This work considers the anode at the indium-tin oxide (ITO)/poly[2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylene vinylene] (MEH-PPV) interface in polymer light-emitting diodes (PLEDs). The surface morphology of ITO is studied by scanning probe microscopy (SPM). The mechanical properties of ITO and MEH-PPV are measured by nanoindentation. The results indicate that the surface roughness, defined as the root-mean-square of the surface height on the surface of the ITO substrate, influences the injection of hole-carriers. The injected current is dominated by the tunneling of hole-carriers at the low bias. Increasing the effect contact area at the ITO/MEH-PPV interface lowers the barrier to the injection of holes through the ITO anode to the MEH-PPV light-emitting layer. (c) 2007 The Electrochemical Society.