A transition solvent strategy to print polymer:fullerene films using halogen-free solvents for solar cell applications
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- 作者：Guan-Hui Lim ; Jing-Mei Zhuo ; Loke-Yuen Wong ; Soo-Jin Chua ; Lay-Lay Chua ; Peter K.H. Ho
- 关键词：Organic solar cells ; Ink-jet printing ; Morphology ; Solvent effects ; Processing
- 刊名：Organic Electronics
- 出版年：February, 2014
- 年：2014
- 卷：15
- 期：2
- 页码：449-460
- 全文大小：1804 K
文摘
Inkjet printing is a mask-less non-contact deposition technique that is potentially suited for prototyping and manufacturing of thin-film polymer organic semiconductor devices from digital images. However new strategies are needed to achieve films with good macromorphology (i.e., high-fidelity footprint and uniform cross-section) and nanomorphology on unstructured substrates using a conventional ink-jet. Here we report a new transition solvent strategy to provide the desired film macromorphology and ultrafine nanomorphology in regioregular poly(3-hexylthiophene):phenyl-C61-butyric acid methyl ester (P3HT:PCBM) model films, without using chlorinated solvents. This strategy employs a good volatile solvent in combination with a miscible poor solvent that is much less volatile, which is the reverse of the usual low鈭抙igh boiling-point solvent method. The good solvent suppresses premature aggregation in the ink head. Its removal by evaporation on the substrate leaves the poor solvent that triggers early 蟺-stacking ordering and/or gelation of the polymer matrix that immobilizes the printed fluid on the substrate, suppressing both contact-line depinning and evaporation-induced solvent flow effects. The resultant donor-acceptor nanomorphology is further improved by vacuum drying at an optimal rate that avoids bubble formation. We have systematically characterized P3HT:PCBM films deposited with different solvents and platen temperatures to identify key macro- and nano-morphology determining processes. High-performance printed P3HT:PCBM solar cells were realized. These findings are applicable also to other printing and coating techniques based on low-viscosity inks.