Linear Side Chains in Benzo[1,2-b:4,5-b鈥瞉dithiophene鈥揟hieno[3,4-c]pyrrole-4,6-dione Polymers Direct Self-Assembly and Solar Cell Performance

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• 作者：Cl茅ment Cabanetos ; Abdulrahman El Labban ; Jonathan A. Bartelt ; Jessica D. Douglas ; William R. Mateker ; Jean M. J. Fr茅chet ; Michael D. McGehee ; Pierre M. Beaujuge
• 刊名：The Journal of the American Chemical Society
• 出版年：2013
• 出版时间：March 27, 2013
• 年：2013
• 卷：135
• 期：12
• 页码：4656-4659
• 全文大小：249K
• 年卷期：v.135,no.12(March 27, 2013)
• ISSN：1520-5126

文摘

While varying the size and branching of solubilizing side chains in 蟺-conjugated polymers impacts their self-assembling properties in thin-film devices, these structural changes remain difficult to anticipate. This report emphasizes the determining role that linear side-chain substituents play in poly(benzo[1,2-b:4,5-b鈥瞉dithiophene鈥搕hieno[3,4-c]pyrrole-4,6-dione) (PBDTTPD) polymers for bulk heterojunction (BHJ) solar cell applications. We show that replacing branched side chains by linear ones in the BDT motifs induces a critical change in polymer self-assembly and backbone orientation in thin films that correlates with a dramatic drop in solar cell efficiency. In contrast, we show that for polymers with branched alkyl-substituted BDT motifs, controlling the number of aliphatic carbons in the linear N-alkyl-substituted TPD motifs is a major contributor to improved material performance. With this approach, PBDTTPD polymers were found to reach power conversion efficiencies of 8.5% and open-circuit voltages of 0.97 V in BHJ devices with PC₇₁BM, making PBDTTPD one of the best polymer donors for use in the high-band-gap cell of tandem solar cells.