Universal Display Corporation
ORGANIC ELECTROLUMINESCENT MATERIALS AND DEVICES

Abstract:

An OLED is disclosed whose emissive layer has a first host and an emitter, where the emitter is a phosphorescent metal complex that is a Pt(II) or Pd(II) complex having a square planar coordinating geometry or has the formula of M(L.sup.1).sub.x(L.sup.2).sub.y(L.sup.3).sub.z, where E.sub.H1T, the T.sub.1 triplet energy of the first host, is higher than E.sub.ET, the T.sub.1 triplet energy of the emitter, where E.sub.ET is at least 2.50 eV, where the LUMO energy of the first host is higher than the HOMO energy of the emitter, where the absolute value of the difference between the HOMO energy of the emitter and the LUMO energy of the first host is .DELTA.E1, where a.ltoreq..DELTA.E1-E.sub.ET.ltoreq.b; and where a.gtoreq.0.05 eV, and b.ltoreq.0.60 eV.