利用染料掺杂双频率液晶胶体材料制备反射式直视显示器

利用染料掺杂双频率液晶胶体材料制备了一种对比度高、响应速度快且无需偏光片的反射式显示器。器件的高对比度是由于聚合物胶体材料对光的散射和黑色染料分子对光的吸收。对双频率液晶材料进行频率调制使得器件产生较快的响应速度。     

高双折射液晶化合物的研究进展

近年来,液晶器件的响应速度得到了很大的改善,响应时间已经从25ms减少到3ms甚至更短。虽然这种改善与液晶层厚度的变薄有关,但主要原因应该归因于新型液晶材料的发展和使用。色序液晶显示能产生更高质量的图像,但前提是必须有能快速工作的液晶材料。液晶材料的旋转黏度系数、双折射和液晶层的厚度是影响液晶器件响应时间的3个主要因素。本文以液晶双折射这一因素为主线,从液晶化合物结构的角度介绍了影响液晶双折射数值的若干因素,包括中心环结构、中心基团上的桥键、极性基团和侧位-F对液晶双折射的影响等,延长分子的π电子共轭长度能有效提高液晶的双折射。本文列举了国内外已合成的高双折射向列相液晶的分子结构及双折射值,最后对高双折射液晶的研究进行了展望。     

利用Alq3掺杂在NPB中制备白光OLED

利用Alq3掺杂在NPB中作为空穴传输层,并以DPVBi和rubrene作为发光层,制备了多层的白光有机发光器件(OLED).与在同一条件下的对比器件相比,掺杂的器件在相同电压下亮度和效率都有所增加.掺杂的器件的最大亮度在17 V时达到了19 921 cd/m2,最大效率在7 V时达到了3.69 cd/A,色坐标(CIE)在5～16 V内几乎没有改变,我们认为,掺杂器件性能的提高是由于掺杂剂Alq3分子对空穴有散射作用,阻挡了部分空穴的传输,降低了空穴的迁移率;而Alq3又是很好的电子传输材料,Alq3掺杂提高了空穴和电子在发光层中的注入平衡,有利于激子的形成,从而提高了器件的性能.     

顶发光单色绿光OLED微型显示器件发光层掺杂特性研究

本文设计了一种磷光顶发射结构制备单色高亮绿光OLED微型显示器件,器件结构为:ITO/2-TNATA/NPB/MCP:Ir(ppy)_3/Bphen/LiF/Mg:Ag。为获得低功耗、高亮度的绿光OLED微型显示器件,采用开口率大、益于集成的顶发射结构器件,并对发光层掺杂机制进行实验研究,通过改变掺杂比例获得较佳的器件性能。研究表明,在掺杂比分别为1.0%、1.5%、1.8%、2.0%、2.3%、2.5%的绿光OLED器件中,2.0%的掺杂器件较其他比例的性能更优,通过进一步优化掺杂研究显示,发光层主体材料MCP与掺杂料Ir(ppy)_3的最佳掺杂比例为1:0.02,主体材料薄膜厚度为250?。在20 mA/cm~2的电流密度下,得到器件电压为3.62 V,亮度为4622 cd/cm~2,色坐标(X,Y)为(0.33,0.61)。     

高电子迁移率晶体管材料结构的制备及分析

针对高电子迁移率晶体管(HEMT)器件,分析了双δ掺杂 GaAs HEMT的结构组成,基于固源分子束外延方法制备了双δ掺杂 GaAs HEMT的缓冲层、沟道层、平面掺杂层和隔离层等多层材料结构。采用 X-ray射线衍射、透射电镜研究了多层材料的结构。范德堡霍尔测试结果表明, HEMT的2DEG测试浓度为1.82×1012 cm-3,电子迁移率大于6520 cm2·V-1·s-1。     

侧位含氟苯乙炔类液晶化合物的微波介电性能

近年来基于液晶材料的微波通信器件研究发展迅速,液晶材料的介电损耗成为制约微波器件发展的瓶颈,然而目前对微波用液晶材料性能报道较少。本文以低熔点高双折射侧位含氟苯乙炔类液晶作为研究对象,将其按一定比例掺杂到母体液晶MA中,采用矩形谐振腔微扰法测试所选液晶化合物在微波频段(10～30GHz)下的介电性能,探讨分子结构对微波频段液晶介电性能的影响作用。实验结果表明:在高频时的液晶介电各向异性与分子极性和双折射率相关,侧位含氟苯乙炔类和端基异硫氰基苯乙炔类液晶化合物均具有较大的介电各向异性(Δ_(ε_r)0.85);对于具有较高双折射率的对称含氟三苯二炔类和三苯乙炔异硫氰基类液晶化合物表现出较低的介电损耗(tanδ_(ε_r⊥)8.0×10~(-3),18GHz),而异硫氰基的含氟二苯乙炔类和不对称含氟三苯二炔类液晶化合物则表现出较高的介电损耗(tanδ_(ε_r⊥)8.0×10~(-3),18GHz)。     

