Photo-induced excited molecule quenching

We have previously shown that when PPV is self-assembled with specific electronically active polyanions such as poly(thiophene acetic acid) (PTAA) or sulfonated fiillerenes (S-C60 )(7), the photoluminescence of the PPV is essentially completely quenched by the polyanion. The mechanism of this quenching is believed to be due to a photoinduc electron transfer process taking place between the excited PPV and the adjacent electroactive polyanion molecules. The quenching process, in this case, is not associated with a Forster type energy transfer since in both cases, the required spectral overlap of a donor emission band with an acceptor absorption band is not fulfilled. In addition, photo-induced electron transfer processes have previously been confirmed in PPV/C60 systems and can be exploited to fabricate thin film photovoltaic devices (77). In order to mediate this electron transfer process, we have constructed multilayer heterostructures in which the PPV donor and the polyanion electron acceptor are separated from each other with electronically inert spacer layers of known thickness. In addition to allowing studies of the electron transfer process, such structures provide important insights into the thermal stability of the multilayer structure. The "spacers" used in this study were bilayers of SPS/PAH with an experimentally determined bilayer thickness of 30 +/-5 A. 

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