Importance of Disordered Polymer Segments to Microstructure-Dependent Photovoltaic Properties of Polymer鈥揊ullerene Bulk Heterojunction Solar Cells

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• 作者：Fu-Chiao Wu ; Ying-Chou Huang ; Horng-Long Cheng ; Wei-Yang Chou ; Fu-Ching Tang
• 刊名：Journal of Physical Chemistry C
• 出版年：2011
• 出版时间：August 4, 2011
• 年：2011
• 卷：115
• 期：30
• 页码：15057-15066
• 全文大小：1172K
• 年卷期：v.115,no.30(August 4, 2011)
• ISSN：1932-7455

文摘

While regulation of the nanoscale microstructure of the active layers in organic bulk heterojunction (BHJ) solar cells, particularly for conjugated polymer鈥揻ullerene blend systems, has been shown to be highly important when maximizing power conversion efficiency, little is known about the role of disordered polymer chains in the photovoltaic (PV) behaviors and electrochemical potential drops of polymer鈥揻ullerene interfaces. In this study, the microstructural-dependent PV properties of a series of poly(3-hexylthiophene) (P3HT):fullerene (i.e., [6,6]-phenyl-C61-butyric acid methyl ester, or PCBM) blending films with different compositions have been investigated using several experiments (i.e., absorption spectroscopy, Raman spectroscopy, X-ray diffraction, and atomic force microscopy) and theoretical methods (i.e., spectroscopic simulation and quantum mechanical calculations). A strong correlation exists between amorphous P3HT chain properties, characterized by degree of conjugation (L_eff), and PV parameters. The impact of L_eff of amorphous P3HT on exciton dissociation is addressed, thus providing an ideal structural model for organic BHJ solar cells. Although bigger P3HT and PCBM domains favor carrier transport, the control of disordered P3HT segments and PCBM contact is crucial to exciton dissociation, which can consequently optimize PV performance.