Compounds exhibiting high hole mobility and/or high glass transition temperatures are provided which are of the formula [Ar1]m[Ar2]n wherein: m is an integer from 1-3 and n is an integer and may be 1 or 2; according to claim 1. The compounds may be used in electron transport layers and may be doped with p-type dopants. They may be incorporated into OLEDs organic photovoltaic devices, imaging members and thin film transistors.