Novel Ir(III) complexes ligated with 2-(2,6-difluoropyridin-3-yl)benzo[d]thiazole for highly efficient OLEDs with mild efficiency roll-off

Abstract 2-phenylbenzothiazole-based Ir(III) complex [(bt) 2 Ir(acac)] is a class of typical yellow phosphorescence material, which has been widely used in OLEDs. However, (bt) 2 Ir(acac) exhibited only mild photoluminescence quantum efficiency (PLQY) of 0.26–0.28. To further improve the luminous efficiency of benzothiazole-based Ir(III) complex and then boost the corresponding electroluminescent performance, (fpbt) 2 Ir(pic) and (fpbt) 2 Ir(tftp) were successfully synthesized, where 2-(2,6-difluoropyridin-3-yl)benzo[ d ]thiazole (fpbt) was applied as C ∩ N main ligand, and 2-pyridine carboxylic acid (pic), 2-(3-(trifluoromethyl)-1H-1,2,4-triazol-5-yl)pyridine (tftp) acted as different auxiliary ligands. Both (fpbt) 2 Ir(pic) and (fpbt) 2 Ir(tftp) presented excellent PLQYs (0.93–0.95) and high thermostability (330–360 °C). The vacuum-deposited devices following the architecture of ITO/TAPC/CBP: dopant/TPBi/Liq/Al demonstrated prominent performances. Of them, (fpbt) 2 Ir(pic)-doped OLEDs exhibited better efficiencies of 20.6%, 68.8 cd A −1 , and 40.8 l m W −1 while maintaining very mild efficiency roll-off. Such outstanding electrophosphorescent performances were further investigated, which was probably attributed to the following factors: 1) high PLQY; 2) good electron mobility; 3) uniform film-forming property.