Issue 37, 2022

Effects of the rigid and sterically bulky structure of non-fused nonfullerene acceptors on transient photon-to-current dynamics

Abstract

Non-fused electron-accepting π-conjugated compounds have been investigated recently for application to nonfullerene acceptors (NFAs) in organic solar cells (OSCs). However, the establishment of rational molecular design for non-fused NFAs is still lagging because the influence of flexible non-fused structures on the dynamics of electron–hole pairs in OSCs is not entirely understood. In this study, we utilized cyclopentene-annelated thiophene with spiro-substituted 2,7-bis(2-ethylhexyl)fluorene (FT) as a rigid and sterically bulky linker unit and developed a non-fused NFA (TT–FT–DCI) containing FT units. Photophysical measurements indicated that the introduction of the FT unit leads to the formation of rigid molecular structure. OSCs based on donor polymer (PBDB-T) and TT–FT–DCI showed an improved power conversion efficiency of 7.13% due to the increase in the short-circuit current density and fill factor. Time-resolved optical and microwave spectroscopies showed that the FT unit contributes to the long lifetimes of excited state and charge-separated state in the PBDBT:TT–FT–DCI blend films. Time-resolved electron paramagnetic resonance measurements showed that the distant charge-separated states of the face-to-face PBDB-T:TT–FT–DCI structure, which is derived by avoiding over-crystallization by the steric bulkiness of TT–FT–DCI, can interact with the cathodes for preferential electron injection following charge generations. This study highlights that by using the rigid π-conjugated framework and suppressed self-aggregation of the non-fused acceptor, effective molecular design for the appropriate dynamics of photocurrent generation is possible.

Graphical abstract: Effects of the rigid and sterically bulky structure of non-fused nonfullerene acceptors on transient photon-to-current dynamics

Supplementary files

Article information

Article type
Paper
Submitted
01 apr 2022
Accepted
21 jun 2022
First published
09 aug 2022
This article is Open Access
Creative Commons BY license

J. Mater. Chem. A, 2022,10, 20035-20047

Effects of the rigid and sterically bulky structure of non-fused nonfullerene acceptors on transient photon-to-current dynamics

S. Jinnai, K. Murayama, K. Nagai, M. Mineshita, K. Kato, A. Muraoka, A. Yamakata, A. Saeki, Y. Kobori and Y. Ie, J. Mater. Chem. A, 2022, 10, 20035 DOI: 10.1039/D2TA02604J

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