STM Induced Electroluminescence From a Soluble PPV Derivative

A scanning tunnelling microscope was used to generate electroluminescence from thin films of the conjugated polymer poly(1,3-phenylene vinylene-co-2,5-dioctyloxy-1,4-phenylene vinylene). This allowed the spatial distribution of EL to be mapped across the film, and also measurements of local EL emission spectra to be recorded. It was observed that both the emission spectra and their intensity are highly non-uniform on length scales greater than approximately 2 nm. This is important in the context of light emitting diodes since it indicates that control of nanostructure can greatly improve device performance.