Synthesis and luminescence properties of two cross-linkable Ir(iii) complexes

Abstract

Two cross-linkable iridium(III) complexes, Ir(L)₂(acac) and Ir(L)₂(Stpip), where L = 1-phenyl-2-(4′-vinyl-[1,1′-biphenyl]-4-yl)-1H-benzo[d]imidazole, acac = acetylacetonate, and Stpip = bis(diphenylphorothioyl)amide, were synthesized and characterized by elemental analysis, NMR (¹H and ¹³C) spectroscopy and HRMS. The iridium(III) complexes exhibited excellent thermal stability and green–yellow emission with a maximum main peak at 563 nm. The photoluminescence quantum yields of Ir(L)₂(acac) and Ir(L)₂(Stpip) were 2.77% and 1.80%, respectively, in CH₂Cl₂ solution. The vacuum-processed electroluminescence device fabricated from Ir(L)₂(acac) at 4 wt% doping concentration exhibited a maximum current efficiency (CE_max) of 26.3 cd A⁻¹, a maximum brightness of 9645 cd m⁻² and a maximum external quantum efficiency (EQE_max) of 14.7%. The solution-processed electroluminescence device based on Ir(L)₂(acac) exhibited a maximum current efficiency (CE_max) of 3.71 cd A⁻¹, a maximum brightness of 2237 cd m⁻² and a maximum external quantum efficiency (EQE_max) of 1.36%.