Syntheses and characterization of functionalized polynorbornene dicarboximides for flexible substrates

In this study, we synthesized polynorbornene (PNB) dicarboximides substituted by monochlorophenyl group (PMCPhNDI) and dichlorophenyl group (PDCPhNDI) via ring‐opening polymerization using a ruthenium catalyst and investigated their thermal, mechanical, and optical properties. We also discussed the performance and application of the functionalized PNB dicarboximide films as flexible substrates for organic light‐emitting devices (OLEDs). The polymer films exhibited good optical transparency with an average transmittance of around 97% in the visible light region and good thermal stability with a 5% degradation temperature of >440°C. The polymers were applied for flexible displays, which were coated on indium tin oxide (ITO) thin films using a radio‐frequency planar magnetron sputtering system with changing the deposition substrate temperatures. A flexible OLED that was fabricated on the ITO‐grown polymer substrates exhibited a performance as comparable to the corresponding ITO‐grown glass substrates. Copyright © 2012 John Wiley & Sons, Ltd.     

Photolithographic patterning of highly conductive PEDOT:PSS and its application in organic light‐emitting diodes

Photolithographically patterned highly conductive (～1400 S/cm) poly(3,4‐ethylenedioxythio‐phene):poly(styrenesulfonate) (PEDOT:PSS) films are demonstrated as electrodes for organic light emitting diodes (OLEDs). With the assistance of hydrofluoroether (HFE) solvents and fluorinated photoresists, high‐resolution passive‐matrix OLEDs with PEDOT:PSS electrodes are fabricated, in which the OLEDs show comparable performance to those devices prepared on the indium tin oxide (ITO) electrodes. This photolithographic patterning process for PEDTO:PSS has great potential for applications which require flexible electrodes. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 1221–1226     

Influence of the substrate type on the microstructural,optical and electrical properties of sol–gel ITO films

Indium tin oxide (ITO) is recognized as the best transparent and conductive material [transparent conducting oxide (TCO)] until now and its properties are dependent on the preparation method. In the present work ITO films with In:Sn atomic ratio 9:1 were prepared by a sol–gel route on different substrates (microscope glass slides, microscope glass covered with one layer of SiO₂ and Si wafers) for TCO applications. The multilayer ITO films were obtained by successive deposition by the dip-coating method and the films were characterized from the structural, morphological, optical, and electrical points of view using X-ray diffraction, scanning electron microscopy, atomic force microscopy, spectroscopic ellipsometry and by Hall effect measurements, respectively. The results showed that the thickness, optical constants and carrier numbers depend strongly on the type of substrate, number of deposited layers and sol concentration. The optical properties of ITO films are closely related to their electrical properties. The enhancement of the conductivity was possible with the increase of crystallite size (which occurred after thermal treatment) and with the reduction of surface roughness.     

Photochromism and electrochemistry of a dithienylcyclopentene electroactive polymer

A bifunctional substituted dithienylcyclopentene photochromic switch bearing electropolymerisable methoxystyryl units, which enable immobilization of the photochromic unit on conducting substrates, is reported. The spectroscopic, electrochemical, and photochemical properties of a monomer in solution are compared with those of the polymer formed through oxidative electropolymerization. The electroactive polymer films prepared on gold, platinum, glassy carbon, and indium titanium oxide (ITO) electrodes were characterized by cyclic voltammetry, X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). The thickness of the films formed is found to be limited to several monolayer equivalents. The photochromic properties and stability of the polymer films have been investigated by UV/vis spectroscopy, electrochemistry, and XPS. Although the films are electrochemically and photochemically stable, their mechanical stability with respect to adhesion to the electrode was found to be sensitive to both the solvent and the electrode material employed, with more apolar solvents, glassy carbon, and ITO electrodes providing good adhesion of the polymer film. The polymer film is formed consistently as a thin film and can be switched both optically and electrochemically between the open and closed state of the photochromic dithienylethene moiety.     

