Impedance Spectroscopy Analysis of Organic Light-Emitting Diodes Fabricated on Plasma-Treated Indium-Tin-Oxide surfaces

In this work, impedance spectroscopy analysis was used to study the effects of plasma treatment on the surface of indium-tin oxide (ITO) anodes using CF4, O2 and Ar gases and to model an equivalent circuit for organic light-emitting diodes (OLEDs). The devices with an ITO/TPD/Alq3/LiF/Al structure could be modeled as a simple combination of resistors and capacitors. For modifications of the ITO surface, the samples were treated in an inductively-coupled tubular reactor system. The OLEDs fabricated on plasma-treated ITO anodes showed a lower impedance and a higher capacitance. The changes in the impedance and the capacitance were attributed to removal of contaminants and to changes in the work function of ITO. The impedance spectroscopy analysis showed that the devices with plasma-treated ITO anodes had different values of the contact resistance (RC), the parallel resistance (RP ) and the parallel capacitance (CP ). KCI Citation Count: 10