Essential optical states in $\pi$-conjugated polymer thin films

TL;DR

This paper develops a theoretical framework to understand the electronic states and photophysical behavior of $$-conjugated polymer thin films, explaining differences from solutions and key optical phenomena.

Contribution

It introduces a new theory that describes the electronic structure and photophysics of interacting polymer chains in films, highlighting the roles of excitons and excimers.

Findings

Photoexcitation in solutions produces only excitons.

Films generate both excitons and weakly allowed excimers.

Photoluminescence features are explained by excimer dynamics.

Abstract

We develop a theory of the electronic structure and photophysics of interacting chains of $\pi$-conjugated polymers to understand the differences between solutions and films. While photoexcitation generates only the exciton in solutions, the optical exciton as well as weakly allowed excimers are generated in films. Photoinduced absorption in films is primarily from the lowest excimer. We are also able to explain peculiarities associated with photoluminescence, including delayed photoluminescence and its quenching by electric field.