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Molecular Ordering (molecular + ordering)
Selected AbstractsMolecular Ordering of High-Performance Soluble Molecular Semiconductors and Re-evaluation of Their Field-Effect Transistor Characteristics,ADVANCED MATERIALS, Issue 18 2008Takafumi Izawa Intermolecular hydrophobic interactions between long alkyl chains (fastener effect) can enhance the intermolecular overlap of the semiconducting layer of 2,7-dialkyl[1]benzothieno[3,2- b][1]benzothiophenes (Cn -BTBTs; n,=,8, 10, 12), which contributes to improvements of the electric characteristics of their organic field-effect transistors. The molecular ordering of Cn -BTBTs in the thin-film state is elucidated by means of in-plane and out-of-plane X-ray diffraction of spin-coated thin films, and single crystal X-ray analysis. [source] Alkyl-Chain-Length-Independent Hole Mobility via Morphological Control with Poly(3-alkylthiophene) NanofibersADVANCED FUNCTIONAL MATERIALS, Issue 5 2010Wibren D. Oosterbaan Abstract The field-effect transistor (FET) and diode characteristics of poly(3-alkylthiophene) (P3AT) nanofiber layers deposited from nanofiber dispersions are presented and compared with those of layers deposited from molecularly dissolved polymer solutions in chlorobenzene. The P3AT n -alkyl-side-chain length was varied from 4 to 9 carbon atoms. The hole mobilities are correlated with the interface and bulk morphology of the layers as determined by UV,vis spectroscopy, transmission electron microscopy (TEM) with selected area electron diffraction (SAED), atomic force microscopy (AFM), and polarized carbon K -edge near edge X-ray absorption fine structure (NEXAFS) spectroscopy. The latter technique reveals the average polymer orientation in the accumulation region of the FET at the interface with the SiO2 gate dielectric. The previously observed alkyl-chain-length-dependence of the FET mobility in P3AT films results from differences in molecular ordering and orientation at the dielectric/semiconductor interface, and it is concluded that side-chain length does not determine the intrinsic mobility of P3ATs, but rather the alkyl chain length of P3ATs influences FET diode mobility only through changes in interfacial bulk ordering in solution processed films. [source] Solubility-Induced Ordered Polythiophene Precursors for High-Performance Organic Thin-Film TransistorsADVANCED FUNCTIONAL MATERIALS, Issue 8 2009Yeong Don Park Abstract With the aim of enhancing the field-effect mobility of self-assembled regioregular poly(3-hexylthiophene), P3HT, by promoting two-dimensional molecular ordering, the organization of the P3HT in precursor solutions is transformed from random-coil conformation to ordered aggregates by adding small amounts of the non-solvent acetonitrile to the solutions prior to film formation. The ordering of the precursor in the solutions significantly increases the crystallinity of the P3HT thin films. It is found that with the appropriate acetonitrile concentration in the precursor solution, the resulting P3HT nanocrystals adopt a highly ordered molecular structure with a field-effect mobility dramatically improved by a factor of approximately 20 depending on the P3HT concentration. This improvement is due to the change in the P3HT organization in the precursor solution from random-coil conformation to an ordered aggregate structure as a result of the addition of acetonitrile. In the good solvent chloroform, the P3HT molecules are molecularly dissolved and adopt a random-coil conformation, whereas upon the addition of acetonitrile, which is a non-solvent for aromatic backbones and alkyl side chains, 1D or 2D aggregation of the P3HT molecules occurs depending on the P3HT concentration. This state minimizes the unfavorable interactions between the poorly soluble P3HT and the acetonitrile solvent, and maximizes the favorable ,,, stacking interactions in the precursor solution, which improves the molecular ordering of the resulting P3HT thin film and enhances the field-effect mobility without post-treatment. [source] Enhancement of Carrier Mobilities of Organic Semiconductors on Sol,Gel Dielectrics: Investigations of Molecular Organization and Interfacial Chemistry EffectsADVANCED FUNCTIONAL MATERIALS, Issue 3 2009Tommy Cahyadi Abstract The dielectric-semiconductor interfacial interactions critically influence the morphology and molecular ordering of the organic semiconductor molecules, and hence have a profound influence on mobility, threshold voltage, and other vital device characteristics of organic field-effect transistors. In this study, p-channel small molecule/polymer (evaporated pentacene and spin-coated poly(3,3,;-didodecylquarterthiophene) , PQT) and n-channel fullerene derivative ({6}-1-(3-(2-thienylethoxycarbonyl)-propyl)-{5}-1-phenyl-[5,6]-C61 , TEPP-C61) show a significant enhancement in device mobilities ranging from ,6 to ,45 times higher for all classes of semiconductors deposited on sol,gel silica gate-dielectric than on pristine/octyltrichlorosilane (OTS)-treated thermally grown silica. Atomic force microscopy, synchrotron X-ray diffraction, photoluminescence/absorption, and Raman spectroscopy studies provide comprehensive evidences that sol,gel silica dielectrics-induced enhancement in both p- and n-channel organic semiconductors is attributable to better molecular ordering/packing, and hence reduced charge trapping centers due to lesser structural defects at the dielectric-semiconductor interface. [source] Direct Correlation of Organic Semiconductor Film Structure to Field-Effect Mobility,ADVANCED MATERIALS, Issue 19 2005M. DeLongchamp Near-edge X-ray fine structure spectroscopy is used to measure simultaneous chemical conversion, molecular ordering, and defect formation in soluble oligothiophene precursor films. Film structure is correlated to OFET performance. Molecular orientation is determined by evaluating antibonding orbital overlap with the polarized electric field vector of incident soft X-rays (see Figure and cover). Upon conversion, the molecules become vertically oriented, allowing , overlap in the plane of hole transport. [source] Feature Article: Bound exciton and donor,acceptor pair recombinations in ZnOPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 2 2004B. K. Meyer The article [1] features the current state of knowledge on the optical properties of excitonic and donor,acceptor pair recombination in bulk n-ZnO, as revealed by recent photo- and cathodoluminescence measurements. The cover picture is a photograph showing an unusual look at the green luminescence of rod-shaped ZnO crystals under ultraviolet excitation. The first author, Bruno K. Meyer, is professor of physics at the Justus Liebig University of Giessen. His scientific interests include synthesis of semiconductor oxides by chemical vapour deposition and magnetron sputtering, in particular with respect to doping issues, materials science of electro- and thermochromic materials, recombination phenomena and defect characterization by magnetic resonance. This issue also contains an Editor's Choice on "Evolution of molecular ordering and phase transitions in C60/C70 solid solutions" by Gabriela Rueda-Morales and Jaime Ortiz-López [2]. [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] | ||||||||||