Machining of metal cathode of OLED by femtosecond laser

Organic light emitting diode (OLED) is now in practical use and also a subject of active research and development. One of the key technologies in industrial production of the OLED display is machining of electrodes, especially a metal electrode, which is usually made on a thin layer of organic compounds. We have developed a selective machining technique of a thin top electrode of aluminum (Al) using an ultra-short fiber laser and test pieces of the OLED display are fabricated successfully. It is found that the machining characteristics of aluminum electrode vary with the local structure of the specimen: the threshold fluence of the removal of the Al electrode becomes lower and the ablated size becomes larger for Al on ITO layer than that without ITO. The results suggest that the change of the threshold energy would due to the change of relevant machining mechanisms. Detailed study by custom-made ultra-fast photography systems is presented. The Al layer on ITO is removed by only one pulse so long as it is above its threshold energy. It is important to avoid multiple irradiations to machine the Al selectively and to keep the structures beneath undamaged.