High triplet energy crosslinkable hole transport material for blue phosphorescent organic light-emitting diodes

A high triplet energy crosslinkable hole transport material was developed for solution processed blue phosphorescent organic light-emitting diodes. A high triplet energy core structure, 3,3-di(9H-carbazol-9-yl)biphenyl, was functionalized with a vinylbenzene crosslinking unit to form the crosslinked hole transport layer. Crosslinking of the hole transport layer at 220 °C produced an insoluble film which is stable under exposure to solvents. A blue emitting layer of iridium(III) bis(2-(4,6-difluorophenyl)-pyridinato-N,C2)picolinate doped diphenyldi(4-(9-carbazolyl)phenyl)silane was spin-coated on the crosslinked hole transport layer without damaging the underlying hole transport layer, which afforded solution processed blue phosphorescent organic light-emitting diodes with an external quantum efficiency of 19.1%.