High stability and luminance efficiency thieno[2,3-d]pyridazine-based iridium complexes and their applications in...

Three novel phosphorescent iridium(iii) complexes with thieno[2,3-d]pyridazine derivatives as cyclometalating chelates were successfully synthesized. These complexes exhibited intense green or yellow phosphorescence emission with short lifetimes of 1.71-1.91 μs and very high quantum yields of over 85% in PMMA films. Even in air-equilibrated CH2Cl2, their quantum yields could be up to 36%. They also showed good thermal stability with Td > 338 °C. The electronic structure information of these complexes was discussed by density functional theory. The tris-cyclometalated complex Ir1 was an excellent yellow phosphorescent dopant for OLED applications, and the maximum CE and PE based on it were 58.5 cd A-1 and 45.9 lm W-1, respectively, with the maximum EQE of 18.2% which was ca. 1.4 times more efficient than that of PO-01. These results indicate that these new complexes have potential applications as efficient phosphors in OLEDs.