新型有机电致蓝色磷光器件的研究

研究了基于FIrpic的超薄非掺杂有机电致蓝色磷光器件的光电特性.改变超薄非掺杂FIrpic发光层以及其隔离层的厚度,可以调控FIrpic分子的聚集及激子相互作用强度对器件性能的影响.研究结果表明,具有TCTA 5 nm/FIrpic 1 nm/TCTA 5 nm/FIrpic 1 nm/TPBI 5 nm/FIrpic 1 nm多发光层结构的器件性能较优,最大发光效率为9.9 cd/A,超薄非掺杂发光层结构避免了掺杂方法中共沉积磷光材料浓度的精确控制,有利于简化器件制备工艺.     

聚合物分散液晶的应用

聚合物分散液晶是液晶分子以微滴的形式分散于高分子聚合物中,所形成的性能优异的一种液晶薄膜材料。文中介绍了PDLC的3大应用领域,在大屏弯曲显示方面具有传统液晶显示技术无可比拟的优势,是制作智能玻璃的核心材料,且可用于研制性能更好的可变光衰减器、波带片、透镜和调制器等重要光学器件,并指出纳米掺杂是改进PDLC性能的研究方向。聚合物分散液晶具有广阔的应用前景,且其生产工艺简单、成本低廉,应引起国内学者足够的重视,避免未来国外形成技术垄断。     

Au纳米颗粒对向列相液晶取向性能的影响

液晶分子的初始排列在液晶显示器中起着关键的作用。纳米粒子掺杂到液晶体系可扰乱液晶分子的排列,从而改变液晶的自组装特性,进而影响液晶的各项性能。将制备的Au八面体纳米颗粒掺杂到向列相液晶4-氰基-4′-正戊基联苯(5CB)中,灌入液晶盒后,通过使用偏光显微镜对液晶盒的观察发现,掺杂的八面体Au纳米颗粒诱导5CB液晶分子发生了垂直取向,而球形Au纳米颗粒不能诱导液晶分子垂直取向。这归因于八面体Au纳米颗粒的表面能比较小,液晶分子间的作用力比较大,使液晶分子易于垂直取向。随着O-Au NPs的浓度增大,液晶分子的取向效果先变好又逐渐变差。这是因为O-Au NPs的浓度越高,可诱导越多的液晶分子垂直取向排列,但随着纳米粒子浓度的增加,纳米粒子团聚,减少了与液晶分子的作用,使取向效果变差。动态过程实验显示,0.1%的八面体金纳米颗粒可诱导向列相液晶5CB在2 min内快速完成垂直取向,表明O-Au NPs具有优异的诱导5CB取向的动态效果。     

