TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preparation: No preparation method is given. Preferred Components: The organic layer is deposited using solution processing. The organic layer is an emissive layer and (I) is a host. The organic layer further comprises an emissive dopant, which is (tris(2-phenyl-pyridine)) iridium, (tris(4-methyl-2-phenyl-pyridine)) iridium, (tris(5-methyl-2-phenyl-pyridine)) iridium, (tris(2-p-tolyl-pyridine)) iridium, (tris(3-methyl-2-phenyl-pyridine)) iridium, (tris(2-biphenyl-3-yl-pyridine)) iridium, (tris(2-biphenyl-3-yl-4-methyl-pyridine)) iridium, (tris(2-biphenyl-3-yl-3-methyl-pyridine)) iridium, (tris(2-biphenyl-3-yl-3,4-dimethyl-pyridine)) iridium, (tris(2-biphenyl-3-yl-5-methyl-pyridine)) iridium, (tris(2-biphenyl-4-yl-pyridine)) iridium, (bis(2-phenyl-pyridine)(2-biphenyl-3-yl-pyridine)) iridium, (bis(2-phenyl-pyridine)(2-biphenyl-3-yl-4-methyl-pyridine)) iridium, (bis(2-phenyl-pyridine)(2-biphenyl-3-yl-5-methyl-pyridine)) iridium, (bis(2-phenyl-pyridine)(2-biphenyl-4-yl-pyridine)) iridium, (bis(2-phenyl-pyridine)(2-biphenyl-4-yl-5-methyl-pyridine)) iridium, (bis(2-phenyl-pyridine)(2-biphenyl-4-yl-4-methyl-pyridine)) iridium, (bis(2-phenyl-pyridine)(4-methyl-2,5-diphenyl-pyridine)) iridium, (bis(2-methyl-6-phenyl-pyridine)(4-methyl-2,5-diphenyl-pyridine)) iridium, (bis(2-phenyl-pyridine)(2-phenyl-5-o-tolyl-pyridine)) iridium, (bis(2-phenyl-pyridine)(2,5-diphenyl-pyridine)) iridium, (bis(2-methyl-6-phenyl-pyridine)(2,5-diphenyl-pyridine)) iridium, (bis(2-phenyl-pyridine)(1,3-di(pyridin-2-yl)benzene)) iridium, (bis(2-phenyl-pyridine)(2-(3-(pyridin-2-yl)phenyl)pyrimidine)) iridium, (bis(2-phenyl-pyridine)(2,4-diphenyl-pyridine)) iridium, (bis(2-methyl-6-phenyl-pyridine)(2,4-diphenyl-pyridine)) iridium, (bis(2-phenyl-pyridine)(2'-phenyl-(2,4')bipyridinyl)) iridium, ((2-phenyl-pyridine)bis(4-methyl-2,5-diphenyl-pyridine)) iridium, (bis(2-phenyl-pyridine)(4-ethyl-2,5-diphenyl-pyridine)) iridium, ((2-phenyl-pyridine)bis(4-ethyl-2,5-diphenyl-pyridine)) iridium, (bis(2-phenyl-pyridine)(2-dibenzofuran-4-yl-pyridine)) iridium, (bis(2-phenyl-pyridine)(2-dibenzothiophen-4-yl-pyridine)) iridium, (bis(2-phenyl-pyridine)(2-dibenzofuran-3-yl-pyridine)) iridium, (bis(1-phenyl-isoquinoline)(2,4-dioxo)pent-3-ene)) iridium, (tris(1-phenyl-isoquinoline)) iridium, (bis(2-phenyl-quinoline)(2,4-dioxo)pent-3-ene)) iridium, (bis(1-phenyl-benzo(4,5)thieno(2,3-c)pyridine)(2,4-dioxo)pent-3-ene)) iridium, (bis(1-(3,5-dimethyl-phenyl)-benzo(4,5)thieno(2,3-c)pyridine)(2,4-dioxo)pent-3-ene)) iridium, (bis(3-methyl-2-phenyl-quinoline)(2,4-dioxo)pent-3-ene)) iridium, (bis(2-(3,5-dimethyl-phenyl)-quinoline)(2,4-dioxo)pent-3-ene)) iridium, (bis(7-methyl-2-m-tolyl-quinoline)(2,4-dioxo)pent-3-ene)) iridium, (bis(2-(3,5-dimethyl-phenyl)-7-isobutyl-quinoline)(2,4-dioxo)pent-3-ene)) iridium, (bis(2-(3,5-dimethyl-phenyl)-quinoline)((4,6-dioxo-2,8-dimethyl)non-4-ene)) iridium, (bis(2-(3,5-dimethyl-phenyl)-7-isobutyl-quinoline)((4,6-dioxo-2,8-dimethyl)non-4-ene)) iridium, (bis(1-(3,5-dimethyl-phenyl)-isoquinoline)(2,4-dioxo)pent-3-ene)) iridium, (bis(1-(3,5-dimethyl-phenyl)-7-isopropyl-isoquinoline)(2,4-dioxo)pent-3-ene)) iridium