The effects induced by different electrical contacts, both for the anode and for the cathode, have been analyzed in
Organic Light Emitting Diodes (OLEDs). The properties of anode electrode, Indium Tin Oxide (ITO), have been varied
through different surface treatments allowing roughness control, carbon impurity removal, spikes decrement. These
induce changes of ITO surface chemical-physical characteristics as roughness, surface energy and surface polarity.
OLEDs manufactured employing treated ITO have showed an improvement of 25 times in luminance. Thermionic
injection model has been used to estimate decrement in effective hole barrier at ITO-organic layer. It is shown that this
effect is correlated to ITO surface energy. The second step of process optimization has concerned the cathode electrode
investigation. In order to perform this task, Al, Ca/Al, Ag, Mg/Ag have been used to realize different
ITO/PEDOT:PSS/PF6/Alq3/Metal OLEDs. Measurements of electrical and optical behaviour have been performed. A
thermionic injection model, with and without Schottky barrier decrement, has been used to calculate the change of the
cathode electrical barrier.