Determining exciton bandwidth and film microstructure in polythiophene films using linear absorption spectroscopy

TL;DR

This paper uses linear absorption spectroscopy to analyze the microstructure and exciton properties of polythiophene films, linking processing conditions to film quality and transistor performance.

Contribution

It introduces a quantitative method to estimate exciton bandwidth and aggregate content in polythiophene films from absorption spectra.

Findings

Exciton bandwidth correlates with film microstructure.

Higher aggregate content improves transistor performance.

The method enables microstructure characterization from optical data.

Abstract

We analyze the linear absorption spectrum of regioregular poly(3-hexylthiophene) films spun from a variety of solvents to probe directly the film microstructure and how it depends on processing conditions. We estimate the exciton bandwidth and the percentage of the film composed of aggregates quantitatively using a weakly interacting H-aggregate model. This provides a description of the degree and quality of crystallites within the film and is in turn correlated with thin-film field-effect transistor characteristics.