TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: The first host compound is at least 10% deuterated. The second host is: carbazole, indolocarbazole, chrysene, phenanthrene, triphenylene, phenanthroline, triazine, naphthalene, anthracene, quinoline, isoquinoline, quinoxaline, phenylpyridine, benzodifuran, metal quinolinate complex or their deuterated analogs; substituted amine of formula (Ar4-N(Ar4)-Q(-N(Ar4)2)m); or substituted indole of formula (II).Ar4 = aryl;Q = multivalent aryl or substituted phenyl of formula (III), preferably chrysene, phenanthrene, triphenylene, phenanthroline, naphthalene, anthracene, quinoline, isoquinoline or their deuterated analogs;T1 = (CRa)g, SiR2, S, SO2, PRb, PO, PO2, BR or Rb;Rb = alkyl, aryl, silyl or their deuterated analogs;Ra = H, deuterium, alkyl or silyl;Q1 = fused ring linkage comprising substituted phenyl of formula (IV);R3 = deuterium, alkyl, aryl, silyl, alkoxy, aryloxy, cyano, styryl, vinyl or allyl; eitherR4 = H, deuterium, alkyl, hydrocarbyl aryl or styryl; orR4R4 = N-heterocyclyl;R5 = alkyl, aryl, silyl, alkoxy, aryloxy, cyano, styryl, vinyl or allyl;p = 0-4;g = 1-6; andm = 0-6.The dopant is a luminescent organometallic complex which is a cyclometalated complex of iridium or platinum. Preferred Definitions:    Ar1, Ar2, Ar3 = phenyl, naphthyl (optionally substituted), styryl, carbazolyl, N-, O- S- heterocyclyl, biphenyl, terphenyl, naphthyl phenyl, phenyl naphthyl, N-carbazolyl, their deuterated analogs or a substituted phenyl moiety of formula (V); either    R1, R2 = deuterium, alkyl, aryl, silyl, alkoxy, aryloxy, cyano, vinyl, allyl or their deuterated analogs; or    R1R2 = 6 membered aromatic ring;    a, b, c, d = 0-5; and    e = 0 or 1.    Provided that: when a is 5, d and e are 0; and when b is 5, e is 0.    EXAMPLE - Typical composition comprised (in wt.%) of: tris (3-fluoro-2-(3-fluorophenyl)-5-methylpyridine) iridium (III) complex (16 wt.%); 2,4,6-tris(3'-(3,6-diphenyl-9H-carbazol-9-yl)-2-methylbiphenyl-4-yl)-1,3,5-triazine (49 wt.%); and 5,12-dihydro-5,12-bis(3'-phenylbiphenyl-3-yl)-indolo(3,2-a)carbazole (35 wt.%).