Single molecule spectroscopy of conjugated polymers
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This dissertation is focuses on applying single molecule spectroscopy to the study of photophysical and photochemical properties of conjugated polymers. By investigating the fluorescence intensity fluctuation, the fluorescence spectra and the absorption anisotropy of individual conjugated polymer molecules, we were able to study in detail about the fast singlet exciton migration pathway in conjugated polymers that is energetically downhill to low energy funnel site. The exciton migration is facilitated by the ordered chain packing of these polymers as evidenced by the high single molecule absorption anisotropy values. As a direct result, singlet exciton can be quenched efficiently by occasionally generated quencher species, i.e. hole polarons and triplet excitons. The generations and eliminations of the quenchers were monitored by tracking the temporal fluctuation vii of the fluorescence signal. We have demonstrated that the generation of hole polarons is a low yield photon-excitation driven process with assists from O2. Triplet excitons can be generated in relatively high quantum yield. Its concentration in single conjugated polymer molecules is limited by very efficient exciton-exciton annihilation process.