Exciton dissociation in organic solar cells: An embedded charge transfer state model

TL;DR

This paper presents a detailed model of exciton dissociation in organic solar cells, analyzing how interface properties and recombination processes affect quantum efficiency and charge transfer states.

Contribution

The study introduces a comprehensive embedded charge transfer state model that explores exciton dissociation, recombination, and injection regimes in organic photovoltaic interfaces.

Findings

Interface significantly influences injection process

Attractive potentials create localized electron states

Three distinct injection regimes based on initial electron energy

Abstract

Organic solar cells are a promising avenue for renewable energy, and our study introduces a comprehensive model to investigate exciton dissociation processes at the donor-acceptor interface. Examining quantum efficiency and emitted phonons in the charge transfer state (CTS), we explore scenarios like variations of the environment beyond the CTS and repulsive/attractive potentials. The donor-acceptor interface significantly influences the injection process, with minimal impact from the environment beyond the CTS. Attractive potentials can create localized electron states at the interface, below the acceptor band, without necessarily hampering a good injection at higher energies. Exploring different recombination processes, including acceptor-side and donor-side recombination, presents distinct phases for the injection process versus the initial energy of the electron and the recombination rate. Our study highlights the important role of the type of recombination in determining the quantum efficiency and the existence of hot or cold charge transfer states. Finally, depending on the initial energy of the electron on the donor side, three distinct injection regimes are exhibited. The present model should be helpful for optimizing organic photovoltaic cell interfaces, highlighting the critical parameter interplay for enhanced performance.