The invention provides a host material for organic light emitting diodes, having the general formula: ##STR00001## wherein R.sub.1 is selected from a C.sub.1-8 alkyl group, each R.sub.2 is independently selected from a hydrogen or a C.sub.1-8 alkyl group, Ar is selected from a C.sub.5-14 aromatic or hetero aromatic group, R.sub.3 is selected from a C.sub.5-14 aromatic or hetero aromatic group, a C.sub.1-8 alkyl group, a C.sub.5-8 cycloalkyl group, a C.sub.1-8 fluoroalkyl group, or a C.sub.1-8 alkoxyl group, and n is an integer of 1-10. The host materials have a higher energy gap (greater than 4.0 eV), and high thermal stability.