Ab-initio calculation of the electronic and optical excitations in polythiophene: effects of intra- and interchain screening

TL;DR

This paper uses ab-initio methods to study how intra- and interchain screening affect electronic and optical excitations in polythiophene, revealing significant effects on band gaps and exciton binding energies.

Contribution

It introduces a detailed ab-initio calculation of excitations in polythiophene considering interchain screening effects, which was not thoroughly explored before.

Findings

Interchain screening reduces band gaps and exciton binding energies in bulk polythiophene.

Optical gap remains largely unchanged despite screening effects.

The results are relevant for understanding conjugated polymers generally.

Abstract

We present an calculation of the electronic and optical excitations of an isolated polythiophene chain as well as of bulk polythiophene. We use the GW approximation for the electronic self-energy and include excitonic effects by solving the electron-hole Bethe-Salpeter equation. The inclusion of interchain screening in the case of bulk polythiophene drastically reduces both the quasi-particle band gap and the exciton binding energies, but the optical gap is hardly affected. This finding is relevant for conjugated polymers in general.