Preparation of hole transporting polymers by condensation polymerization of triphenylamine derivatives

Hole transporting polymers were prepared by condensation polymerization of triphenylamine and N,N,N',N'‐tetraphenylbenzidine (TPD) having alkyl group with aldehydes in the presence of p‐toluenesulfonic acid. The obtained polymers had molecular weight higher than 10,000 and good film formation ability. It was found that the aromatic amine monomers were connected with aldehyde monomer at the p‐position of the phenyl group. TPD‐aldehyde polymers had almost the same UV absorption and redox potentials as those of TPD monomer indicating that the electronic structure of amine unit did not change by the polymerization. The hole transporting mobility was in the range of 10⁻³‐10⁻⁶cm²/Vs. The electroluminescent device consisting of ITO/TPD polymer/Alq/Mg‐Ag had a maximum luminance of 9000 cd/m².     

A solution-processable small-organic molecules containing carbazole or phenoxazine structure as hole-transport materials for perovskite solar cells

Three low molecular weight compounds bearing carbazole units (1,6-di{3-[2-(4-methylphenyl)vinyl]carbazol-9-yl}hexane and 9,9'-di{6-[3-(2-(4-methylphenyl)vinyl)-9-carbazol-9-yl]hexyl}-[3,3']bicarbazole) and phenoxazine structure (10-butyl-3,7-diphenylphenoxazine) were tested as hole-transporting materials in perovskite solar cells. Two of them were successfully applied as hole transporting layers in electroluminescent light emitted diodes. The examined compounds were high-thermally stable with decomposition temperature found at the range of 280–419 °C. Additionally, DSC measurement revealed that they can be converted into amorphous materials. The compounds possess adequate ionization potentials, to perovskite energy levels, being in the range of 5.15–5.36 eV. The significant increase in power conversion efficiency from 1.60% in the case of a device without hole-transporting layer, to 5.31% for device with 1,6-di{3-[2-(4-methylphenyl)vinyl]carbazol-9- yl}hexane was observed.     

紫外臭氧处理增强溶液法MoO3薄膜的空穴注入能力

空穴注入层对有机发光二极管的性能有重要的影响,尤其是当器件中的空穴传输材料的最高占据分子轨道能级较深的时候。近年来有许多关于新型的溶液法空穴注入材料的研究。在本文中,我们对溶液法MoO₃薄膜使用了三种不同的处理方法来研究其对空穴注入性能的影响,即：在空气中150 ℃退火;在空气中150 ℃退火再紫外臭氧处理(UVO) 15 min;只进行UVO处理15 min。结果发现当MoO₃薄膜在空气中150 ℃退火后,器件的电流最小,空穴注入能力最差。而当MoO₃薄膜经过UVO处理后,器件的电流显著增大,工作电压大幅下降,器件性能接近于蒸镀的MoO₃薄膜的器件。更惊喜的是,这种改善在MoO₃薄膜仅作UVO处理后也可获得。经定量计算发现MoO₃薄膜经过UVO处理后的空穴注入效率能提高到约0.1。XPS分析表明通过UVO处理后,MoO₃薄膜中Mo⁵⁺成分减少并且薄膜表面的富氧吸附物被有效地消除,使得其化学计量基本与蒸镀的MoO₃薄膜相同。基于这种经UVO处理的溶液法MoO₃作为空穴注入层,器件的最大电流效率可达到48.3 cd∙A⁻¹。     

量子点发光二极管功能层厚度确定方法

为改善量子点发光二极管器件载流子注入平衡,提出一种量子点发光二极管各功能层厚度的确定方法.首先选定量子点发光层厚度,基于隧穿模型进行仿真分析确定电子传输层厚度;然后采用空间电荷限制电流模型进行仿真分析确定空穴传输层厚度.采用CdSe/ZnS量子点作为发光层、poly-TPD作为空穴传输层、Alq_3作为电子传输层,按照该方法仿真分析得到各功能层厚度进行旋涂-蒸镀法实物器件制备.对比实验结果表明:当poly-TPD、QDs及Alq_3厚度分别为45nm、25nm及35nm时,获得了较高的发光效率及色纯度,器件性能最好.该方法确定的各功能层厚度有助于减少载流子在发光界面积累,获得载流子的注入平衡,从而改善QLEDs发光性能.     

基于MADN空穴传输层的双层结构高效率黄绿光OLED及其阻抗谱分析

以MADN为空穴传输层,主-客掺杂体系[Alq₃∶0.7 Wt%rubrene]为发光兼电子传输层,构建了双层结构的高效率黄绿光OLED器件。该器件的黄绿光由主发光体Alq₃通过不完全能量转移到客发光体rubrene实现,电致发光峰值位于560 nm,1931CIE色坐标为(0.46, 0.52),最大发光效率达到了7.63 cd·A-1,比相应的NPB做空穴传输层的双层结构器件提高了30%。通过构建以MADN或NPB为空穴传输层的空穴单载流子器件并进行阻抗谱分析,结果表明MADN可以作为一种非常有效的空穴传输层,其空穴迁移性略低于NPB,这恰好弥补了OLED器件中空穴迁移比电子迁移快这一缺陷,为改善OLED发光层中载流子的平衡性创造了条件,从而提高了器件的发光效率。此外,MADN做空穴传输层的双层结构OLED的发光效率与传统三层结构器件(MADN和Alq₃分别作为空穴传输层和电子传输层)基本相当,表明了这种双层结构器件在简化器件结构的同时并不以牺牲发光效率为代价,发光层[Alq₃∶0.7 Wt%rubrene]兼具有优良的电子传输性能。     

