Properties of Blue Polymer Light Emitting Diodes According to the Doping Concentrations of FIrpic Phosphorescence

Abstract

PFO [poly(9,9-dioctylfluorene-2-7-diyl) end capped with N,N-Bis(4-methylphenyl)-4-aniline] based blue polymer light emitting diodes (PLEDs) that use a FIrpic [iridium(III) bis[4,6-(difluorophenyl) pyridinato-N,C20 picolinate] phosphorescent dopant as an emission layer were fabricated using a host-dopant system in order to achieve high luminance and efficiency properties. To find the optimum doping concentration, the FIrpic was doped at various concentrations, ranging from 1 to 4 wt%, into the PFO host. Blue phosphorescence PLEDs with the structure of ITO/PEDOT:PSS/PFO:FIrpic/TPBI/LiF/Al were prepared. The electrical and optical properties were investigated and compared in the prepared PLED devices with and without the FIrpic dopant. The luminance and the current efficiency were improved by introducing the FIrpic dopant. For the PLED device with a 2 wt% FIrpic concentration, the maximum luminance and current efficiency was found to be 4128 cd/m2 and 0.92 cd/A, respectively. The CIE color coordinates was (x, y = 0.19, 0.28), exhibiting a sky-blue color.