NOVELTY - Fused (hetero)aryl compounds (I), are new.    USE - (I) or the oligomers, polymers or dendrimers are useful: in an electronic device, which is organic electroluminescent devices, organic integrated circuits, organic field-effect transistors, organic thin film transistors, organic light emitting transistors, organic solar cells, organic optical detectors, organic photoreceptors, organic field-quench devices, light-emitting electrochemical cells and organic laser diodes; as matrix material in an emitting layer, which contains one or more phosphorescent emitter; as a hole transport material, a hole transport layer and/or in a hole injection layer; and as an emitting material in an emitting layer (all claimed).    ADVANTAGE - (I): provide organic light emitting diodes with a long operational life, good efficiency and low operating voltage; and exhibit high thermal stability and high glass transition temperature and can be sublimed without decomposition.    DETAILED DESCRIPTION - Fused (hetero)aryl compounds of formula (I), are new.    X = N (preferred), P or P=O;    Y1, T = C(R1)2, C=O, C=NR1, O, S, SO, SO2, PR1, POR1, NAr11, NR1 or a single bond, provided that at least one Y1 is a single bond;    A = Ar3 or X (Ar4)2, where the bonding to the group T proceeds from (hetero)aryl ring of the group Ar3 or Ar4, and both the groups Ar4 of X(Ar4)2 are bonded together over a group T;    Ar11, Ar1-Ar4 = 5-30 membered (hetero)aryl ring atoms (optionally substituted with one or more R2);    R1, R2 = H, D, F, Cl, Br, I, CHO, NAr112, N(R3)2, C(=O)R3, P(=O)(R3)2, S(=O)R3, S(=O)2R3, C(R3)=C(R3)2, CN, NO2, Si(R3)3, B (OR3)2, OSO2R3 or OH, or linear 1-40C-(thio)alkyl or -alkoxy, branched or cyclic 3-40C-(thio)alkyl or -alkoxy or 2-40C-alkenyl or -alkynyl (all optionally substituted by one or more R3, where one or more non-adjacent CH2-groups are optionally replaced by R3C=CR3, CC, Si(R3)2, Ge(R3)2, Sn(R3)2, C=O, C=S, C=Se, C=NR3, P(=O)(R3), SO, SO2, NR3, O, S or CONR3, and one or more H-atoms are replaced by D, F, Cl, Br, I, CN or NO2), or 5-60 membered mono- or polycyclic (hetero)aromatic ring system and/or 5-60 membered (hetero)aryloxy (both optionally substituted by one or more R3); either    R3 = H, D, F, Cl, Br, I, CHO, NAr112, N(R4)2, C(=O)R4, P(=O)(R4)2, S(=O)R4, S(=O)2R4, C(R4)=C(R4)2, CN, NO2, Si(R4)3, B (OR4)2, OSO2R4 or OH, or linear 1-40C-(thio)alkyl or -alkoxy, branched or cyclic 3-40C-(thio)alkyl or -alkoxy or 2-40C-alkenyl or -alkynyl (all optionally substituted by one or more R3, where one or more non-adjacent CH2-groups are optionally replaced by R4C=CR4, CC, Si(R4)2, Ge(R4)2, Sn(R4)2, C=O, C=S, C=Se, C=NR4, P(=O)(R4), SO, SO2, NR4, O, S or CONR4, and one or more H-atoms are replaced by D, F, Cl, Br, I, CN or NO2), or 5-60 membered mono- or polycyclic (hetero)aromatic ring system and/or 5-60 membered (hetero)aryloxy (both optionally substituted by one or more R4); or    two or more R3 bonded together = mono- or polycyclic, aliphatic or aromatic ring system; either    R4 = H, D, F or 1-20C-aliphatic or (hetero)aromatic organic radical, in which one or more H atoms are optionally replaced by F; or    two or more R4 bonded together = mono-or polycyclic, aliphatic or aromatic ring system; and    m, n = 0 or 1, where the sum of all values for m or n is greater than or equal to 1.    INDEPENDENT CLAIMS are included for:    (1) the preparation of (I); and    (2) oligomers, polymers or dendrimers containing one or more (I).