Charge-transfer state dynamics in all-polymer solar cells: Formation, dissociation and decoherence

TL;DR

This study models the ultrafast charge-transfer dynamics in all-polymer solar cells, revealing how interface properties influence charge separation, dissociation, and decoherence, with implications for improving device efficiency.

Contribution

It introduces a simulation based on the Su-Schrieffer-Heeger model to analyze charge-transfer state formation and dissociation in all-polymer solar cells, highlighting the role of electrostatic potential and quantum coherence.

Findings

Stable CT state formation depends on polaron distance and electrostatic potential.

Optimal interfacial width enables ultrafast charge dissociation.

Quantum coherence diminishes during charge separation, indicating decoherence.

Abstract

All-polymer solar cells gained substantial achievements in recent years, offering numerous unsettled subjects for mechanical researchers. Based on the Su-Schrieffer-Heeger model, we then simulate the ultrafast dynamics of charge-transfer (CT) state considering a molecular electrostatic potential drop at the interface between two polymer chains, which are respectively regarded as donor and acceptor in all-polymer solar cells. The formation of a stable CT state is found to be sensitive to the distance between two oppositely charged polarons and the relevant critical electrostatic potential is thus quantified. In order to get insight into the dependence of dissociation of CT state on the width of interfacial layer, two quantities are calculated: One is the Coulomb capture radius between two polarons and the other is the quantum trace distance which serves as the fingerprint of the quantum coherence between them. The dissociation of CT state is found to take place within an ultrafast timescale for an optimum interfacial width. The classical spatial distance and the quantum trace distance manifest converging trend suggesting a decoherence scenario for the charge separation in all-polymer solar cells.