in this case, pyromellitic diimide (PmI) and 1,4,5,8-naphthalenetetracarboxylate diimide (NpI) units separated from each other along the rod section of the rotaxane's dumbbell component, and from the para positions of the fourth aryl group of the two stoppers by pentamethylene chains, a modular approach was employed in the synthesis of the dumbbell-shaped compound NpPmD, as well as of its two degenerate counterparts, one (PmPmD) which contains two PmI units and the other (NpNpD) which contains two NpI units. The bistable [2]rotaxane NpPmR, as well as its two degenerate analogues PmPmR and NpNpR, were obtained from the corresponding dumbbell-shaped compounds NpPmD, PmPmD, and NpNpD and 1/5DNP38C10 by slippage. Dynamic 1H NMR spectroscopy in CD2Cl2 revealed that shuttling of the 1/5DNP38C10 ring occurs in NpNpR and PmPmR, with activation barriers of 277 K of 14.0 and 10.9 kcal mol(-1), respectively, reflecting a much more pronounced donor-acceptor stabilizing interaction involving the NpI units over the PmI ones. The photophysical and electrochemical properties of the three neutral [2]rotaxanes and their dumbbell-shaped precursors have also been investigated in CH2Cl2. Interactions between 1/5DNP38C10 and PmI and NpI units located within the rod section of the dumbbell components of the [2]rotaxane give rise to the appearance of charge-transfer bands, the energies of which correlate with the electron-accepting properties of the two diimide moieties. Comparison between the positions of the visible absorption bands in the three [2]rotaxanes shows that, in NpPmR, the major translational isomer is the one in which 1/5DNP38C10 encircles the NpI unit. Correlations of the reduction potentials for all the compounds studied confirm that, in this non-degenerate [2]rotaxane, one of the translational isomers predominates. Furthermore, after deactivation of the NpI unit by one-electron reduction, the 1/5DNP38C10 macrocycle moves to the PmI unit. Li+ ions have been found to strengthen the interaction between the electron-donating crown ether and the electron-accepting diimide units, particularly the PmI one. Titration experiments show that two Li+ ions are involved in the strengthening of the donor-acceptor interaction. Addition of Li+ ions to NpPmR induces the 1/5DNP38C10 macrocycle to move from the NpI to the PmI unit. The Li+-ion-promoted switching of NpPmR in a 4:1 mixture of CD2Cl2 and CD3COCD3 has also been shown by 1H NMR spectroscopy to involve the mechanical movement of the 1/5DNP38C10 macrocycle from the NpI to the PmI unit, a process that can be reversed by adding an excess of [12]crown-4 to sequester the Li+ ions.     

基于curvelet变换的光学器件表面特征识别

为了精确识别复杂精密光学器件在制造过程中由于工艺要求不可避免产生的缺陷特征,基于曲线波(Curvelet)变换优良的曲线特征识别和强大的稀疏表示能力,提出了一种基于曲线波变换的缺陷特征识别方法,该方法采用变换域特征分离,在空间域获得特征识别后的器件表面图像.仿真结果和实验结果证明,提出的方法比传统小波算法精度和准确度更...     

导电聚苯胺线膜修饰ZnO纳米棒阵列的可控制备及其紫外探测性能

基于p-n结的光生伏特效应可构筑性能优异的UV探测器,本文采用水热法可控制备竖直排列的氧化锌纳米棒阵列(n型ZnO-NRs),利用原位聚合法在ZnO-NRs表面上修饰p型聚苯胺线膜(PANI-NWs),再组装成ZnO-NRs与ZnO-NRs/PANI-NWs紫外探测器.通过扫描电镜(SEM)、X射线衍射仪(XRD)、紫...     

准单色光照射轴锥镜的衍射特性

为了研究准单色光照射轴锥镜的衍射特性,在讨论单色平面波照射轴锥镜衍射理论的基础上,利用准单色光可以分解为不同频率单色光线性组合的特性,得到了准单色光照射轴锥镜的衍射光斑的强度分布形式。并根据仿真和实验结果比较了准单色光和单色光产生的衍射光斑强度分布的差异。结果表明,准单色光照射轴锥镜产生的衍射光斑的强度为不同频率单色光照射轴锥镜产生的强度之和,衍射条纹数比单色光的少,离轴方向的光强比单色光的衰减快。     

