Compound of a formula where the following applies to the symbols occurring: Ar 1 is a condensed aryl group having 14 to 18 aromatic ring atoms, which may be substituted by one or more radicals R 2; R° is Si(R 3) 3, a straight-chain alkyl or alkoxy group having 1 to 10 C atoms or a branched or cyclic alkyl or alkoxy 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; R 2 is on each occurrence, identically or differently, H, D, F, CN, Si(R 3) 3, a straight-chain alkyl or alkoxy group having 1 to 10 C atoms or a branched or cyclic alkyl or alkoxy 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 ring system having 6 to 24 aromatic ring atoms, which may be substituted by one or more radicals R 3, or a heteroaromatic ring system having 5 to 24 aromatic ring atoms, which may be substituted by one or more radicals R 3; R 3 is on each occurrence, identically or differently, H, D, F, CN, Si(R 4) 3, a straight-chain alkyl or alkoxy group having 1 to 10 C atoms or a branched or cyclic alkyl or alkoxy group having 3 to 10 C atoms, where the above-mentioned groups may in each case be substituted by one or more radicals R 4, or an aromatic ring system having 6 to 24 aromatic ring atoms, which may be substituted by one or more radicals R 4, or a heteroaromatic ring system having 5 to 24 aromatic ring atoms, which may be substituted by one or more radicals R 4; R 4 is on each occurrence, identically or differently, H, D, F, CN or an aliphatic, aromatic or heteroaromatic organic radical having 1 to 20 C atoms, in which, in addition, one or more H atoms may be replaced by D, F or CN. Ar 1 is a condensed aryl group having 14 to 18 aromatic ring atoms, which may be substituted by one or more radicals R 2; R° is Si(R 3) 3, a straight-chain alkyl or alkoxy group having 1 to 10 C atoms or a branched or cyclic alkyl or alkoxy 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; R 2 is on each occurrence, identically or differently, H, D, F, CN, Si(R 3) 3, a straight-chain alkyl or alkoxy group having 1 to 10 C atoms or a branched or cyclic alkyl or alkoxy 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 ring system having 6 to 24 aromatic ring atoms, which may be substituted by one or more radicals R 3, or a heteroaromatic ring system having 5 to 24 aromatic ring atoms, which may be substituted by one or more radicals R 3; R 3 is on each occurrence, identically or differently, H, D, F, CN, Si(R 4) 3, a straight-chain alkyl or alkoxy group having 1 to 10 C atoms or a branched or cyclic alkyl or alkoxy group having 3 to 10 C atoms, where the above-mentioned groups may in each case be substituted by one or more radicals R 4, or an aromatic ring system having 6 to 24 aromatic ring atoms, which may be substituted by one or more radicals R 4, or a heteroaromatic ring system having 5 to 24 aromatic ring atoms, which may be substituted by one or more radicals R 4; R 4 is on each occurrence, identically or differently, H, D, F, CN or an aliphatic, aromatic or heteroaromatic organic radical having 1 to 20 C atoms, in which, in addition, one or more H atoms may be replaced by D, F or CN.