NOVELTY - Fluorene derivative (I) is new.    USE - (I), or the dimers, trimers, tetramers, pentamers, oligomers, polymers or the dendrimers, or the mixture are useful in electronic devices, preferably organic electroluminescent devices (organic light emitting diodes or polymer light-emitting diodes), 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 (all claimed).    ADVANTAGE - (I) exhibits high thermal stability, high solubility in common organic solvents, and excellent film forming properties. The organic light emitting diodes comprising (I) exhibits long life and very high quantum efficiency.    DETAILED DESCRIPTION - Fluorene derivative of formula (I) is new.    Y1 = covalent single bond, C(R1)2, CO, O, S, SO, SO2, NR3, PR3 or P(O)R3;    X = CR1 or N, where in each ring maximum 3 groups X represents N;    A = CR2 or N, where in each ring maximum 3 groups A represents N; either    R1, R2 = 1-40C straight chain (thio)alkoxy, branched or cyclic 3-40C alkyl or 3-40C (thio)alkoxy, or 2-40C alkenyl or 2-40C alkynyl (all optionally substituted with at least one R4 and at least one non-adjacent CH2 group may be 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 at least one H may be replaced by D, F, Cl, Br, I, CN or NO2), or (hetero)aromatic ring with 5-60 aromatic ring atoms, (hetero)aryloxy with 5-60 aromatic ring atoms or (hetero)aralkyl with 5-60 aromatic ring atoms (all optionally substituted by at least one R4), H, D, Cl, Br, I, F, CN, NO2, N(R4)3, Si(R4)3, B(OR4)2, C(=O)R4, P(=O)(R4)2, S(=O)R4, S(=O)2R4, -CR4=CR4 or OSO2R4, where at least one R1 that is bonded to X, represents triazine (optionally substituted by at least one R4), and at least one R2 is 6-membered heteroaromatic compound (optionally substituted by at least one R4) and at least one residue R1 simultaneously represents (hetero)aromatic ring with 5-60 aromatic ring atoms (optionally substituted by at least one R4); or    at least two adjacent R1 or R2 together with atoms to which they are bonded or R1R1 or R2R2 = mono- or polycyclic, aliphatic or aromatic ring;    R3 = (hetero)aromatic ring with 5-60 ring atoms (optionally substituted by at least one R4) and/or (hetero)aryloxy with 5-60 aromatic ring atoms (optionally substituted by at least one R3); either    R4 = straight chain 1-40C alkyl or 1-40C (thio)alkoxy, or branched or cyclic 3-40C alkyl or 3-40C (thio)alkoxy, or 2-40C alkenyl or 2-40C alkynyl (all optionally substituted with at least one R5 and at least one non-adjacent CH2 group may be replaced by R5C=CR5, CC, Si(R5)2, Ge(R5)2, Sn(R5)2, C=O, C=S, C=Se, C=NR5, P(=O)(R5), SO, SO2, NR5, O, S or CONR5, and at least one H may be replaced by D, F, Cl, Br, I, CN or NO2), or (hetero)aromatic ring with 5-60 aromatic ring atoms, (hetero)aryloxy with 5-60 aromatic ring atoms or (hetero)aralkyl with 5-60 aromatic ring atoms (all optionally substituted by at least one R5), H, D, F, Cl, Br, I, CN, NO2, N(R5)3, Si(R5)3, B(OR5)2, C(=O)R5, P(=O)(R5)2, S(=O)R5, S(=O)2R5, -CR5=CR5 or OSO2R5; or    at least two R4 together with atoms to which they are bonded or R4R4 = mono- or polycyclic, aliphatic or aromatic ring; and either    R5 = 1-20C aliphatic hydrocarbon and/or 1-20C (hetero)aromatic hydrocarbon; or    at least two R5 together with atoms to which they are bonded or R5R5 = mono- or polycyclic, aliphatic or aromatic ring.    INDEPENDENT CLAIMS are also included for:    (1) preparing (I);    (2) a dimer, trimer, tetramer, pentamer, oligomer, polymer, or dendrimer comprising at least one compound (I), where at least one residue R1 or R2 or at least one hydrogen atom of (I) forms bonds between (I) in the dimer, trimer, tetramer or pentamer, or forms bonds from (I) to polymer, oligomer or dendrimer;    (3) a mixture comprising at least one compound (I), or the dimer, trimer, tetramer, pentamer, oligomer or the polymer, and at least one further compound, preferably a fluorescent or phosphorescent dopant;    (4) a formulation comprising at least one compound (I), or the dimer, trimer, tetramer, pentamer, oligomer or the polymer or the above mixture, and at least one solvent, preferably organic solvent; and    (5) electronic devices, preferably organic electroluminescent devices (organic light emitting diodes or polymer light-emitting diodes), 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.