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排序方式: 共有6799条查询结果,搜索用时 328 毫秒
941.
Georgy Grancharov Mariya-Desislava Atanasova Radostina Kalinova Rositsa Gergova Georgi Popkirov Christosko Dikov Marushka Sendova-Vassileva 《Molecules (Basel, Switzerland)》2021,26(22)
In this study, some crucial parameters were determined of flexible polymer–organic solar cells prepared from an active layer blend of poly(3-hexylthiophene) (P3HT) and the fullerene derivative [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) mixed in 1:1 mass ratio and deposited from chlorobenzene solution by spin-coating on poly(ethylene terephthalate) (PET)/ITO substrates. Additionally, the positive effect of an electron transport layer (ETL) prepared from zinc oxide nanoparticles (ZnO np) on flexible photovoltaic elements’ performance and stability was investigated. Test devices with above normal architecture and silver back electrodes deposed by magnetron sputtering were constructed under environmental conditions. They were characterized by current-voltage (I–V) measurements, quantum efficiency, impedance spectroscopy, surface morphology, and time–degradation experiments. The control over morphology of active layer thin film was achieved by post-deposition thermal treatment at temperatures of 110–120 °C, which led to optimization of device morphology and electrical parameters. The impedance spectroscopy results of flexible photovoltaic elements were fitted using two R||CPE circuits in series. Polymer–organic solar cells prepared on plastic substrates showed comparable current–voltage characteristics and structural properties but need further device stability improvement according to traditionally constructed cells on glass substrates. 相似文献
942.
943.
Hans R. Kricheldorf Thomas Stukenbrock 《Journal of polymer science. Part A, Polymer chemistry》1998,36(1):31-38
Telechelic oligo(ether–ketone)s containing two trimethylsiloxy end groups and one methyl group per repeating unit were prepared by polycondensation of 4-fluoro-2′-methyl-4′-(trimethylsiloxy)benzophenone. The telechelic character was achieved by cocondensation of a small amount of silylated bisphenol-P. The end groups of the silylated oligo(ether–ketone)s were acetylated by means of acetyl chloride. On the basis of 1H-NMR end group analyses two samples of α,ω-bis(acetoxy) oligo(ether–ketone)s with DP = 14 and DP ∼ 28 were obtained. These oligo(ether-ketone)s and a 70 or 140 fold molar amount of silylated 3,5-bis(acetoxy)benzoic acid were polycondensed at 270°C in bulk. The resulting A–B–A triblock copolymers were fractionated by dissolution in tetrahydrofuran. In three out of four experiments a small fraction of precipitated material rich in oligo(ether–ketone) was isolated. The purified triblock copolymers were characterized by inherent viscosities and NMR spectra. For those samples containing the long oligo(ether–ketone) block a low degree of crystallinity was observed after annealing. Four additional polycondensations were conducted with an initial reaction temperature of 290°C. In this way a completely soluble and amorphous triblock copolymer was obtained. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 31–38, 1998 相似文献
944.
抑制系统是抑制型(双柱型)离子色谱系统极为重要的一个组成部分,也是离子色谱有别于其它类型的液相色谱的最重要特点之一。抑制器的发展经历了多个发展时期,而目前商品化的离子色谱仪亦分别采用不同形式的抑制手段。近年来,还发展了一些特殊的辅助抑制器,如接在抑制器后面CO2除去装置,用于提高被测离子的信号或进一步降低背景电导值。 相似文献
945.
On the bases of the topological structures of the three big classes of icosahedral fullerenes: (1) Cn(Ih, n=60h2; h=1, 2,…), (2) Cn(Ih, n=20h2; h=1, 2,…), and (3) Cn(I, n=20(h2+hk+k2), h>k; h, k=1, 2,…), we derived formulas for the decomposition of their nuclear motions into irreducible representations. Hence, we obtained the infrared and Raman active modes for all of the icosahedral (Ih and I) fullerenes theoretically. © 1998 John Wiley & Sons, Inc. Int J Quant Chem 66 : 113–117, 1998 相似文献
946.
Ian H. Campbell John P. Ferraris Thomas W. Hagler Michael D. Joswick Ian D. Parker Darryl L. Smith 《先进技术聚合物》1997,8(7):417-423
A widely applicable electroabsorption technique to measure internal electric fields in organic light-emitting diodes is presented. The technique exploits the change in the a.c. electroabsorption response in the presence of a d.c. electric field. The electroabsorption signal is modulated at the fundamental frequency of the a.c. test signal, in addition to the usual modulation at the second harmonic frequency, when a d.c. bias is present. In metal/organic film/metal devices employing different metal contacts there is a built-in electric field in the organic film caused by the difference in work function between the two contacts. The electroabsorption response at the fundamental frequency of the applied a.c. bias is measured as a function of an external d.c. bias. The electroabsorption signal is nulled when the applied d.c. bias cancels the built-in electric field established by the different metals. We apply this technique to measure changes in metal–polymer Schottky barrier heights as a function of the contact metal. In metal/multiple organic films/metal structures the electroabsorption signals from the constituent organic films are identified spectroscopically and measured at both the fundamental and second harmonic frequency of the a.c. test signal. The amplitudes of the electroabsorption responses are then used to determine the a.c. and d.c. electric fields present in the organic layers. We apply this technique to determine the d.c. electric field distribution within a multi-layer organic light-emitting diode. These results highlight the general applicability of electroabsorption methods to probe internal electric fields in organic light-emitting diodes. © 1997 John Wiley & Sons, Ltd. 相似文献
947.
