Unsymmetric Ir(iii) phosphorescent complexes with both 2-phenylpyridine(ppy)- and 2-vinylpyridine(vpy)-type ligands bearing functional groups and their optoelectronic properties

Abstract

Inspired by the advanced optoelectronic characteristics of 2-phenylpyridine(ppy)-type Ir(III) complexes, we develop a molecular design strategy by introducing functional groups with different charge carrier injection/transport features into the ppy- and 2-vinylpyridine(vpy)-type ligands to confer ambipolar ability to the phosphorescent Ir(III) complexes. In this way, three unsymmetric Ir^III(ppy–vpy)acac-type complexes are successfully prepared. Their photophysical and electrochemical properties prove that vpy-type ligands can exert substantial influence on these properties, resulting in a pronounced red-shifted phosphorescence >610 nm in CH₂Cl₂ with a high phosphorescence quantum yield (Φ_P) of ca. 0.6. Hence, these Ir^III(ppy–vpy)acac-type phosphorescent complexes can show decent EL performance of 15.9%, 46.8 cd A⁻¹ and 45.6 lm W⁻¹, representing the best EL results ever achieved by Ir(III) phosphorescent emitters with vpy-type ligands. Benefiting from these outstanding electroluminescent (EL) performances, we have successfully fabricated a series of complementary color WOLEDs utilizing Ir-3 as an orange component, affording the peak EL performances of 12.6%, 34.3 cd A⁻¹ and 28.8 lm W⁻¹. These impressive results have demonstrated the superiority of these novel unsymmetric ambipolar phosphorescent emitters in optimizing EL ability, which proposes a new idea toward the development of promising Ir(III) phosphors based on the novel vpy-type ligands.