Red polymer light-emitting devices based on an oxadiazole-functionalized europium(III) complex

A novel tris(dibenzoylmethanato)[5-(2-(4-tert-butylbenzenyl)-5-benzenyl-1, 3,4-oxadiazole-4′)-1,10-phenanthroline]europium(III) [Eu(DBM) ₃(BuOXD-Phen)] containing an electron-transporting oxadiazole-functionalized phenanthroline ligand was synthesized and characterized. Its UV-vis absorption and photoluminescence (PL), as well as the electroluminescence (EL) in polymer light-emitting devices (PLEDs) were investigated. The double-layer PLEDs with a configuration of ITO/PEDOT:PSS (50 nm)/PVK (40 nm)/PFO:PBD (30%):Eu(DBM)₃(BuOXD-Phen) (1-8 wt %) (80 nm)/Ba (4 nm)/Al (150 nm) were fabricated. Saturated red Eu³⁺ ion emission, based on the ⁵D₀ → ⁷F ₂ transition, is centered at a wavelength of 614 nm with a full width at half maximum (FWHM) of 10 nm. The highest external quantum efficiency (QE_ext) of 1.26% at current density of 1.65 mA cm^-2, with a maximum brightness of 568 cd m^-2 at 137.8 mA cm^-2 was achieved from the device at 1 wt % dopant concentration.