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. Enhance d hole-injection efficiency improves dramatically the performance of s ingle-layer doped-polymer devices: the drive voltage drops from > 20 t o < 10 V, the external electroluminescence quantum efficiency (backsid e 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 brightne ss (maximum brightness similar to 10,000 cd/m(2) at 1000 mA/cm(2)), an d 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 i s also enhanced by two orders of magnitude. (C) 1997 American Institut e of Physics.