Highly Conductive PEDOT:PSS Films with 1,3‐Dimethyl‐2‐Imidazolidinone as Transparent Electrodes for Organic Light‐Emitting Diodes

Highly conductive poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) films as transparent electrodes for organic light‐emitting diodes (OLEDs) are doped with a new solvent 1,3‐dimethyl‐2‐imidazolidinone (DMI) and are optimized using solvent post‐treatment. The DMI doped PEDOT:PSS films show significantly enhanced conductivities up to 812.1 S cm⁻¹. The sheet resistance of the PEDOT:PSS films doped with DMI is further reduced by various solvent post‐treatment. The effect of solvent post‐treatment on DMI doped PEDOT:PSS films is investigated and is shown to reduce insulating PSS in the conductive films. The solvent posttreated PEDOT:PSS films are successfully employed as transparent electrodes in white OLEDs. It is shown that the efficiency of OLEDs with the optimized DMI doped PEDOT:PSS films is higher than that of reference OLEDs doped with a conventional solvent (ethylene glycol). The results present that the optimized PEDOT:PSS films with the new solvent of DMI can be a promising transparent electrode for low‐cost, efficient ITO‐free white OLEDs.

     

石墨烯透明导电薄膜

石墨烯是一种新型二维晶体材料,它独特的单原子层结构显示出许多优异的物理化学性质。以石墨烯为原料制备的透明导电薄膜继承了石墨烯的优点,与氧化铟锡(ITO)薄膜相比,具有更好的力学强度、透光性以及化学稳定性,已逐渐成为全世界范围内的研究热点。本文首先介绍了石墨烯的光电性能,然后分别从石墨烯透明导电薄膜的前驱体和制备方法两个不同的角度,归纳总结了最近几年石墨烯透明导电薄膜的研究进展,就目前所面临的问题进行了讨论,并展望了石墨烯透明导电薄膜的未来发展。     

基于N-对甲氧苯基咔唑-2-乙烯基-8-羟基喹啉锌的白色和黄色有机电致发光器件的性能

通过研究新型荧光染料N-对甲氧苯基咔唑-2-乙烯基-8-羟基喹啉锌(MoBCzHQZn)的电致发光(EL)特性, 发现MoBCzHQZn具有较强的发光特性和空穴传输特性, 利用此特性制备了非掺杂型的有机电致白光器件和掺杂型的有机电致黄光器件. 白光器件的结构为ITO/2T-NATA(20 nm)/MoBCzHQZn(25 nm)/NPBX(13 nm)/BCP(8nm)/Alq3(34 nm)/LiF(0.5 nm)/Al, 器件在15 V电压下实现了白光发射, 色坐标为(0.3719, 0.3275), 最大发光亮度为3414 cd·m-2, 在14 V 电压下的最大发光效率为1.69 cd·A-1、黄光器件的结构为ITO/2T-NATA(20 nm)/CBP:6%Ir(ppy)3:10%MoBCzHQZn(25 nm)/TPBi:6%Ir(ppy)3(47 nm)/LiF(0.5 nm)/Al, 器件在15 V电压下实现了黄绿光发射, 色坐标为(0.3590, 0.5787), 最大发光亮度为11073 cd·m-2, 在9 V电压下的最大发光效率为2.51 cd·A-1.     

Covalently bound hole-injecting nanostructures. Systematics of molecular architecture, thickness, saturation, and electron-blocking characteristics on organic light-emitting diode luminance, turn-on voltage, and quantum efficiency

