A new thermally crosslinkable hole injection material for OLEDs

A new thermal cross-linkable hole injection monomer VB-DATA derived from famous m-MTDATA as core peripherally functionalized with styryl (vinylbenzene) moiety as polymerizable group has been synthesized and characterized. The propensity of VB-DATA thin films formation is sensitive to the nature of solvent, in which the dichloroethane solution gave smooth polymeric thin films with surface roughness of RMS ∼0.84nm by spin-casting followed by thermal treatment at 190°C. The introduction of oxygen-linked vinylbenzene group shifted HOMO energy level of VB-DATA to −5.1eV along with good nondispersive hole transport property (μh∼10–6cm2V–1s–1) makes it suitable for serving as HIL on top of ITO electrode. The replacement of PEDOT:PSS by thermally cross-linked VB-DATA films showed comparable OLEDs performance, giving more flexibility on material selection for future OLEDs applications, especially solution-processed ones.