An OLED device comprises a cathode and an anode and has located therebetween a light-emitting layer comprising a phosphorescent light-emitting material and a host comprising a compound of a tetravalent atom wherein the four groups bonded to the atom are aromatic rings, at least one of which contains an electron-withdrawing group (EWG) substituent comprising at least three atoms, the compound having a triplet energy of at least 2.7 eV and a LUMO energy within 0.6 eV of the LUMO energy of at least one material in an adjacent layer on the cathode side of the light-emitting layer. Particular embodiments include certain tetravalent silicon compounds. The light-emitting layer emits blue light and provides good luminance and reduced drive voltage.