Luminescent Diiridium Complexes with Bridging Pyrazolates: Characterization and Fabrication of OLEDs Using Vacuum Thermal Deposition

Abstract

AbstractA series of novel diiridium complexes (1–4) bearing both functional 2‐pyrazolyl‐6‐phenyl pyridine chelate and bidentate phenyl imidazolylidene chelate are synthesized, for which the pyrazolate fragment of the tridentate 2‐pyrazolyl‐6‐phenyl pyridine also behaves as the bridge to hold two iridium atoms in close vicinity. Their structure is unambiguously confirmed using X‐ray structure determination on the corresponding derivative 2a bearing 1,3‐bis(4‐fluorophenyl)‐1H‐Imidazolyl cyclometalate. Their photophysical and electrochemical properties are studied and further affirmed by the computational approaches. All these Ir(III) metal complexes 1–4 are very stable in both solution and solid film with near unity emission quantum efficiency. As opposed to most of diiridium complexes documented in literature, 1–4 are volatile and suitable for fabrication of organic light emitting diodes (OLEDs) under vacuum evaporation. The corresponding electroluminescent devices exhibit superior performance, among which external quantum efficiency of 27.6% using 2 as dopant stands for the record high of OLEDs using dinuclear Ir(III) complexes. They also offer a low roll‐off at high luminance, demonstrating their potential en route to high performance OLEDs.