Efficient phosphorescent red iridium(III) complexes containing a four-membered Ir-S-C-S ring backbone and large hindered spacers for high-performance OLEDs

Two efficient red iridium(III) complexes, (4tfmpq)(2)Ir((t)Budpdtc) and (4tfmpq)(2)Ir((t)BuCzdtc), containing a unique four-membered ring Ir-S-C-S backbone with flexible dithiocarbamate derivatives ((t)Budpdtc = N,N-bis(4-(tert-butyl)phenyl)dithiocarbamate and (t)BuCzdtc = N-3,6-di-tert-butyl-9H-carbazole dithiocarbamate) with large hindered spacers as ancillary ligands, respectively, and 4-(4-(trifluoromethyl)phenyl)quinazoline (4tfmpq) as the main ligand were synthesized at room temperature in 10 min and investigated in detail. Due to the electron-deficient 4tfmpq main ligand and two ancillary ligands with bulky electron-donating substituents, the photophysical properties of two complexes can be effectively regulated (lambda(peak) = 630 nm, Phi(P) = 75.0% for (4tfmpq)(2)Ir((t)Budpdtc), and 614 nm and 85.0% for (4tfmpq)(2)Ir((t)BuCzdtc), respectively). Employing the two complexes as emitters, organic light emitting diodes (OLEDs) with double emissive layers exhibit superior performances with a maximum current efficiency of 34.72 cd A(-1), a maximum external quantum efficiency (EQE(max)) of 26.66% with low efficiency roll-off and an EQE of 24.62% was still obtained at a practical luminance of 1000 cd m(-2). These results suggest that Ir(III) complexes with a four-membered ring Ir-S-C-S backbone containing flexible dithiocarbamate derivatives have potential application in OLEDs.