氧化石墨烯作为共蒸镀掺杂材料在OLED中的应用

通过共蒸镀掺杂的方法,分别用氧化石墨烯和NPB掺杂作为空穴传输层以及氧化石墨烯和Alq3掺杂作为电子传输层和发光层,制备了两种不同的有机电致发光器件。器件性能测试结果表明:相对于未掺杂的参比器件,氧化石墨烯与NPB共蒸镀掺杂的器件性能降低,与Alq3共蒸镀掺杂的器件性能提高。其中,氧化石墨烯掺杂量为Alq3的10%时,器件发光亮度为掺杂前的1.2倍,电流效率为掺杂前的2倍。这一工作为进一步提高OLED性能提供了新的途径。     

OLED薄膜干燥剂的制备及其对OLED的影响

有机电致发光显示器对水和氧气非常敏感,渗入器件后会和有机功能层及电极材料反应而影响器件的寿命及稳定性。本文提出了一种液体可涂覆干燥剂的制备方法,采用了氯化物干燥剂和价格低廉的阳离子成膜剂结合合成一种具有很好成膜性、且吸水效果很强的涂覆干燥剂。封装240 h后,使用薄膜干燥剂的器件的亮度分别为平均值的103.5%、83.3%以及119.8%,效率为平均值的130.7%、65.6%以及126.0%。与传统干燥剂相比,该薄膜干燥剂的吸湿效果更佳,且可延缓OLED的老化。     

顶发射白光OLED微型显示器的蓝光掺杂特性研究

白光OLED微型显示器在信息显示领域具有重要的应用。采用真空镀膜系统,依次蒸镀Ag/ITO复合薄膜作为阳极结构,共蒸制备Mg∶Ag复合膜作为半透明阴极结构,NPB作为空穴传输材料和黄光主体材料,rubrene作为黄光掺杂料,AND作为蓝光主体料,DSA-Ph作为蓝光掺杂料,Alq3作为电子传输材料,以结构和工艺简化的蓝、黄光互补色来实现白光,通过共蒸发形式制备了结构为Ag/ITO/NPB/NPB∶rubrene（1.5%）/ADN∶DSA-Ph（x%/x=2,5,8）/Alq3/Mg∶Ag的白光OLED微型显示器,利用由Photo Research PR655光谱仪、Keithley 2400程控电源组成的光谱测试系统对器件的光电性能进行表征,研究了蓝光掺杂比对白光OLED微型显器性能的影响。结果表明,随着蓝光掺杂比的增加,白光OLED微型显示器的亮度先增加后降低,蓝光、黄光峰位有所偏移,色坐标发生一定的漂移,蓝光色纯度增加,可通过调控发光材料掺杂比实现白光OLED微型显示器性能的可控制备。初步优化获得的蓝、黄混合白光OLED微型显示器的器件,当驱动电压为5.0 V时,器件亮度达到3 679 cd·m-2,CIE坐标为（0.263,0.355）。     

不同主体材料对红色磷光OLED器件性能的影响

制作了结构为ITO/2T-NATA (20 nm)/NPB(60 nm)/Zn(BTZ)₂ : Ir(DBQ)₂(acac) (80 nm)/Alq₃(70 nm)/LiF(1 nm)/Al(200 nm)的红光器件,其中2T-NATA是4,4',4″-tris(N-(2-naphthyl)-N-phenyl-amino)-triphenylamine,NPB是N,N'-di(naphthalen-1-yl)-N,N'-diphenyl-benzidine, Zn(BTZ)₂是Bis-(2-(2-hydroxyphenyl) benzothiazole)zinc,Ir(DBQ)₂(acac)是iridium complex,Alq₃ 是tris(8-hydroxyquinolato)aluminum。基于Ir(DBQ)₂(acac) 掺杂的Zn(BTZ)₂体系的器件给出最高电致发光(EL)性能。结果显示:10％Ir(DBQ)₂-(acac) 掺杂Zn(BTZ)₂器件的亮度和效率分别为25 000 cd/m²和12 cd/A,其相应的EL峰位于620 nm,色坐标(x=0.63,y=0.37)。由于未使用激子阻挡层,所以,比通常磷光器件的制作工艺简单并且操作过程容易控制。     

