luminescent emission occurring only during the period during which an excitation such as a driving voltage is applied and is created mostly if not exclusively by relaxation from the singlet state phosphorescence is luminescent emission which persists after the period of excitation phosphorescence involves photons created by relaxation from triplet states of particular importance in the present invention is triplet enhanced fluorescent emissions the internal efficiency of many oled emissive materials is limited by the fact that singlet and triplet excited states are produced in these materials at a ratio of 1 3 but emission typically only involves singlet relaxation accordingly efficiency can only approach a theoretical maximum of 25 it is believed that the carbon iridium covalent bond in the complexes according to the invention causes spin orbital coupling such that the triplet state has quantum mechanical properties similar to the singlet state and therefore relaxation from the triplet state in these complexes contributes to emissions in this manner theoretical efficiencies greater than 25 can be obtained the examples below exhibit yellow phosphorescent emissions although other pure colors can be obtained by incorporating other conjugated groups into the complexes to a round flask were added iridium iii chloride 0 298 g 1 mmol 2 phenylpyridine 0 62 g 4 mmol 30 ml of 2 ethoxyethanol and 10 ml of water the mixture was fluxed under n 2 overnight after cooling the solid was filtrated and washed with a small amount of ethanol and acetone the product was dissolved in dichloromethane and filtrated thereafter a mixture of hexanes and toluene was added to the filtrate and the solution was concentrated the intermediate product tetrakis 2 phenylpyridine c 2 n u2032 diiridium irppy 2 cl 2 structure shown.