Electrical and Optical Properties of Organic Diodes

Abstract

Two groups of samples have been prepared and some characteresations are studied. Every sample represents an organic diode. The first group is double layer device. Twelve samples with the structure ITO/PVK/dye/InGa have been prepared and studied. Three dyes were used namely Rhodamine B, Crystal violet, and Bromophenol blue. Four different thicknesses of the PVK layers hav been prepared. The thicknesses of thin films were measured using homemade spectroscopic ellipsometer. J-V characteristics curves for all samples have been measured and studied. The conduction mechanisms have been presented. The J-V characteristics show an exponential increase of current with the applied voltage, which is similar to a typical diode characteristics. The samples ITO/35.33nm PVK/50nm Rhodamine B /InGa device and ITO/44.3nm PVK/50nm Rhodamine B /InGa work as organic light emitting diodes (OLEDs). The threshold voltage is found to be 8 and 10 volt respectively. The second group is single layer device. Sixteen samples with the structure ITO/blend of Poly(9-vinylcarbazole) (PVK) and dye/ InGa have been studied. Three dyes were used: Rhodamine B, Fluorescein, Bromophenol blue with concentrations 1%, 2%, 3%, 4% and 5% by weight. J-V characteristics curves have been carried out. The relative light intensity versus voltage and current have been plotted and fabricates samples work as OLED devices. The concentration dependence of electroluminescence have been studied.