Critical Role of Pendant Group Substitution on the Performance of Efficient All-Polymer Solar Cells

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• 作者：Kedar D. Deshmukh ; Shyamal K. K. Prasad ; Naresh Chandrasekaran ; Amelia C. Y. Liu ; Eliot Gann ; Lars Thomsen ; Dinesh KabraJustin M. Hodgkiss ; Christopher R. McNeill
• 刊名：Chemistry of Materials
• 出版年：2017
• 出版时间：January 24, 2017
• 年：2017
• 卷：29
• 期：2
• 页码：804-816
• 全文大小：695K
• ISSN：1520-5002

文摘

Most high-performance all-polymer solar cell systems employ donor polymers with side groups containing bulky aromatic units. The rationale behind the use of bulky side groups in efficient all-polymer systems, however, is not well-understood. In this study, we investigate the doubling of power conversion efficiency in all-polymer solar cells that occurs when substituting the pendant oxygen group in polymer donor PTB7 for thiophene. Specifically, polymer blends using either PTB7 or PTB7-Th as donor with P(NDI2OD-T2) as acceptor are compared. We comprehensively examine the photophysics, morphology, and device physics of these two systems and find that PTB7-Th:P(NDI2OD-T2) blends have suppressed geminate recombination and improved charge collection efficiencies compared to PTB7:P(NDI2OD-T2) blends. While the switching of oxygen for thiophene does not have a dramatic effect on blend morphology, the bulky side group in PTB7-Th helps to destabilize the interfacial charge transfer state, with 5-fold higher hole mobility of PTB7-Th also resulting in improved charge collection.