聚合物太阳能电池中石墨烯量子点掺杂材料的优化

采用溶剂热法,以氧化石墨烯为前驱体制备了石墨烯量子点(GQDs),将不同制备条件和质量分数的GQDs掺杂到聚3-己基噻吩和[6,6\]-苯基-C61-丁酸甲酯(PCBM∶P3HT)中作为敏感层制备了太阳能电池器件。实验结果表明,敏感层掺杂0.2%质量分数的GQDs时,太阳能电池光电转换效率较未掺杂器件提高了16.45%。敏感层掺杂反应时间4 h和温度220℃制备的GQDs,获得低粗糙度和高紫外可见光吸收强度的敏感层薄膜,制备的太阳能电池器件光电转换效率为1.34%,较未掺杂GQDs器件提高了12.60%。因此,GQDs适宜的制备条件和掺杂浓度可以提高太阳能电池器件的光电转换效率。     

发光层掺杂对红光OLED性能影响研究

制备高效率、高亮度的红光有机发光二极管是显示器实现全彩色的关键,对高性能的红光有机发光二极管器件研究具有十分重要的意义.本文主要研究了掺杂剂(DCJTB)浓度对红光有机发光二极管性能影响.实验采用真空热蒸镀的方法,选取结构为ITO／2-TNATA(20 nm)/NPB(30 nm)/AlQ(50 nm):(X%)DCJTB／AlQ(30 nm)／LiF(0.8 nm)／Al(100 nm)的红光器件,在高准确度膜厚控制仪的监控下,实现了有机薄膜功能材料的精确蒸镀.研究表明:红光掺杂剂掺杂浓度为(2.5~3.0)%时,在12 V电压下,可以得到发光亮度最高达到8 900 cd/m²,发光效率大于2.8 cd/A,且发光光谱波长为610~618 nm较为理想的红光有机发光二极管器件.     

双量子阱结构OLED效率和电流的磁效应

通过结构为ITO/NPB(60 nm)/ Alq₃ ∶1 wt% rubrene(20 nm)/ Alq₃(3 nm)/ Alq₃ ∶1 wt% rubrene(20 nm)/ Alq₃(20 nm)/LiF/Al的双量子阱的黄色有机电致发光器件,研究了不同磁场强度下的发光效率和电流变化特性. 研究结果表明该器件的电流是随着磁场强度的增加而单调下降的,显示了器件的电阻是随着磁场强度的增加而增加的. 同时也得到了该结构有 关键词： 量子阱 磁场 OLED 磁效应     

B/N掺杂对于石墨烯纳米片电子输运的影响

选用锯齿(zigzag)型石墨烯纳米片为研究对象, Au作为电极, 分子平面与Au的(111)面垂直, 并通过末端S原子化学吸附于金属表面, 构成两种分子器件: 一种是在纳米片的边缘掺杂N(B)原子, 发现电流-电压具有非线性行为, 但是整流系数较小, 特别是掺杂较多时, 整流具有不稳定性; 另一种是用烷链把两个石墨烯片连接, 在烷链附近和石墨烯片的边缘进行N(B)掺杂, 发现在烷链附近掺杂具有较大的整流, 但是掺杂的原子个数和位置会影响整流性能. 研究表明: 整流主要为正负电压下分子能级的移动方向和空间轨道分布不同导致. 部分体系中的负微分电阻现象主要由于偏压导致能级移动和透射峰形态的改变, 并且在某些偏压下主要透射通道被抑制而引起. 关键词： 石墨烯纳米片 电子输运 整流行为 非平衡格林函数方法     

利用磷光敏化改善聚合物白光OLED性能

基于新型聚合物白光材料PF-DTFO制备了一种聚合物白光发光二极管(PWOLED),通过在聚合物发光层中掺杂蓝光磷光染料FIrpic,利用磷光敏化发光原理,改善器件电致发光性能。在敏化PWOLED中,掺杂的FIrpic染料作为给体将产生的三重态能量传递给白光聚合物的长波发射基团,进一步提高了长波基团的发光强度,改善了白光光谱,使基色更平衡并且光谱更稳定。驱动电压从8 V增加到16 V时,器件电致发光光谱基本不变,色坐标仅从(0.33,0.38)移动至(0.32,0.38)。敏化后的器件发光效率相对于未掺杂器件提高了38%。     

基于OLED微显示器和变形目镜的全景显示技术

全景成像在特种车辆内夜间驾驶与观察、警戒监视等应用中具有广泛的应用需求。本文提出了一种基于OLED微显示器和变形目镜的全景图像显示方法,并设计了一套全景显示实验系统,通过图像处理模块完成全景图像数据的存储、缓存、图像预处理和传输,以OLED微显示器的子像素作为显示像素进行驱动信号重编码,实现全景灰度图像的水平3倍压缩显示,最后利用变形目镜将OLED微显示器上显示的压缩图像复原,以供人眼正常观察。实验结果表明:采用现有系统搭建的变形目镜基本实现了双像素靶标条纹的亚像素分辨,并验证了本文全景显示方案的可行性。     

