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Electronic and Structural Properties of Fluorene-Thiophene Copolymers as Function of the Composition Ratio Between the Moieties: A Theoretical Study

Abstract

Here we study theoretically the main properties of some molecular structures formed by oligothiophenes (T) and dioctilfluorenes (F) units, commonly employed in the fabrication of different kinds of optical and electronic devices. For so, we first consider F-(T)n-F molecules with different numbers of thiophene rings (n). Among other characteristics, we calculate the dipole moment change between ground and excited state (Δμge), a quantity that greatly influences the exciton dissociation and charge carrier mobility. We unveil a relevant dependence of Δμ ge with the odd-even parity of n and that Δμ ge assumes higher values when the molecule is composed by bithiophene (instead of simple thiophenes) moieties in the syn-conformation (with the two heteroatoms pointing in the same direction). From the results for the molecules, we then study larger systems, formed by different oligomers of F-T copolymers containing blocks of dioctilfluorenes and bithiophenes (T2). We systematic investigate their electronic and structural properties as a function of the composition ratio between the T2 and F moieties. Similar to the molecules, we deduce that the magnitude of Δμ ge is higher for the syn conformer of the T2 unit. Moreover, the highest values of Δμ ge are achieved when the number of the T2 increases relative to a fixed number of the F units in the mer. Such results are in agreement and actually can qualitative explain experimental results in the literature on the quantum efficiency of charge carrier generation in F-T copolymers. Our findings can be helpful in designing novel materials with improved photoelectric responses.

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Publication details

The article was received on 24 Apr 2018, accepted on 26 Jun 2018 and first published on 26 Jun 2018


Article type: Paper
DOI: 10.1039/C8CP02622J
Citation: Phys. Chem. Chem. Phys., 2018, Accepted Manuscript
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    Electronic and Structural Properties of Fluorene-Thiophene Copolymers as Function of the Composition Ratio Between the Moieties: A Theoretical Study

    L. Benatto, C. F. N. Marchiori, M. E. G. gomes eleuterio da luz and M. Koehler, Phys. Chem. Chem. Phys., 2018, Accepted Manuscript , DOI: 10.1039/C8CP02622J

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