Superexchange Induced Charge Transport in Organic Donor–Acceptor Cocrystals and Copolymers: A Theoretical Perspective

• Published in: Chemistry of materials 2019-09, Vol.31 (17), p.6424-6434
• Main Authors: Geng, Hua, Zhu, Lingyun, Yi, Yuanping, Zhu, Daoben, Shuai, Zhigang
• Format: Article
• Language: English
• ISSN: 0897-4756; 1520-5002
• DOI: 10.1021/acs.chemmater.9b01545

Organic donor–acceptor (D–A) blending systems have displayed great potential in the application of organic optoelectronics. Conventionally, charge transport is not allowed along the stacking direction for D–A mixed-stack organic cocrystals or along the intrachain backbone direction for D–A copolymers, since the nearest-neighbored D or A molecules/units are too far away to interact directly with each other. In fact, for hole (electron) transport, an effective electronic coupling between adjacent D (A) molecules/units can be manifested by a superexchange mechanism with the in between A (D) molecule/unit as a bridge. In this perspective, we have briefly summarized our recent progress in understanding the long-range superexchange electronic couplings to assess the charge transport and polarities of D–A cocrystals and copolymers. The energy-splitting and partition-based methods are first introduced to evaluate the bridge-mediated superexchange couplings. The important role of the superexchange mechanism in the charge transport is then discussed, and the similarity and difference between D–A cocrystals and copolymers are elucidated. Finally, the factors that determine the charge carrier polarities and the magnitudes of superexchange couplings are analyzed to provide some insightful principles for the design of high-mobility organic semiconductors based on D–A blending systems.