Building Blocks for n-Type Molecular and Polymeric Electronics. Perfluoroalkyl- versus Alkyl-Functionalized Oligothiophenes (nT; n = 2−6). Systematics of Thin Film Microstructure, Semiconductor Performance, and Modeling of Majority Charge Injection in Field-Effect Transistors
| Autor: | Melissa Mushrush, Mark A. Ratner, Geoffrey R. Hutchison, Myung-Han Yoon, Antonio Facchetti, Tobin J. Marks |
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| Rok vydání: | 2004 |
| Předmět: |
chemistry.chemical_classification
Chemistry Scanning electron microscope business.industry General Chemistry Substrate (electronics) Biochemistry Catalysis Crystallography chemistry.chemical_compound Colloid and Surface Chemistry Semiconductor Vacuum deposition Thiophene Organic chemistry Field-effect transistor Thin film business Alkyl |
| Zdroj: | Journal of the American Chemical Society. 126:13859-13874 |
| ISSN: | 1520-5126 0002-7863 |
| DOI: | 10.1021/ja0489846 |
| Popis: | The solid-state properties and FET electrical behavior of several series of alpha,omega- and beta,beta'-fluorocarbon- and alkyl-substituted and unsubstituted oligothiophenes nTs (n = 2-6) are compared and contrasted. The thin films were grown by slow vacuum deposition over a range of substrate temperatures and/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 degrees C affords films with remarkably similar microstructures despite the extensive H --F substitution. Trends in observed d spacing versus molecular core extension provide quantitative information on molecular orientation. Field-effect transistor measurements performed for all systems and having the same device structure, components, and fabrication conditions demonstrate that all nTs functionalized with fluorocarbon chains at the thiophene termini are n-type semiconductors, in contrast to the p-type activity of the remaining systems. One of these systems, alpha,omega-diperfluorohexyl-4T, exhibits a mobility of 0.22 cm2/(V s) and an Ion:Ioff ratio of 10(6), one of the highest so far reported for an n-type organic semiconductor. The effect of substitution regiochemistry on FET majority charge carrier was additionally studied, in the case of a 6T core, by shifting the fluorocarbon substituents from the terminal to the central thiophene units. Finally, we propose a simple theoretical model for electrode/organic interfacial carrier injection. The results suggest why modest substituent-induced changes in the injection barrier can produce working n-type materials. |
| Databáze: | OpenAIRE |
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