Hole transporting materials are widely used in multilayer organic and polymer light-emitting diodes (OLEDs, PLEDs, respectively) and are indispensable if device electroluminescent response and durability are to be truly optimized. This contribution analyzes the relative effects of tin-doped indium oxide (ITO) anode-hole transporting layer (HTL) contact versus the intrinsic HTL materials properties on OLED performance. Two siloxane-based HTL materials, N,N'-bis(p-trichlorosilylpropyl)-naphthalen-1-yl)-N,N'-diphenyl-biphenyl-4,4'-diamine (NPB-Si(2)) and 4,4'-bis[(p-trichlorosilylpropylphenyl)phenylamino]biphenyl (TPD-Si(2)), are designed and synthesized. They have the same hole transporting triarylamine cores as conventional HTL materials such as 1,4-bis(1-naphthylphenylamino)biphenyl (NPB) and N,N-diphenyl-N,N-bis(3-methylphenyl)-1,1-biphenyl)-4,4-diamine (TPD), respectively. However, they covalently bind to the ITO anode, forming anode-HTL contacts that are intrinsically different from those of the anode to TPD and NPB. Applied to archetypical tris(8-hydroxyquinolato)aluminum(III) (Alq)-based OLEDs as (1) the sole HTLs or (2) anode-NPB HTL interlayers, NPB-Si(2) and TPD-Si(2) enhance device electroluminescent response significantly versus comparable devices based on NPB alone. In the first case, OLEDs with 36 000 cd/m(2) luminance, 1.6% forward external quantum efficiency (eta(ext)), and 5 V turn-on voltages are achieved, affording a 250% increase in luminance and approximately 50% reduction in turn-on voltage, as compared to NPB-based devices. In the second case, even more dramatic enhancement is observed (64 000 cd/m(2) luminance; 2.3% eta(ext); turn-on voltages as low as 3.5 V). The importance of the anode-HTL material contact is further explored by replacing NPB with saturated hydrocarbon siloxane monolayers that covalently bind to the anode, without sacrificing device performance (30 000 cd/m(2) luminance; 2.0% eta(ext); 4.0 V turn-on voltage). These results suggest new strategies for developing OLED hole transporting structures.     

Thin Film of Perovskite Oxide with Atomic Scale p-n Junctions

Thin films of perovskite manganese oxide La_0.66Ca_0.29K_0.05MnO₃(LCKMO) on Au/ITO(ITO=indium tin oxide) substrates were prepared by off-axis radio frequency magnetron sputtering and characterized by X-ray diffraction( XRD), high-resolution transmission electron microscopy(HRTEM), and conductive atomic force microscopy (C-AFM) at room temperature. The thin films with thickness ranged from 100 nm to 300 nm basically show cubic structures with a=0.3886 nm, the same as that of the raw material used, but the structures are highly modulated. C-AFM results revealed that the atomic scale p-n junction feature of the thin films was the same as that of the single crystals. The preparation of the thin films thus further confirms the possibility of their application extending from micrometer-sized single crystals to macroscopic thin film.     

Surface modification and characterization of indium-tin oxide for organic light-emitting devices

In this work, we used different treatment methods (ultrasonic degreasing, hydrochloric acid treatment, and oxygen plasma) to modify the surfaces of indium-tin oxide (ITO) substrates for organic light-emitting devices. The surface properties of treated ITO substrates were studied by atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), sheet resistance, contact angle, and surface energy measurements. Experimental results show that the ITO surface properties are closely related to the treatment methods, and the oxygen plasma is more efficient than the other treatments since it brings about smoother surfaces, lower sheet resistance, higher work function, and higher surface energy and polarity of the ITO substrate. Moreover, polymer light-emitting electrochemical cells (PLECs) with differently treated ITO substrates as device electrodes were fabricated and characterized. It is found that surface treatments of ITO substrates have a certain degree of influence upon the injection current, brightness, and efficiency, but hardly upon the turn-on voltages of current injection and light emission, which are in agreement with the measured optical energy gap of the electroluminescent polymer. The oxygen plasma treatment on the ITO substrate yields the best performance of PLECs, due to the improvement of interface formation and electrical contact of the ITO substrate with the polymer blend in the PLECs.     

