Deposition-Pressure-Induced Optimization of Molecular Packing for High-Performance Organic Thin-Film Transistors Based on Copper Phthalocyanine

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• 作者：Yi Li ; Shuang Chen ; Qi Liu ; Leyong Wang ; Takao Someya ; Jing Ma ; Xizhang Wang ; Zheng Hu
• 刊名：The Journal of Physical Chemistry C
• 出版年：2012
• 出版时间：February 16, 2012
• 年：2012
• 卷：116
• 期：6
• 页码：4287-4292
• 全文大小：383K
• 年卷期：v.116,no.6(February 16, 2012)
• ISSN：1932-7455

文摘

Copper phthalocyanine (CuPc) films have been prepared on SiO₂ and octadecyltrichlorosilane (OTS)-treated SiO₂ (OTS/SiO₂) substrates by vacuum deposition under different deposition pressures (P_dep) ranging from 10^鈥? to 10^鈥? Pa. Experimental results indicate that P_dep has an obvious influence on the morphologies and molecular packing structures of the CuPc films and, therefore, the performance of the resulting thin-film transistors (TFTs). Specifically, the grain sizes of the CuPc films keep almost unchanged for P_dep below 10^鈥? Pa and significantly increase for further increasing P_dep to 10^鈥? Pa on both SiO₂ and OTS/SiO₂. The interplanar spacings (D values) of the films increase on SiO₂ and keep unchanged on OTS/SiO₂ with increasing P_dep, which has also been rationalized by the molecular dynamics simulation. Field-effect measurements indicate that the electronic properties of the CuPc thin films are closely correlated with their microstructures, and the film prepared at higher P_dep gives the higher mobility. In addition to the general results that larger grain size favors the higher mobility similar to literature reports, both our experimental and theoretical results reveal that the interplanar spacing of the film also has a sensitive influence on the mobility of the CuPc TFTs, and the larger D value leads to the higher mobility. This study provides a convenient way to tune the morphology and molecular packing of the CuPc films to optimize the performance simply by regulating P_dep and discloses an important parameter, that is, the D value, associated with the device performance, which is significant for basic understanding and potential applications.