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Morphology Control for Fully Printable Organic–Inorganic Bulk-heterojunction Solar Cells Based on a Ti-alkoxide and Semiconducting Polymer
Published on: January 10, 2017
Copolymers comprising 2,7-carbazole and bis-benzothiadiazole units for bulk-heterojunction solar cells
Jonggi Kim1, Myoung Hee Yun, Piyush Anant
1Interdisciplinary School of Green Energy and KIER-UNIST, Advanced Center for Energy, Ulsan National Institute of Science and Technology, 100 Banyeon-ri, Eonyang-eup, Ulju-gu, Ulsan, 689-798, South Korea.
Abstract:
On the basis of theoretical considerations of the intramolecular charge transfer (ICT) effect, we have designed a series of donor (D)-acceptor (A) conjugated polymers based on bis-benzothiadiazole (BBT). A PPP-type copolymer of electron-rich 2,7-carbazole (CZ) and electron-deficient BBT units poly[N-(2-decyltetradecyl)-2,7-carbazole-co-7,7'-{4,4'-bis-(2,1,3-benzothiadiazole)}] (PCZ-BBT), a PPV-type copolymer poly[N-(2-decyltetradecyl)-2,7-carbazolevinylene-co-7,7'-{4,4'-bis-(2,1,3-benzothiadiazolevinylene)}] (PCZV-BBTV), and a tercopolymer based on carbazole, thiophene, and BBT poly[N-(2-decyltetradecyl)-2,7-(di-2-thienyl)carbazole-co-7,7'-{4,4'-bis-(2,1,3-benzothiadiazole)}] (PDTCZ-BBT) have been synthesized to understand the influence of BBT acceptor structure and linkage on the photovoltaic characteristics of the resulting materials. Both the HOMO and LUMO of the resulting polymers are found to be deeper-lying than those of benzothiadiazole-based polymers. The measured electrochemical band gaps (eV) are in the following order: PDTCZ-BBT (1.65 eV) < PCZV-BBTV (1.69 eV) < PCZ-BBT (1.75 eV). All the polymers provide a photovoltaic response when blended with a fullerene derivative as an electron acceptor. The best cell reaches a power conversion efficiency of 2.07 % estimated under standard solar light conditions (AM1.5G, 100 mW cm(-2)). We demonstrate for the first time that BBT-based polymers are promising materials for use in bulk-heterojunction solar cells.
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