Highly efficient yellow electroluminescence of iridium complexes with good electron mobility

Abstract

Herein, two iridium(III) complexes with yellow emission using 1-(3,5-bis(trifluoromethyl)phenyl)isoquinoline (tfmphiq) and 4-(3,5-bis(trifluoromethyl)phenyl)quinazoline (tfmphqz) as the main ligands and tetraphenylimidodiphosphinate (tpip) as the ancillary ligand were applied in organic light-emitting diodes (OLEDs). The quinazoline moiety greatly influenced the nature of the complexes, and both the quantum yield and the electron mobility of Ir(tfmphqz)₂(tpip) were much higher than that of Ir(tfmphiq)₂(tpip) (Ir(tfmphiq)₂(tpip) (λ_em: 581 nm and Φ: 0.61) and Ir(tfmphqz)₂(tpip) (λ_em: 566 nm and Φ: 0.97)). Moreover, the device based on Ir(tfmphqz)₂(tpip) displayed far better performance than that based on the Ir(tfmphiq)₂(tpip) emitter. The device with a structure of ITO/MoO₃ (3 nm)/TAPC (50 nm)/Ir(tfmphqz)₂(tpip) (6 wt%): 26DCzPPy (10 nm)/TmPyPB (50 nm)/LiF (1 nm)/Al (100 nm) displayed a maximum luminance of 96 377 cd m⁻² and a maximum current efficiency and a maximum power efficiency of 106.66 cd A⁻¹ and 64.72 lm W⁻¹, respectively, with low efficiency roll-off. The current efficiency still remains as high as 89.91 cd A⁻¹ at the brightness of 1000 cd m⁻² and 79.73 cd A⁻¹ at the brightness of 5000 cd m⁻². These results suggest that the Ir(III) complexes with quinazoline units are potential yellow phosphorescent materials for OLEDs.