Optimization of high-performance blue organic light-emitting diodes containing tetraphenylsilane molecular glass materials

Molecular glass material (4-(5-(4-(diphenylamino)phenyl)-2-oxadiazolyl)phenyl)triphenylsilane (Ph(3)Si(PhTPAOXD)) was used as the blue light-emitting material in the fabrication of high-performance organic light-emitting diodes (OLEDs). In the optimization of performance, five types of OLEDs were constructed from Ph(3)Si(PhTPAOXD): device I, ITO/NPB/Ph(3)Si(PhTPAOXD)/Alq(3)/Mg:Ag, where NPB and Alq(3) are 1,4-bis(1-naphylphenylamino)biphenyl and tris(8-hydroxyquinoline)aluminum, respectively; device II, ITO/NPB/Ph(3)Si(PhTPAOXD)/TPBI/Mg:Ag, where TPBI is 1,3,5-tris(N-phenylbenzimidazol-2-yl)benzene; device III, ITO/Ph(2)Si(Ph(NPA)(2))(2)/Ph(3)Si(PhTPAOXD)/TPBI/Mg:Ag, where Ph(2)Si(Ph(NPA)(2))(2) is bis(3,5-bis(1-naphylphenylamino)phenyl)-diphenylsilane, a newly synthesized tetraphenylsilane-containing triarylamine as hole-transporting material; device IV, ITO/Ph(2)Si(Ph(NPA)(2))(2)/NPB/Ph(3)Si(PhTPAOXD)/TPBI/Mg:Ag; device V, ITO/CuPc/NPB /Ph(3)Si(PhTPAOXD)/Alq(3)/LiF/Al, where CuPc is Cu(II) phthalocyanine. Device performances, including blue color purity, electroluminescence (EL) intensity, current density, and efficiency, vary drastically by changing the device thickness (100-600 A of the light-emitting layer) and materials for hole-transporting layer (NPB and/or Ph(2)Si(Ph(NPA)(2))(2)) or electron-transporting material (Alq(3) or TPBI). One of the superior OLEDs is device IV, showing maximum EL near 19 000 cd/m(2) with relatively low current density of 674 mA/cm(2) (or near 3000 cd/m(2) at 100 mA/cm(2)) and high external quantum efficiency of 2.4% (1.1 lm/W or 3.1 cd/A). The device possesses good blue color purity with EL emission maximum (lambda(max)(EL)) at 460 nm, corresponding to (0.16, 0.18) of blue color chromaticity on CIE coordinates. In addition, the device is reasonably stable and sustains heating over 100 degrees C with no loss of luminance on the basis of the annealing data for device V. Formation of the exciplex at the interface of NPB and Ph(3)Si(PhTPAOXD) layers is verified by EL and photoluminescence (PL) spectra studies on the devices with a combination of different charge transporting materials. The EL due to the exciplex (lambda(max)(EL) at 490-510 nm) can be properly avoided by using a 200 A layer of Ph(3)Si(PhTPAOXD) in device I, which limits the charge-recombination zone away from the interface area.     

Molecular Designs and Properties of Highly Efficient Blue Emitters for OLEDs

Advances made in the molecular design of modern optoelectronic materials have made significant contributions toward the development of organic electronics. The organic light-emitting devices (OLEDs) employing monodisperse or polymeric conjugated materials possess the most promising prospects. However, materials suitable for long-term use as blue light emitters are still far from optimization in terms of stability.In the past few years, interesting materials based on 9,9-diaryl-substituted fluorene as a core structure have been developed in our laboratory. We developed a series of efficient and morphologically stable pyrimidine-containing 9,9'-spirobifluorene-cored oligoaryls as pure blue emitters. The steric hindrance inherent with the molecular structure renders the material with a record-high thin-film PL quantum yield of ～95% and a glass transition temperature (Tg) of ～200 ℃.Blue OLEDs employing this thermally stable compound as the emitting host exhibit unusual endurance for high currents. Injection current over 5,000 mA/cm2 and maximal brightness of～80,000 cd/m2 had been demonstrated, representing the highest values reported for blue OLEDs under dc driving. In addition, a series of oligofluorene homologues have been synthesized. These oligofluorenes exhibit interesting reversible bipolar redox properties and excellent morphological and thermal stability. Furthermore, nondispersive ambipolar high hole and electron mobilities over 10-3 cm2/V.s can be achieved with these oligo(9,9-diarylfluorene)s. In particular, the electron mobility observed represents the highest ever reported for amorphous molecular solids. These intriguing properties together with the high quantum yields in thin films make these oligo(9,9-diarylfluorene)s are promising for OLEDs applications as efficient blue emitters. In this meeting, the synthesis and properties of these materials and their highly efficient OLEDs device characteristics will be discussed.     

