Surface treatment effects of indium–tin oxide in organic light-emitting diodes

Abstract Effects of mechanically polished and annealed indium–tin oxide (ITO) substrate in tris-(8-hydroxyquinoline) aluminum (Alq3)-based light-emitting diodes were studied. It was found that roughness and oxygen content at ITO surface were reduced after the mechanical polishing. The organic light-emitting diodes (OLEDs) fabricated on the polished ITO surface showed 10 times better electroluminescence and current injection than the OLEDs based on as-received ITO surface, due to the increase of smooth contact area between the ITO surface and organic layer. The nucleation of TPD on ITO shows different feature according to the surface condition of ITO. As a result, the mechanical polishing is an effective treatment to enhance the performance of the OLEDs.