Optoelectronic and Charge Transport Properties of Oligomers Based on Phenylethynylene Units Linked to Thieno-acenes: A DFT Study

The geometries and electronic properties of a series of pi-conjugated oligomers, as possible precursors of n-type materials, have been studied with the help of density functional theory. The selected compounds are based on phenylethynylene moieties alternated with thieno-acene units containing up to four fused thiophene rings, PhEtTx=1-4. The optoelectronic properties and conducting capability were investigated through the HOMO -> LUMO excitation energies, LUMO energy levels, electron affinities, intramolecular reorganization energies, and electronic coupling. All studied properties agree that oligomers based on PhEtTx=1-4 show adequate values concerning electron affinities, LUMO levels, and intramolecular reorganization energy to be considered n-type semiconductor candidates. Besides, the optical bandgaps are close to 2 eV, which is the threshold for a material to be considered as potentially suitable in the field of solar cells.