Materials for organic electroluminescent devices

An organic electroluminescent device comprising in the emissive layer a mixture of a phosphorescent emitter and a compound of the formula (1),

• where the following applies to the symbols used:
• A is on each occurrence, identically or differently, CR1;
• Y1 is O or S;
• L is on each occurrence, identically or differently, a single bond or an aromatic or heteroaromatic ring system having 5 to 30 aromatic ring atoms, which may be substituted by one or more radicals R1;
• HetAr is a group of the formula (2), (3) or (4),
• where the dashed bond represents the linking of this group;
• X is on each occurrence, identically or differently, CR2 or N, with the proviso that at least one symbol X stands for N;
• N1 is a group of formula (6),
• where the dashed bond represents the linking of this group;
• precisely two adjacent groups W together stand for a group of the formula (7), and the remaining groups W stand, identically or differently on each occurrence, for CR1 or N,
• where the dashed bonds indicate the linking of this group;
• Y2 are, identically or differently on each occurrence, O, NR4, S, C(R4)2, Si(R4)2, BR4 or C═O, where the radical R4 which is bonded to N is not equal to H for the groups of formulae (7) and (8);
• R1 is selected on each occurrence, identically or differently, from the group consisting of H, D, F, a straight-chain alkyl group having 1 to 20 C atoms or a branched or cyclic alkyl group having 3 to 20 C atoms, each of which may be substituted by one or more radicals R5, where one or more H atoms may be replaced by D, F, or CN or, an aromatic ring system having 5 to 40 aromatic ring atoms, which may in each case be substituted by one or more radicals R5;
• R2, R4 are selected on each occurrence, identically or differently, from the group consisting of H, D, F, CN, a straight-chain alkyl group having 1 to 20 C atoms or a branched or cyclic alkyl group having 3 to 20 C atoms, each of which may be substituted by one or more radicals R5, where one or more H atoms may be replaced by D, F, or CN or, an aromatic or heteroaromatic ring system having 5 to 40 aromatic ring atoms, which may in each case be substituted by one or more radicals R5;
• two adjacent substituents R4 may form an aliphatic or aromatic ring system, which may be substituted by one or more radicals R5;
• R5 is selected on each occurrence, identically or differently, from the group consisting of H, D, F, CN, an aliphatic hydrocarbon radical having 1 to 20 C atoms or an aromatic or heteroaromatic ring system having 5 to 30 aromatic ring atoms, in which one or more H atoms may be replaced by D, F, Cl, Br, I or CN and which may be substituted by one or more alkyl groups, each having 1 to 4 carbon atoms;
• two or more adjacent substituents R5 here may form an aliphatic ring system with one another.