Work function tuning for flexible transparent electrodes based on functionalized metallic single walled carbon nanotubes

We present a method to control the work function of metallic carbon nanotube transparent electrodes by functionalization of the random network with metallic nanoparticles. Flexible functionalized electrodes with high transparency (～90%) can be obtained with work function values ranging from ～4.6 up to ～5.1 eV, depending on the nature of the nanoparticles. The work function values were obtained by comparative in situ Kelvin probe force microscopy under ultra high vacuum and ultraviolet photoelectron spectroscopy measurements. Interestingly, by appropriate choice of the metal source for functionalization, work function engineering can lead to work function values higher or lower than that for pristine metallic nanotubes. This could be of great interest for adjusting the work function of transparent electrodes to active layers in many optoelectronics devices.     

Towards molecular spintronics: magnetotransport and magnetism in carbon nanotube-based systems

We describe first approaches towards a carbon nanotube (CNT) based spintronics. The building blocks consist of pristine multi-wall CNTs and metallic ferromagnetic electrodes. The devices exhibit magnetoresistive effects up to several 10% at 4.2 K the origin of which is tentatively attributed to spin-dependent tunneling through an insulating barrier between the CNT and the electrode. We also show results of filling multi-wall CNTs with ferromagnetic materials. These magnetic quantum wires are fascinating objects in itself, revealing unusual magnetic properties. They may also be used, however, as magnetic electrodes to contact to the innermost shell of the nanotube in future molecular spintronics devices.     

Carbon nanotube modified electrodes for enhanced brightness in organic light emitting devices

Acid oxidised multiwall carbon nanotubes (COOH-MWCNT) have been introduced as a hole injection buffer layer in an organic light emitting diodes (OLED). We show that the OLED with COOH-MWCNT as a buffer layer provides higher brightness with lower operating voltages. The addition of a COOH-MWCNT buffer layer has enabled a further increase in the brightness of our OLED devices operating in excess of 20,000 cd/m² due to enhanced hole injection by several orders of magnitude. The increase in current injection and brightness does not alter the optical emission spectrum at different operating voltages in these devices. A model is proposed to explain this increase in current injection and brightness based on the modified electron energy band alignment.     

Influence of nickel oxide nanolayer and doping in organic light-emitting devices

Here we report the effect of introducing nickel oxide (NiO) on the performance of organic light-emitting devices (OLEDs) based on small molecules. For the purpose of aligning the NiO deposition with the conventional OLED process, we employed a thermal evaporation method using the NiO powders. To understand the influence of the NiO introduction, we fabricated two types of devices: (1) OLED with the NiO nanolayer and (2) OLED with the NiO-doped hole transport layer. Results show that the NiO introduction improved the hole injection in both types of OLED. However, the device with the NiO nanolayer exhibited greatly improved efficiency, whereas the efficiency was significantly lowered for the device with the NiO-doped hole transport layer.     

Titanium foam made with saccharose as a space holder

In this work we show a very promising method of titanium foam preparation with saccharose crystals (table sugar) as a space holder particles. The mixture of Ti and sugar particles was compacted to form a green compacts. In the next step the saccharose crystals were dissolved in the water, leaving open spaces surrounded by metallic scaffold. The sintering of the scaffold leads to foam with typical morphology and porosity. We found that 1:1 Ti/sugar ratio leads to porosities of about 72 % with pore diameter of about 0.8–1.0 mm, when we used 0.8–1.0 mm diameter sugar crystals. The foams morphology was investigated by SEM, porosity and internal structure was investigated using computed tomography and the structure was shown using XRD. The foam morphology pointed theirs potential applications in medical as well as catalyst devices.     

Formation of single-walled carbon nanotube thin films enriched with semiconducting nanotubes and their application in photoelectrochemical devices

Single-walled carbon nanotube (SWCNT) thin films, containing a high-density of semiconducting nanotubes, were obtained by a gel-centrifugation method. The agarose gel concentration and centrifugation force were optimized to achieve high semiconducting and metallic nanotube separation efficiency at 0.1 wt% agarose gel and 18,000g. The thickness of SWCNT films can be precisely controlled from 65 to 260 nm with adjustable transparency. These SWCNT films were applied in photoelectrochemical devices. Photocurrents generated by semiconducting SWCNT enriched films are 15-35% higher than those by unsorted SWCNT films. This is because of reducing exciton recombination channels as a result of the removal of metallic nanotubes. Thinner films generate higher photocurrents because charge carriers have less chances going in metallic nanotubes for recombination, before they can reach electrodes. Developing more scalable and selective methods for high purity semiconducting SWCNTs is important to further improve the photocurrent generation efficiency by using SWCNT-based photoelectrochemical devices.     

