Strategic Fluorine Atom Positioning in Carbazolyl Oxadiazole Derivatives: Constructing Asymmetric Ir(III) Complexes for Enhanced Electroluminescent Performance

Abstract

The asymmetric coordination Ir(III) complexes hold promise as luminescent materials for organic light-emitting diodes (OLEDs). This study provides an efficient synthetic strategy for the construction of asymmetric complexes through novel carbazolyl oxadiazole-based cyclometalating ligands. This approach circumvents the need for multiple structurally distinct ligands, thereby simplifying the synthetic procedures. Comprehensive characterization of the asymmetric complex (Ir-op-CB) and its symmetric isomers showed that variations in coordination modes had a great impact on emission properties, enabling a wide range adjustment of luminous colors from green to orange-red. Particularly, the complex Ir-op-CB has a high dipole moment and a dominant metal-to-ligand charge transfer nature, resulting in excellent electroluminescent performance. The device incorporating asymmetric complex Ir-op-CB as the emissive layer achieved a maximum brightness of 11187 cd m-2 and a current efficiency of 14.93 cd A-1. These findings reveal an effective strategy for designing an asymmetric coordination complex to enhance electroluminescence efficiency.