Thermally Cross-Linkable Hole-Transporting Materials on Conducting Polymer: Synthesis, Characterization, and Applications for Polymer Light-Emitting Devices

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• 作者：Yen-Ju Cheng ; Michelle S. Liu ; Yong Zhang ; Yuhua Niu ; Fei Huang ; Jae-Won Ka ; Hin-Lap Yip ; Yanqing Tian ; Alex K.-Y. Jen
• 刊名：Chemistry of Materials
• 出版年：2008
• 出版时间：January 22, 2008
• 年：2008
• 卷：20
• 期：2
• 页码：413 - 422
• 全文大小：626K
• 年卷期：v.20,no.2(January 22, 2008)
• ISSN：1520-5002

文摘

A series of novel hole-transporting materials (HTMs) bearing thermally cross-linkable styryl groups have been synthesized and characterized. These HTMs could be in situ cross-linked under mild thermal polymerization without any initiator. The cross-linking temperatures (150–180 °C) for these HTMs are substantially lower than that typically used for curing perfluorocyclobutane (PFCB)-based HTMs (230 °C). After cross-linking, the resultant HTMs form robust, smooth, and solvent-resistant networks, which enables the subsequent spin-coating of emissive layer (EML). The HTMs based on an ether linkage connecting triarylamine dimers exhibited better hole-transporting ability compared to their corresponding monotriarylamine compounds due to higher content and closer distance of the hole-transporting units. Most importantly, the milder cross-linking condition for these HTMs allows the commonly used conducting polymer, poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS), to be incorporated as the bottom hole-injecting layer to improve turn-on voltage and power efficiency of the devices. This PEDOT/HTM double-layer hole-injecting/hole-transporting configuration also provides the combined advantages of preventing acidic PEDOT:PSS-induced quenching of emission, facilitating cascade hole injection and transport, and functioning as an efficient electron blocker. One of the devices that combines 2-NPD with PEDOT:PSS showed much improved performance of low turn-on voltage (3.3 V), high luminous efficiency (10.8 cd/A), and brightness (21 500 cd/m²).