Takashi Uemura Nobuyuki Okuda Hiroya Kirmura Yasuko Okuda Yoshinobu Ueba Tuguru Shirakawa 《先进技术聚合物》1997,8(7):437-442
Electroluminescent(EL) devices have been fabricated using four different polymers with different glass transition temperatures (Tg) dispersed with N,N′-bis-(3-methylphenyl)-N,N′-diphenyl-1,1′-biphenyl-4,4′-diamine (TPD) as a hole transport layer and tris(8-hydroxyquinoline) aluminum (Alq3) as an emitting layer. It was found that the higher the Tg of the polymer, the longer the lifetime of the device. From observations of TPD-doped polymer films with optical microscope and atomic force microscope, dispersing TPD in the polymers was found to suppress the crystallization that causes the roughness of the film surface. It was also observed that the higher the Tg of the host polymers, the more difficult TPD crystallization was. The property of the EL device with polyethersulfone (PES) dispersed with TPD was also investigated. The lifetime of EL device with the TPD doped PES film was improved more than five times at a current density below 10 mA/cm2 compared with the device with a conventional TPD hole transport layer. © 1997 John Wiley & Sons, Ltd. 相似文献
948.
Applications of high polymers, especially conventional polymers used in an extracorporeal blood purification system, are discussed through the development of an LDL (low-density lipoprotein) apheresis system. An adsorption-based blood purification system designed to remove LDL selectively (a major risk factor leading to severe heart disease) was developed using dextransulfate as the specific ligand to adsorb LDL. Dextransulfate, in order to give a novel function similar to that of an LDL receptor, was covalently bound to porous cellulose beads with optimized morphology. The sophisticated function of an LDL receptor was successfully mimicked by the appropriate combination of well-defined conventional polymers, namely dextransulfate and cellulose. A total apheresis system, including a plasma separator, was also designed solely utilizing high polymers. This enabled the total system to be disposable, ensuring reliability. High polymers used in the system were all conventional polymers, those already qualified and evaluated for medical use. In designing this new blood purification system, our approach was to employ many of the conventional and qualified polymers, leading to a system industrially manufacturable, reliable and accepted as standard treatment in the medical community. This system demonstrated efficacy for the treatment of familial hypercholesterolemia, and is widely used in the world as standard treatment. © 1997 John Wiley & Sons, Ltd. 相似文献
949.
Joanna Korec Karol A. Stasiewicz Katarzyna Garbat Leszek R. Jaroszewicz 《Molecules (Basel, Switzerland)》2021,26(24)
This paper is a continuation of previous work and shows the enhancement of the surface plasmon resonance effect in a tapered optical fiber device. The study investigated liquid crystal cells containing a tapered optical fiber covered with a silver nanolayer, surrounded by a low refractive index liquid crystal in terms of the properties of light propagation in the taper structure. Silver films with a thickness of d = 10 nm were deposited on the tapered waist area. Measurements were performed at room temperature; liquid crystal steering voltage U from 0 to 200 V, with and without any amplitude modulation with a frequency of f = 5 Hz, and the wavelength λ ranged from 550 to 1200 nm. A significant influence of the initial arrangement of liquid crystals molecules on light propagation was observed. Three types of liquid crystal cells—orthogonal, parallel, and twist—were considered. During the measurements, resonant peaks were obtained—the position of which can also be controlled by the type of liquid crystal cells and the steering voltage. Based on the obtained results, the best parameters, such as highest peak’s width reduction, and the highest SNR value were received for twisted cells. In addition, the present work was compared with the previous work and showed the possibility of improving properties of the manufactured probes, and consequently, the surface plasmon resonance effect. In the presented paper, the novelty is mainly focused on the used materials as well as suitable changes in applied technological parameters. In contrast to gold, silver is characterized by different optic and dielectric properties, e.g., refractive index, extension coefficient, and permittivity, which results in changes in the light propagation and the SPR wavelengths. 相似文献
950.
分子电子学已成为21世纪研究的热点. 通过将具有特定功能的分子连接在纳米尺度金属电极之间从而构筑包括分子导线、开关、整流器在内的各种分子尺度电子器件, 这引起了科学家们广泛的研究兴趣. 在分子电子学研究中, 构筑金属/分子/金属(MMM)分子结是研究分子器件中电子传输性质的关键. 尽管已经取得了很大的进展, 目前在纳米尺度下构筑稳定可靠的MMM分子结并测试单个分子的电学性质仍然面临很多挑战. 本文着重对单分子电学性质的测试技术和相关理论研究的最新进展以及存在的挑战做了概述. 相似文献