Surface modification of indium tin oxide by plasma treatment: An effective method to improve the efficiency, brightness, and reliability of organic light emitting devices

We demonstrate the improvement of an indium tin oxide anode contact to an organic light emitting device via oxygen plasma treatment. Enhanced hole-injection efficiency improves dramatically the performance of single-layer doped-polymer devices: the drive voltage drops from > 20 to < 10 V, the external electroluminescence quantum efficiency (backside emission only) increases by a factor of 4 (from 0.28% to 1%), a much higher drive current can be applied to achieve a much higher brightness (maximum brightness similar to 10,000 cd/m(2) at 1000 mA/cm(2)), and the forward-to-reverse bias rectification ratio increases by orders of magnitude (from 10(2) to 10(6)-10(7)). The lifetime of the device is also enhanced by two orders of magnitude. (C) 1997 American Institute of Physics.