Excited state complex and electroluminescence in TPD-based single layer device

N-N′-diphenyl-N,N′-(bis(3-methylphenyl)-1,1′-biphenyl-4,4′-diamine) (TPD), was used to fabricate single layer devices (ITO/TPD/Ca/Al). A near-white emission (CIE coordinate of 0.25, 0.24) is observed in electroluminescence (EL) of the single layer device with prominent emission bands at 400, 475 and 670 nm. Steady state and time-resolved emission spectra of spin-coated and annealed TPD films and TRES and TRANES analysis confirmed that emission at 400 and 475 nm are due to monomer and excimer emission, respectively. The origin of the red emission at 670 nm in EL is discussed.     

The effects of temperature on the formation and stability of bipolarons in conjugated polymers

Within the one-dimensional tight-binding Su-Schrieffer-Heeger (SSH) model modified to include thermal effects and electron-electron interactions, the transition from polaron to bipolaron and the formation of bipolaron induced by injecting charges are separately simulated using a nonadiabatic evolution method. For the transition process, it is found that with the temperature effects taken into account, two separate polarons with the same charge and antiparallel spins can recombine into a bipolaron. The results show that with the temperature increasing, the time taken for the recombination of two polarons decreases. The effects of different distances between the polarons are also numerically simulated. For the bipolaron formation, we investigate the evolution of two charges injected into a polymer chain with the thermal effects. We find that the bipolaron is always quickly formed and its dynamical stability is less sensitive to the temperature change. Thermal effects can only affect the degree of the charges localization.     

Segmented conjugated polymers

Segmented conjugated polymers, wherein the conjugation is randomly truncated by varying lengths of non-conjugated segments, form an interesting class of polymers as they not only represent systems of varying stiffness, but also ones where the backbone can be construed as being made up of chromophores of varying excitation energies. The latter feature, especially when the chromophores are fluorescent, like in MEHPPV, makes these systems particularly interesting from the photophysics point of view. Segmented MEHPPV-x samples, wherex represents the mole fraction of conjugated segments, were prepared by a novel approach that utilizes a suitable precursor wherein selective elimination of one of the two eliminatable groups is affected; the uneliminated units serve as conjugation truncations. Control of the compositionx of the precursor therefore permits one to prepare segmented MEHPPV-x samples with varying levels of conjugation (elimination). Using fluorescence spectroscopy, we have seen that even in single isolated polymer chains, energy migration from the shorter (higher energy) chromophores to longer (lower energy) ones occurs — the extent of which depends on the level of conjugation. Further, by varying the solvent composition, it is seen that the extent of energy transfer and the formation of poorly emissive inter-chromophore excitons are greatly enhanced with increasing amounts of non-solvent. A typical S-shaped curve represents the variation of emission yields as a function of composition suggestive of a cooperative collapse of the polymer coil, reminiscent of conformational transitions seen in biological macromolecules.     

Intermolecular interaction effects on the ultrafast depolarization of the optical emission from conjugated polymers

We have investigated the effect of interchain interactions on the ultrafast depolarization of the photoluminescence from solid films of a conjugated polymer. Accurate control was exercised over the interchain separation by threading of the conjugated chains with insulating macrocycles or complexation with an inert host polymer. Our measurements indicate that excitation into the higher electronic states of a chain aggregate is followed by a fast (<100 fs) relaxation into lower excited states with an associated rotation of the transition dipole moment. These findings emphasize the need for consideration of initial excitonic delocalization across more than one polymeric chain.     

Local-field anisotropy in conjugated polymers

The experimental values of the Lorentz tensor components L _j have been obtained for uniaxial optically positive and negative films of conjugated polymers with thicknesses of tens of nanometers. The correlation between the components L _j and the measurable parameter η has been revealed and the analytical dependence L _j (η) has been derived in agreement with the experiment.     

Polarons in organic conjugated polymers

An unified treatment of the electronic structure of organic conjugated polymers based on a renormalization approach is presented. The changes in the electronic structures of trans-polyacetylene, poly-(p-phenylene), polypyrrole and polythiophene, brought about by the presence of polarons in these systems, are studied. For all systems, two localized states, which can be interpreted as the symmetric and antisymmetric combinations of soliton wavefunctions, are created at the central gap.