Studies on electro‐optical properties of polymer matrix/LC/ITO nanoparticles composites

In this paper, polymer‐dispersed liquid crystal (PDLC) films consisting of liquid crystal (LC)/monomers/indium tin oxide (ITO) nanoparticles with good near‐infrared absorption property had been fabricated, and the influence of the ITO nanoparticles modified with 3‐methacryloxypropyltrimethoxysilane (KH570) on the PDLC films was systematically studied. First, different liquid crystal content was studied to obtain PDLC films with good electro‐optical properties. And then, various weight ratio of ITO nanoparticles was added to samples. While the content of ITO nanoparticles was increased, the saturation voltage increased and the CR decreased. Though the electro‐optical properties of PDLC samples reduced with the addition ITO nanoparticles, the near‐infrared absorption property of films was enhanced.     

Surface modification of indium tin oxide via electrochemical reduction of aryldiazonium cations

The facile deposition of para-substituted aryl films onto indium-tin oxide (ITO) electrodes by the electrochemical reduction of aryl diazonium salts in acetonitrile is reported. For the deposition conditions used in this report, the aryl film thicknesses are on the order of 1-6 nm, suggesting a multilayer structure. Regardless of the functional group on the aryl diazonium cation, (NO(2), CO(2)H, or fluorene) the electrodeposition behavior onto ITO electrodes is similar to that seen on other electrode materials. XPS and UV-vis data support the introduction of organic functional surface groups to ITO. The blocking behavior of the aryl films on ITO toward the Ru(NH(3))(6)(3+/2+) redox couple is in agreement with electron transfer through conjugated organic layers. The facile preparation of patterned aryl films with regular-spaced 700 nm voids on ITO is also described. Atomic force microscopy and scanning surface potential microscopy on patterned NO(2) aryl films are used to assess the molecular structure and orientation. A 100 mV decrease in the contact potential over NO(2) aryl films relative to bare ITO suggests that the aryl films are loosely structured as deposited with the NO(2) groups oriented at a small angle away from the ITO surface.     

New carbazole-substituted siloles for the fabrication of efficient non-doped OLEDs

New aggregation-induced emission molecules of carbazole-substituted siloles are prepared, based on which efficient non-doped OLEDs are fabricated, offering high external quantum efficiencies of up to 5.63%.     

基于印刷电子的透明导电薄膜研究进展

透明导电薄膜是一种在可见光范围内透光率较高、导电性优良的薄膜材料.近年来随着智能手机、平板电脑等电子产品日益普及,透明导电薄膜受到越来越多的关注.本文分析了目前占据市场统治地位的掺锡氧化铟透明导电薄膜的缺点以及近年来国内外对透明导电薄膜开展的研究工作,总结了目前在印刷电子领域透明导电薄膜的主要研究方向,一方面是在传统金属氧化物薄膜基础上的改进;另一方面是寻找新型透明导电薄膜材料,并分别综述了各个研究方向的最新进展.     

Preparation of polymer-dispersed liquid crystal doped with indium tin oxide nanoparticles

To study polymer-dispersed liquid crystal (PDLC) films doped with indium tin oxide (ITO) nanoparticles (NPs), samples were prepared by ultraviolet-initiated polymerisation based on the thiol–acrylate system. Owing to the interaction between PDLC system and ITO NPs, the content and the size of ITO NPs are the main determinants to the microstructure which plays an essential role on the electro-optical and anti-infrared properties of the PDLC films. In the polymer matrix, a novel microstructure consisting of a dense surface, micron-sized meshes and submicron meshes is found to benefit the better performances of the low driven voltage (20.7 V), the relatively high contrast ratio (8.3) and the lowest transmittance(500–2500 nm) on average at about 3.55% with maximum of merely 7.6%. Thus, it lays a solid foundation for the further investigations on the microstructure and the performance of the PDLC films. Meanwhile, it is proved that the PDLC film, improved performance through doping ITO NPs, is promising to be a superior choice in the field of energy-saving.     

