Tuning the position of methyl groups to realize highly efficient deep-red PhOLEDs

Abstract

As the promising candidates for red phosphorescent organic light-emitting diodes (PhOLEDs), aryl quinoline Ir(III) complexes have attracted enormous and continual attention. The molecular design strategy of introducing methyl group to aryl quinoline unit to tune their optoelectronic properties is reported here. The synthesis, structures, electrochemical and photophysical properties of a series of methyl-substituted aryl quinoline Ir(III) complexes were systematically studied. Red and deep-rep phosphorescent emission with the maximum wavelength from 610 nm to 646 nm were accessed by combing the electron-donating effect of the 3-methyl group to centered Ir atom and increased twist angle between phenyl unit and quinoline group induced by the 2-methyl group. Deep-red PhOLEDs with the emission peak at 620 nm, CIE coordinates of (0.68, 0.32), luminescence of 23720 cd/m2, and an EQE of 40.5% were realized.