Synthesis and characterization of low‐bandgap copolymers based on dihexyl‐2h‐benzimidazole and cyclopentadithiophene |
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| Authors: | Suhee Song Sung Heum Park Youngeup Jin Jina Park Joo Young Shim Il Kim Heesoo Lee Kwanghee Lee Hongsuk Suh |
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| Affiliation: | 1. Department of Chemistry and Chemistry Institute for Functional Materials, Pusan National University, Busan 609‐735, Korea;2. Center for Polymers and Organic Solids, University of California at Santa Barbara, Santa Barbara, California 93106‐5096;3. Department of Materials Science and Engineering, Gwangju Institute of Science and Technology, Gwangju 500‐712, Korea;4. Department of Industrial Chemistry, Pukyong National University, Busan 608‐739, Korea;5. The WCU Center for Synthetic Polymer Bioconjugate Hybrid Materials, Department of Polymer Science and Engineering, Pusan National University, Busan 609‐735, Korea;6. School of Materials Science and Engineering, Pusan National University, Busan 609‐735, Korea |
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| Abstract: | A series of new semiconducting polymers based on 4,4‐dihexyl‐4H‐cyclopenta[2,1‐b:3,4‐b′]dithiophene, 2,2‐dihexyl‐2H‐benzimidazole, and thiophene units was synthesized. The polymers show good solubility at room temperature in organic solvents owing to long alkyl chain in new acceptor, 2,2‐dihexyl‐2H‐benzimidazole. The advantage of dihexyl‐2H‐benzimidazole compared to the benzothiadiazole is to improve the solubility of the polymer. It was found that these polymers can finely be tuned for photovoltaic application by adjusting the contents ratio of the dihexyl‐2H‐benzimidazole unit. The spectra of the solid films show absorption bands with maximum peaks in the range of 421–577 nm and the absorption onsets at 588–683 nm, corresponding to band gaps of 2.11–1.82 eV. The devices with PCPDTDTHBI‐1 :PC71BM showed an open‐circuit voltage (VOC) of 0.46 V, a short‐circuit current density (JSC) of 3.83 mA/cm2, and a fill factor of 0.36, giving a power conversion efficiency of 0.64%. Decrease of the dihexyl‐2H‐benzimidazole contents in the polymers induced red‐shift of the UV absorptions, and increased VOC and JSC values, to improve the efficiency of organic photovoltaics. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010 |
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| Keywords: | 2H‐benzimidazole conjugated polymers copolymerization cyclopentadithiophene thin films |
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