Control of colour and charge injection in conjugated dendrimer polypyridine bilayer LEDs

Conjugated dendrimers are an interesting class of materials for light emitt ing diodes, and can be used either as light-emitting or charge-transporting layers. We report a study of the use of a solution-processible dendrimer w ith distyrylbenzene core and stilbene dendrons. We find that its use in bil ayer LEDs with polypyridine gives efficiencies ten times greater than for s ingle layer polypyridine LEDs. The light emission can be either from the po lypyridine or the dendrimer layer, depending on the layer thicknesses. This offers a way of tuning the colour of bilayer LEDs.