Organic electroluminescent device comprising anode, cathode and either at least one emitting layer which comprises at least one fluorescent emitter and where an electron-transport layer has been introduced between the emitting layer and the cathode or at least one emitting layer which comprises at least one phosphorescent emitter and which is employed in combination with a following hole-blocking layer and where an electron-transport layer has been introduced between the hole-blocking layer and the cathode, characterised in that the electron-transport layer comprises at least one compound of the formula or formula, where the following applies to the symbols and indices used: Ar is a group of the following formula, where the dashed bond indicates the bond to the spirobifluorene; Ar' is a group of the following formula, where the dashed bonds indicate the bonds to the spirobifluorene; R 1, R 2 are on each occurrence, identically or differently, H, D, F, Cl, Br, I, CHO, N(R 3) 2, N(Ar 1) 2, B(Ar 1) 2, C(=O)Ar 1, P(=O)(Ar 1) 2, S(=O)Ar 1, S(=O) 2 Ar 1, CR 3 =CR 3 Ar 1, CN, NO 2, Si(R 3) 3, B(OR 3) 2, B(R 3) 2, B(N(R 3) 2) 2, OSO 2 R 3, a straight-chain alkyl, alkenyl, alkynyl, alkoxy or thioalkoxy group having 1 to 40 C atoms or a branched or cyclic alkyl, alkenyl, alkynyl, alkoxy or thioalkoxy group having 3 to 40 C atoms, which may in each case be substituted by one or more radicals R 3, where one or more non-adjacent CH 2 groups may be replaced by R 3 C=CR 3, C≡C, Si(R 3) 2, Ge(R 3) 2, Sn(R 3) 2, C=O, C=S, C=Se, C=NR 3, P(=O)(R 3), SO, SO 2, NR 3, O, S or CONR 3 and where one or more H atoms may be replaced by D, F, Cl, Br, I, CN or NO 2, or an aromatic or heteroaromatic ring system having 5 to 60 aromatic ring atoms, which may in each case be substituted by one or more radicals R 3, or an aryloxy or heteroaryloxy group having 5 to 60 aromatic ring atoms, which may be substituted by one or more radicals R 3, or a combination of these systems; two or more adjacent substituents R 1 may also form a mono- or polycyclic, aliphatic or aromatic ring system with one another; Ar 1 is on each occurrence, identically or differently, an aromatic or heteroaromatic ring system having 5 to 30 aromatic ring atoms, which may be substituted by one or more radicals R 3; two radicals Ar 1 which are bonded to the same nitrogen, phosphorus or boron atom may also be linked to one another by a single bond or a bridge selected from B(R 3), C(R 3) 2, Si(R 3) 2, C=O, C=NR 3, C=C(R 3) 2, O, S, S=O, SO 2, N(R 3), P(R 3) and P(=O)R 3; R 3 is on each occurrence, identically or differently, H, D or an aliphatic, aromatic and/or heteroaromatic hydrocarbon radical having 1 to 20 C atoms, in which, in addition, H atoms may be replaced by D or F; two or more adjacent substituents R 3 may also form a mono- or polycyclic, aliphatic or aromatic ring system with one another; n is 0 or 1; m is 0, 1, 2 or 3; o is 0, 1, 2, 3 or 4 if n = 0 in the same ring and is 0, 1, 2 or 3 if n = 1 in the same ring. Ar is a group of the following formula, where the dashed bond indicates the bond to the spirobifluorene; Ar' is a group of the following formula, where the dashed bonds indicate the bonds to the spirobifluorene; R 1, R 2 are on each occurrence, identically or differently, H, D, F, Cl, Br, I, CHO, N(R 3) 2, N(Ar 1) 2, B(Ar 1) 2, C(=O)Ar 1, P(=O)(Ar 1) 2, S(=O)Ar 1, S(=O) 2 Ar 1, CR 3 =CR 3 Ar 1, CN, NO 2, Si(R 3) 3, B(OR 3) 2, B(R 3) 2, B(N(R 3) 2) 2, OSO 2 R 3, a straight-chain alkyl, alkenyl, alkynyl, alkoxy or thioalkoxy group having 1 to 40 C atoms or a branched or cyclic alkyl, alkenyl, alkynyl, alkoxy or thioalkoxy group having 3 to 40 C atoms, which may in each case be substituted by one or more radicals R 3, where one or more non-adjacent CH 2 groups may be replaced by R 3 C=CR 3, C≡C, Si(R 3) 2, Ge(R 3) 2, Sn(R 3) 2, C=O, C=S, C=Se, C=NR 3, P(=O)(R 3), SO, SO 2, NR 3, O, S or CONR 3 and where one or more H atoms may be replaced by D, F, Cl, Br, I, CN or NO 2, or an aromatic or heteroaromatic ring system having 5 to 60 aromatic ring atoms, which may in each case be substituted by one or more radicals R 3, or an aryloxy or heteroaryloxy group having 5 to 60 aromatic ring atoms, which may be substituted by one or more radicals R 3, or a combination of these systems; two or more adjacent substituents R 1 may also form a mono- or polycyclic, aliphatic or aromatic ring system with one another; Ar 1 is on each occurrence, identically or differently, an aromatic or heteroaromatic ring system having 5 to 30 aromatic ring atoms, which may be substituted by one or more radicals R 3; two radicals Ar 1 which are bonded to the same nitrogen, phosphorus or boron atom may also be linked to one another by a single bond or a bridge selected from B(R 3), C(R 3) 2, Si(R 3) 2, C=O, C=NR 3, C=C(R 3) 2, O, S, S=O, SO 2, N(R 3), P(R 3) and P(=O)R 3; R 3 is on each occurrence, identically or differently, H, D or an aliphatic, aromatic and/or heteroaromatic hydrocarbon radical having 1 to 20 C atoms, in which, in addition, H atoms may be replaced by D or F; two or more adjacent substituents R 3 may also form a mono- or polycyclic, aliphatic or aromatic ring system with one another; n is 0 or 1; m is 0, 1, 2 or 3; o is 0, 1, 2, 3 or 4 if n = 0 in the same ring and is 0, 1, 2 or 3 if n = 1 in the same ring.