Electrically Amplified Circularly Polarized Luminescence by a Chiral Anion Strategy

Abstract

The development of circularly polarized electroluminescence (CPEL) is currently hampered by the high difficulty and cost in the syntheses of suitable chiral materials and the notorious chirality diminishment issue in electrical devices. Herein, diastereomeric Ir^III and Ru^II complexes with chiral (±)-camphorsulfonate counteranions are readily synthesized and used as the active materials in circularly polarized light-emitting electrochemical cells to generate promising CPELs. The addition of the chiral ionic liquid (±)-1-butyl-3-methylimidazole camphorsulfonate into the active layer significantly improves the device performance and the electroluminescence dissymmetry factors (≈10^-3 ), in stark contrast to the very weak circularly polarized photoluminescence of the spin-coated films of these diastereomeric complexes. Control experiments with enantiopure Ir^III complexes suggest that the chiral anions play a dominant role in the electrically-induced amplification of CPELs.

Keywords: Chiral Anions; Circularly Polarized Electroluminescence; Ionic Transition Metal Complexes; Light-Emitting Electrochemical Cells.