Thin Film Transistors Based on Alkylphenyl Quaterthiophenes: Structure and Electrical Transport Properties
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- 作者：Sandra E. Fritz ; Siddharth Mohapatra ; Brian T. Holmes ; Amelia M. Anderson ; Cathal F. Prendergast ; C. Daniel Frisbie ; Michael D. Ward ; Michael F. Toney
- 刊名：Chemistry of Materials
- 出版年：2007
- 出版时间：March 20, 2007
- 年：2007
- 卷：19
- 期：6
- 页码：1355 - 1361
- 全文大小：316K
- 年卷期：v.19,no.6(March 20, 2007)
- ISSN：1520-5002
文摘
Thin films based on the akylphenyl-substituted quaterthiophenes 5,5' ''-bis(4-methylphenyl)-2,2':5',2' ':5' ',2' ''-quaterthiophene (1), 5,5' ''-bis(4-n-propylphenyl)-2,2':5',2' ':5' ',2' ''-quaterthiophene (2), and 5,5' ''-bis(4-hexylphenyl)-2,2':5',2' ':5' ',2' ''-quaterthiophene (3) were grown by vacuum deposition on thermallygrown SiO2 substrates and characterized in a thin film transistor (TFT) configuration. Atomic forcemicroscopy and specular (
-2) X-ray diffraction (XRD) revealed films with small, crystalline grains,in which the oligothiophenes were oriented "end-on" with respect to the SiO2 substrate. Interplanar spacingincreased (1 = 28.0 Å, 2 = 29.5 Å, 3 = 37.7 Å), consistent with increasing alkyl tail length. Grazingincidence X-ray diffraction (GIXD) of the films (ca. 350 Å thick) revealed nearly equivalent in-planeunit-cell areas (1 = 44.1 Å2, 2 = 44.4 Å2, 3 = 43.8 Å2). The films functioned as p-channel semiconductorsin a TFT configuration, exhibiting nearly equivalent hole mobilities (
0.05 ± 0.01, 0.04 ± 0.01, 0.06± 0.01 cm2/Vs for 1, 2, and 3, respectively). Variable-temperature measurements demonstrated that theactivation energy of the mobility for thin films of 3 was ~55 meV. The increasing alkyl chain lengthdoes not appear to improve molecular ordering; however, the addition of a phenyl end-substituent appearsto greatly improve the on-to-off ratio in TFTs.
-2) X-ray diffraction (XRD) revealed films with small, crystalline grains,in which the oligothiophenes were oriented "end-on" with respect to the SiO2 substrate. Interplanar spacingincreased (1 = 28.0 Å, 2 = 29.5 Å, 3 = 37.7 Å), consistent with increasing alkyl tail length. Grazingincidence X-ray diffraction (GIXD) of the films (ca. 350 Å thick) revealed nearly equivalent in-planeunit-cell areas (1 = 44.1 Å2, 2 = 44.4 Å2, 3 = 43.8 Å2). The films functioned as p-channel semiconductorsin a TFT configuration, exhibiting nearly equivalent hole mobilities ( 0.05 ± 0.01, 0.04 ± 0.01, 0.06± 0.01 cm2/Vs for 1, 2, and 3, respectively). Variable-temperature measurements demonstrated that theactivation energy of the mobility for thin films of 3 was ~55 meV. The increasing alkyl chain lengthdoes not appear to improve molecular ordering; however, the addition of a phenyl end-substituent appearsto greatly improve the on-to-off ratio in TFTs.