or (bis(1-(3,5-dimethyl-phenyl)-7-isopropyl-isoquinoline) ((4,6-dioxo-2,8-dimethyl)non-4-ene)) iridium. Preferred Definitions:    Ar1-Ar3 = phenyl, pyridine, naphthalene, biphenyl, terphenyl, fluorene, dibenzofuran, dibenzothiophene, phenanthrene or triphenylene (all optionally substituted with H, alkyl, alkoxy, amino, alkenyl, alkynyl or (hetero)aryl, where the substituent is not an (hetero)aryl fused directly to Ar1, Ar2 and Ar3); and    R1-R4 = H.    SPECIFIC COMPOUNDS - 184 Compounds (I) are specifically claimed e.g. 9-(4,6-diphenyl-(1,3,5)triazin-2-yl )-9'-phenyl-9H,9'H-(3,3')bicarbazolyl of formula (Ia), 9'-biphenyl-4-yl-9-(4,6-diphenyl-(1 ,3,5)triazin-2-yl)-9H,9'H-(3,3')bicarbazolyl, 9-(4,6-diphenyl-(1,3,5)triazin-2-yl )-9'-(1,1';3',1'')terphenyl-5'-yl-9H,9'H-(3,3')bicarbazolyl, 9'-dibenzofuran-4-yl-9-(4,6-dipheny l-(1,3,5)triazin-2-yl)-9H,9'H-(3,3')bicarbazolyl and 9'-dibenzothiophen-4-yl-9-(4,6-diph enyl-(1,3,5)triazin-2-yl)-9H,9'H-(3,3')bicarbazolyl.    EXAMPLE - Solution of 9H-carbazole (5.57 g) and potassium iodide (3.68 g) in acetic acid (92 ml) was heated to 100 degrees C for 1 hour. Potassium iodate (3.57 g) was added in portions to the solution, and the resulting mixture was stirred for another 2 hours at 100 degrees C. The mixture was poured into water (500 ml) and worked up to give 3-iodo-9H-carbazole (A). To a solution of 3-bromo-9-phenyl-9-carbazole (20.3 g) in tetrahydrofuran (150 ml) at -78 degrees C was added n-butyllithium (1.6M in hexane) (47.25 ml). The mixture was stirred at -78 degrees C for 1 hour. 2-isopropoxy-4,4,5,5-tetramethyl-(1,3,2)-dioxaborolane (21 ml) was added to the solution, and the resulting mixture was warmed, stirred for 8 hours and worked up to give 9-phenyl-3-(4,4,5,5-tetramethyl-1,3,2-dioxoborolan-2-yl)-9H-carbazole (B). A solution of (A) (879 mg), tetrakis(triphenylphosphine)palladium (165 mg), (B) (1.29 g) and potassium phosphate (1.8 g) in dioxane (5 ml) was heated to 85 degrees C with vigorous stirring for 48 hours under argon atmosphere. The mixture was poured into water and extracted with dichloromethane and the organic extracts were washed with brine and dried over magnesium sulfate and worked up to give 3-(9-phenyl-9H-carbazol-3-yl)-9H-carbazole (C). A solution of sodium hydride (100 mg) and (C) (816 mg) in dry dimethyl formamide (40 ml) was stirred for 1 hour under argon atmosphere. 2-Chloro-4,6-diphenyl-1,3,5-triazine (448 mg) was added to the solution, then refluxed overnight. The mixture was poured into water and the precipitation was collected by filtration and washed with water, methanol and dichloromethane to give 9-(4,6-diphenyl-(1,3,5)triazin-2-yl )-9'-phenyl-9H,9'H-(3,3')bicarbazolyl (75%).