Effect of Distance between Molecules on the Optoelectronic Property of PEDOT

We investigated both the atomic and the electronic structures of poly(3,4-ethylene dioxythiophene) (PEDOT) by performing first-principles calculations and the optical properties by performing experiments. In our first-principles calculation, the use of different exchange-correlation potentials and van der Waals corrections optimize the distance between molecules differently, directly influencing the calculated band gap of PEDOT. In order to experimentally obtain the optical band gap, high-quality semiconducting PEDOT thin films were prepared using vapor-phase polymerization and chemical reduction process. The bandgap of PEDOT was then extracted from the absorption edge in the measured extinction spectrum. Direct comparison between the measured and calculated bandgap shows that the hybrid density functional theory improves the agreement with the experiments.