Influence of Alkyl Side Chain on the Crystallinity and Trap Density of States in Thiophene and Thiazole Semiconducting Copolymer Based Inkjet-Printed Field-Effect Transistors
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- 作者：Jiyoul Lee ; Jong Won Chung ; Jaeman Jang ; Do Hwan Kim ; Jeong-Il Park ; Eunkyung Lee ; Bang-Lin Lee ; Joo-Young Kim ; Ji Young Jung ; Joon Seok Park ; Bonwon Koo ; Yong Wan Jin ; Dae Hwan Kim
- 刊名：Chemistry of Materials
- 出版年：2013
- 出版时间：May 14, 2013
- 年：2013
- 卷：25
- 期：9
- 页码：1927-1934
- 全文大小：531K
- 年卷期：v.25,no.9(May 14, 2013)
- ISSN：1520-5002
文摘
The influence of alkyl side chains on the crystallinity of semiconducting copolymer films and their sub-bandgap density-of-states (DOS), the latter being closely related to the stability and the device performance of organic field-effect transistors (OFETs), is investigated. Three different poly(hexathiophene-alt-bithiazole) (PHTBTz) based polymer semiconductors, with identical backbones but different side chain positions and lengths, were synthesized. The crystallinity examined by grazing incidence X-ray diffraction (GIXRD) strongly depends on the number, position, and length of each type of alkyl side chain attached to the thiophene and thiazole copolymer backbones. Also, the sub-bandgap trap DOS distributions were extracted by performing multiple-frequency capacitance鈥搗oltage (MF-CV) spectroscopy on the field effect devices. The relationship between film crystallinity and trap DOS in the field-effect transistors can be interpreted in terms of the complex interplay between the number, position, and length of each alkyl side chain for efficient 蟺鈥撓€ stacking. In particular, the number and position of the alkyl side chain attached to the polymer backbone significantly affects the device performance. Poly(tetryloctylhexathiophene-alt-dioctylbithiazole) (PHTBTz-C8) exhibits the best electrical performance among the different semiconductors synthesized, with a relatively low bulk trap density of 2.0 脳 1020 cm鈥? eV鈥? as well as reasonable hole mobility of 0.25 cm2 V鈥? s鈥?. The microstructural analyses of this organic material strongly suggest that the short 蟺鈥撓€ stacking distance induces strong interaction between adjacent polymer backbones, which in turn results in enhanced electrical properties.