Supramolecularly Caged Cyclometalated Iridium Complex With a New Imidazole Type Ancillary Ligand for Stable and Bright Green Light-Emitting Electrochemical Cell

Abstract

A new imidazole-based ligand and its cyclometalated iridium (III) complex, namely, [Ir (ppy)₂(Imdipy)](ClO₄): IrL, were designed and successfully synthesized with a combination approach and employed as an emissive layer in the fabrication of light-emitting electrochemical cell (LEC). This complex exhibits intense structured green emissions centered at 490 and 515 nm with a high photoluminescence quantum yield of 17% in a CH₂Cl₂ solution. Moreover, an intense structureless yellow-green emission was observed in its spin-coated neat film at a maximum wavelength of 540 nm. Compared with archetype complex [Ir (ppy)₂(bpy)]⁺, IrL illustrates a 3% higher PL quantum yield (PLQY) with a 100-nm blue shift in emission, which is attributed to the strong field nature of Imdipy ancillary ligand in IrL. Electrochemical studies confirmed the electrochemical stability of the IrL complex as a consequence of its quasi-reversible redox behavior in the solution. The IrL-based LEC shows stable yellow-green electroluminescence centered at 546-nm. This study demonstrates the importance of such ligands in achieving optoelectronic devices (LECs and OLEDs) with long lifetime at short wavelengths.