The role of intermolecular coupling in the photophysics of disordered organic semiconductors: Aggregate emission in regioregular polythiophene

TL;DR

This study investigates how intermolecular excitonic coupling influences the photophysical behavior of regioregular poly(3-hexylthiophene), revealing that aggregate emission is dominated by weakly coupled H-aggregates with quantifiable coupling energies.

Contribution

It demonstrates the dominant role of weakly coupled H-aggregates in emission and introduces a simple method to estimate intermolecular coupling energies from absorption spectra.

Findings

Optical emission is dominated by weakly coupled H-aggregates.

Intermolecular coupling energies are approximately 5 and 30 meV for different solvents.

A simple spectral analysis method can quantify coupling energies.

Abstract

We address the role of excitonic coulping on the nature of photoexcitations in the conjugated polymer regioregular poly(3-hexylthiophene). By means of temperature-dependent absorption and photoluminescence spectroscopy, we show that optical emission is overwhelmingly dominated by weakly coupled H-aggregates. The relative absorbance of the 0-0 and 0-1 vibronic peaks provides a powerfully simple means to extract the magnitude of the intermolecular coupling energy, approximately 5 and 30 meV for films spun from isodurene and chloroform solutions respectively.