Sulfur atom contained ligands induced rapid room temperature synthesis of red iridium(III) complexes with Ir-S-P-S structures for OLEDs
Two novel sulfur atom contained ligands (triethylamine salts of di-p-tolylphosphinodithioic acid (mess) and di(naphthalen-1-yl)phosphinodithioic acid (niss)) were firstly developed for red iridium(III) complexes (tfmpqz)2Ir(mess) and (tfmpqz)2Ir(niss) with Ir-S-P-S four membered ring structures, in which 4-(4-(trifluoromethyl)phenyl)-quinazoline (tfmpqz) was used as cyclometalated ligand. Both Ir(III) complexes were obtained rapidly at room temperature in 5 min with high yields due to the strong coordination ability of S atom with iridium atom, and the calculated Gibbs free energy changes of both complexes formation reactions further prove that they are exothermic and thermodynamically beneficial processes. They show similar PL emissions at 623 and 619 nm with high phosphorescence quantum yields of 0.62 and 0.65, respectively. Using the two complexes as dopants, both organic light emitting devices (OLEDs) with the structure of ITO/ HATCN (hexaazatriphenylenehexacabonitrile, 5 nm)/ TAPC ((bis(4-(N,N-ditolylamino)phenyl)cyclohexane, 30 nm)/ (tfmpqz)2Ir(mess) or (tfmpqz)2Ir(niss): 26DCzppy (2,6-bis-(3-(carbazol-9-yl)phenyl)pyridine) (12 wt%, 10 nm)/ TmPyPB (1,3,5-tri((3-pyridyl)-phen-3-yl)benzene, 30 nm)/ LiF (1 nm)/ Al (100 nm) achieve good performances. Especially, the device using (tfmpqz)2Ir(niss) complex exhibits better device performances with the maximum luminance of 43 643 cd m-2, the maximum current efficiency of 31.32 cd A-1, the maximum power efficiency of 22.35 lm W-1 and the maximum external quantum efficiency of 19.90%.