Disclosed is a useful electroluminescent device comprising a cathode, an anode, and therebetween a light emitting layer containing a host material and a phosphorescent light-emitting material wherein the host material is represented by formula (1): X′-A-X″  (1) wherein: A is selected from the group consisting of an unsubstituted phenylene ring, a biphenylene group, a terphenylene group, a naphthylene group, and a fluorene group; and each of X′ and X″ is an independently selected aromatic group bearing an ortho aromatic substituent.