Synthesis and electrophosphorescent performances of alkyl-substituted bicycloiridium complexes in polymer light-emitting diodes

In this paper, two complexes (mppy)2Ir(tmd) and (bppy)2Ir(tmd) were synthesized and doped into PVK. We find that the alkyl substitution of bicycloiridium complexes on acetylacetonate ligand has a great effect on optimizing the PLED performances. The best device performance is observed for the (bppy)2Ir(tmd)-doped PVK–PBD (40 wt%) device with the concentration of 1 wt%. A maximal external quantum efficiency of QEext = 14.2% ph/el and the luminous efficiency of LE = 33 cd/A with a luminance of 2099 mA/cm2 were achieved at a current density of 6.4 mA/cm2.