Electronic, optical, and charge transport properties of A-π-A electron acceptors for organic solar cells: Impact of anti-aromatic π structures

作     者：Yan Zeng Ruihong Duan Yuan Guo Guangchao Han Qingxu Li Yuanping Yi 

作者机构：School of Science Chongqing University of Posts and Telecommunications CAS Key Laboratory of Organic Solids CAS Research/Education Center for Excellence in Molecular Sciences Institute of Chemistry Chinese Academy of Sciences 

出 版 物：《Chinese Chemical Letters》 (中国化学快报（英文版）)

年 卷 期：2019年第30卷第1期

页      面：211-216页

核心收录：

学科分类：08[工学] 080502[工学-材料学] 0805[工学-材料科学与工程（可授工学、理学学位）] 

基　　金：financially supported by the National Natural Science Foundation of China (No. 51773208) the Ministry of Science and Technology of China (No. 2014CB643506) the Strategic Priority Research Program of the Chinese Academy of Sciences (No. XDB12020200) 

主　　题：A-π-A electron acceptor Anti-aromatic structure Strong absorption Reorganization energy Organic solar cells 

摘      要：Organic solar cells based on acceptor-p-acceptor(A-π-A) electron acceptors have attracted intensive attention due to their increasing and record power conversion efficiencies. To date, almost all of the reported A-π-A electron acceptors are based on aromatic p structures. Here, we have investigated the impact of anti-aromatization of the p-bridges on the optoelectronic properties of A-π-A electron acceptors by(time-dependent) density functional theory. Our calculations show that besides the frontier molecular orbitals corresponding to the aromatic p-bridge based acceptors(aromatic acceptors),additional and unique occupied and unoccupied frontier orbitals are found for the acceptors based on the anti-aromatic p-bridges(anti-aromatic acceptors). Moreover, by tuning isomeric structures of the p-bridges(e.g., fusion orientations or linking positions of thiophene moieties), the optical excitation energies for the transition between the additional occupied and unoccupied levels turn to be close to or substantially lower with respect to those for the transition between the aromatic frontier orbitals. The optical absorption of the anti-aromatic acceptors is thus either stronger or broader than the aromaticacceptors. Finally, the reorganization energies for electron transport are tunable and dependent on the p-bridge structures. These results indicate a great potential of anti-aromatic electron acceptors in organic photovoltaics.