A layer-wise topographic study of a polymeric light-emitting diode: indium-tin oxide/poly (2,3-diphenyl-p-phenylene vinylene) / Ag

Scanning tunneling microscopy was used to characterize surface topographies relevant to polymeric light-emitting diodes (LEDs) whose active medium is a thin film of poly(2,3-diphenyl-p-phenylene vinylene) (DP-PPV). We performed a sequence of topographic studies on an indium-tin oxide (ITO) substrate, a DP-PPV film deposited on the ITO substrate, and a Ag layer of thickness of about 100 إ as evaporated on the DP-PPV film. ITO showed a granular structure, DP-PPV exhibited a fibrous-like bundled structure, and the Ag layer formed clusters whose surface roughness was comparable to the layer thickness. The different surface topographies were quantified by using the scaling of the height-height correlation functions.