与蛋白质调控DNA空穴迁移相关的具有负离解能特征的亚稳态氢键

利用密度泛函理论方法研究了作为空穴迁移载体的蛋白质复合的DNA三聚体(Protonated arginine…guanine…cytosine, ArgH⁺-GC)的氢键性质. 结果表明, 空穴迁移通过该载体单元时此类氢键表现为亚稳态, 且具有明显的负离解能. 正常情况下ArgH⁺基团在大小沟均能与GC碱对形成氢键, 且具有正的离解能. 然而, 当空穴转移至此将削弱氢键至亚稳态, 使之具有一定的离解势垒和负的离解能. 这种势垒抑制的负离解能现象意味着由于空穴俘获导致此三聚体结构单元在它的ArgH⁺…N7/O6键区储存了一定的能量(约108.78 kJ/mol). 该氢键离解通道受控于此键区两个相关组分之间的静电排斥和氢键吸引之间的平衡以及这两个相反作用随氢键距离不同的衰减速率. 基于电子密度分布的拓扑性质以及键临界点的Laplacian数值分析澄清了此类特殊的能量现象主要源自通过高能氢键(ArgH⁺…N7/O6)连接的授受体间的静电排斥. 进一步空穴俘获诱导的G→C质子转移可扩展负离解能区至ArgH⁺…N7/O6和Watson-Crick(WC) 氢键区. 另外, ArgH⁺ 结合到GC的大小沟增加其电离势, 因此削弱其空穴传导能力, 削弱程度取决于ArgH⁺与GC的距离. 推而广之, 在protonated lysine-GC和protonated histidine-GC体系也可观察到类似的现象. 显然, 此类性质可调的亚稳态氢键可调控DNA空穴迁移机理. 此工作为理解蛋白质调控的DNA空穴迁移机理提供了重要的能量学信息.     

Many-electron effect in the Fe L3-M4,5M4,5 Auger electron spectrum of ultrathin Fe films grown on Cu(1 0 0)

D’Addato et al. [S. D’Addato, P. Luches, R. Gotter, L. Floreano, D. Cvetko, A. Morgante, A. Newton, D. Martin, P. Unsworth, P. Weightman, Surf. Rev. Lett. 9 (2002) 709] studied the variation with Fe coverages in the relative Fe L₃-M_4,5M_4,5 Auger electron spectroscopy (AES) spectral satellite intensity of ultrathin Fe films grown on Cu(1 0 0) by sweeping photon excitation energy through the Fe L₂-level ionization threshold. They interpreted that the M_4,5 hole in the L₃M_4,5 double-hole state created by the L₂-L₃M_4,5 Coster–Kronig (CK) decay remains localized for longer than the L₃-hole lifetime for the 0.3 and 10 ML coverages but has a lifetime comparable to the L₃-hole lifetime for the 1 ML coverages. The present many-body theory shows that when the M_4,5 hole created either by the CK decay or by the L₃M_4,5 shakeoff hops away from the ionized atomic site and becomes completely screened out prior to the L₃-hole decay, the Fe L₂-L₃M_4,5-L₃-M_4,5M_4,5 AES main line as well as the Fe L₃ M_4,5 (satellite)-L₃-M_4,5M_4,5 one, both of which are identical in line shape to the Fe L₃-M_4,5M_4,5 one, dominate in the Fe CK preceded AES spectrum. The present analysis shows that the delocalization time of the M_4,5 hole created in the 1 ML Fe/Cu(1 0 0) system by the L₂-L₃M_4,5 CK decay is much shorter than the L₃-hole lifetime so that the Fe L₃-M_4,5M_4,5 AES spectral line shape hardly changes, except for the presence of a very weak spectator L₂-L₃M_4,5-M_4,5M_4,5M_4,5 AES satellite, when the photon excitation energy is swept through the Fe L₂-level ionization threshold. For the 0.3 ML coverages the M_4,5-hole delocalization time is still shorter than the L₃-hole lifetime.     

Race for the Kerr field

Roy P. Kerr has discovered his celebrated metric 45 years ago, yet the problem to find a generalization of the Schwarzschild metric for a rotating mass was faced much earlier. Lense and Thirring, Bach, Andress, Akeley, Lewis, van Stockum and others have tried to solve it or to find an approximative solution at least. In particular Achilles Papapetrou, from 1952 to 1961 in Berlin, was interested in an exact solution. He directed the author in the late autumn of 1959 to work on the problem. Why did these pre-Kerr attempts fail? Comments based on personal reminiscences and old notes.     

孔助光纤(Hole-assisted lightguide fiber)色散和双折射特性的研究

通过改变包层中空气孔的参数,孔助光纤（hole-assisted lightguide fiber）具有比传统光纤更容易调节的色散和双折射特性.采用有限差分法研究了包层空气孔数目、大小和位置等参数对孔助光纤色散和双折射特性的影响.数值计算结果表明：增加空气孔的数目和尺寸以及减小空气孔到纤芯的距离都能够使得零色散向短波长方向移动,减小空气孔与纤芯的距离有助于获得更大的双折射.     

Effect of surfactant adsorption time on the observation of Newton black film in foam film

Observation of Newton black film (NBF) in foam film is possible only with a certain probability W which depends on the concentration C of surfactant in the solution and on the time t_a during which adsorption of surfactant at the solution/air interface has taken place. In the paper, the W(C,t_a) dependence is derived and used to analyze the effect of t_a on the critical surfactant concentration C_c below which NBF in foam film practically cannot be observed. An expression for the C_c(t_a) function is obtained which reveals that C_c decreases substantially with increasing t_a. This expression is found to describe well experimental C_c(t_a) data for foam films obtained from aqueous solution of the therapeutic surfactant INFASURF.