title: π-π Interaction among violanthrone molecules: observation, enhancement, and resulting charge transport properties.
abstract: To investigate the relationship between π-π stacking and charge transport property of organic semiconductors, a highly soluble violanthrone derivative, 16,17-bis(2-ethylhexyloxy)anthra[9,1,2-cde-]benzo[rst]pentaphene-5,10-dione (3), is designed and synthesized. The π-π stacking behavior and the aggregation of compound 3 in both solution and thin film were studied in detail by (1)H nuclear magnetic resonance (NMR) spectroscopy, ultraviolet-visible (UV-vis) absorption, X-ray diffraction (XRD), and atomic force microscopy (AFM). When (1)H NMR spectroscopy and theoretical modeling results were combined, the arrangements of compound 3 molecules in the aggregates are demonstrated, where the dipole moments of the two adjacent molecules are nearly reversed to achieve efficient intermolecular π-π overlapping. Furthermore, it is interesting to find that the π-π stacking of compound 3, in both solution and thin films, can be enhanced by introducing a poor solvent n-hexane into the dilute chloroform solution. The resulting film exhibits more red-shifted absorption and higher crystallinity than the film made from pure chloroform solvent, suggesting that π-π interactions in the solid state are intensified by the poor solvent. Organic field-effect transistors (OFETs) with compound 3 film as the transportation layer were fabricated. It is disclosed that the compound 3 film obtained from the chloroform/n-hexane mixed solvents exhibits 1 order of magnitude higher hole mobility than that from the pure chloroform solvent because of the enhanced π-π interactions and the higher crystallinity in the former film. This work provided us valuable information in the improvement of electronic and optoelectronic performances of organic semiconductors by tuning their aggregate structures.
authors.affiliation: Department of Polymer Science and Engineering, Ministry of Education Key Laboratory of Macromolecule Synthesis and Functionalization, Zhejiang University, Hangzhou 310027, People's Republic of China.
authors.forename: Min-Min
authors.initials: MM
authors.lastname: Shi
authors.forename: Yi
authors.initials: Y
authors.lastname: Chen
authors.forename: Ya-Xiong
authors.initials: YX
authors.lastname: Nan
authors.forename: Jun
authors.initials: J
authors.lastname: Ling
authors.forename: Li-Jian
authors.initials: LJ
authors.lastname: Zuo
authors.forename: Wei-Ming
authors.initials: WM
authors.lastname: Qiu
authors.forename: Mang
authors.initials: M
authors.lastname: Wang
authors.forename: Hong-Zheng
authors.initials: HZ
authors.lastname: Chen