Manipulating Crystal Stacking by Sidechain Engineering for High‐Performance N‐Type Organic Semiconductors

• Published in: Advanced functional materials 2023-12, Vol.33 (50), p.n/a
• Main Authors: Chen, Yuzhong, Wu, Zeng, Ding, Lu, Zhang, Shuixin, Chen, Zekun, Li, Wenhao, Zhao, Yan, Wang, Yang, Liu, Yunqi
• Format: Article
• Language: English
• Subjects: branched alkyl/alkoxy substitutions; Brickwork; Charge transport; charge transport property; crystal stackings; Electron mobility; Energy levels; Field effect transistors; Materials science; N-type semiconductors; Optical properties; organic field‐effect transistors; Organic semiconductors; Photovoltaic cells; Semiconductors; Single crystals; Solar cells; Stacking; Transport properties; Y‐series non‐fullerene acceptors
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.202304316

Y‐series non‐fullerene acceptors (NFAs) have achieved great progress in organic solar cells (OSCs). Most research attention is currently paid to their molecular engineering to improve the efficiency of OSCs. However, as n‐type organic semiconductors, the relationship between their molecular packing structures and charge transport properties is mostly ignored. Herein, it is clarified how the molecular packing of Y‐series NFAs fundamentally determines their charge transport properties by manipulating their crystal stacking via sidechain engineering. Therefore, branched alkyl/alkoxy substitutions are taken on a reference NFA (Y6‐1O), affording three derivatives, namely 1OBO‐1, 1OBO‐2, and 1OBO‐3. Results show that while the replacement of branched alkyl/alkoxy sidechains has little impact on optical properties and energy levels, it can change crystal stacking motifs significantly. The single crystal of Y6‐1O with all linear sidechains forms a 2D‐brickwork structure and shows lower mobility. In contrast, 1OBO‐2 with all branched sidechains exhibits a favorable 3D interpenetrating porous network, displaying an electron mobility of 1.42 cm2 V−1 s−1 in single‐crystal organic field‐effect transistors (SC‐OFETs). This value is among the highest for NFA‐based n‐type OFETs. This study not only reveals the fundamental structure–property relationships of Y‐series NFAs, but also suggests the potential of Y‐series NFAs for high‐performance n‐type organic semiconductors. How the molecular packing of Y‐series non‐fullerene acceptors fundamentally determines their charge‐transport properties is clarified by manipulating their crystal stacking via sidechain engineering. Therefore, the all‐branched‐chains‐substituted derivative, namely 1OBO‐2, exhibits single crystal structure with a favorable 3D interpenetrating porous network. It thus results in an excellent electron mobility of 1.42 cm2 V−1 s−1 in organic single‐crystal transistors.