Article

Quantum chemical analysis of electronic structure and n- and p-type charge transport in perfluoroarene-modified oligothiophene semiconductors.

Department of Chemistry and Materials Research Center, Northwestern University, Evanston, Illinois 60208, USA.
The Journal of Physical Chemistry B (Impact Factor: 3.61). 01/2006; 110:24361. DOI: 10.1021/jp064840x
Source: PubMed

ABSTRACT Density-functional theory (DFT) is employed to investigate the structural, electronic, and transport properties of several isomeric fluoroarene-oligothiophene-based semiconductors. Three oligothiophene systems varying in the perfluoroarene group positions within the molecule are studied to understand the electronic structure leading to the observed mobility values and to the n- or p-type behavior in these structures. Analyses of both intermolecular interactions in dimers and extended interactions in crystalline structures afford considerable insight into the electronic properties and carrier mobilities of these materials, as well as the polarity of the charge carriers. From the calculated carrier effective masses, we find that sterically governed molecular planarity plays a crucial role in the transport properties of these semiconductors. Our calculations correlate well with experimentally obtained geometries, highest-occupied molecular orbital (HOMO)/lowest-unoccupied molecular orbital (LUMO) energies, and the experimental carrier mobility trends among the systems investigated.

0 Bookmarks
 · 
55 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: HOMO-LUMO engineering of coordination-based oligomers covalently bound to silicon or glass has been achieved by the use of a partially fluorinated chromophore (see graphic). The experimental and computationally derived physical chemical properties of these assemblies are compared to their non-fluorinated analogues.
    Chemistry 06/2010; 16(23):6744-7. · 5.93 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The temperature dependence of field-effect transistor (FET) mobility is analyzed for a series of n-channel, p-channel, and ambipolar organic semiconductor-based FETs selected for varied semiconductor structural and device characteristics. The materials (and dominant carrier type) studied are 5,5′′′-bis(perfluorophenacyl)-2,2′:5′,2″:5″,2′′′-quaterthiophene (1, n-channel), 5,5′′′-bis(perfluorohexyl carbonyl)-2,2′:5′,2″:5″,2′′′-quaterthiophene (2, n-channel), pentacene (3, p-channel); 5,5′′′-bis(hexylcarbonyl)-2,2′:5′,2″:5″,2′′′-quaterthiophene (4, ambipolar), 5,5′′′-bis-(phenacyl)-2,2′: 5′,2″:5″,2′′′-quaterthiophene (5, p-channel), 2,7-bis((5-perfluorophenacyl)thiophen-2-yl)-9,10-phenanthrenequinone (6, n-channel), and poly(N-(2-octyldodecyl)-2,2′-bithiophene-3,3′-dicarboximide) (7, n-channel). Fits of the effective field-effect mobility (µeff) data assuming a discrete trap energy within a multiple trapping and release (MTR) model reveal low activation energies (EAs) for high-mobility semiconductors 1–3 of 21, 22, and 30 meV, respectively. Higher EA values of 40–70 meV are exhibited by 4–7-derived FETs having lower mobilities (µeff). Analysis of these data reveals little correlation between the conduction state energy level and EA, while there is an inverse relationship between EA and µeff. The first variable-temperature study of an ambipolar organic FET reveals that although n-channel behavior exhibits EA = 27 meV, the p-channel regime exhibits significantly more trapping with EA = 250 meV. Interestingly, calculated free carrier mobilities (µ0) are in the range of ∼0.2–0.8 cm2 V−1 s−1 in this materials set, largely independent of µeff. This indicates that in the absence of charge traps, the inherent magnitude of carrier mobility is comparable for each of these materials. Finally, the effect of temperature on threshold voltage (VT) reveals two distinct trapping regimes, with the change in trapped charge exhibiting a striking correlation with room temperature µeff. The observation that EA is independent of conduction state energy, and that changes in trapped charge with temperature correlate with room temperature µeff, support the applicability of trap-limited mobility models such as a MTR mechanism to this materials set.
    Advanced Functional Materials 11/2009; 20(1):50 - 58. · 9.77 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Fully fluorinated arylenevinylene polymers have been synthesized via a methodology based on the Stille cross-coupling reaction and characterized by FTIR spectroscopy and MALDI-TOF mass spectrometry. Investigation of thin film properties by cyclic voltammetry and ellipsometry shows that complete substitution of hydrogen atoms with fluorine atoms on the conjugated backbone of the poly(arylenevinylene)s results in a strong increase of the band gap. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 285–291, 2010
    Journal of Polymer Science Part A Polymer Chemistry 12/2009; 48(2):285 - 291. · 3.54 Impact Factor

Full-text (2 Sources)

View
10 Downloads
Available from
May 22, 2014