Semiconducting Oligomers of 1,4-dimethoxybenzene, Thiophene and Thiazole: A Theoretical Study

Organic semiconducting oligomers containing three to nine heterocyclic units and based on 1,4-dimethoxybenzene, thiophene and thiazole have been studied by DFT and TDDFT at the B3LYP/6-31G(d,p) level. The energy of each molecule, those of the frontier orbitals HOMO and LUMO, the width of the band gaps and the optical properties have been calculated. The inter-ring distances, dihedral angles and torsional angles have been elucidated. These molecules are planar π-conjugated systems. The band gaps of the longer oligomers studied range from 2.53 to 2.72 eV and their excitation energies calculated by TDDFT vary from 2.22 to 2.36 eV. Wavelengths of absorption bands of 524 to 556 nm are also obtained by TDDFT. The results of this theoretical study show that these organic molecules have interesting properties and can potentially be used as components in solar cells.