Compound of the formula where: Ar 1 is on each occurrence, identically or differently, an aromatic or heteroaromatic ring system having 5 to 24 aromatic ring atoms, which may be substituted by one or more radicals R 2; Ar 2 is on each occurrence, identically or differently, an aromatic or heteroaromatic ring system having 5 to 24 aromatic ring atoms, which may be substituted by one or more radicals R 2, where at least one group Ar 2 in the compound of the formula represents a group Ar 2 *; Ar 2 * is on each occurrence, identically or differently, an aromatic or heteroaromatic ring system having 12 to 24 aromatic ring atoms, which may be substituted by one or more radicals R 2, where the aromatic ring system contains no condensed aryl or heteroaryl group having more than 10 aromatic ring atoms; R 1 is selected on each occurrence, identically or differently, from an aromatic or heteroaromatic ring system having 5 to 30 aromatic ring atoms, which may be substituted by one or more radicals R 3; R 2 is selected on each occurrence, identically or differently, from H, a straight-chain alkyl group having 1 to 10 C atoms or a branched alkyl group having 3 to 10 C atoms, where the above-mentioned groups may in each case be substituted by one or more radicals R 3, or an aromatic or heteroaromatic ring system having 5 to 20 aromatic ring atoms, which may in each case be substituted by one or more radicals R 3; R 3 is selected on each occurrence, identically or differently, from H, a straight-chain alkyl group having 1 to 10 C atoms or a branched alkyl group having 3 to 10 C atoms, or an aromatic or heteroaromatic ring system having 5 to 20 aromatic ring atoms; n is equal to 1, 2, 3 or 4; where, for n=1, the group Ar 1 is not phenylene which is optionally substituted by R 2 or carbazole which is optionally substituted by R 2; and where Ar 1 is not optionally R 2 -substituted fluorene bonded via positions 9 and 9' which is optionally substituted by R 2; and where the compound of the formula contains precisely one amino group. Ar 1 is on each occurrence, identically or differently, an aromatic or heteroaromatic ring system having 5 to 24 aromatic ring atoms, which may be substituted by one or more radicals R 2; Ar 2 is on each occurrence, identically or differently, an aromatic or heteroaromatic ring system having 5 to 24 aromatic ring atoms, which may be substituted by one or more radicals R 2, where at least one group Ar 2 in the compound of the formula represents a group Ar 2 *; Ar 2 * is on each occurrence, identically or differently, an aromatic or heteroaromatic ring system having 12 to 24 aromatic ring atoms, which may be substituted by one or more radicals R 2, where the aromatic ring system contains no condensed aryl or heteroaryl group having more than 10 aromatic ring atoms; R 1 is selected on each occurrence, identically or differently, from an aromatic or heteroaromatic ring system having 5 to 30 aromatic ring atoms, which may be substituted by one or more radicals R 3; R 2 is selected on each occurrence, identically or differently, from H, a straight-chain alkyl group having 1 to 10 C atoms or a branched alkyl group having 3 to 10 C atoms, where the above-mentioned groups may in each case be substituted by one or more radicals R 3, or an aromatic or heteroaromatic ring system having 5 to 20 aromatic ring atoms, which may in each case be substituted by one or more radicals R 3; R 3 is selected on each occurrence, identically or differently, from H, a straight-chain alkyl group having 1 to 10 C atoms or a branched alkyl group having 3 to 10 C atoms, or an aromatic or heteroaromatic ring system having 5 to 20 aromatic ring atoms; n is equal to 1, 2, 3 or 4;