A novel approach is proposed for determining exciton transport parameters in conjugated polymers. Exciton dynamics of conjugated polymer nanoparticles doped with dyes were investigated by time-resolved fluorescence spectroscopy. Highly efficient energy transfer from the polymer PFBT to the dye perylene red was evident in the fluorescence spectra and excited state kinetics. Exciton transport parameters were obtained by fitting to a model that included the effects of nanoparticle size, exciton diffusion, energy transfer, and quenching by defects. The results indicate substantial quenching by defects, owing primarily to exciton diffusion, which can greatly increase the effective quenching volume of defects. We estimated the amount of quenching by defects, and included quenching by defects in our model, yielding an estimated exciton diffusion length of 12 nm and diffusion constant of 8.0 × 10 −9 m 2 s −1 for nanoparticles of PFBT. The results indicate that quenching by defects can lead to substantial error in determined exciton transport parameters, unless such quenching is properly accounted for in the model.
Conjugated polymer nanoparticles with incorporated antifade agents were prepared, and ensemble and single particle measurements showed that incorporation of antifade agents effectively improves the fluorescence quantum yield and photostability of the conjugated polymer nanoparticles, likely by a combination of triplet quenching and suppression of processes involved in photogeneration of hole polarons (cations), which act as fluorescence quenchers. The photostability of conjugated polymer nanoparticles and CdSe quantum dots was compared, at both the ensemble and single particle level. The results provide confirmation of the hypothesis that quenching by photogenerated hole polarons is a key factor limiting the fluorescence quantum yield and maximum emission rate in conjugated polymer nanoparticles. Additionally, the results indicate the involvement of oxygen in photogeneration of hole polarons. The results also provide insight into the origin of quenching processes that could limit the performance of conjugated polymer devices.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.