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Charge Transport Properties (charge + transport_property)
Selected AbstractsTetrachloro-substituted Perylene Bisimide Dyes as Promising n-Type Organic Semiconductors: Studies on Structural, Electrochemical and Charge Transport PropertiesCHEMPHYSCHEM, Issue 1 2004Zhijian Chen Twisted ,-systems: The highly twisted 1,6,7,12-tetrachloro-substituted perylene bisimides possess an improved electron affinity. The nonplanar nature of these molecules facilitates a slipped brickstone-type rather than a columnar stacking of the ,-systems, with a potentially useful two dimensional contact feature. These compounds show isotropic charge carrier mobilities as high as up to 0.14 cm2,V,1 s,1 (see graphic). [source] Effect of Alkyl Side-Chain Length on Photovoltaic Properties of Poly(3-alkylthiophene)/PCBM Bulk HeterojunctionsADVANCED FUNCTIONAL MATERIALS, Issue 20 2009Abay Gadisa Abstract The morphological, bipolar charge-carrier transport, and photovoltaic characteristics of poly(3-alkylthiophene) (P3AT):[6,6]-phenyl-C61-butyric acid methyl ester (PCBM) blends are studied as a function of alkyl side-chain length m, where m equals the number of alkyl carbon atoms. The P3ATs studied are poly(3-butylthiophene) (P3BT, m,=,4), poly(3-pentylthiophene) (P3PT, m,=,5), and poly(3-hexylthiophene) (P3HT, m,=,6). Solar cells with these blends deliver similar order of photo-current yield (exceeding 10,mA cm,2) irrespective of side-chain length. Power conversion efficiencies of 3.2, 4.3, and 4.6% are within reach using solar cells with active layers of P3BT:PCBM (1:0.8), P3PT:PCBM (1:1), and P3HT:PCBM (1:1), respectively. A difference in fill factor values is found to be the main source of efficiency difference. Morphological studies reveal an increase in the degree of phase separation with increasing alkyl chain length. Moreover, while P3PT:PCBM and P3HT:PCBM films have similar hole mobility, measured by hole-only diodes, the hole mobility in P3BT:PCBM lowers by nearly a factor of four. Bipolar measurements made by field-effect transistor showed a decrease in the hole mobility and an increase in the electron mobility with increasing alkyl chain length. Balanced charge transport is only achieved in the P3HT:PCBM blend. This, together with better processing properties, explains the superior properties of P3HT as a solar cell material. P3PT is proved to be a potentially competitive material. The optoelectronic and charge transport properties observed in the different P3AT:PCBM bulk heterojunction (BHJ) blends provide useful information for understanding the physics of BHJ films and the working principles of the corresponding solar cells. [source] Photoelectrochemical Study of Nanostructured ZnO Thin Films for Hydrogen Generation from Water SplittingADVANCED FUNCTIONAL MATERIALS, Issue 12 2009Abraham Wolcott Abstract Photoelectrochemical cells based on traditional and nanostructured ZnO thin films are investigated for hydrogen generation from water splitting. The ZnO thin films are fabricated using three different deposition geometries: normal pulsed laser deposition, pulsed laser oblique-angle deposition, and electron-beam glancing-angle deposition. The nanostructured films are characterized by scanning electron microscopy, X-ray diffraction, UV-vis spectroscopy and photoelectrochemical techniques. Normal pulsed laser deposition produces dense thin films with ca. 200,nm grain sizes, while oblique-angle deposition produces nanoplatelets with a fishscale morphology and individual features measuring ca. 900 by 450,nm on average. In contrast, glancing-angle deposition generates a highly porous, interconnected network of spherical nanoparticles of 15,40,nm diameter. Mott-Schottky plots show the flat band potential of pulsed laser deposition, oblique-angle deposition, and glancing-angle deposition samples to be ,0.29, ,0.28 and +0.20,V, respectively. Generation of photocurrent is observed at anodic potentials and no limiting photocurrents were observed with applied potentials up to 1.3,V for all photoelectrochemical cells. The effective photon-to-hydrogen efficiency is found to be 0.1%, 0.2% and 0.6% for pulsed laser deposition, oblique-angle deposition and glancing-angle deposition samples, respectively. The photoelectrochemical properties of the three types of films are understood to be a function of porosity, crystal defect concentration, charge transport properties and space charge layer characteristics. [source] Recent Advances in White Organic Light-Emitting Materials and Devices (WOLEDs)ADVANCED MATERIALS, Issue 5 2010Kiran T. Kamtekar Abstract WOLEDs offer new design opportunities in practical solid-state lighting and could play a significant role in reducing global energy consumption. Obtaining white light from organic LEDs is a considerable challenge. Alongside the development of new materials with improved color stability and balanced charge transport properties, major issues involve the fabrication of large-area devices and the development of low-cost manufacturing technology. This Review will describe the types of materials (small molecules and polymers) that have been used to fabricate WOLEDs. A range of device architectures are presented and appraised. [source] Effects of alcoholic solvents on the conductivity of tosylate-doped poly(3,4-ethylenedioxythiophene) (PEDOT-OTs)POLYMER INTERNATIONAL, Issue 1 2006Tae Young Kim Abstract The effects of alcoholic solvents on the charge transport properties of tosylate-doped poly(3,4-ethylenedioxythiophene) (PEDOT-OTs) are investigated. The use of different alcoholic solvents in the oxidative chemical polymerization of 3,4-ethylenedioxythiophene (EDOT) with iron(III)- p -tosylate led to a change in the electrical conductivity of PEDOT-OTs. For example, PEDOT-OTs prepared from methanol shows a conductivity of 20.1 S cm,1 which is enhanced by a factor of 200 as compared to PEDOT-OTs prepared from hexanol. The variation of charge transport properties on the use of different alcoholic solvents is consistent with the data recorded by UV-visible and electrospin resonance (ESR) measurements. From XPS experiments, the PEDOT-OTs samples prepared from different alcoholic solvents were found to have almost the same doping level, suggesting that the number of charge carriers is not responsible for the change in conductivity. Supported by XRD results, it was found that the use of alcoholic solvents with shorter chain length induces more efficient packing of PEDOT chains. It is proposed that the alcoholic solvents associated with the counter ion of PEDOT via hydrogen bonding give rise to a change in the molecular ordering of PEDOT chains during the polymerization step, hence enhancing or depressing the inter-chain hopping rate of the resulting PEDOT-OTs. Copyright © 2005 Society of Chemical Industry [source] Theoretical Characterization of Charge Transport in One-Dimensional Collinear Arrays of Organic Conjugated MoleculesCHEMPHYSCHEM, Issue 5 2010Lucas Viani Abstract A great deal of interest has recently focused on host,guest systems consisting of one-dimensional collinear arrays of conjugated molecules encapsulated in the channels of organic or inorganic matrices. Such architectures allow for controlled charge and energy migration processes between the interacting guest molecules and are thus attractive in the field of organic electronics. In this context, we characterize here at a quantum-chemical level the molecular parameters governing charge transport in the hopping regime in 1D arrays built with different types of molecules. We investigate the influence of several parameters (such as the symmetry of the molecule, the presence of terminal substituents, and the molecular size) and define on that basis the molecular features required to maximize the charge carrier mobility within the channels. In particular, we demonstrate that a strong localization of the molecular orbitals in push,pull compounds is generally detrimental to the charge transport properties. [source] | ||||||||||