Diimide nanoclusters play hole trapping and electron injection roles in organic light-emitting devices

We report thermally stable diimide nanoclusters that could potentially replace the conventional thick electron transport layer (ETL) in organic light-emitting devices (OLEDs). Bis-[1,10]phenanthrolin-5-yl-bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic diimide (Bphen-BCDI) was synthesized from the corresponding dianhydride and amine moieties, and its purified product exhibited a high glass transition temperature (232 °C) and a wide band gap (3.8 eV). The Bphen-BCDI subnanolayers deposited on substrates were found to form organic nanoclusters, not a conventional layer. The OLED made with a subnanolayer of Bphen-BCDI nanoclusters, instead of a conventional ETL, showed greatly improved efficiency (about 2-fold) compared with an OLED without the diimide nanoclusters. The role of the BPhen-BCDI nanoclusters was assigned to hole trapping and electron injection in the present OLED structure.     

功能小分子电致发光材料的研究进展

有机电致发光(OLED)是近年来国际上的一个研究热点。有机电致发光器件具存低压驱动、高亮度、高效率以及能实现大面积彩色显示等优点。本文综述了有机电致发光材料的发展过程,重点介绍了目前应用于有机电致发光的各类功能小分子电致发光材料,文末展望了OLED的应用前景。     

含有芘基团的电致发光材料的研究进展

综述了近几年芘的衍生物在有机电致发光中的研究情况,展示了一些新结构并做了分析,总结了含芘基团电致发光材料的优点和缺点,并指出了芘的衍生物在有机电致发光材料中的应用前景。     

Edge reconstructions induce magnetic and metallic behavior in zigzag graphene nanoribbons

The edge reconstructions of zigzag graphene nanoribbons with one and two lines of alternating fused five and seven membered rings along one edge with hydrogen passivation are studied using first principles density functional theory. Reconstructions on one edge stabilize the systems in a metallic ground state with finite magnetic moment. The reconstructed edge suppresses the local spin density of atoms and contributes a finite density of states at the Fermi energy. Our study shows the possibilities of fabricating the metallic electrodes for semiconducting graphene devices with full control over their magnetic behavior without any lattice mismatch between leads and the channel.     

有机电致发光材料研究新进展

简要介绍了有机电致发光器件的结构、工作原理。重点从有机电致发光材料器件结构的角度出发,对电致发光材料最新研究进展进行了综述。     

The formation and properties of single nuclei

The formation and growth of single metallic nuclei of silver, mercury and copper have been studied at microscopically small electrodes of platinum and carbon. Once formed, metallic nuclei act as point sinks, growing under hemispherical mass-transfer control. The rate of growth at low overpotential is a function of the mean surface concentration as determined by the Nernst relation.The rate of formation of isolated nuclei has been determined as the inverse of the delay time attending their birth as indicated by the onset of the growth current. A distribution of delay times is observed in keeping with the statistical nature of the nucleation process.The nuclei or crystallites formed are spherical droplets in the case of mercury or microscopic single crystals in the case of solid metals, their size being accessible from the current—time integral of their growth. They are stable on open circuit and exhibit the residual overpotential of their excess surface free energy, ie their Gibbs—Kelvin potential. This potential is a linear function of their inverse equivalent spherical radius. The surface tensions calculated from the simplest application of the Gibbs—Kelvin equations appear to be higher than the known or estimated bulk values.The microscopic metallic crystallites have been used as reactive electrodes. The high mass-transfer flux to their surface enabled the exchange current to be determined by a simple, steady state small amplitude dc procedure.These studies confirm the considerable promise of microscopically small electrodes in electrochemistry.     

有机电致发光功能色素材料的研究

介绍了有机电致发光材料的发展过程，阐述了空穴、电子传输材料。详细叙述了发光材料尤其是悬挂体系有机电致发光材料。提出了研究新材料的意义。     

Molecular junctions: from tunneling to function

Thanks to the development of appropriate experimental techniques, molecular devices and their electrical transport properties have recently been the focus of a major research effort. This brief review describes how individual molecules can be contacted with metallic electrodes to form molecular junctions and addresses their basic formation mechanisms. An extension to molecular junctions networks is also discussed. Functionality could be demonstrated in such systems, and examples where conductance modulation using light or chemical stimuli was achieved will be presented.     

Electrical double layer in solid electrolytes—silver ion conductors

Published data and the results of authors' investigations of the electrical double layer properties in silver ion conducting solid electrolytes are discussed. These are classical systems with point defects AgBr,AgCl (pure and doped), β-AgI and superionic conductors α-AgI and RbAg₄I₅. The comparative analysis of the results for the different systems is made. The double layer structure on graphite electrodes in crystals with Frenkel defects corresponds to the Helmholtz layer. In the case of metallic electrodes (Pt,Au) it was found that double layer properties are strongly influenced by the electrode nature; it means that the specific absorption of electrolyte ions plays the essential part. Some results may be satisfactorily explained in terms of the intrinsic surface disorder model.     

