Rapid room temperature synthesis of red iridium(iii) complexes containing a four-membered Ir-S-C-S chelating ring for highly efficient OLEDs with EQE over 30%

Abstract

Three red cyclometalated iridium(iii) complexes (4tfmpq)2Ir(dipdtc), (4tfmpq)2Ir(dpdtc) and (4tfmpq)2Ir(Czdtc) (4tfmpq = 4-(4-(trifluoromethyl)phenyl)quinazoline, dipdtc = N,N-diisopropyl dithiocarbamate, dpdtc = N,N-diphenyl dithiocarbamate, and Czdtc = N-carbazolyl dithiocarbamate) containing the unique four-membered Ir-S-C-S backbone ring were synthesized in five minutes at room temperature with good yields, and the Gibbs free energy calculation results indicate that all reactions are exothermic and thermodynamically favorable processes. The emission colors (λpeak = 641-611 nm), photoluminescence quantum efficiencies (ΦP = 58.3-93.0%) and bipolar properties can be effectively regulated by introducing different electron-donating substituents into the dithiocarbamate ancillary ligands. Employing these emitters, organic light emitting diodes (OLEDs) with double emissive layers exhibit excellent performances with a maximum brightness over 60000 cd m-2, a maximum current efficiency of 40.68 cd A-1, a maximum external quantum efficiency (EQEmax) of 30.54%, and an EQE of 26.79% at the practical luminance of 1000 cd m-2. These results demonstrate that Ir(iii) complexes with sulfur-containing ligands can be rapidly synthesized at room temperature, which is key to the production of metal luminescent materials for large-scale application in highly efficient OLEDs.