Four-membered red iridium(iii) complexes with Ir–S–P–S structures: rapid room-temperature synthesis and application in OLEDs

Abstract

In this work, with sulfur-containing ancillary ligands of triethylamine salts of bis(4-methoxyphenyl)-phosphinodithioic acid (omess) and bis(3,5-di-tert-butyl-4-methoxyphenyl)phosphinodithioic acid (tbuss), two four-membered red iridium(III) complexes (tfmpqz)₂Ir(omess) and (tfmpqz)₂Ir(tbuss) with Ir–S–P–S structures were synthesized rapidly at room temperature within 5 min, in which 4-(4-(trifluoromethyl)phenyl)quinazoline (tfmpqz) was used as the main ligand. The calculated Gibbs free energy changes of the complex formation reactions prove that they are exothermic and thermodynamically beneficial processes. Both Ir(III) complexes show almost the same PL emissions at 624 and 623 nm with high phosphorescence quantum yields of 0.60 and 0.72, respectively. Using the two complexes as emitters, 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(omess) or (tfmpqz)₂Ir(tbuss):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. Particularly, due to the introduction of tert-butyl groups into the (tfmpqz)₂Ir(tbuss) complex, its device exhibits better device properties with a maximum luminance of 26 184 cd m⁻², maximum current efficiency of 30.24 cd A⁻¹, maximum power efficiency of 22.61 lm W⁻¹ and maximum external quantum efficiency of 21.50% with CIE coordinates at (0.65, 0.34).