A compound comprising a ligand L being coordinated to Ir, wherein the ligand L is selected from the group consisting of: wherein X 1 is N and A is selected from the group consisting of: wherein X is selected from the group consisting of S, NZ, O, Se, BZ, CZZ', and C=O, wherein Z and Z' are independently selected from the group consisting of hydrogen, alkyl, and aryl; wherein R 1, R 2, and R 3 are independently selected from the group consisting of hydrogen, alkyl, amino, alkenyl, alkynyl, arylkyl, aryl, and heteroaryl; wherein the term alkyl means a straight or branched alkyl group containing from one to 15 carbon atoms, which is optionally substituted with one or more substituents selected from halo, CN, CO 2 H, C H, NH 2, NO 2, and OH; the term alkenyl means a straight or branched alkenyl group containing from 2 to 15 carbon atoms, which is optionally substituted with one or more substituents selected from halo, CN, CO 2 H, C H, NH 2, NO 2, and OH; the term alkynyl means a straight or branched alkynyl group containing from 2 to 15 carbon atoms, which is optionally substituted with one or more substituents selected from halo, CN, CO 2 H, C H, NH 2, NO 2, and OH; the term arylkyl means an alkyl group that has as a substituent an aryl group, which aryl group is optionally substituted with one or more substituents selected from halo, CN, CO 2 H, C H, NH 2, NO 2, and OH; the term aryl means an aryl group with a single aromatic ring, which is optionally substituted with one or more substituents selected from halo, CN, CO 2 H, C H, NH 2, NO 2, and OH; and the term heteroaryl means a single-ring heteroaromatic group that includes from 1 to three heteroatoms, which is optionally substituted with one or more substituents selected from halo, CN, CO 2 H, C H, NH 2, NO 2, and OH. wherein X is selected from the group consisting of S, NZ, O, Se, BZ, CZZ', and C=O, wherein Z and Z' are independently selected from the group consisting of hydrogen, alkyl, and aryl; wherein R 1, R 2, and R 3 are independently selected from the group consisting of hydrogen, alkyl, amino, alkenyl, alkynyl, arylkyl, aryl, and heteroaryl; wherein the term alkyl means a straight or branched alkyl group containing from one to 15 carbon atoms, which is optionally substituted with one or more substituents selected from halo, CN, CO 2 H, C H, NH 2, NO 2, and OH; the term alkenyl means a straight or branched alkenyl group containing from 2 to 15 carbon atoms, which is optionally substituted with one or more substituents selected from halo, CN, CO 2 H, C H, NH 2, NO 2, and OH; the term alkynyl means a straight or branched alkynyl group containing from 2 to 15 carbon atoms, which is optionally substituted with one or more substituents selected from halo, CN, CO 2 H, C H, NH 2, NO 2, and OH; the term arylkyl means an alkyl group that has as a substituent an aryl group, which aryl group is optionally substituted with one or more substituents selected from halo, CN, CO 2 H, C H, NH 2, NO 2, and OH; the term aryl means an aryl group with a single aromatic ring, which is optionally substituted with one or more substituents selected from halo, CN, CO 2 H, C H, NH 2, NO 2, and OH; and the term heteroaryl means a single-ring heteroaromatic group that includes from 1 to three heteroatoms, which is optionally substituted with one or more substituents selected from halo, CN, CO 2 H, C H, NH 2, NO 2, and OH.