Charge-transfer excitons in strongly coupled organic semiconductors

TL;DR

This study investigates the nature of excitations in organic semiconductors, revealing a significant formation of dark charge-transfer excitons with implications for optoelectronic properties.

Contribution

It provides the first detailed experimental evidence of intrinsic branching to charge-transfer excitons in strongly coupled organic semiconductors.

Findings

Charge-transfer excitons have >5% yield in the studied materials.

Charge-transfer excitons have radii of 2-3 sites.

Large exciton bandwidth (~400 meV) promotes charge-transfer character.

Abstract

Time-resolved and temperature-dependent photoluminescence measurements on one-dimensional sexithiophene lattices reveal intrinsic branching of photoexcitations to two distinct species: self-trapped excitons and dark charge-transfer excitons (CTX; > 5% yield), with radii spanning 2-3 sites. The significant CTX yield results from the strong charge-transfer character of the Frenkel exciton band due to the large free exciton bandwidth (~400 meV) in these supramolecular nanostructures.