Abstract: A method of treating a cathode of an OLED device having a substrate and which has a spaced anode and organic layers between the anode and cathode includes evacuating a chamber so that it has a pressure no greater than 10?6 Torr; heating the OLED substrate in the chamber to a temperature less than 100° C.; and delivering gas, including ozone, to the evacuated chamber which includes the heated OLED substrate at a sufficient rate so that the pressure is less than 1 atmosphere, so that the life of the OLED substrate is increased and the operating voltage is decreased.