Issue 4, 2022

Cascaded energy landscape as a key driver for slow yet efficient charge separation with small energy offset in organic solar cells

Abstract

Recent studies have shown that efficient free carrier (FC) generation with a small voltage loss can be achieved in organic solar cells (OSCs); however, the photophysical insights underpinning this remain unclear. Herein, we examined the mechanisms underlying the FC generation in a state-of-the-art OSC consisting of PM6 and Y6 as electron donor and acceptor, respectively, wherein the energy offset between the lowest excited singlet state and the charge transfer state is as small as ∼0.12 eV. We used transient absorption spectroscopy to track the time evolution of electroabsorption caused by electron–hole pairs generated at donor/acceptor interfaces. After hole transfer from Y6 to PM6, we observed slow yet efficient spatial charge dissociation on a time scale of picoseconds. Based on temperature-dependence measurements, we found that this slow yet efficient FC generation is driven by downhill energy relaxation of charges through the energy cascade generated near the interfaces. We provide here direct experimental evidence for the FC generation mechanism in the very topical PM6/Y6 blend system.

Graphical abstract: Cascaded energy landscape as a key driver for slow yet efficient charge separation with small energy offset in organic solar cells

Supplementary files

Article information

Article type
Paper
Submitted
15 Nov 2021
Accepted
04 Feb 2022
First published
22 Feb 2022

Energy Environ. Sci., 2022,15, 1545-1555

Cascaded energy landscape as a key driver for slow yet efficient charge separation with small energy offset in organic solar cells

S. Natsuda, T. Saito, R. Shirouchi, Y. Sakamoto, T. Takeyama, Y. Tamai and H. Ohkita, Energy Environ. Sci., 2022, 15, 1545 DOI: 10.1039/D1EE03565G

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements