Fast synthesis of iridium(iii) complexes with sulfur-containing ancillary ligand for high-performance green OLEDs with EQE exceeding 31%

Abstract

Three green iridium(III) cyclometalated complexes, namely, (4tfmppy)₂Ir(dipdtc), (24btfmppy)₂Ir(dipdtc), and (TN₄T)₂Ir(dipdtc), with the sulfur-containing ancillary ligand N,N-diisopropyldithiocarbamate (dipdtc) were synthesized within 15 min at room temperature. The emission colors (λ_peak = 497–534 nm) and photoluminescence quantum efficiencies (Φ_P = 71.6–94.2%) can be effectively regulated by introducing different main ligands, namely, 2-(4-(trifluoromethyl)phenyl)pyridine (4tfmppy), 2-(2,4-bis(trifluoromethyl)phenyl)pyridine (24btfmppy), and 2′,6′-bis(trifluoromethyl)-2,4′-bipyridine (TN₄T). Employing these complexes as emitters, organic light-emitting diodes (OLEDs) with double-emitting layers were fabricated. In particular, the device based on the (TN₄T)₂Ir(dipdtc) complex showed superior performances with maximum current efficiency of 86.59 cd A⁻¹ and maximum external quantum efficiency of 31.24% with low efficiency roll-off. These results suggest that the Ir(III) complexes with a four-membered ring Ir–S–C–S backbone containing dipdtc have potential applications in OLEDs.