Correlation between Phase-Separated Domain Sizes of Active Layer and Photovoltaic Performances in All-Polymer Solar Cells

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• 作者：Changyeon Lee ; Yuxiang Li ; Wonho Lee ; Youngmin Lee ; Joonhyeong Choi ; Taesu Kim ; Cheng Wang ; Enrique D. Gomez ; Han Young Woo ; Bumjoon J. Kim
• 刊名：Macromolecules
• 出版年：2016
• 出版时间：July 26, 2016
• 年：2016
• 卷：49
• 期：14
• 页码：5051-5058
• 全文大小：454K
• 年卷期：0
• ISSN：1520-5835

文摘

The control of the bulk-heterojunction (BHJ) morphology in polymer/polymer blends remains a critical hurdle for optimizing all-polymer solar cells (all-PSCs). The relationship between donor/acceptor phase separation, domain size, and the resulting photovoltaic characteristics of PDFQx3T and P(NDI2OD-T2)-based all-PSCs was investigated. We varied the film-processing solvents (chloroform, chlorobenzene, o-dichlorobenzene, and p-xylene), thereby manipulating the phase separation of all-polymer blends with the domain size in the range of 30–300 nm. The different volatility and solubility of the solvents strongly influenced the aggregation of the polymers and the BHJ morphology of polymer blends. Domain sizes of all-polymer blends were closely correlated with the short-circuit current density (J_SC) of the devices, while the open-circuit voltage (0.80 V) and fill factor (0.60) were unaffected. All-PSCs with the smallest domain size of ∼30 nm in the active layer (using chloroform), which is commensurate with the domain size of highly efficient polymer/fullerene solar cells, had the highest J_SC and power conversion efficiency of 5.11% due to large interfacial areas and efficient exciton separation. Our results suggest that the BHJ morphology was not fully optimized for most of the previous high-performance all-PSC systems, and their photovoltaic performance can be further improved by fine-engineering the film morphology, i.e., domain size, domain purity, and polymer packing structure.