Electroluminescent devices including organic eil layer

An OLED device comprising a cathode, an anode, and having therebetween a light emitting layer (LEL) comprising a phosphorescent emitting compound disposed in a host comprising a mixture of at least one electron transporting co-host represented by

• wherein:
• m is an integer from 0 to 5;
• each x is an integer from 0 to 4;
• y is an integer from 0 to 3;
• R2 and R3 are independently selected from hydrogen;
• alkyl of from 1 to 24 carbon atoms, aryl or hetero-atom substituted aryl of from 5 to 20 carbon atoms, halo, or atoms necessary to complete a fused aromatic ring;
• and at least one hole transporting co-host which is a triphenylamine containing only one nitrogen atom;
• wherein the phosphorescent emitting compound is:
• wherein
• A is a substituted or unsubstituted heterocyclic ring containing at least one N atom;
• B is a substituted or unsubstituted aromatic or heteroatomic ring, or a ring containing a vinyl carbon bonded to M;
• X—Y is an anionic bidentate ligand;
• m is an integer from 1 to 3 and n is an integer from 0 to 2 such that the sum of m and n is 3;
• and
• M is Ir;
• wherein there is present an electron transporting layer contiguous to the LEL on the cathode side and
• wherein there is present an electron-injection layer (EIL) containing a heteroaromatic compound contiguous to the cathode;
• wherein the electron transporting layer comprises an aromatic hydrocarbon material selected from:
• an anthracene represented by:
• wherein
• Ar9 and Ar10 independently represent an aryl group;
• v1, v2, v3, v4, v5, v6, v7, and v8 independently represent hydrogen or a substituent;
• and
• a fluoranthene represented by:
• wherein
• each R1 is independently selected from alkyl, aryl, and heteroaryl groups;
• R2 through R7 are independently selected from H, alkyl, phenyl, cyano and alkoxy groups;
• and
• n is an integer selected from 0 to 4;
• wherein the electron-injection layer comprises a heteroaromatic compound selected from:
• wherein
• each R5 is independently selected from hydrogen, alkyl, aryl groups and at least one of R5 is aryl or substituted aryl;
• and
• wherein
• M is Li;
• R8 and R9 are independently selected substituent groups, provided adjacent substituents may combine to form ring groups;
• h and i are independently integers from 0 to 3;
• and
• j is an integer from 1 to 6.