InGaAs固体微光器件研究进展

InGaAs器件具有光谱响应宽、量子效率高、响应速度快、数字化读出、高温工作、可靠性好以及寿命长等优点,符合新一代微光器件的发展需求,在国际上成为固体微光器件的一种新选择,获得了重要的发展和应用。文章就 InGaAs 固体微光器件材料属性、器件性能以及成像特点等几方面进行了详细分析,介绍了当前InGaAs器件的发展趋势,以及研制320×256 InGaAs阵列的最新进展。研究结果表明 InGaAs 材料生长及器件工艺具有较好的可控性和稳定性,为实现高性能、实用化的InGaAs固体微光器件提供了技术支撑。     

Fluorination of Terminal Groups Promoting Electron Transfer in Small Molecular Acceptors of Bulk Heterojunction Films

The fluorination strategy is one of the most efficient and popular molecular modification methods to develop new materials for organic photovoltaic (OPV) cells. For OPV materials, it is a broad agreement that fluorination can reduce the energy level and change the morphology of active layers. To explore the effect of fluorination on small molecule acceptors, we selected two non-fullerene acceptors (NFA) based bulk heterojunction (BHJ) films, involving PM6:Y6 and PM6:Y5 as model systems. The electron mobilities of the PM6:Y5 and PM6:Y6 BHJ films are 5.76 × 10⁻⁷ cm²V⁻¹s⁻¹ and 5.02 × 10⁻⁵ cm²V⁻¹s⁻¹ from the space-charge-limited current (SCLC) measurements. Through molecular dynamics (MD) simulation, it is observed that halogen bonds can be formed between Y6 dimers, which can provide external channels for electron carrier transfer. Meanwhile, the “A-to-A” type J-aggregates are more likely to be generated between Y6 molecules, and the π–π stacking can be also enhanced, thus increasing the charge transfer rate and electron mobility between Y6 molecules.     

太赫兹半导体器件与应用——纪念刘惠春教授

文章是以作者和刘惠春教授多年合作的研究工作为基础写成的,主要内容为太赫兹(THz)半导体器件及其通信和成像应用,以此深切缅怀刘惠春教授。近十年来,THz科学与技术已取得了长足进步,它在物理学、材料科学、生命科学、天文学、信息技术和国防安全等多个领域的应用也已初现端倪。在这些应用中,半导体THz器件的发展起着举足轻重的作用。文章着重介绍了作者近年来在半导体THz器件与应用方面的研究进展,主要内容包括基于负有效质量的电子学THz振荡器、飞秒激光泵浦半导体THz辐射源、基于量子阱子带间跃迁的THz量子级联激光器和THz量子阱探测器,以及基于这些器件的THz无线通信和成像应用研究。此外,文章还对未来THz技术的发展进行了简要的探讨。     

改进加权支持向量机回归方法器件易损性评估

加权支持向量机回归算法,几乎都是以样本输入空间中的一个重要特征量的函数来确定权值,造成了在高维特征空间中作回归可能存在较大误差。针对这一问题,提出利用高维特征空间中的欧基里德距离来确定权值的方法,构造了一种改进的加权支持向量机回归算法,并将其应用到电子器件高功率微波易损性评估中。仿真结果表明：该方法具有比模糊神经网络法、标准支持向量机回归算法和一般的加权支持向量机回归算法更高的预测精度。由于增加了权值的计算过程,相对于标准支持向量机回归和模糊神经网络方法,该方法的效率较低,但与一般的加权支持向量机回归算法相当。     

化合物半导体光伏产品发展趋势探讨

目前世界上能源消耗以化石燃料为主。化石燃料消耗所带来的能源供应危机以及环境污染,使人类社会的可持续发展承受着越来越重的压力,因此,新能源的推广应用已成为全球共识。太阳能有可能成为满足未来能源需求的战略性能源。其中化合物半导体光伏产品是未来地面太阳能应用的重要发展方向,而铜铟镓硒（CIGS）体系由于其本身的优点,是新一代化合物半导体光伏产品的重要发展方向。该体系在产业化技术方面已经取得很大的进展,并已逐步开始大规模产业化实践。     

薄膜生长速率对有机光伏器件性能的影响

采用真空热蒸发镀膜的方法制备了酞菁铜(CuPc)和富勒烯(C60)构成的平面异质结结构光伏器件,并初步研究了CuPc薄膜生长速率对器件光伏性能的影响,我们发现以较大薄膜生长速率制备的器件表现出较大的短路电流和能量转换效率。X射线衍射和原子力显微镜观察的结果表明生长速率较大的CuPc薄膜结晶相含量较少,薄膜结构较均匀、致密、平整,这可能使得CuPc薄膜激子扩散和载流子迁移特性得到提高,也可能改善其与C60受主薄膜和ITO阳极的接触,并有利于载流子的分离和收集,从而表现出较好的光伏特性。