Polyfluorene Electrolytes Interfacial Layer for Efficient Polymer Solar Cells: Controllably Interfacial Dipoles by Regulation of Polar Groups

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• 作者：Huimin Liu ; Lin Hu ; Feiyan Wu ; Lie Chen ; Yiwang Chen
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2016
• 出版时间：April 20, 2016
• 年：2016
• 卷：8
• 期：15
• 页码：9821-9828
• 全文大小：510K
• 年卷期：0
• ISSN：1944-8252

文摘

The polar groups in the conjugated polyelectrolytes (CPEs) can create the favorable dipoles at the electrode/active layer interface, which is critical for the CPEs to minimize the interfacial energy barrier in polymer solar cells (PSCs). Herein, a series of CPEs based on poly [(9,9-bis(3′-(N,N-dimethylamino)propyl)-2,7-fluorene)-co-2,7-(9,9-dioctylfluorene)] derivates (PFNs) (PFN₃₀, PFN₅₀, PFN₇₀, and PFN₁₀₀) with different mole ratio of polar groups (−N(C₂H₅)₂) were designed and synthesized to investigate the effect of the numbers of polar groups on the interfacial dipoles. Controllably interfacial dipoles could be readily achieved by only tuning the numbers of −N(C₂H₅)₂ in PFNs, as revealed by the work function of the PFNs modified ITO gradually reduced as the loadings of the −N(C₂H₅)₂ increased. In addition, increasing the numbers of −N(C₂H₅)₂ in PFNs were also favorable for developing the smooth and homogeneous morphology of the active layer. As a result, the content of the polar amine in the PFNs exerted great influence on the performance of polymer solar cells. Increasing the numbers of the pendent −N(C₂H₅)₂ could effectively improve the power conversion efficiency (PCE) of the devices. Among these PFNs, PFN₁₀₀ with the highest content of −N(C₂H₅)₂ polar groups delivered the device with the best PCE of 3.27%. It indicates tailoring the content of the polar groups in the CPEs interlayer is a facial and promising approach for interfacial engineering to developing high performance PSCs.