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

Abstract

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 T_d > 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.