《液晶与显示》1999年和2000年刊登的主要论文题目

为使广大读者更多地了解《液晶与显示》,现将1999年和2000年在本刊发表的主要论文题目刊出。您若想了解有关论文的详细内容,可到当地图书馆查阅,也可直接与本刊编辑部联系,我们将竭诚为您服务。联系方法与地址请见本刊封底。 -编者- 1999　年　目　录 高温显示液晶的合成 1：1 弱锚定条件下混合排列向列液晶显示的动态响应 1：6 液晶含量对聚合物/液晶复合膜电光特性的影响——从正型向反型显示模式的转变 　　 1：12 有机小分子掺杂的聚合物共混发光二极管 1：18 低阻高透过率ITO薄膜的制备与性能 1：23 TFT工艺中的反应性离子刻蚀 1：29 TN LCD字朦的盒内因素 1：34 以陶瓷厚膜为绝缘层的绿色薄膜电致发光器件 1：39 液晶显示动态驱动信号发生器的研制 1：42 拓展图形式液晶显示模块负温工作范围的方法 1：46 卤代液晶进展 1：50 染料掺杂型有机电致发光器件 1：64 有机电致发光器件的研究与专利 1：70 TFT LCD技术的进步 2：79 含氟二苯乙炔类液晶材料的合成和性质研究 2：90 液晶中形成的聚合物网络织构及形貌的研究 2：94 胆甾相液晶双轴特性的计算 2：105 AlGaInP高亮度发光二极管 2：110 无色移共面转换液晶显示 2：115 TFT AMLCD像素矩阵电路中栅延迟的模拟研究 2：121 TFT栅线及阵列的缺陷分析 2：126 LCD图形模块的控制技术 2：131 硅基TFT有源矩阵液晶显示技术 2：137 激基复合物与有机聚合物EL性能的关系 2：145 椭圆偏光解析法对液晶界面层分子有序度的研究 3：153 高开口率TFT LCD的黑矩阵设计 3：162 提高共面转换液晶显示器件响应时间的研究 3：167 一种具有空间变化的轴对称偏振特性的液晶偏振光器件 3：175 高性能a-Si∶H TFT开关器件的研制 3：181 周边集成AMLCD的信号失真和缓冲寄存器TFT尺寸计算 3：187 氢化非晶硅的红外光谱及氢释放的研究 3：193 正模式PSCT光阀透过率随波长分布特性的研究及其应用 3：199 AC PDP介质膜的实验研究 3：207 一种低压驱动TFT液晶显示屏的方法 3：211 液晶显示器的设计与光绘 3：216 表面双稳铁电液晶中的层结构 3：220 三氟甲基芳环类液晶的合成新方法 4：231 液晶聚合物薄膜的介电性能 4：238 利用微锥膜改善反射式液晶显示器件的视角 4：243 电控位相型液晶菲涅耳波带片的特性 4：250 双面电极共面转换液晶光阀 4：257 液晶/聚合物显示器件中的聚合物栅和墙结构 4：265 一种用于液晶分子取向排列的紫外光聚合物PV4研究 4：271 淀积条件对a-SiNx∶H薄膜中含氢基团的影响 4：278 佳化幅选寻址LCD模块响应时间的测量方法 4：284 有机电致发光器件的Buffer Layer及其金属掺杂 4：289 高画质、低功耗的TFT LCD直接驱动方法 4：296 2000　年　目　录 显示技术新进展 1：1 用偏光显微镜解析界面层分子有序度 1：6 磁场对双轴分子液晶的影响 1：17 4-(trans-4-n-烷基环己基甲氧基)-4′-氰基联苯的合成 1：23 低阻α-Ta栅电极材料的制备与研究 1：28 CdSe薄膜晶体管制备工艺的研究 1：35 新型平板显示技术——BSD技术 1：39 PDLC器件显示迟滞效应的改善 1：40 激光退火法低温制备多晶硅薄膜的研究 1：46 光控取向弱锚定表面的液晶分子排列 1：53 PI厚度对LCD功耗电流的影响 1：61 电致磷光及其有机EL的量子效率提高 1：67 激励膜显示器 1：71 薄盒中液晶分子预倾角的测试方法 2：79 铁电液晶SmC*相介电特性的研究 2：85 表面无小丘Al双层栅电极结构研究 2：92 各向异性PDLC散射膜的特性研究 2：101 用于有机EL器件的电极材料 2：108 电致发光显示屏原理、 结构及驱动电路 2：114 液晶材料电阻率测试方法研究 2：120 MAX686在液晶显示技术中的应用 2：125 液晶物理——液晶的连续体理论 2：131 世界TFT LCD产业现状 2：154 OLED显示开发的最新进展 2：159 液晶显示技术的最新进展 3：163 LPP聚酰亚胺取向膜的制备及其取向研究 3：171 光散射液晶偏振片电光特性的研究 3：178 一种新型单偏振片反射式液晶显示器的设计 3：185 液晶调谐滤光片的设计 3：192 掺杂对CdSe-TFT稳定性影响的研究 3：196 一种低成本的立体显示头跟踪装置 3：208 无机显示荧光体研究动态和进展 3：209 液晶物理——液晶的统计理论 3：217 4-烷氧基联苯-4′-甲酸-(4-羧基)苯酯的合成 4：243 金属诱导法低温多晶硅薄膜的制备与研究 4：250 PDLC膜光透射率温度特性的研究 4：255 TFT阵列金属电极的制备与性能 4：260 多孔硅场致电子发射 4：268 阳极氧化条件对多孔硅冷阴极场发射特性的影响 4：273 无机、 有机LED和EL白色发光及绿色照明 4：278 电致发光显示屏在飞机座舱仪表中的应用 4：283 发光二极管光柱显示器 4：288 液晶物理——液晶的流体力学理论 4：295 TFT LCD行业标准的探讨 4：312     

Cesium carbonate-doped 1,4,5,8-naphthalene-tetracarboxylic-dianhydride used as efficient electron transport material in polymer solar cells

