TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preparation: No preparation method is given.    TECHNOLOGY FOCUS - POLYMERS - Preferred Components: The organic thin layer is an electron transport layer, an electron injection layer and/or an emission layer (130) (all preferred), a hole transport layer, a hole injection layer and/or a hole blocking layer. Preferred Definitions:    Ar3 = 4-carbazol-9-yl-phenyl, 4'-carbazol-9-yl-biphenyl-4-yl, phenyl, 4-biphenyl, 4,6-diphenyl-3,4-dihydro-pyridin-2-yl, 2,4-diphenyl-1,2-dihydro-(1,3,5)triazin-6-yl, 9-phenyl-9H-carbazol-3-yl or 9,9'-spirobi(fluorene)-3-yl.    SPECIFIC COMPOUNDS - 70 Compounds (I) are specifically claimed e.g. 1,3-bis(9H-carbazol-9-yl)-9-phenyl-9H-carbazole of formula (Ia), 9'-(4-carbazol-9-yl-phenyl)-9'H-(9,1';3',9'')tercarbazole, 9'-(4-carbazol-9-yl-phenyl)-6'-phenyl-9'H-(9,1';4',9'')tercarbazole, 9'-(4'-carbazol-9-yl-biphenyl-4-yl)-9'H-(9,1';4',9'')tercarbazole and 9'-(4'-carbazol-9-yl-biphenyl-4-yl)-6'-phenyl-9'H-(9,1';4',9'')tercarbazole.    EXAMPLE - 9-(3-boryl-5-(9H-carbazol-9-yl)phenyl)-9H-carbazole (5 g), ortho-nitro-boronic ester (2.5 g), tetrakis-(triphenylphosphine)palladium (1.15 g) and potassium carbonate (1.38 g) were refluxed in toluene (100 ml) and water (20 ml) for 12 hours. The reaction fluid was worked up to give 9-(3-(9H-carbazol-9-yl)-5-(2-nitrophenyl)phenyl)-9H-carbazole. 9-(3-(9H-carbazol-9-yl)-5-(2-nitrophenyl)phenyl)-9H-carbazole (4 g) and triphenylphosphine (3.96 g) were refluxed with dichlorobenzene (40 ml) for 48 hours. The reaction fluid was worked up to give 9-(3-(9H-carbazol-9-yl)-9H-carbazol-1-yl)-9H-carbazole. 9-(3-(9H-carbazol-9-yl)-9H-carbazol-1-yl)-9H-carbazole (3 g), bromobenzene (0.94 g) and copper chloride (59 mg) were refluxed with of toluene (100 ml) for 24 hours. After separating the reaction fluid into 2 layers, the organic layer was washed with a saturated sodium chloride aqueous solution and dried with anhydrous sodium sulfate. The organic solvent was removed by distillation under reduced pressure, and then the residue was recrystallized with methanol to provide a crystal. The crystal was separated by filtration and washed with toluene to give 1,3-bis(9H-carbazol-9-yl)-9-phenyl-9H-carbazole (2.68 g, yield: 78%).