Narrow band gap D–A copolymer of indacenodithiophene and diketopyrrolopyrrole with deep HOMO level: Synthesis and application in field‐effect transistors and polymer solar cells |
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Authors: | Xiaochen Wang Hao Luo Yeping Sun Maojie Zhang Xiaoyu Li Gui Yu Yunqi Liu Yongfang Li Haiqiao Wang |
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Institution: | 1. Key Laboratory of Carbon Fiber and Functional Polymers, Ministry of Education, College of Materials Science and Engineering, Beijing University of Chemical Technology, Beijing 100029, People's Republic of China;2. Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, People's Republic of China |
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Abstract: | A novel fused ladder alternating D–A copolymer, PIDT–DPP, with alkyl substituted indacenodithiophene (IDT) as donor unit and diketopyrrolopyrrole (DPP) as acceptor unit, was designed and synthesized by Pd‐catalyzed Stille‐coupling method. The copolymer showed good solubility and film‐forming ability combining with good thermal stability. PIDT–DPP exhibited a broad absorption band from 350 to 900 nm with an absorption peak centered at 735 nm. The optical band gap determined from the onset of absorption of the polymer film was 1.37 eV. The highest occupied molecular orbital level of the polymer is as deep as ?5.32 eV. The solution‐processed organic field‐effect transistor (OFETs) was fabricated with bottom gate/top contact geometry. The highest FET hole mobility of PIDT–DPP reached 0.065 cm2 V?1 s?1 with an on/off ratio of 4.6 × 105. This mobility is one of the highest values for narrow band gap conjugated polymers. The power conversion efficiency of the polymer solar cell based on the polymer as donor was 1.76% with a high open circuit voltage of 0.88 V. To the best of our knowledge, this is the first report on the photovoltaic properties of alkyl substituted IDT‐based polymers. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 |
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Keywords: | conjugated polymers diketopyrrolopyrrole indacenodithiophene organic field‐effect transistors polymer solar cells |
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