Quantum motion of charges in $\pi$-conjugated polymers: kinkiness induces localization

TL;DR

This paper models charge trapping in conjugated polymers, showing that chain kinks cause localization and buckling, significantly affecting charge dynamics in photovoltaic systems.

Contribution

It introduces a continuous chain model revealing how kinks induce charge localization and chain buckling, impacting photovoltaic charge transfer.

Findings

Kinks act as attractive points causing charge localization.

Geometric fluctuations create deep potential traps.

Traps can surpass Coulomb interactions in strength.

Abstract

We develop a model for charge trapping on conjugated polymer chains using a continuous representation of the polymer. By constraining the motion to along the chain, we find that kinks along the chain serve as points of attraction and can induce localization and spontaneous buckling of the chain. We implement this in a model system of a conjugated polymer donor and fullerene acceptor to mimic a polymer based photovoltaic system. We find that geometric fluctuations of the polymer give rise to deep potential energy traps at kinks which are often stronger than the Coulomb interaction between the electron and hole.