Synthesis of a new iridium complex and its yellow efficient electroluminescence with low efficiency roll-off by exhaustive optimization of device

A new iridium complex [(DfPPy)(2)Ir(PhCzKt)] was synthesized, its the cyclometalated ligand and auxiliary ligand are 2-(2,4-difluorophenyl)pyridine and 1-(4-(tert-butyl)phenyl)(3)(9-ethyl-9H-carbazol-3-yl)propane-1,3-dione, respectively. The thermally stability, UV-vis absorption, photoluminescence, quantum yield, phosphorescent lifetime, electrochemistry, and electroluminescent performances of (DfPPy)(2)Ir(PhCzKt) were investigated. This Ir complex shows a yellow emission in light-emitting device. We optimized device for many times, and finally achieved higher efficient light-emitting devices, the maximum external quantum efficiency of device reaches 7.58% without host's emission, and the efficiency roll-off is low at high luminance. The good performances of devices are related to this Ir(IIII) complex grafted by carbazolyl and tert-butyl. In addition, TCTA and Bepp(2) in emitting layer acted as host materials play an important role for the improvement of devices' performances.