On the Possibility of Singlet Fission in Crystalline Quaterrylene

TL;DR

This study investigates the potential for singlet fission in crystalline quaterrylene using advanced theoretical methods, suggesting it as a promising material for organic photovoltaics due to its favorable excitonic properties and stability.

Contribution

The paper introduces a new method for analyzing charge transfer character in excitons and applies many-body perturbation theory to assess singlet fission potential in quaterrylene.

Findings

Crystalline quaterrylene shows potential for intermolecular singlet fission.

A novel double-Bader analysis method links exciton charge transfer to crystal packing.

Perylene is unlikely to exhibit singlet fission but can harvest sub-gap photons.

Abstract

Singlet fission (SF), the spontaneous down-conversion of a singlet exciton into two triplet excitons residing on neighboring molecules, is a promising route to improving organic photovoltaic (OPV) device efficiencies by harvesting two charge carriers from one photon. However, only a few materials have been discovered that exhibit intermolecular SF in the solid state, most of which are acene derivatives. Recently, there has been a growing interest in rylenes as potential SF materials. We use many-body perturbation theory in the GW approximation and the Bethe-Salpeter equation (BSE) to investigate the possibility of intermolecular SF in crystalline perylene and quaterrylene. A new method is presented for determining the percent charge transfer character (%CT) of an exciton wave-function from double-Bader analysis. This enables relating exciton probability distributions to crystal packing. Based on comparison to known and predicted SF materials with respect to the energy conservation criterion (ES-2ET) and %CT, crystalline quaterrylene is a promising candidate for intermolecular SF. Furthermore, quaterrylene is attractive for OPV applications thanks to its high stability and narrow optical gap. Perylene is not expected to exhibit SF, however it is a promising candidate for harvesting sub-gap photons by triplet-triplet annihilation.