Highly‐Efficient 2D Nonfullerene Acceptors Enabled by Subtle Molecular Tailoring Engineering

• Published in: Small (Weinheim an der Bergstrasse, Germany) Germany), 2024-05, Vol.20 (21), p.e2309169-n/a
• Main Authors: Ding, Yafei, Xiong, Shilong, Li, Mingpeng, Pu, Mingrui, Zhu, Yiwu, Lai, Xue, Wang, Yunpeng, Qiu, Dongsheng, Lai, Hanjian, He, Feng
• Format: Article
• Language: English
• Subjects: 2D conjugate expansion; Absorption spectra; aromatic‐ring substitution; Charge efficiency; Charge transport; Conjugates; Electronic structure; Energy conversion efficiency; Excitons; Expansion; Molecular structure; Morphology; nonfullerene acceptor; organic solar cell; Phase separation; Photovoltaic cells; power conversion efficiency; Quinoxalines; Solar cells; Transport properties
• ISSN: 1613-6810; 1613-6829
• DOI: 10.1002/smll.202309169

The conjugate expansion of nonfullerene acceptors is considered to be a promising approach for improving organic photovoltaic performance because of its function in tuning morphological structure and molecular stacking behavior. In this work, two nonfullerene acceptors are designed and synthesized using a 2D π‐conjugate expansion strategy, thus enabling the construction of highly‐efficient organic solar cells (OSCs). Compared with YB2B (incorporating dibromophenanthrene on the quinoxaline‐fused core), YB2T (incorporating dibromobenzodithiophene on the quinoxaline‐fused core) has red‐shifted spectral absorption and better charge transport properties. Moreover, the more orderly and tightly intermolecular stacking of YB2T provides the possibility of forming a more suitable phase separation morphology in blend films. Through characterization and analysis, the YB2T‐based blend film is found to have higher exciton dissociation efficiency and less charge recombination. Consequently, the power conversion efficiency (PCE) of 17.05% is achieved in YB2T‐based binary OSCs, while YB2B‐based devices only reached 10.94%. This study demonstrates the significance of the aromatic‐ring substitution strategy for regulating the electronic structure and aggregation behavior of 2D nonfullerene acceptors, facilitating the development of devices with superior photovoltaic performance. By introducing diverse aromatic‐ring structures into the quinoxaline core, two small‐molecule acceptors, namely YB2B and YB2T, are meticulously designed and synthesized. YB2T, in contrast to YB2B, demonstrates a narrower band gap and superior charge transfer properties. It is noteworthy that the device based on PM6:YB2T achieves the highest efficiency of 17.05%, significantly surpassing its PM6:YB2B counterpart.