Thermally cross-linkable hole-transporting materials on conducting polymer: Synthesis, characterization, and applications for polymer light-emitting devices

Yen Ju Cheng, Michelle S. Liu, Yong Zhang, Yuhua Niu, Fei Huang, Jae Won Ka, Yanqing Tian, Alex K.Y. Jen

Research output: Contribution to journalArticle

100 Scopus citations

Abstract

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).

Original languageEnglish (US)
Pages (from-to)413-422
Number of pages10
JournalChemistry of Materials
Volume20
Issue number2
DOIs
StatePublished - Jan 22 2008

ASJC Scopus subject areas

  • Chemistry(all)
  • Chemical Engineering(all)
  • Materials Chemistry

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