The use of appropriate charge carrier transport materials in organic solar cells strongly influences the device performance. In this work, we focused on the molecular electron transport material 1,4,5,8-naphthalene-tetracarboxylic-dianhydride (NTCDA) doped by cesium carbonate (Cs₂CO₃). We first investigated the electrical properties of such n-type doped material as a function of the doping concentration before using it as electron transport layer (ETL) in polymer solar cells. The doped transparent ETL reduces the series resistance leading to an increased open circuit voltage. A power conversion efficiency of 3.8% was finally achieved in a device with a blend of poly(3-hexylthiophene-2,5-diyl):phenyl-C61-butyric acid methyl ester (P3HT:PCBM) as the active layer and a 5 nm-thick NTCDA:Cs₂CO₃ film with a molar ratio of 30% as ETL.     

Enhanced performance of inverted organic solar cell by a solution-based fluorinated acceptor doped P3HT:PCBM layer

An inverted organic solar cell based on strong electron acceptor 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4-TCNQ) doped poly (3-hexylthiophene) P3HT: [6,6]-phenyl-C₆₁-butyric acid methyl ester (PCBM) was fabricated to figure out the p-type doping effect on the device performance. It was found that the doping concentration played a critical role on the electrical output of the devices. An enhanced power conversion efficiency (PCE) of 4.22% was achieved, in comparison of PCE of 3.68% for the device based on pristine P3HT:PCBM. The topography morphology of the active film, the hole mobility, the ultraviolet–visible absorption spectrum, the photoluminescence (PL) lifetime and the Fermi energy level of P3HT film with and without F4-TCNQ doping were characterized to investigate the doping effect. The measured results indicated that the hole mobility and absorption of P3HT film was slightly modified with F4-TCNQ doping. On the contrary, the active film morphology, the PL lifetime and the Fermi energy level of P3HT changed dramatically with doping. It was found that F4-TCNQ preferred to approach to the air/liquid interface during the solvent dry process, leading to F4-TCNQ-rich upper layer due to its low surface energy. The layer with proper thickness between anode and active layer dramatically improve the interface contact, resulting in the enhanced device performance.     

Chiroptical 3D Actuators for Smart Sensors

Examples of anisotropic movement paired with helical geometry abound in the animal and plant kingdoms are used for a variety of reasons, such as diverse social signaling directed at conspecifics or camouflage to avoid predation. Inspired by these natural phenomena, a smart sensor is developed with a chiroptical 3D actuator that can fold, bend, and twist in response to external stimuli, reflecting light of specific wavelengths, and possessing circular polarization properties. Chirophotonic crystal actuators are constructed with an asymmetric Janus structure and are fabricated by self-assembly, screen printing, and in situ photopolymerization. The optically active layer consists of cholesteric liquid crystal polymer, and the mechanically active layer is composed of a polymeric gel thin film. The programmed in-planar and out-of-planar asymmetric Janus structures control the directionality of various shapes morphing from 2D to 3D. Finite element simulations allow to predict the shape changes associated with these chirophotonic crystal actuators: flower blooming, tendril climbing, eagle hunting, ant lifting, and inchworm moving motions. By utilizing the chirophotonic crystal actuator, a reusable and portable methanol-laced water identifier is developed.     

胶囊化胆甾液晶薄膜在不同基板下的光电性能

采用紫外光聚合诱导相分离法制备了胶囊化胆甾液晶薄膜,系统研究了玻璃和塑料基板对于驱动电压、反射率及对比度等显示性能的影响。研究表明:不论是玻璃或塑料基板,液晶胶囊化均有助于显示对比度的提升,同时相应的驱动电压也有所增加。相较于刚性的玻璃基板,在柔性基板下液晶胶囊化前后的驱动电压由70V增加到200V,显示对比度达到6.2∶1。总体而言,初步实现了胆甾液晶的柔性显示。     

The doping effect of cesium-based compounds on carrier transport and operational stability in organic light-emitting diodes

The doping effect of cesium compounds (i.e., Cs₂CO₃, CsN₃ and CsF) doped electron injection layer (EIL) on charge transport properties and operational stability of organic light-emitting diodes (OLEDs) was systematically investigated in this work. It has been found that device characteristics and lifetime are highly dependent on the doping constituent materials. The doping of cesium compounds in EIL can improve the charge injection and transport of OLEDs, due to the increase in conductivity and reduction in electron injection barrier. Apart from the difference in electrical characteristics, the operational stability of OLEDs is strongly influenced by the doping mechanism of different cesium compounds in the EILs. The OLED device using Cs₂CO₃ as the n-type dopant for the EIL shows a superiority in both electrical property and operational lifetime.     

