Rational Design of Efficient Organometallic Ir(III) Complexes for High-Performance Flexible Monochromatic and White Light-Emitting Electrochemical Cells

Development of highly efficient light-emitting electrochemical cells (LECs) has attracted tremendous interest as they show simple and low-cost fabrication processing in both full-color display and solid-state lighting. In this work, we rationally design and synthesize two red-emitting cationic Ir(III) complexes, namely [Ir(tBuPBI)2(biq)]PF6 (R1) and [Ir(tBuPBI)2(qibi)]PF6 (R2), in which tert-butyl functionalized 1,2-diphenyl-1H-benzo[d]imidazole (pbi) unit and conjugated 2,2'-biquinoline (biq) and 2-(1-phenyl-1H-benzo[d]imidazol-2-yl)quinolone (qibi) are employed as cyclometalated and ancillary ligands, respectively. The introduced tert-butyl group not only increases the solubility but also suppresses the strong intermolecular interaction due to the steric hindrance, resulting in homogeneous and highly emissive thin film. Efficient red-emitting LECs fabricated on glass substrate achieve the current efficiency (hC) of 7.18 cd/A and external quantum efficiency (hext) of 9.32 %, respectively. By doping both ...