Syntheses, photoluminescence and electroluminescence of two novel platinum(ii) complexes

Two new platinum(ii) cyclometalated complexes with 2-(4-trifluoromethyl)phenylpyridine (4-tfmppy) as the main ligand and tetraphenylimidodiphosphinate (tpip) (Pt-tpip) and tetra(4-fluorophenyl)imidodiphosphinate (ftpip) (Pt-ftpip) as ancillary ligands were developed. Both complexes were green phosphors with photoluminescence quantum efficiency yields of 71.5% and 79.2% in CH₂Cl₂ solution at room temperature, respectively. The organic light-emitting diodes with a double emissive layers structure of ITO/TAPC (1,1-bis(4-(di-p-tolylamino)phenyl)cyclohexane), 40 nm/Pt-tpip or Pt-ftpip: TcTa (4,4',4''-tri(9-carbazoyl)-triphenylamine) (5 wt%, 10 nm)/Pt-tpip or Pt-ftpip: 2,6DCzPPy (2,6-bis(3-(carbazol-9-yl)phenyl)pyridine) (5 wt%, 10 nm)/TmPyPB (1,3,5-tri(m-pyrid-3-yl-phenyl)benzene, 40 nm)/LiF (1 nm)/Al (100 nm) showed good performances. In particular, the device based on the Pt-ftpip complex with a 5 wt% doped concentration showed superior performance with a low drive voltage of 3.3 V, a maximum current efficiency of 48.3 cd A^-1, a maximum external quantum efficiency of 14.0%, and a maximum power efficiency of 35.7 lm W^-1, respectively. Even at a brightness of 1000 cd m^-2, a current efficiency of 47.0 cd A^-1 could still be obtained, suggesting that the ancillary ligands (tpip and ftpip) can be employed well in Pt(ii) complexes, which could find potential applications in OLEDs.