Patent ID: 7553560

Claim:
An organic light emitting device having an emissive layer comprising an organometallic compound, wherein the organometallic compound consists of a metal having an atomic number of at least 72; at least one mono-anionic bidentate, carbon coordination ligand bound to the metal, and at least one non mono-anionic bidentate, carbon coordination ligand bound to the metal, wherein the mono-anionic bidentate, carbon coordination ligand has the structure wherein R is halogen or alkyl, and R 1 , R 2 and R 3 are, independently, hydrogen, halogen, alkyl, or aryl, wherein at least one of R 1 and R 2 is hydrogen, with the proviso that the at least one mono-anionic bidentate, carbon-coordination ligand is substituted with at least one of an electron donating substituent and an electron withdrawing substituent.