Building Blocks for n-Type Molecular and Polymeric Electronics. Perfluoroalkyl- versus Alkyl-Functionalized Oligothiophenes (nT; n = 2-6). Systematics of Thin Film Microstructure, Semiconductor
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- 作者：Antonio Facchetti ; Melissa Mushrush ; Myung-Han Yoon ; Geoffrey R. Hutchison ; Mark A. Ratner ; and Tobin J. Marks
- 刊名：Journal of the American Chemical Society
- 出版年：2004
- 出版时间：October 27, 2004
- 年：2004
- 卷：126
- 期：42
- 页码：13859 - 13874
- 全文大小：470K
- 年卷期：v.126,no.42(October 27, 2004)
- ISSN：1520-5126
文摘
The solid-state properties and FET electrical behavior of several series of 
gifchars/alpha.gif" BORDER=0>,gifchars/omega.gif" BORDER=0 >- and gifchars/beta2.gif" BORDER=0 ALIGN="middle">,gifchars/beta2.gif" BORDER=0 ALIGN="middle">'-fluorocarbon- and alkyl-substituted and unsubstituted oligothiophenes nTs (n = 2-6) are compared andcontrasted. The thin films were grown by slow vacuum deposition over a range of substrate temperaturesand/or by casting from solution and were investigated by X-ray diffraction and scanning electron microscopy.Our results indicate that vacuum deposition at 60-80 
gif">C affords films with remarkably similar microstructuresdespite the extensive H 
gif"> F substitution. Trends in observed d spacing versus molecular core extensionprovide quantitative information on molecular orientation. Field-effect transistor measurements performedfor all systems and having the same device structure, components, and fabrication conditions demonstratethat all nTs functionalized with fluorocarbon chains at the thiophene termini are n-type semiconductors, incontrast to the p-type activity of the remaining systems. One of these systems, gifchars/alpha.gif" BORDER=0>,gifchars/omega.gif" BORDER=0 >-diperfluorohexyl-4T,exhibits a mobility of 0.22 cm2/(V s) and an Ion:Ioff ratio of 106, one of the highest so far reported for ann-type organic semiconductor. The effect of substitution regiochemistry on FET majority charge carrierwas additionally studied, in the case of a 6T core, by shifting the fluorocarbon substituents from the terminalto the central thiophene units. Finally, we propose a simple theoretical model for electrode/organic interfacialcarrier injection. The results suggest why modest substituent-induced changes in the injection barrier canproduce working n-type materials.
gifchars/alpha.gif" BORDER=0>,gifchars/omega.gif" BORDER=0 >- and gifchars/beta2.gif" BORDER=0 ALIGN="middle">,gifchars/beta2.gif" BORDER=0 ALIGN="middle">'-fluorocarbon- and alkyl-substituted and unsubstituted oligothiophenes nTs (n = 2-6) are compared andcontrasted. The thin films were grown by slow vacuum deposition over a range of substrate temperaturesand/or by casting from solution and were investigated by X-ray diffraction and scanning electron microscopy.Our results indicate that vacuum deposition at 60-80 gif">C affords films with remarkably similar microstructuresdespite the extensive H gif"> F substitution. Trends in observed d spacing versus molecular core extensionprovide quantitative information on molecular orientation. Field-effect transistor measurements performedfor all systems and having the same device structure, components, and fabrication conditions demonstratethat all nTs functionalized with fluorocarbon chains at the thiophene termini are n-type semiconductors, incontrast to the p-type activity of the remaining systems. One of these systems, gifchars/alpha.gif" BORDER=0>,gifchars/omega.gif" BORDER=0 >-diperfluorohexyl-4T,exhibits a mobility of 0.22 cm2/(V s) and an Ion:Ioff ratio of 106, one of the highest so far reported for ann-type organic semiconductor. The effect of substitution regiochemistry on FET majority charge carrierwas additionally studied, in the case of a 6T core, by shifting the fluorocarbon substituents from the terminalto the central thiophene units. Finally, we propose a simple theoretical model for electrode/organic interfacialcarrier injection. The results suggest why modest substituent-induced changes in the injection barrier canproduce working n-type materials.