Enhanced hindrance from phenyl outer side chains on nonfullerene acceptor enables unprecedented simultaneous enhancement in organic solar cell performances with 16.7% efficiency. (October 2020)

• Record Type: Journal Article
• Authors: Chai, Gaoda; Chang, Yuan; Peng, Zhengxing; Jia, Yanyan; Zou, Xinhui; Yu, Dian; Yu, Han; Chen, Yuzhong; Chow, Philip C.Y.; Wong, Kam Sing; Zhang, Jianquan; Ade, Harald; Yang, Liwei; Zhan, Chuanlang
• Is Part Of: Nano energy. Volume 76(2020)
• Publication Date: 2020-10
• Subjects: Fullerene-free -- Side-chain engineering -- Organic solar cell -- Isomerization -- Aggregated structure; Nanoscience -- Periodicals; Nanotechnology -- Periodicals; Nanostructured materials -- Periodicals; Power resources -- Technological innovations -- Periodicals; Nanoscience; Nanostructured materials; Nanotechnology; Power resources -- Technological innovations; Periodicals; 621.042
• DOI: 10.1016/j.nanoen.2020.105087
• Languages: English
• ISSNs: 2211-2855

Abstract

Abstract: Inner side-chain engineering on Y6 has been proven successful in improving short-circuit current density ( J SC ) through fine-tuning aggregated structures of acceptors. However, it fails in tuning the lowest unoccupied molecular orbital level (LUMO) and open-circuit voltage ( V OC ). In this paper, we turn to focus on engineering the outer side chains on the flanking thienothiophene units with 4-hexylphenyl (PhC6) and 6-phenylhexyl (C6Ph) chains. Use of PhC6 enhances the steric effect between the attached phenyl and the ending group, which in combination with the additional conjugation effect provided by the linking phenyl leads to upshifted energy levels and increased V OC as a result. Again, substitution with the bulkier PhC6 unprecedentedly improves film-morphology with reduced paracrystalline disorder and long period and increased root-mean-square composition variations as well, leading to increased electron and hole mobilities and suppressed monomolecular recombination with J SC and fill-factor (FF) simultaneously enhanced. The PM6:BTP-PhC6-based devices yield a higher efficiency value of 16.7% than the PM6:BTP-C6Ph-based one (15.5%). Therefore, this study shows a conceptual advance in materials design towards reducing the conflict between V OC and J SC in binary blended organic solar cells, which can be achieved by introducing bulkier chains to twist the backbone and simultaneously enhance the packing order. Graphical abstract: Image 1 Highlights: Two isomeric nonfullerene acceptors, BTP-C6Ph and BTP-PhC6 are reported. This work shows a conceptual advance in materials design towards reducing the conflict between V OC and J SC . 4-hexylphenyl (PhC6) as the outer side chains leads to upshifted energy levels and increased V OC . The bulkier PhC6 chains provided enhanced hindrance acts as conformation-locking to reduce the number of stereoisomers. Higher PCE of 16.7% was obtained on the PM6:BTP-PhC6-based devices.