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  • 1
    Electronic Resource
    Electronic Resource
    An analytical model for organic-based thin-film transistors (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 469-475 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A model describing the current-voltage characteristics of organic thin-film transistors (TFTs) is presented. The model is based on the trap distribution deduced from temperature-dependent current-voltage measurements on Au/alpha-sexithienyl (α6T)/Au symmetrical structures, which comprises a dominant single shallow trap level located near the valence-band edge. Numerical and approximate analytical derivations of the saturation current density as a function of the gate voltage have been made. From these calculations, the dependence of the threshold voltage on the parameters of the trap level (density and energy) is deduced. It appears that the threshold voltage corresponds to the filling of traps, and is a surface equivalent of the trap-filled limit voltage in bulk space-charge-limited current. The model is in good agreement with experimental data on α6T TFTs. The energy of the trap level compares well with that obtained from the temperature-dependent conductivity. However, the mobility is much lower in the TFT than in a bulk structure. This is tentatively explained by the strong influence of the state of the insulator-semiconductor interface on the characteristics of a TFT.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350250
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  • 2
    Electronic Resource
    Electronic Resource
    Influence of the molecular structure on the refractive index of semiconducting di-β-alkylated sexithiophenes (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 4873-4876 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The optical absorption of thin solid films of dialkylated sexithiophene derivatives (2A6T) has been measured at incident energies below the fundamental absorption edge, where these semiconducting organic materials are transparent. The absorption spectra present interference patterns that have been used for determining their refractive index n. A value of 1.904 was measured on unsubstituted sexithiophene. Alkyl substitution leads to a decrease of n, which is more pronounced as the alkyl chain length increases. This behavior is attributed to the corresponding decrease of the density of the material. Our data are compared to other experimental determinations of the optical parameters of thiophene oligomers and polymers published to date.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352052
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  • 3
    Electronic Resource
    Electronic Resource
    Temperature and gate voltage dependence of hole mobility in polycrystalline oligothiophene thin film transistors (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 4456-4463 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have performed current–voltage measurement on polycrystalline sexithiophene (6 T) thin film transistors at temperatures ranging from 10 to 300 K. A method is developed to extract the carrier mobility from an analysis of the transfer characteristics. In particular, data are corrected for contact resistance. The carrier mobility is found to increase quasilinearly with gate voltage at room temperature. The dependence becomes superlinear at low temperatures. The temperature dependence shows three domains. For 100 K〈T〈300 K, the mobility is thermally activated with an activation energy of around 0.1 eV. The activation energy reduces to 5 meV for 25 K〈T〈100 K. Finally, the mobility is practically temperature independent for temperatures lower than 25 K. The data are explained by a model where charge transport is limited by a high concentration of traps at grain boundaries. At high temperatures, charge transfer at boundaries occurs via thermionic emission, while tunnel effect takes place at low temperatures. The energy distribution of traps is determined, and various features predicted by the model are outlined. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.373091
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  • 4
    Electronic Resource
    Electronic Resource
    Gate voltage dependent mobility of oligothiophene field-effect transistors (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 3202-3206 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Organic field-effect transistors, in which the active semiconductor is made of oligothiophenes of various lengths, have been fabricated and characterized. A method is developed to estimate the field-effect mobility μ corrected for the contact series resistance. The mobility is found to increase by a factor of nearly 100 from quaterthiophene (4T) to octithiophene (8T). More importantly, μ increases quasilinearly with gate voltage. The origin of this gate bias dependence is discussed. One explanation could be the presence of traps that limit charge transport. Alternatively, the gate-voltage dependence is tentatively attributed to a dependence of the mobility with the concentration of carriers in the accumulation layer. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.369661
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  • 5
    Electronic Resource
    Electronic Resource
