Efficient electroluminescence of platinum complexes containing pinene sterically hindered spacer

Two new platinum(II) cyclometallated complexes (R/S)-(pppy)Pt(acac) with chiral (R/S)-4-pinene-2-phenylpyridine (pppy) main ligands and acetylacetone (acac) ancillary ligand have been developed. The complexes are all green phosphors with photoluminescence quantum efficiency yields of 51.6% in CH2C12 solutions at room temperature. The electron circular dichroism (ECD) and circularly polarized phosphorescence luminescence (CPPL) spectra were detected for (R/S)-(pppy)Pt(acac) enantiomers. The organic light -emitting diodes with the double emissive layers structure of ITO/TAPC (1,1-bis(4-(di-p-tolylamino)phenyl)cyclohexane, 40 nm/(R)-(pppy)Pt(acac): TCTA (4,4',4 ''-tri (9-carbazoyl)-triphenylamine) (5 wt%, 10 nm)/(R)-(pppy)Pt(acac): 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. Particularly, device based on complex (R)-(pppy)Pt(acac) with 5 wt% doped concentration showed superior performances with low drive voltage of 3.0 V, a maximum current efficiency of 40.4 cd A(-1), a maximum external quantum efficiency of 13.7% and a maximum power efficiency of 33.7 cd W-1, respectively. Even at the brightness of 1000 cd m(-2), a current efficiency of 39.1 cd A(-1) can still be obtained suggesting that the main ligand chiral 4-pinene-2-phenylpyridine can be employed well in Pt(II) complexes, which would have potential applications in OLEDs. (C) 2017 Elsevier B.V. All rights reserved.