The Pt(II) complexes (1-3) bearing tetradentate O^N^C^N ligands display high emission quantum yields (0.76-0.90) and good thermal stability (T(d) > 400 °C). Complex is an excellent green phosphorescence dopant for OLEDs with excellent efficiency and low efficiency roll-off (η(L), η(Ext)(max) = 66.7 cd A(-1), 18.2%; η(L), η(Ext) (1000 cd m(-2)) = 65.1 cd A(-1), 17.7%).