    All-organic thin-film transistors made of alpha-sexithienyl semiconducting and various polymeric insulating layers (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 2013-2015 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thin-film transistors (TFTs) were fabricated with a variety of organic polymer insulators topped with a vacuum evaporated organic semiconductor, α-sexithienyl (α6T). No field-enhanced source-drain current was obtained with polystyrene (PSt) and polymethylmethacrylate (PMMA). The field-enhanced current is weak with polyvinyl chloride (PVC), but much stronger with polyvinyl alcohol (PVA) and cyanoethylpullulan (CYEPL), a cyanoethylated polysaccharide which possesses a high dielectric constant (εr=18.5 at 10 kHz). In these last two instances, the field-effect mobility surpasses the one measured on TFTs made on a SiO2 insulating layer. A strong correlation is found between the dielectric constant of the insulator and the field-effect mobility.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.103994
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  • 6
    Electronic Resource
    Electronic Resource
    The four-level stimulated emission in sexithiophene single crystals (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 72 (1998), S. 2087-2089 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Single crystal of conjugated sexithiophene oligomer shows stimulated emission when excited with a low-energy photonic pulse. This phenomenon is interpreted in terms of the excitonic energy diagram of the crystal, which presents a four-level pathway for the photoexcitation and emission, similar to the one observed in classical inorganic-based laser materials. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.121284
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  • 7
    Electronic Resource
    Electronic Resource
    Experimental determination of excitonic levels in α-oligothiophenes (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 113 (2000), S. 385-391 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The effects of intermolecular interactions on the optical spectra of oligothiophenes are examined. Absorption spectra of isolated molecules are calculated and experimentally recorded in a rigid host matrix whereby molecules are distributed randomly or organized unidirectionally. Absorption spectra of thin films in an ordered and disordered state are given. Ordered films have three principal spectral regions which are discussed in terms of classical exciton theory. Absorption spectra in transmission of single crystals of quinquethiophene and sexithiophene are analyzed. The lowest optically allowed transition in the crystal corresponds to the lowest Davydov component. It consists of a sharp peak that is observed for even-numbered oligothiophenes in b polarization, and absent for odd-numbered rings due to the perfect alignment of the transition dipole moment with the long molecular axis. The upper Davydov component is viewed in both thin film and single crystal spectra. In between the two principal Davydov components lies a broadband that is tentatively attributed to charge-transfer states or to a noninteracting molecular transition reminiscent of isolated matrix spectra. The Davydov splitting of the first optically allowed transition is determined to be about 10 000 cm−1 and increases slightly with chain length. The Herzberg–Teller region in 6T reveals a dominant coupling mode of 340 cm−1. Vibronic structure in excitation and emission spectra shows peaks of 1460 cm−1 spacing. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.481804
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  • 8
    Electronic Resource
    Electronic Resource
    Growth and Characterization of Sexithiophene Single Crystals (1995)
    s.l. : American Chemical Society
    Chemistry of materials 7 (1995), S. 1337-1341 
    Details
    ISSN: 1520-5002
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/cm00055a010
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  • 9
    Electronic Resource
    Electronic Resource
    Molecular engineering of organic semiconductors: design of self-assembly properties in conjugated thiophene oligomers (1993)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 115 (1993), S. 8716-8721 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja00072a026
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  • 10
    Electronic Resource
    Electronic Resource
    The oligothiophene-based field-effect transistor: How it works and how to improve it (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 528-532 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Metal-insulator-semiconductor field-effect transistors (MISFETs) based on organic semiconductors, mainly conjugated organic polymers and oligomers, have been reported recently. Unlike conventional MISFETs, these devices work through the modulation of an accumulation layer at the semiconductor-insulator interface. A model for organic MISFETs, derived by changing the classical equations according to this particular operating mode is proposed. The ohmic current, parallel to the channel current, and due to the nonrectifying character of source and drain contacts, has also been taken into account. According to this model, the characteristics of these organic devices can be improved by decreasing the doping level and the thickness of the semiconducting layer. Simple rules are deduced and applied to devices based on α-conjugated sexithienyl.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.345238
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