Theoretical investigation into optical and electronic properties of oligothiophene derivatives with phenyl ring as core or end-capped group in linear and V-shape

A series of thiophene-based oligomers has been designed to explore their optical, electronic, and charge transport properties for charge transport materials. These oligomers consist of oligothiophene, oligo(thienylenevinylene), and m- or p-phenyl as the core in two shapes (linear shape and V-shape). Phenyl ring as the end-capped group is also investigated in the linear shape. The DFT-PBE0/6-31G(d,p) and the TD-PBE0/6-31+G(d,p) calculated results reported herein show that the V-shape oligomers have larger HOMO-LUMO gaps because of meta-substitutions on phenyl cores, corresponding to blue shifts of absorption spectra. The linear oligomers with phenyl ring as end-capped group display red shifts of absorption spectra. The V-shape oligomers provide small reorganization energies. Our recommended polymer possessing 1,2,4-phenyl core and longer OTV side fragments is a good candidate for the design of charge transport and/or solar cell materials.