The aggregation/crystallinity of classic n-type terpolymers based on naphthalene diimide and perylene diimide is challenging to tune due to their rigid and extended cores, leading to suboptimal film morphology. A new strategy for developing high-performance n-type terpolymers by incorporating imide-functionalized heteroarenes is reported here to balance crystallinity and miscibility without sacrificing charge carrier mobilities. The introduction of thienopyrroledione (TPD) into the copolymer f-BTI2-FT results in a series of terpolymers BTI2-xTPD having distinct TPD content. The irregular backbone reduces crystallinity, yielding improved miscibility with the polymer donor. More importantly, TPD triggers noncovalent S⋯O interactions, increasing backbone planarity and in-chain charge transport. Such interactions also promote face-on polymer packing. As a result, all-polymer solar cells (all-PSCs) based on BTI2-30TPD achieve an optimal power conversion efficiency (PCE) of 8.28% with a small energy loss (0.53 eV). This efficiency is substantially higher than that of TPD (4.4%) or a BTI2-based copolymer (6.8%) and is also the highest for additive-free all-PSCs based on a terpolymer acceptor. Moreover, the BTI2-30TPD cell exhibits excellent stability with the PCE retaining 90% of its initial value after 400 h of aging. The results demonstrate that random polymerization using imide-functionalized heteroarenes is a powerful approach to develop terpolymer acceptors toward efficient and stable all-polymer solar cell PSCs.
Bibliographical noteFunding Information:
H.S. and B.L. contributed equally to this work. The authors thank NSFC (21774055, 51573076, and 21801124), Shenzhen Basic Research Fund ((JCYJ20170817105905899), and Shenzhen Peacock Plan Project (KQTD20140630110339343). H.Y.W. are grateful to the financial support from the NRF of Korea (2016M1A2A2940911 and 2019R1A6A1A11044070). The authors thank Dr. Yinhua Yang at the Materials Characterization and Preparation Center, Southern University of Science and Technology (SUSTech) for NMR measurement. Our work was also supported by Center for Computational Science and Engineering of SUSTech.
© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
- all-polymer solar cells
- imide-functionalized heteroarenes
- n-type polymers
- organic electronics
- random terpolymers
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Materials Science(all)