The Trapped Charges at Grain Boundaries in Perovskite Solar Cells

The performance of perovskite solar cells is greatly affected by the crystallization of the perovskite active layer. Perovskite crystal grains should neatly arrange and penetrate the entire active layer for an ideal perovskite crystallization. These kinds of crystallized perovskite films exhibit fewer defects and longer carrier lifetime, which is beneficial to enhance the performance of perovskite solar cells. Here, by testing the residual charge of perovskite solar cells with different crystallization conditions, it is demonstrated that the residual charge exists widely at the grain boundary, which is parallel to the device, and the residual charge is related to the performance of the perovskite solar cells. Single crystal grains neatly arranged and penetrate the entire active layer can generate less residual charge and improve device performance of the perovskite solar cells. The results also show that the long decay time of open-circuit voltage comes from the detrapping of trapped carriers. The residual charge testing technology provides a new idea for the investigation of carrier trap and detrap characteristics in photovoltaic devices.     

Structural and electrical contact properties of LPE grown GaAs doped with indium

We have studied the effects of In doping on the structural and electrical properties of a liquid phase epitaxially (LPE) grown GaAs. The results of surface morphology studies show that macroscopically, a terrace-free area in certain regions can be seen on the surface of a GaAs layer doped with In of 2.4 × 10¹⁹ cm³. The full widths at half-maximum (FWHM) of x-ray double crystal rocking curves show that a GaAs epi-layer of good crystalline quality can be obtained by doping In to a concentration up to 4.3 × 10¹⁹ cm^-3, beyond which a sharp increase in the FWHM is observed. Etch pit density (EPD) study also shows that the dislocation density is reduced by doping the epi-layer with In. At an optimum In concentration, 2.4 × 10¹⁹ cm^-3, the EPD was reduced by a factor of 20 when measured at the surface of a 9μm thick epi-layer. The I-V characteristics of Au-GaAs Schottky diodes show, for the layer with an optimal In concentration, an ideality factor close to 1.04 over more than seven decades of current. For the same layer, the reverse I-V characteristics are close to an ideal Schottky diode and could be fitted by a theoretical curve, combining the thermionic field emission and thermionic emission. For doping levels higher than 6 × 10¹⁹ cm^-3, the epitaxial layer quality deteriorated. We report the results obtained from the Nomarski optical microscope, double crystal x-ray rocking curves, etch pit density, forward and reverse I-V characteristics, and the theoretical current transport models.     

Engineering of charge transport materials for universal low optimum doping concentration in phosphorescent organic light-emitting diodes

A universal low optimum doping concentration of below 5% was demonstrated in phosphorescent organic light-emitting diodes (PHOLEDs) by managing the energy levels of charge transport materials. The device performances of PHOLEDs could be optimized at a low doping concentration of 3% irrespective of the host material in the emitting layer. The suppression of charge trapping and hopping by the dopant through charge transport layer engineering optimized the device performance at low doping concentration. In addition, it was revealed that PHOLEDs with low optimum doping concentration show better quantum efficiency, low efficiency roll-off and low doping concentration dependency of the device performance.     

Alcohol‐Responsive,Hydrogen‐Bonded,Cholesteric Liquid‐Crystal Networks

Hydrogen‐bridged, cholesteric liquid‐crystal (CLC) polymer networks are adopted as an optical sensor material to distinguish between ethanol and methanol. Fast uptake of the alcohols is facilitated by an incorporated porosity created by breaking the hydrogen bridges and by a previously removed non‐reactive liquid‐crystal agent. The discrimination between the alcohols is based on the diversity in molecular affinity of ethanol and methanol with the hydrogen‐bridged CLC polymer networks. The CLC networks are molecular‐helix‐based, one‐dimensional bandgap materials with a discrete reflection band in the visible part of the spectrum that depends on the pitch of the molecular helix. The changes in positions of the reflection bands of the CLC network accurately discriminate between the alcohol types and provide information on their ratio in case they are blended.     

An Optically Active Polythiophene Exhibiting Electrochemically Driven Light‐Interference Modulation

Optically active polythiophene (PT*) is successfully prepared by electrochemical polymerization using a cholesteric liquid crystal (CLC) electrolyte solution. Polarizing optical microscopy observations of the polymer reveal a well‐resolved fingerprint texture similar to the optical texture of the CLC. Circular dichroism measurements indicate a Cotton effect. The PT* film produced by the asymmetric polymerization in CLC exhibits a variable diffraction function, electrochemically driven refractive index modulation, and electrochromism originating from the periodic dielectric structure, representing a form of structural electrochromism.