Density functional study of the electronic and optical properties of fluorene-thieno[3,2-b]thiophene-based conjugated copolymers |
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| Authors: | Zhijun Gong |
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| Affiliation: | 1. College of Chemistry and Environmental Engineering , Yangtze University , Jingzhou, Hubei, 434023, P.R. China;2. Department of Physics and Physical Oceanography , Memorial University of Newfoundland , St. John's, Newfoundland, Canada , A1B 3X7 |
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| Abstract: | Quantum mechanical techniques are applied to investigate a family of π-conjugated copolymers: poly(9,9′-dimethylfluorene-alt-thiophene) (PFT), poly(9,9′-dimethylfluorene-alt-thieno[3,2-b]-thiophene) (PFTT), poly(9,9′-dimethylfluorene-alt-bithiophene) (PFT2), and poly(9,9′-dimethylfluorene-alt-α,α′-bisthieno[3,2-b]-thiophene) (PFTT2). Linear extrapolation is employed to obtain polymers' properties from oligomer calculations. That is, the HOMO–LUMO gaps (ΔH–Ls), band gaps (E g s), ionisation potentials and electron affinities of the copolymers are obtained by plotting the corresponding quantities of the oligomers as a function of the inverse chain length (1/n) and extrapolating them to infinite chain length. The electronic properties of the neutral, positive and negative oligomers are determined using the density functional theory (DFT) at B3LYP/6-31G* approximation. The lowest singlet excitation energies of the oligomers of PFT, PFTT, PFT2, and PFTT2 are also determined with the use of the time-dependent DFT again at B3LYP/6-31G* approximation. Comparisons are made with experimental values when possible. |
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| Keywords: | fluorene thiophene DFT band gaps excitation energies |
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