Use of transition metal complexes of the formula (I) in organic light-emitting diodes where: M1 is a metal atom; carbene is a carbene ligand; L is a monoanionic or dianionic ligand; K is an uncharged monodentate or bidentate ligand selected from the group consisting of phosphines; CO; pyridines; nitriles and conjugated dienes which form a π complex with M1; n is the number of carbene ligands and is at least 1; m is the number of ligands L, where m can be 0 or ≧1; o is the number of ligands K, where o can be 0 or ≧1; where the sum n+m+o is dependent on the oxidation state and coordination number of the metal atom and on the denticity of the ligands carbene, L and K and also on the charge on the ligands carbene and L, with the proviso that n is at least 1, and also an OLED comprising these transition metal complexes, a light-emitting layer comprising these transition metal complexes, OLEDs comprising this light-emitting layer, devices comprising an OLED according to the present invention, and specific transition metal complexes comprising at least two carbene ligands.