Iridium(iii) complexes incorporating thieno[2,3-d]pyrimidine units for efficient orange-to-yellow electroluminescence with low efficiency roll-off

In this study, two cyclometalated iridium(iii) complexes, named (4tfptp)(2)Ir(tpip) and (4tfptp)(2)Ir(Stpip), with 4-(4-(trifluoromethyl)phenyl)thieno[2,3-d]pyrimidine (4tfptp) as the main ligand and bis(diphenylphosphoryl)amide (tpip) or bis(diphenylphorothioyl)amide (Stpip) as the ancillary ligand, were synthesized for organic light-emitting diodes (OLEDs). (4tfptp)(2)Ir(Stpip) was obtained in a few minutes at room temperature due to the strong coordination ability of the sulfur atom and the Ir metal center. (4tfptp)(2)Ir(tpip) and (4tfptp)(2)Ir(Stpip) exhibit different emission peaks at 589 and 564 nm with photoluminescence quantum efficiencies (phi(PL)) of 35% and 52% in CH2Cl2 solutions, respectively, which may result from the different heteroatoms introduced into the ancillary ligands. Furthermore, the phi(PL) of (4tfptp)(2)Ir(Stpip) in co-deposited films is improved greatly up to 90%. The OLEDs employing these complexes as emitters exhibit good performance. Particularly, the OLED based on the (4tfptp)(2)Ir(Stpip) complex with Stpip as the ancillary ligand exhibits better performance with a maximum brightness of 38 560 cd m(-2), a maximum current efficiency of 86.3 cd A(-1), a maximum external quantum efficiency (EQE(max)) of 24.7% and an EQE of 20.9% at a luminance of 10 000 cd m(-2), suggesting that these materials have potential applications in efficient OLEDs.

Automated summary

Two new cyclometalated iridium(iii) complexes with different emission peaks were synthesized for OLEDs. One complex exhibited better performance and showed potential for efficient OLED applications.