Strong luminescence intensity modulation near a metal-organic interface

The dependence of the luminescence intensity on the distance between an ultra thin PPV probe layer and a metal surface is investigated. We have employed a new Layer-by-Layer method, which allows control of layer deposition at the monolayer level. A precise variation of the metal/PPV separation over the entire substrate surface was achieved by the deposition of an inert spacer layer. A strong dependence of the PPV emission on the spacer layer and metal thickness is observed. The effect of the morphology of the metal surface is also discussed. These results are explained in terms of a competing short range radiationless energy transfer and intensity modulation due to interference effects produced by the optical cavity formed by metal and polymer films.