Use of transition metal carbene complexes represented by formula in organic light-emitting diodes wherein the symbols have the following meanings: M 1 is a metal atom selected from the group consisting of transition metals of groups IIB, IIIB, IVB, VB, VIB, VIIB, VIII of the Periodic Table of the Elements (CAS-Version) and Cu, each in any oxidation state possible for the corresponding metal atom; K is an uncharged mono- or bidentate ligand; L is a mono- or dianionic ligand, which can be mono- or bidentate; m is from 0 to 5; o is from 0 to 5; n is from 1 to 6; p is the charge of the complex: 0, 1, 2, 3, 4; W - is a monoanionic counter ion; wherein m, o, n and p depend on the oxidation state and coordination number of the metal atom utilized and on the charge of the ligands and on the total charge of the complex, carben is a carbene ligand selected from the group consisting of wherein R 1 and R 2 are each independently hydrogen, alkyl, cycloalkyl, heterocycloalkyl, aryl, heteroaryl, aralkyl, alkenyl, alkynyl, wherein the groups can be substituted or unsubstituted, BR 3 2, NR 22 2, PR 23 2, OR 24, SR 25 or SiR 4 3; X 1, X 2, X 3, X 4 are each independently CH 2, CH=CH, 1,2-phenylene; R 3, R 4, R 5, R 6, R 7, R 8, R 8, R 9, R 10, R 11, R 22, R 23, R 24, R 25 are each independently hydrogen, alkyl, cycloalkyl, heterocycloalkyl, aryl, aralkyl, heteroaryl, alkenyl, alkynyl, alkoxy, wherein the groups can be substituted or unsubstituted, preferably hydrogen, alkyl, cycloalkyl, aryl, alkoxy, particularly preferred hydrogen, alkyl or alkoxy; R 12, R 13 are each independently hydrogen, alkyl, cycloalkyl, heterocycloalkyl, aryl, aralkyl, heteroaryl, aralkyl, alkynyl, alkenyl, wherein the groups can be substituted or unsubstituted, or groups having donor- or acceptor action; A, A', A", A′′′ are R 18; B,B′,Bʺ,B′′′ are R 19; wherein R 18 and R 19 are hydrogen, alkyl, cycloalkyl, heterocycloalkyl, aryl, aralkyl, heteroaryl, alkynyl, alkenyl, wherein the groups can be substituted or unsubstituted, or a group having donor- or acceptor action, and wherein R 18 in groups A, A′, A", A′′′ or R 19 in groups B, B', B", B′′′ is each having the same or different meanings. M 1 is a metal atom selected from the group consisting of transition metals of groups IIB, IIIB, IVB, VB, VIB, VIIB, VIII of the Periodic Table of the Elements (CAS-Version) and Cu, each in any oxidation state possible for the corresponding metal atom; K is an uncharged mono- or bidentate ligand; L is a mono- or dianionic ligand, which can be mono- or bidentate; m is from 0 to 5; o is from 0 to 5; n is from 1 to 6; p is the charge of the complex: 0, 1, 2, 3, 4; W - is a monoanionic counter ion; R 1 and R 2 are each independently hydrogen, alkyl, cycloalkyl, heterocycloalkyl, aryl, heteroaryl, aralkyl, alkenyl, alkynyl, wherein the groups can be substituted or unsubstituted, BR 3 2, NR 22 2, PR 23 2, OR 24, SR 25 or SiR 4 3; X 1, X 2, X 3, X 4 are each independently CH 2, CH=CH, 1,2-phenylene; R 3, R 4, R 5, R 6, R 7, R 8, R 8, R 9, R 10, R 11, R 22, R 23, R 24, R 25 are each independently hydrogen, alkyl, cycloalkyl, heterocycloalkyl, aryl, aralkyl, heteroaryl, alkenyl, alkynyl, alkoxy, wherein the groups can be substituted or unsubstituted, preferably hydrogen, alkyl, cycloalkyl, aryl, alkoxy, particularly preferred hydrogen, alkyl or alkoxy; R 12, R 13 are each independently hydrogen, alkyl, cycloalkyl, heterocycloalkyl, aryl, aralkyl, heteroaryl, aralkyl, alkynyl, alkenyl, wherein the groups can be substituted or unsubstituted, or groups having donor- or acceptor action; A, A', A", A′′′ are R 18; B,B′,Bʺ,B′′′ are R 19; wherein R 18 and R 19 are hydrogen, alkyl, cycloalkyl, heterocycloalkyl, aryl, aralkyl, heteroaryl, alkynyl, alkenyl, wherein the groups can be substituted or unsubstituted, or a group having donor- or acceptor action, and wherein R 18 in groups A, A′, A", A′′′ or R 19 in groups B, B', B", B′′′ is each having the same or different meanings.