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

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 b...