基于N-乙基咔唑-2-乙烯基-8-羟基喹啉锌的黄绿色有机电致发光器件的性能

通过用一种既具有空穴传输特性又具有发光特性的新型荧光染料N-乙基咔唑-2-乙烯基-8-羟基喹啉锌((E)-2-(2-(9-ethyl-9H-carbazol-3-yl)vinyl) quinolato-zinc, CzHQZn)作为受主, 制备了结构为ITO/2T-NATA (30 nm)/CBP: 6%Ir(ppy)3:wCzHQZn(20 nm)/Alq3(50 nm)/LiF/Al(ITO: indium-tin oxide, 2T-NATA: 4,4',4'-{N,N-(2-naphthyl)-N-phenylamino}-triphenylamine, CBP: 4,4-N,N'-dicarbazole-biphenyl, Ir(ppy)3: factris (2-phenylpyridine) iridium, Alq3: tris(8-quinolinolato) aluminum; w 是CzHQZn 的质量分数)的黄绿色有机电致发光器件(OLEDs). 研究了掺杂体系在不同掺杂浓度(w=5%、10%、12%、15%)时的电致发光(EL)特性. 结果表明, CzHQZn 掺杂浓度为10%的器件在11 V 电压下实现了黄绿光发射, 色坐标为(0.4045, 0.5113), 最大发光亮度为16110 cd·m-2; 而在7 V电压下的最大发光效率为2.19 cd·A-1, 最大外量子效率为0.775%.     

Photo switchable pendant furyl and thienyl fulgimides containing polypyrroles

We report the new pendant furyl and thienyl fulgimides photochromic switch bearing polypyrroles. The functionalized pyrrole monomers synthesized and structures are ascertained by NMR and mass spectral techniques. The yield of fulgides and fulgimides are improved by using trifluoroacetic anhydride (TFA) as a dehydrating agent. The photo-switching properties of fulgimides monomers are explained by electronic structures of HOMO–LUMO of the monomers using Gaussian 03 packages. The electro-active polymer films deposited on indium tin oxide (ITO) electrodes are characterized by cyclic voltammetry and atomic force microscopy (AFM). The electrochemically formed thin films undergoes photo-switching between open and closed state of fulgimides moiety. The photo-switching properties of the polymer films have been confirmed by UV/vis spectroscopy. Though the films are photochemically stable, their mechanical stability with respect to adhesion to electrode is found to be sensitive to the solvent and electrode material.     

Free-standing highly conductive transparent ultrathin single-walled carbon nanotube films

Transparent and conductive single-walled carbon nanotube (SWNT) films are of great importance to a number of applications such as optical and electronic devices. Here, we describe a simple approach for preparing free-standing highly conductive transparent SWNT films with a 20-150 nm thickness by spray coating from surfactant-dispersed aqueous solutions of SWNTs synthesized by an improved floating-catalyst growth method. After the HNO(3) treatment, dipping the SWNT films supporting on glass substrates in water resulted in a quick and nondestructive self-release to form free-standing ultrathin SWNT films on the water surface. The obtained films have sufficiently high transmittance (i.e., 95%), a very low sheet resistance (i.e., ～120 Ω/sq), and a small average surface roughness (i.e., ～3.5 nm for a displayed 10 × 10 μm area). Furthermore, the floating SWNT films on the water surface were easily transferred to any substrates of interest, without intense mechanical and chemical treatments, to preserve their original sizes and network structures. For example, the transferred SWNT films on poly(ethylene terephthalate) films are mechanically flexible, which is a great advantage over conventional indium-tin oxide (ITO) and therefore strongly promise to be "post ITO" for many applications.