Narrow bandwidth red electroluminescence from solution-processed lanthanide-doped polymer thin films

Narrow bandwidth red electroluminescence from OLED devices fabricated using a simple solution-based approach is demonstrated. A spin-casting method is employed to fabricate organic light emitting diode (OLED) devices comprising a poly(N-vinylcarbazole) (PVK) host matrix doped with a europium β-diketonate complex, Eu(dbm)₃(Phen) (dibenzoylmethanate, dbm; 1,10-phenanthroline, Phen) on glass/indium tin oxide (ITO)/3,4-polyethylene-dioxythiophene-polystyrene sulfonate (PEDOT) substrates. Saturated red europium ion emission, based on the ⁵D₀ → ⁷F₂ transition, is centered at a wavelength of 612 nm with a full width at half maximum of 3.5 nm. A maximum external quantum efficiency of 6.3 × 10^{- 2} cd/A (3.1 × 10^{- 2}%) and a maximum luminance of 130 cd/m² at 400 mA/cm² and 25 V is measured for ITO/PEDOT/PVK:Eu(dbm)₃(Phen)/Ca/Al devices. This measured output luminance is comparable to that of devices fabricated using more sophisticated small molecule evaporation techniques.