FRET-Enhanced Singlet Fission in Pentacene Derivatives

TL;DR

This paper demonstrates that FRET can enhance singlet fission in pentacene derivatives, offering a new approach to improve solar energy conversion efficiency by optimizing energy transfer mechanisms.

Contribution

It reveals how FRET influences singlet fission in pentacene derivatives, providing insights into energy transfer processes in organic photovoltaic materials.

Findings

SF rate depends on R^6, consistent with FRET behavior

FRET can be used to optimize singlet fission in organic materials

Two pentacene derivatives show similar FRET-enhanced SF mechanisms

Abstract

Conversion of solar energy with high quantum efficiencies is a key challenge in energy technologies. Excitation energy transfer (EET) mechanisms, such as F\"orster resonance energy transfer (FRET), play a crucial role in facilitating minimal energy loss in biological light-harvesting systems by directing excitation energy to conversion centers. Inspired by this, we show that singlet fission (SF) sensitizers are multi-exciton generation centers, to which surrounding molecules funnel excitation energy via FRET. We study the impact of such EET on SF using two structurally distinct yet optically similar pentacene derivatives: a stability-enhanced ''Gel\"ander'' pentacene, and the well-studied TIPS-pentacene. Transient absorption spectroscopy reveals a $R^{6}$ dependence of the SF rate on molecular separation $R$ in binary acene:polymethylmetacrylate thin film blends, which is typical for FRET. Optimizing FRET is a promising direction for future improvements in light harvesting using SF materials, inspired by natural light-harvesting complexes.