Conformation-Induced Electrical Bistability in Non-conjugated Polymers with Pendant Carbazole Moieties

详细信息    查看全文

• 作者：Siew Lay Lim ; Qidan Ling ; Eric Yeow Hwee Teo ; Chun Xiang Zhu ; Daniel Siu Hung Chan ; En-Tang Kang ; Koon Gee Neoh
• 刊名：Chemistry of Materials
• 出版年：2007
• 出版时间：October 16, 2007
• 年：2007
• 卷：19
• 期：21
• 页码：5148 - 5157
• 全文大小：713K
• 年卷期：v.19,no.21(October 16, 2007)
• ISSN：1520-5002

文摘

Conformation-induced volatile and nonvolatile conductance switching effects were demonstrated innon-conjugated polymers containing the same electroactive pendant groups. Single-layer devices of thestructure indium-tin-oxide/polymer/aluminum were fabricated from two non-conjugated polymers withpendant carbazole groups in different spacer units. The device based on poly(2-(N-carbazolyl)ethylmethacrylate) (PMCz) exhibited nonvolatile write-once-read-many-times (WORM) memory behavior withan ON/OFF current ratio up to 10⁶, while the device based on poly(9-(2-((4-vinylbenzyl)oxy)ethyl)-9H-carbazole) (PVBCz) exhibited volatile memory behavior with an ON/OFF current ratio of approximately10³. The formation of carbazole excimers resulting from conformation-induced conductance switchingunder an electric field was revealed in situ by fluorescence spectroscopy. The corresponding voltage-induced conformation ordering in the polymer film was captured by transmission electron microscopy.In the absence of a spacer unit between the pendant carbazole group and the main chain, regioregularpoly(N-vinylcarbazole) (PVK) exhibited only one conductivity state (ON state). The differences in memorybehavior among the three polymers were attributed to their inherent differences in the degree ofregioregularity and ease of conformational relaxation of the field-induced regioregular carbazole groups.These conformational effects were in turn dictated by the chemical structure and steric effect of thespacer unit between the pendant carbazole group and the main chain.