NOVELTY - Fused (hetero)aryl compounds (A) are new.    USE - (A) or the oligomers, polymers or dendrimers are useful: in an electronic device, preferably an organic electroluminescent device, where the electronic devices are integrated organic electroluminescent devices, organic field-effect transistors, organic thin film transistors, organic light emitting transistors, organic integrated circuits, organic solar cells, organic field-quench devices, light-emitting electrochemical cells, organic laser diodes and organic photoreceptors; and as matrix material for phosphorescent dopant or as electron transport material (all claimed).    ADVANTAGE - (A) provide organic electroluminescent device with improved durability, efficiency and operating voltage.    DETAILED DESCRIPTION - Fused (hetero)aryl compounds (A) of formulae (I) and (II) are new.    Ar1-Ar3=5-60 membered (hetero)aromatic ring system (optionally substituted with one or more R1);    HetAr=5-60 membered heteroaryl (optionally substituted with one or more RHet);    Cz=a group of formula (a1), in which dotted lines represent possible bonding positions to Ar1 or X, or the central carbazole derivatives, and the nitrogen atom is the preferred bonding position;    A=N (preferred) or P;    X=B(R1), N(R1), P(R1), P(R1) 3, PO(R1), C(R1) 2, Si(R1) 2, C=O, C=NR1, C=C(R1) 2, O, S, Se, S=O or SO 2;    Y1=C (when Y1 is linked to X or Ar1 or Ar3 or Cz), CRcz or N;    Z=CRHet or N, where at least one Z per six-membered ring is N; either    R1, RHet, Rcz=linear 1-40C-alkyl or -(thio)alkoxy, linear 2-40C-alkenyl or -alkynyl, branched or cyclic 3-40C-alkyl or (thio)alkoxy, branched or cyclic 4-40C-alkenyl or alkynyl (all optionally substituted with one or more R2, where one or more adjacent or non-adjacent CH 2groups are replaced by R2C=CR2, Si(R2) 2, Ge(R2) 2, Sn(R2) 2, C=O, C=S, C=Se, C=NR2, P(=O)(R2), SO, SO 2, NR2, O, S, COO or CONR2), 5-60 membered (hetero)aromatic ring system, (hetero)aryloxy or (hetero)aralkyl (all optionally substituted with one or more R2), H, D, F, Cl, Br, I, N(R2) 2, CN, NO 2, Si(R2) 3, B(OR2) 2, C(=O)R2, P(=O)(R2) 2, S(=O)R2, S(=O) 2R2 or OSO 2R2; or    two or more R1, RHet, Rcz bonded together=mono- or poly-cyclic aliphatic or (hetero)aromatic ring system; either    R2=H, D or 1-20C-aliphatic or (hetero)aromatic organic residue, in which one or more H atoms are optionally replaced by D or F; or    two or more R2 bonded together=mono- or poly-cyclic aliphatic or (hetero)aromatic ring system;    s=0 or 1 (preferred), with the proviso that at least one s is 1; and    x, q=0 or 1.    INDEPENDENT CLAIMS are included for:    (1) the preparation of (A);    (2) oligomers, polymers or dendrimers containing one or more (A), where one or more bonds of (A) remain(s) to the polymer, oligomer or dendrimer, in the place of one or more radicals or hydrogen atoms; and    (3) a formulation comprising (A) or the polymer, oligomer or dendrimer, and at least one solvent.