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Chem. J. Chinese Universities

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Side-Chain Engineering of “Bridging” Polymer Acceptors with Donor/Acceptor Dual Similarity for High-Performance Ternary Organic Solar Cells

LIU Miaomiao1,2, FU Mengran1,2, GAO Die2, ZHANG Wanpeng1, LIANG Ying2, HE Yuanyuan3, ZHAO Qiaoqiao1*, ZHAO Tingxing2*, LI Hongbo2, DING Zicheng5, HAN Yanchun4*   

  1. 1. State Key Laboratory of Green Papermaking and Resource Recycling, Qilu University of Technology, Shandong Academy of Sciences

    2. School of Materials and Chemistry, Southwest University of Science and Technology

    3. College of Materials Science and Engineering, Chongqing University

    4. State Key Laboratory of Polymer Science and Technology, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences 5. School of Materials Science and Engineering, Shaanxi Normal University

  • Received:2025-10-31 Revised:2025-12-23 Online First:2026-01-10 Published:2026-01-10
  • Supported by:
    Supported by the Shandong Provincial Natural Science Foundation, China(No.ZR2022QE135), the National Natural Science Foundation of China(No.52203024), the Youth Innovation Team Project of Shandong Provincial University, China(No.2023KJ330), the Major Scientific Research Project for the Construction of State Key Lab, China(No.2025ZDGZ02), the Doctoral Research Foundation of SWUST, China(No.22zx7129) and the Natural Science Foundation of Sichuan Province of China(No.2024NSFSC2006)

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Abstract: The active layer morphology plays a critical role in determining photovoltaic performance of organic solar cells(OSCs). However, binary blends often suffer from suboptimal phase separation, which limits the efficiency of OSCs. Herein, two bridging polymer acceptors(PAs)—BDT-C2C4(benzodithiophene-(2-ethylhexyl)oxy) and BDT-C8(benzodithiophene-octyloxy)—are designed and synthesized by combining a benzodithiophene(BDT) unit as the donor moiety(analogous to the donor unit of D18(5-(5-(4,8-bis(5-(2-ethylhexyl)-4-fluorothiophen-2-yl)-6-methylbenzo[1,2-b:4,5-b']dithiophen-2-yl)-4-(2-butyloctyl)thiophen-2-yl)-8-(4-(2-butyloctyl)-5-methylthiophen-2-yl)dithieno[3',2':3,4;2'',3'':5,6]benzo[1,2-c][1,2,5]thiadiazole)), and a Y6(2,2'-((2Z,2'Z)-((12,13-Bis(2-butyloctyl)-12,13-dihydro-3,9-dinonylthieno[2,3]thieno[3,2-b]pyrrolo[4,5-g]thieno[2,3-b]indole-2,10-diyl)bis(methanylylidene))bis(3-oxo-2,3-dihydro-1H-indene-2,1-diylidene))dimalononitrile) derivative as the acceptor moiety. BDT-C2C4 and BDT-C8 are functionalized with (2-ethylhexyl)oxy and octyloxy side chains on the BDT unit, respectively. Both PAs show complementary absorption and cascaded energy levels with the donor D18 and the acceptor N3(2,2'-((2Z,2'Z)-((12,13-bis(3-ethylheptyl)-3,9-diundecyl-12,13-dihydro-[1,2,5]thiadiazolo[3,4-e]thieno[2'',3'':4',5']thieno[2',3':4,5]pyrrolo[3,2-g]thieno[2',3':4,5]thieno[3,2-b]indole-2,10-diyl)bis(methaneylylidene))bis(5,6-difluoro-3-oxo-2,3-dihydro-1H-indene-2,1-diylidene))dimalononitrile), but BDT-C8 exhibits better compatibility with D18 and N3 compared to BDT-C2C4. When incorporated as a third component into D18:N3 blend, both PAs improve the active layer morphology. In particular, the D18:N3:BDT-C8 blend shows significantly optimized morphology, featuring reduced phase separation and a fibrous network structure. As a result, the device based on D18:N3:BDT-C8 achieves a power conversion efficiency of 18.18%, significantly higher than that of binary device (ca.17.37%). This work presents a compatibilizer strategy for optimizing blend morphology towards high-performance ternary OSCs.

Key words: Organic solar cell, Ternary strategy, Polymer acceptor, Active layer morphology

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