Photoemission spectroscopy of the interface between indium-tin-oxide and copper phthalocyanine for transparent organic light-emitting devices

We investigated chemical and electronic structures of copper phthalocyanine (CuPc) for the electron-injection layer between indium tin oxide (ITO) and emission layers in transparent organic light-emitting devices (TOLEDs). Me tallic Cu or dicopper oxide (Cu2O) is formed at the ITO/CuPc interface as a damaged layer during the sputtering deposition of ITO and plays a signific ant role in efficient electron injection from ITO to the emission layer. So phisticated photoemission experiments revealed that the cause of the format ion of the damaged layer is due to the exposure of CuPc to the oxygen plasm a, while no significant damage is introduced by argon plasma and reaction w ith indium and tin atoms. To achieve efficient TOLEDs, the control of the o xygen plasma is essential.