Toward the ideal organic light-emitting diode. The versatility and utility of interfacial tailoring by cross-linked siloxane interlayers

Small molecule and polymer organic light-emitting diodes (OLEDs) show promise of revolutionizing display technologies. Hence, these devices and the materials that render them functional are the focus of intense scientific and technological interest. The archetypical multilayer OLED heterostructure introduces numerous chemical and physical challenges to the development of efficient and robust devices. It is demonstrated here that robust, pinhole-free, conformal, adherent films with covalently interlinked structures are readily formed via self-assembling or spin-coating organosilane-functionalized molecular precursors at the anode-hole transport layer interface. In this manner, molecularly "engineered" hole transport and hydrocarbon anode functionalization layers can be introduced with thicknesses tunable from the angstrom to nanometer scale. These investigations unequivocally show that charge injection and continuity at the anode-hole transport layer interface, hence OLED durability and efficiency, can be substantially enhanced by these tailored layers.     

Optical Scattering from Nanostructured Glass Surfaces

Nanostructured glass surfaces enable new and innovative applications for glass substrates. These nanostructures enable trapping as well as extraction of light. They affect the propagation of light such that it scatters and is trapped or extracted based on the index of the propagation media. The diffusive scattering component as opposed to the specular component is what enables the trapping and extraction. Often smooth surfaces are required for growing semiconductor thin films. Scattering sites beneath these surfaces can significantly enhance the optical performance of these films. Example devices utilizing these substrates include organic light-emitting diodes (OLED) displays, OLED lighting components, and microelectromechanical systems reflective displays. We demonstrate methods to fabricate these substrates using nanoparticle deposition processes. Important parameters of these nanoparticles and their agglomerates include both size and refractive index. We characterize these substrates using atomic force microscopy and scanning electron microscopy microscopy, and we simulate their optical properties using optical scattering models.     

Polyaniline electrochromic devices with transparent graphene electrodes

Transparent, conductive and uniform graphene films have been prepared and used as electrodes of the electrochromic devices of polyaniline. Polyaniline films on both graphene and the widely used indium tin oxide (ITO) electrodes showed similar electrochemical and spectroelectrochemical properties. However, graphene electrodes exhibited much higher electrochemical stability than ITO in aqueous acidic electrolytes. The performances of the electrochromic devices with graphene electrodes exhibited slight decrease upon voltage switching while those of the devices with ITO electrodes decreased dramatically. After 300 cycles, the electrochromic devices with graphene electrodes showed much larger optical contrast and shorter switching time than those of the devices with ITO electrodes.     

电润湿纳米压印光刻胶的制备及其特性研究

实现对微纳米模板的充分填充是传统纳米压印胶的一个重要难题.本文设计和制备了一种类离子液体的丙烯酸酯化合物I-M-PET3A.以N,N-二甲基乙醇胺为助引发剂,二苯甲酮为光敏剂,丙烯酸羟丙酯为活性稀释剂与I-M-PET3A共混制备的纳米压印胶具有相对小的粘度（530mpa·s）和好的导电性能（33.98μs/cm）,从而表现出良好的电润湿特性.在200V,10Hz方波交流电额外施加的电毛细驱动下,复配的压印胶大约10s即可充分填充30μm×120μm的微槽.经光固化和脱模后能保持完美的微纳米图案.该纳米压印胶同时具有光固化和电润湿特性,为高性能纳米压印胶的开发提供了新思路.     

Electroluminescence performance of a series of fluorene/2,5-di(2-thienyl)-1H-pyrrole polymers

In this article, a series of fluorene/2,5-dithenyl-1H-pyrrole-based electroactive polymers (HS-X) with different feed ratio of SC12F/OF were synthesized via Suzuki coupling reactions. Chemical characterization of polymers was elucidated by ¹H NMR and Fourier-transform infrared spectroscopy. Electrochemical and electrophysical characterization of the synthesized polymers were investigated by cyclic voltammetry, UV-vis spectroscopy, and fluorescence spectroscopy. Thermal stability of polymers were studied with differential scanning calorimetry and manipulation of the Tg values of HS-X polymers was managed by increasing the numbers of the spiroalkylated fluorene (SAF) moieties incorporated into the polymer backbone. Five different conjugated polymers (HS-1, HS-2, HS-3, HS-4, and HS-5) were used as hole transport layer material in the fabrication of organic light-emitting diode (OLED) devices. The energy levels of the highest occupied molecular orbital as well as the lowest unoccupied molecular orbital and photoluminescence intensities were independent of the number of SAF units. OLED devices based on HS-X polymers were fabricated according to ITO/PEDOT:PSS/HS-X/Alq3/LiF:Al device configuration. Their electroluminescence performances were investigated and the best performance were obtained with the polymer containing 20% SC12F (HS-4) in an OLED device with a turn on voltage of 11.8 V, a maximum luminance of 1202 cd/m² and a maximum luminous efficiency of 0.30 cd/A compared to other polymers with different feed ratio.