Quasiparticles and Band Transport in Organized Nanostructures of Donor-Acceptor Copolymers

TL;DR

This study uses many-body perturbation theory to analyze how nanostructured donor-acceptor copolymers facilitate charge transport, revealing impurity bands and anisotropic transport pathways that impact organic semiconductor performance.

Contribution

It uncovers the existence of impurity conduction bands introduced by acceptors and details the anisotropic charge transport mechanisms in organized copolymer nanostructures.

Findings

Acceptors introduce a conduction impurity band.

Charge transport is enhanced across individual chains.

Regions with inverted electron and hole transport polarity are identified.

Abstract

The performance of organic semiconductor devices is linked to highly-ordered nanostructures of self-assembled molecules and polymers. We employ many-body perturbation theory and study the excited states in bulk compolymers. We discover that acceptors in the polymer scaffold introduce a, hitherto unrecognized, conduction impurity band. The donor units are surrounded by conjugated bands which are only mildly perturbed by the presence of acceptors. Along the polymer axis, mutual interactions among copolymer strands hinder efficient band transport, which is, however, strongly enhanced across individual chains. We find that holes are most effectively transported in the $\pi-\pi$ stacking while electrons in the impurity band follow the edge-to-edge directions. The copolymers exhibit regions with inverted transport polarity, in which electrons and holes are efficiently transported in mutually orthogonal directions.