Naphthalene Diimide-Based Polymer Semiconductors: Synthesis, Structure鈥揚roperty Correlations, and n-Channel and Ambipolar Field-Effect Transistors

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• 作者：Xugang Guo ; Felix Sunjoo Kim ; Mark J. Seger ; Samson A. Jenekhe ; Mark D. Watson
• 刊名：Chemistry of Materials
• 出版年：2012
• 出版时间：April 24, 2012
• 年：2012
• 卷：24
• 期：8
• 页码：1434-1442
• 全文大小：519K
• 年卷期：v.24,no.8(April 24, 2012)
• ISSN：1520-5002

文摘

A series of nine alternating donor鈥揳cceptor copolymer semiconductors based on naphthalene diimide (NDI) acceptor and seven different thiophene moieties with varied electron-donating strength and conformations has been synthesized, characterized, and used in n-channel and ambipolar organic field-effect transistors (OFETs). The NDI copolymers had moderate to high molecular weights, and most of them exhibited moderate crystallinity in thin films and fibers. The LUMO energy levels of the NDI copolymers, at 鈭?.9 to 鈭?.8 eV, were constant as the donor moiety was varied. However, the HOMO energy levels could be tuned over a wide range from 鈭?.3 eV in P8 to 鈭?.9 eV in P1 and P3. As semiconductors in n-channel OFETs with gold source/drain electrodes, the NDI copolymers exhibited good electron transport with maximum electron mobility of 0.07 cm²/(V s) in P5. Although head-to-head (HH) linkage induced backbone torsion, polymer P4 showed substantial electron mobility of 0.012 cm²/(V s) in bottom-gate/top-contact device geometry. Some of the copolymers with high-lying HOMO levels (P7 and P8) exhibited ambipolar charge transport in OFETs with high electron mobilities (0.006鈥?.02 cm²/(V s)) and significant hole mobilities (>10^鈥? cm²/(V s)). Varying the device geometry from top-contact to bottom-contact leads to the appearance or enhancement of hole transport in P4, P6, P7, and P8. Copolymers with smaller alkyl side chains on the imide group of NDI have enhanced carrier mobilities than those with bulkier alkyl side chains. These results show underlying structure鈥損roperty relationships in NDI-based copolymer semiconductors while demonstrating their promise in n-channel and ambipolar transistors.

Keywords:

naphthalene diimide copolymer; n-type polymer semiconductor; electron transport; n-channel organic transistor; ambipolar charge transport; donor鈭抋cceptor conjugated copolymer