Photoluminescence and electroluminescence of four platinum complexes with trifluoromethyl-substituted 2-phenylpyridine and tetraphenylimidodiphosphinate ligands

Abstract

Four cyclometalated platinum complexes with trifluoromethyl-substituted 2-phenylpyridine at different positions on its phenyl group as the main ligands and tetraphenylimidodiphosphinate as the ancillary ligand, Pt1-Pt4 (Pt1 is a trifluoromethyl-free complex), were prepared, and their X-ray crystallography, photoluminescence, thermal stability, electrochemical analyses, theoretical calculation and EL performances were investigated. The positions of trifluoromethyl groups on the phenyl ring affected the emission spectra of platinum complexes greatly, and their corresponding emission peaks at 504/534, 512/545, 495/526 and 510/542 nm were observed at room temperature, respectively. Constructed with complexes Pt1-Pt4 as the emitters, respectively, the organic light-emitting diodes (OLEDs) with double light emitting layers structure of ITO/TAPC (1,1-bis[4-(di-p-tolylamino)phenyl]cyclohexane, 40 nm /Pt complexes (5 wt%): TCTA (4,4′,4″-tri(9-carbazoyl)-triphenylamine, 10 nm /Pt complexes (5 wt%): 2,6DCzPPy (2,6-bis(3-(carbazol-9-yl)phenyl)pyridine, 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 G2 based on 2-trifluoromethyl-substituted complex Pt2 obtained a maximum luminance of 39196 cd m-2, a maximum current efficiency of 40.1 cd A−1 and a maximum power efficiency of 31.0 lm W−1, respectively, with low efficiency roll-off. The results suggested that these complexes Pt1-Pt4 would have potential applications in efficient OLEDs.