Alternating Copolymers of Cyclopenta[2,1-b;3,4-b′]dithiophene and Thieno[3,4-c]pyrrole-4,6-dione for High-Performance Polymer Solar Cells

A series of alternating copolymers of cyclopenta[2,1‐b;3,4‐b′]dithiophene (CPDT) and thieno[3,4‐c]pyrrole‐4,6‐dione (TPD) have been prepared and characterized for polymer solar cell (PSC) applications. Different alkyl side chains, including butyl (Bu), hexyl (He), octyl (Oc), and 2‐ethylhexyl (EH),...

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Veröffentlicht in:Advanced functional materials 2011-09, Vol.21 (17), p.3331-3336
Hauptverfasser: Li, Zhao, Tsang, Sai-Wing, Du, Xiaomei, Scoles, Ludmila, Robertson, Gilles, Zhang, Yanguang, Toll, Floyd, Tao, Ye, Lu, Jianping, Ding, Jianfu
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Sprache:eng
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Zusammenfassung:A series of alternating copolymers of cyclopenta[2,1‐b;3,4‐b′]dithiophene (CPDT) and thieno[3,4‐c]pyrrole‐4,6‐dione (TPD) have been prepared and characterized for polymer solar cell (PSC) applications. Different alkyl side chains, including butyl (Bu), hexyl (He), octyl (Oc), and 2‐ethylhexyl (EH), are introduced to the TPD unit in order to adjust the packing of the polymer chain in the solid state, while the hexyl side chain on the CPDT unit remains unchanged to simplify discussion. The polymers in this series have a simple main chain structure and can be synthesized easily, have a narrow band gap and a broad light absorption. The different alkyl chains on the TPD unit not only significantly influence the solubility and chain packing, but also fine tune the energy levels of the polymers. The polymers with Oc or EH group have lower HOMO (highest occupied molecular orbital) and LUMO (lowest unoccupied molecular orbital) energy levels, resulting higher open circuit voltages (Voc) of the PSC devices. Power conversion efficiencies (PCEs) up to 5.5% and 6.4% are obtained from the devices of the Oc substituted polymer (PCPDTTPD‐Oc) with PC61BM and PC71BM, respectively. This side chain effect on the PSC performance is related to the formation of a fine bulk heterojunction structure of polymer and PCBM domains, as observed with atomic force microscopy. A series of alternating copolymers of cyclopenta[2,1‐b:3,4‐b]dithiophene and thieno[3,4‐ c]pyrrole‐4,6‐dione, (PCPDTTPD) are designed and synthesized. These polymers show a low‐enery band gap and a broad absorption. Polymer solar cell devices based on their blends with PC61BM and PC71BM show a high power conversion efficiency up to 5.5% and 6.4%, respectively.
ISSN:1616-301X
1616-3028
1616-3028
DOI:10.1002/adfm.201100708