A compound of the formula Ir Formula wherein the ligand L has a structure of the following formula: wherein the ligand L coordinates to the iridium atom via the positions identified by * and wherein the hydrogen atoms not explicitly shown may optionally be replaced by D, and wherein the symbols and indices used are as follows: R is the same or different at each occurrence, and is H, D, F, a linear alkyl group having 1 to 10 carbon atoms or a branched or cyclic alkyl group having 3 to 10 carbon atoms, wherein the alkyl group in each case may optionally be deuterated; and wherein, optionally, two adjacent R radicals together can form a ring system; R 1 is the same or different at each occurrence, and is H, D, a linear alkyl group having 1 to 10 carbon atoms or a branched or cyclic alkyl group having 3 to 10 carbon atoms, wherein the alkyl group R 2 in each case may optionally be deuterated; and wherein, optionally, two adjacent R 1 radicals together can form a ring system; is the same or different at each occurrence, and is H, D, a linear alkyl group having 1 to 10 carbon atoms, a branched or cyclic alkyl group having 3 to 10 carbon atoms, wherein the alkyl group in each case may optionally be deuterated; or a phenyl or biphenyl group, each of which may be substituted by one or more alkyl groups having 1 to 10 carbon atoms, wherein the phenyl or biphenyl group, or the alkyl groups, may each optionally be deuterated; and wherein, optionally, two adjacent R 2 radicals together can form a ring system; m is 1, 2 or 3; n is the same or different at each occurrence, and is 0, 1, 2 or 3; o is 0 or 1; p is 0, 1 or 2; q is 0, 1 or 2; and r is 0, 1 or 2. wherein the ligand L has a structure of the following formula: wherein the ligand L coordinates to the iridium atom via the positions identified by * and wherein the hydrogen atoms not explicitly shown may optionally be replaced by D, and wherein the symbols and indices used are as follows: R is the same or different at each occurrence, and is H, D, F, a linear alkyl group having 1 to 10 carbon atoms or a branched or cyclic alkyl group having 3 to 10 carbon atoms, wherein the alkyl group in each case may optionally be deuterated; and wherein, optionally, two adjacent R radicals together can form a ring system; R 1 is the same or different at each occurrence, and is H, D, a linear alkyl group having 1 to 10 carbon atoms or a branched or cyclic alkyl group having 3 to 10 carbon atoms, wherein the alkyl group R 2 in each case may optionally be deuterated; and wherein, optionally, two adjacent R 1 radicals together can form a ring system; is the same or different at each occurrence, and is H, D, a linear alkyl group having 1 to 10 carbon atoms, a branched or cyclic alkyl group having 3 to 10 carbon atoms, wherein the alkyl group in each case may optionally be deuterated; or a phenyl or biphenyl group, each of which may be substituted by one or more alkyl groups having 1 to 10 carbon atoms, wherein the phenyl or biphenyl group, or the alkyl groups, may each optionally be deuterated; and wherein, optionally, two adjacent R 2 radicals together can form a ring system; m is 1, 2 or 3; n is the same or different at each occurrence, and is 0, 1, 2 or 3; o is 0 or 1; p is 0, 1 or 2; q is 0, 1 or 2; and r is 0, 1 or 2. R is the same or different at each occurrence, and is H, D, F, a linear alkyl group having 1 to 10 carbon atoms or a branched or cyclic alkyl group having 3 to 10 carbon atoms, wherein the alkyl group in each case may optionally be deuterated; and wherein, optionally, two adjacent R radicals together can form a ring system; R 1 is the same or different at each occurrence, and is H, D, a linear alkyl group having 1 to 10 carbon atoms or a branched or cyclic alkyl group having 3 to 10 carbon atoms, wherein the alkyl group R 2 in each case may optionally be deuterated; and wherein, optionally, two adjacent R 1 radicals together can form a ring system; is the same or different at each occurrence, and is H, D, a linear alkyl group having 1 to 10 carbon atoms, a branched or cyclic alkyl group having 3 to 10 carbon atoms, wherein the alkyl group in each case may optionally be deuterated; or a phenyl or biphenyl group, each of which may be substituted by one or more alkyl groups having 1 to 10 carbon atoms, wherein the phenyl or biphenyl group, or the alkyl groups, may each optionally be deuterated; and wherein, optionally, two adjacent R 2 radicals together can form a ring system; m is 1, 2 or 3; n is the same or different at each occurrence, and is 0, 1, 2 or 3; o is 0 or 1; p is 0, 1 or 2; q is 0, 1 or 2; and r is 0, 1 or 2.