Compound of formula where the symbols and indices used are as follows: Ar 1, Ar 2 is the same or different at each instance and is an aromatic or heteroaromatic ring system which has 5 to 30 aromatic ring atoms and may be substituted by one or more R radicals; Ar 3 is a group of formula where the dotted bond indicates the linkage of this group to the nitrogen atom and the fluorene or dibenzofuran or dibenzothiophene group is joined to the phenylene group via the 1, 3 or 4 position when p = 1 and to the nitrogen atom when p = 0; X is C(R 1) 2, O or S; R, R 1 is the same or different at each instance and is selected from the group consisting of H, D, F, Cl, Br, I, CN, NO 2, N(R 2) 2, OR 2, SR 2, C(=O)R 2, P(=O)R 2, Si(R 2) 3, a straight-chain alkyl group having 1 to 20 carbon atoms or a branched or cyclic alkyl group having 3 to 20 carbon atoms or an alkenyl or alkynyl group having 2 to 20 carbon atoms, where the alkyl, alkenyl or alkynyl group may be substituted in each case by one or more R 2 radicals and where one or more nonadjacent CH 2 groups may be replaced by R 2 C=CR 2, C≡C, Si(R 2) 2, C=O, C=NR 2, P(=O)(R 2), SO, SO 2, NR 2, O, S or CONR 2 and where one or more hydrogen atoms may be replaced by D, F, Cl, Br, I, CN or NO 2, an aromatic or heteroaromatic ring system which has 5 to 40 aromatic ring atoms and may be substituted in each case by one or more R 2 radicals; at the same time, it is optionally possible for two adjacent R substituents or two adjacent R 1 substituents to form a monocyclic or polycyclic, aliphatic, aromatic or heteroaromatic ring system which may be substituted by one or more R 2 radicals; R 2 is the same or different at each instance and is selected from the group consisting of H, D, F, CN, an aliphatic hydrocarbyl radical having 1 to 20 carbon atoms, or an aromatic or heteroaromatic ring system having 5 to 30 aromatic ring atoms in which one or more hydrogen atoms may be replaced by D, F, CN or an alkyl group having 1 to 10 carbon atoms, where two or more adjacent R 2 substituents together may form a mono- or polycyclic, aliphatic ring system; m is 0, 1, 2 or 3; n is the same or different at each instance and is 0, 1, 2, 3 or 4; p is 0 or 1, where the 1, 3 or 4 position is as defined below: Ar 1, Ar 2 is the same or different at each instance and is an aromatic or heteroaromatic ring system which has 5 to 30 aromatic ring atoms and may be substituted by one or more R radicals; Ar 3 is a group of formula where the dotted bond indicates the linkage of this group to the nitrogen atom and the fluorene or dibenzofuran or dibenzothiophene group is joined to the phenylene group via the 1, 3 or 4 position when p = 1 and to the nitrogen atom when p = 0; X is C(R 1) 2, O or S; R, R 1 is the same or different at each instance and is selected from the group consisting of H, D, F, Cl, Br, I, CN, NO 2, N(R 2) 2, OR 2, SR 2, C(=O)R 2, P(=O)R 2, Si(R 2) 3, a straight-chain alkyl group having 1 to 20 carbon atoms or a branched or cyclic alkyl group having 3 to 20 carbon atoms or an alkenyl or alkynyl group having 2 to 20 carbon atoms, where the alkyl, alkenyl or alkynyl group may be substituted in each case by one or more R 2 radicals and where one or more nonadjacent CH 2 groups may be replaced by R 2 C=CR 2, C≡C, Si(R 2) 2, C=O, C=NR 2, P(=O)(R 2), SO, SO 2, NR 2, O, S or CONR 2 and where one or more hydrogen atoms may be replaced by D, F, Cl, Br, I, CN or NO 2, an aromatic or heteroaromatic ring system which has 5 to 40 aromatic ring atoms and may be substituted in each case by one or more R 2 radicals; at the same time, it is optionally possible for two adjacent R substituents or two adjacent R 1 substituents to form a monocyclic or polycyclic, aliphatic, aromatic or heteroaromatic ring system which may be substituted by one or more R 2 radicals; R 2 is the same or different at each instance and is selected from the group consisting of H, D, F, CN, an aliphatic hydrocarbyl radical having 1 to 20 carbon atoms, or an aromatic or heteroaromatic ring system having 5 to 30 aromatic ring atoms in which one or more hydrogen atoms may be replaced by D, F, CN or an alkyl group having 1 to 10 carbon atoms, where two or more adjacent R 2 substituents together may form a mono- or polycyclic, aliphatic ring system; m is 0, 1, 2 or 3; n is the same or different at each instance and is 0, 1, 2, 3 or 4; p is 0 or 1,