Crosslinkable branched hydrazones as hole transporting materials

Abstract

The new hole transport materials which comprise molecules consisting of two hydrazone branches linked by a central bridge containing a flexible thiophenyl sulfide and two hydroxyl groups were synthesized and investigated. These transporting materials are low molecular weight glasses and allow preparation of layers stable to crystallization. Ionization potential of the materials is in the range 5.03-5.38 eV. The highest hole mobility, reaching 10-4 cm2/Vs at 6 × 105 V/cm electric field, was observed in the transport material with dimethyltriphenylamine or triphenylamine moieties. These transport materials can be used with or, in the case of a solid substrate, without polymer binder. They can be chemically crosslinked in the layer by reaction of the hydroxyl groups with polyisocyanates.