Copolymers of Cyclopentadithiophene and Electron‐Deficient Aromatic Units Designed for Photovoltaic Applications |
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Authors: | Johan C Bijleveld Munazza Shahid Jan Gilot Martijn M Wienk René A J Janssen |
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Affiliation: | 1. Molecular Materials and Nanosystems Eindhoven University of Technology P.O. Box 513 5600 MB Eindhoven (The Netherlands);2. Dutch Polymer Institute (DPI) P.O. Box 902 5600 AX Eindhoven (The Netherlands) |
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Abstract: | Alternating copolymers based on cyclopentadithiophene (CPDT) and five different electron‐deficient aromatic units with reduced optical band gaps are synthesized via Suzuki coupling. All polymers show a significant photovoltaic response when mixed with a fullerene acceptor. The frontier orbital levels of the new polymers are designed to minimize energy losses by increasing the open‐circuit voltage with respect to the optical band gap, while maintaining a high coverage of the absorption with the solar spectrum. The best cells are obtained for a copolymer of CPDT and benzooxadiazole (BO) with a band gap of 1.47 eV. This cell gives a short‐circuit current of 5.4 mA cm?2, an open‐circuit voltage of 0.78 V, and a fill factor of 0.6, resulting in a power conversion efficiency of about 2.5%. |
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Keywords: | conjugated polymers electronic processes solar cells thin films |
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