Asymmetric Electron-Donating 4-Alkyl-8-alkoxybenzo[1,2-b:4,5-b鈥瞉dithiophene Unit for Use in High-Efficiency Bulk Heterojunction Polymer Solar Cells

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• 作者：Quoc Viet Hoang ; Chang Eun Song ; Sang-Jin Moon ; Sang Kyu Lee ; Jong-Cheol Lee ; Bumjoon J. Kim ; Won Suk Shin
• 刊名：Macromolecules
• 出版年：2015
• 出版时间：June 23, 2015
• 年：2015
• 卷：48
• 期：12
• 页码：3918-3927
• 全文大小：556K
• ISSN：1520-5835

文摘

A series of new conjugated polymers based on the asymmetric benzo[1,2-b:4,5-b鈥瞉dithiophene (BDT) unit were designed and synthesized for use in bulk-heterojunction polymer solar cells. Each side chain of the BDT was tuned by introducing alkyl and alkoxy groups. The best solar cell efficiency was achieved in an asymmetric polymer device based on 4-octyl-8-octyloxy-BDT (7.64% PCE), which performed better than devices based on the symmetric dioctyl-BDT (6.48% PCE) or dioctyloxy-BDT (7.18% PCE). Further modification of the side chains, replacing octyloxy with butoxydiethoxy, improved the PCE to 8.12% due to the enhanced hole mobility, hole/electron mobility balance, and formation of tight contacts with the PEDOT:PSS layer. The effects of the side chains on the polymer HOMO energy levels and photovoltaic parameters were investigated.