Preparation and characterization of phosphorescence organic light-emitting diodes using poly-vinylcarbazole: Tris(2-phenylpyridine) iridium(III) emission layer

An emission layer with the poly-vinylcarbazole (PVK) and Ir(ppy) ₃[tris(2-phenylpyridine)iridium(III)] as the host and guest materials, respectively, was prepared on a PEDOT:PSS/ITO substrate. TPBI [2,2′,2″-(1,3,5-benzinetriyl)-tris(1-phenyl-1-H-benzimidazole)] was introduced to improve the light efficiency of the devices. Green phosphorescence polymer LEDs with the structure ITO/PEDOT:PSS/PVK:Ir(ppy)₃/TPBI/LiF/ Al were fabricated and their electrical and optical properties investigated at various doping concentrations (0.5wt%to2.5wt%) of Ir(ppy)₃. The maximum luminance and current density were about 8600cd/m² and 155mA/cm² at 7V, respectively, when the TPBI layer was introduced between the emission layer and cathode electrode film. The emission spectrum and Commission International d'Eclairage (CIE) color coordinates were about 512nm and (x,y=0.27 to 0.28, 0.61 to 0.63), respectively, showing a green color.