Patent ID: 7252895

Claim:
A light-emitting device comprising: a first electrode formed over a substrate; an electroluminescent layer formed over the first electrode; and a second electrode formed over the electroluminescent layer; wherein the electroluminescent layer comprises a phosphorescent compound represented by general formula wherein R 1 is an alkyl group, an aryl group, a substituted aryl group, a heterocyclic group, or a substituted heterocyclic group, wherein R 2 is hydrogen, an alkyl group, an aryl group, a substituted aryl group, a heterocyclic group, or a substituted heterocyclic group, wherein R 3 and R 4 , each of which may be the same or different, are individually hydrogen, a halogen element, an alkyl group, an alkoxy group, an aryl group, a substituted aryl group, a heterocyclic group, or a substituted heterocyclic group, wherein M is one element of group 9 in the periodic table or one element of group 10 in the periodic table, wherein n=2 when the M is one element of group 9 in the periodic table, and n=1 when the M is one element of group 10 in the periodic table, and wherein L is a monoanionic ligand having a β-diketone structure, a monoanionic bidentate chelate ligand having a carboxyl group, or a monoanionic bidentate chelate ligand having a phenolic hydroxyl group.