Organic Light Emitting Diode (OLED) Using Different Hole Transport and Injecting Layers

Abstract

This paper reports the various structures and performances improvements using different hole transporting layer in OLED based on DPVBi as emitter. Here the indium tin oxide (ITO) used as an anode, copper pthalocyanine (CuPc) as the hole injecting layer, PEDOT:PSS and poly-9- vinylcarbozole (PVK) as hole transporting layer, 4,4'-bis(2,2'diphenilvinyl)-1,1' -biphenyl (DPVBi) as the blue emitting layer and aluminum (Al) as the cathode. The CuPc and DPVBi were prepared by thermal evaporation while the PEDOT:PSS and PVK films were prepared using spin coating technique. The effect of inserting additional layer of CuPc, PVK and PEDOT:PSS between anode and the emitting layers was analyzed through the current-voltage (IV) curves and the electroluminescence spectra. The additional layer structure was found to increase the maximum luminance compared to that one of single layer device. The used of PVK as hole transporting layer has improved the diode properties of the device and able to prevent the device from short circuits. The optimized DPVBi layer thickness was observed at 56 nm and the insertion of 10 nm CuPc hole injecting layer show the device reduce it turn on voltage from 7.0 V to 6.5 V.