TECHNOLOGY FOCUS - ELECTRONICS - Preferred Components: The emitting layer comprises (I) as host material in combination with a phosphorescent emitter.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preparation (Claimed): Preparation of (I) comprises: heating 1-(2-amino-phenyl)-1,3-dihydro-benzoimidazol-2-one in phosphoric acid, polyphosphoric acid, methanesulfonic acid/phosphorus pentoxide, methanesulfonic acid or sulfuric acid to obtain 9H-4b,9,10-triaza-indeno(1,2-a)indene (XI); and reacting (XI) to give substituted 4H-imidazo(1.2-a)imidazole compounds of formula (II) (representative of (I)).R2-R5, R11-R14 = H. Preferred Definitions:    A1-A4 = benzen-1,3-diyl, dibenzo(b,d)furan-2,8-diyl, 9H-carbazol-3,9-diyl, substituted 9H-carbazole moiety of formula (a), 9,9'-spirobi(fluorene)-4,4'-diyl, dibenzo(b,d)furan-2,6-diyl, dibenzo(b,d)furan-2,4-diyl, dibenzo(b,d)furan-4,6-diyl, (dibenzo(b,d)furan-2-yl)-benzen-1,3-diyl or dibenzo(b,d)furan-4-yl)-benzen-1,3-diyl;    R6 = carbazol-9-yl, 4b,9,10-triaza-indeno(1,2-a)inden-9-yl, triphenylsilyl or substituted 9H-cabazole moiety of formula (b); and    R15, R16 = 6-18C aryl (optionally substituted by at least one 1-8C alkyl).    SPECIFIC COMPOUNDS - 26 Compounds (I) are specifically claimed e.g. 9-(8-(3-benzimidazolo(1,2-a)benzimidazole-phenyl)-dibenzofuran-2-yl)-benzimidazolo(1,2-a)benzimidazole of formula (Ia), 9-(8-(3-carbazol-9-yl-phenyl)-dibenzofuran-2-yl)-benzimidazolo(1,2-a)benzimidazole, 9-(3-(8-carbazol-9-yl-dibenzofuran-2-yl)-phenyl)- benzimidazolo(1,2-a)benzimidazole, 9-(6-(8-benzimidazolo(1,2-a)benzimidazole-dibenzofuran-2-yl)-9-phenyl-9H-carbazol-3-yl)-benzimidazolo(1,2-a)benzimidazole and 9-(6-(8-carbazol-9-yl-dibenzofuran-2-yl)-9-phenyl-9H-carbazol-3-yl)-benzimidazolo(1,2-a)benzimidazole.    EXAMPLE - 9-(3-Bromo-phenyl)-benzimidazolo(1,2-a)benzimidazole (5.78 g), 4,4,5,5-tetramethyl-2-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-1,3,4-dioxaborolane, potassium acetate (12.5 g) in dimethylformamide (50 ml) were degassed with argon. 1,1-Bis(diphenylphosphino)ferrocene)dichloride-palladium(II) were added and the reaction mixture was degassed with argon. The reaction mixture was stirred for 22 hours at 60 degrees C and poured into a saturated solution of sodium chloride in water and worked up to give 5-(3-(4,4,5,5-tetramethyl-1,3,3-dioxaborolan-2-yl)phenyl)benzimidazolo(1,2-a)benzimidazole (A2). 5-(8-Bromodibenzofuran-2-yl)benzimidazolo(1,2-a)benzimidazole (2.72 g) and potassium phosphate tribasic monohydrate (6.92 g), dioxane (27 ml), toluene (100 ml) and water (21 ml) were added to (A2) (3.2 g). The mixture was degassed with argon. 2-Dicyclohexylphosphino-2',6'-dimethoxybiphenyl and palladium(II) acetate (135 mg) were added. The reaction mixture was degassed with argon and was stirred for 22 hours at 100 degrees C under argon. 1% Sodium cyanide solution (110 ml) were added and the reaction mixture was refluxed for 1 hour. Dichloromethane was added, the organic phase was washed with water and dried with magnesium sulfate. The product was decocted with methanol to give 9-(8-(3-benzimidazolo(1,2-a)benzimidazole-phenyl)-dibenzofuran-2-yl)-benzimidazolo(1,2-a)benzimidazole (1.62 g, 41%).