Low-voltage, high-brightness and deep-red light-emitting electrochemical cells (LECs) based on new ruthenium(ii) phenanthroimidazole complexes

Abstract

Light-Emitting Electrochemical Cells (LECs) with a simple device structure ITO/Ru complex/Ga:In were prepared by using heteroleptic ruthenium(II) complexes containing 2-(2-hydroxyphenyl)-1-(4-bromophenyl)-1h-imidazo[4,5-f][1,10]phenanthroline (hpbpip) as the π-extended ligand. After ancillary ligand modification, the [Ru(hpbpip)(dmbpy)₂](ClO₄)₂ complex shows a deep red electroluminescence emission (2250 cd m⁻² at 6 V) centered at 685 nm, 65 nm red-shifted compared to the [Ru(bpy)₃](ClO₄)₂ benchmark red-emitter at a very low turn voltage (2.6 V), demonstrating its potential for low-cost deep-red light sources. Moreover, the PL quantum yield of the [Ru(hpbpip)(bpy)₂](ClO₄)₂ complex was revealed to be higher (0.121) than the benchmark standard [Ru(bpy)₃]²⁺ (0.095).