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

Abstract

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 (0.5 wt % to 2.5 wt %) of Ir(ppy)(3). The maximum luminance and current density were about 8600 cd/m(2) and 155 mA/cm(2) at 7 V, 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 512 nm and (x, y = 0.27 to 0.28, 0.61 to 0.63), respectively, showing a green color.