Charge separation by photoexcitation in semicrystalline polymeric semiconductors: An intrinsic or extrinsic mechanism?

TL;DR

This study investigates the mechanisms of charge separation in semicrystalline polymeric semiconductors, revealing that exciton dissociation occurs extrinsically at domain interfaces, influenced by molecular order and quantum-chemical factors.

Contribution

It provides detailed experimental and theoretical insights into the intrinsic versus extrinsic mechanisms of charge separation in poly(3-hexylthiophene) films.

Findings

Charge dissociation occurs extrinsically at domain interfaces.

Polaron pairs recombine via tunnelling with distributed rates.

Quantum calculations indicate hot-exciton dissociation involves high charge-transfer character.

Abstract

We probe charge photogeneration and subsequent recombination dynamics in neat regioregular poly(3-hexylthiophene) films over six decades in time by means of time-resolved photoluminescence spectroscopy. Exciton dissociation at 10K occurs extrinsically at interfaces between molecularly ordered and disordered domains. Polaron pairs thus produced recombine by tunnelling with distributed rates governed by the distribution of electron-hole radii. Quantum-chemical calculations suggest that hot-exciton dissociation at such interfaces results from a high charge-transfer character.