Twelve compounds, taking styrene or phenylacetylene as terminal group, bithiophene (2T), benzodithiophene (TPT) and dibenzothiophene (PTP) as conjugated bridges, were studied by density functional theory (DFT, TDDFT) at the B3LYP/6-31G(d) and PBE0/6-31G(d) level. Based on optimized geometries in the neutral state and ionic state, frontier orbital energies, ionization potentials (IPs), electron affinities (EAs), reorganization energy (λ_h/λ_e) and electronic absorption spectrum were obtained. Results show that styrene as terminal group was replaced by phenylacetylene, the lowest unoccupied molecular orbital (LUMO) energy level was little affected while the highest occupied molecular orbital (HOMO) energy level was obviously lowered. Consequently, the HOMO-LUMO energy gaps (ΔE) were increased and absorption spectrum were blue-shifted about 10～30 nm. In addition, reorganization energy (λ_h/λ_e) of majority phenylethynyl compound were decreased. As for different conjugated bridge (2T, TPT and PTP, respectively) with the introduction of same terminal group, the HOMO energy level was lowered, the LUMO energy level was heightened, so the HOMO-LUMO energy gap (ΔE) increased with the absorption spectrum blue-shift of 30～45 nm. Moreover, the compounds with TPT conjugated bridge are easier to balance carrier transport and improve carrier transport rate, due to small reorganization energy and close reorganization energies of the hole and the electron. The diphenylacetylene-benzodithiophene (DPATPT) is expected to become a potential carrier transport material with high transport efficiency and strong antioxidant ability.

Key words: styrene/phenylacetylene group, bithiophene, benzodithiophene, dibenzothiophene, density functional theory (DFT), carrier transport