Electronic states in conjugated polymers probed by excimers

We synthesized an oligomer of O-PPV [ poly(2,5-diphenylene-1,3,4-oxadiazolyle-4,4′-vinylene ] with 4 repeat units. As oxadiazole in the PPV main chain is an acceptor, intermolecular interaction of O-PPV will increase and even produce a charge-transfer complex (excimer) in solid-state. So we may obtain the information of electronic structures on conjugated polymers by detecting the PL characteristics of excimers. The absorption, excitation and photoluminescence spectra were measured on pristine O-PPV and O-PPV/PEO [poly(ethyleneoxide)]. The results indicate that the strength of the interchain charge-transfer is related to the property of excited states. We think that there are two different processes of photoexcitation transitions in conjugated polymers.