New iridium complex as high-efficiency red phosphorescent emitter in polymer light-emitting devices

Abstract

A new heteroleptic iridium complex Ir(1-piq)₂pt with 1-phenylisoquinoline and 3-(pyridin-2′-yl)-1H-1,2,4-triazole was synthesized and characterized. The complex was incorporated into phosphorescent polymer light-emitting devices using polyhedral oligomeric silsesquioxane-terminated polyfluorene (PFO-poss) as a host polymer doped with 30% of electron transport materials 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (PBD). Red electrophosphorescence was observed with a peak emission at 605 nm. The highest-efficiency polymer light-emitting diode was achieved with PFO-poss doped with 2% Ir(1-piq)₂pt. An external quantum efficiency of 10.4% and a luminous efficiency of 9.4 cd A⁻¹ were obtained at 10.8 mA cm⁻². These values were found to be 7.67% and 5.99 cd A⁻¹ at 100 mA cm⁻².