Reduced operating voltage of organic electroluminescent devices by plasma treatment of the indium tin oxide anode

The impact of oxygen plasma treatment of indium tin oxide anodes on perform ance and durability of vapor-deposited organic electroluminescent devices i s shown. Investigations focused on the long-term stability using driving co nditions suitable for passive matrix driven displays. Reliability studies o f solvent only cleaned samples indicate the presence of a predominating deg radation process at the interface between indium tin oxide and the hole inj ection layer which results in a drastic rise of the operating voltage. This voltage increase could be reduced to 0.31 mV/h by oxygen plasma treatment. As hole injection layer copper phthalocyanine is compared with a star-shap ed amine derivative. (C) 1999 American Institute of Physics. [S0003-6951(99 )04423-X].