Abstract:

The frontier molecular orbital energies, ionization potentials(IP), electron affinities(EA), reorganization energies(λ_h/λ_e), carrier mobilities(μ_h/μ_e), and absorption spectra of twenty novel compounds, which were designed by taking benzo dithiophene(TPT) and dithienothiophen(TTT) as the conjugated bridge, acetylene as the linking unit, and oligothiophene as the terminal group, were studied theoretically based on the optimized neutral and ionic geometries using density functional theory(DFT) at the B3LYP/6-31G(d) level. The results show that the acetylene, conjugated bridge, oligothiophene, and thiophene rings fusing exert the remarkable influence on their electronic structure and carrier transport properties. Among these structural units, the acetylene and terminal oligothiophene take much effect on the HOMO, whereas the LUMO is dominated by the conjugated bridge largely, hence the absorption band range and intensity can be tuned conveniently by rationally adjusting the linking unit. According to the calculated results, the designed compounds can act as potential ambipolar materials based on the one-dimensional charge transfer model. Interestingly, 2,7-di([2,2':5',2''-terthiophen]-5-yl)benzo[1,2-b:6,5-b']dithiophene(A3) and 2,7-bis(dithieno[3,2-b:2',3'-d]thiophen-2-ylethynyl)benzo[1,2-b:6,5-b']dithiophene(a-3) are worthy of being synthesized due to their relatively high electron mobilities.

Key words: Oligothiohpene, Benzo[1,2-b:6,5-b']dithiophene, Dithieno[3,2-b:2',3'-d] thiophen, Density functional theory, Carrier transport