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Four new nanolayered heterojunctions of electron-donating poly(3-hexylthiophene-2,5-diyl) and poly(3-octylthiophene-2,5-diyl) with two electron-accepting polyquinolines have been prepared, and the photophysical processes occurring at the polymer/polymer interfaces were investigated by photoluminescence (PL) spectroscopy and picosecond time-resolved PL decay dynamics. Observed nearly complete quenching of the steady-state photoluminescence and a factor of 160 shortening of the fluorescence lifetime of the polyquinolines suggested photoinduced electron transfer from polythiophene to polyquinoline at the polyquinoline/polythiophene interfaces. A new, weak and red shifted, emission band centered at 630 nm and reduced lifetimes show the formation of intermolecular exciplexes at the polyquinoline/polythiophene interfaces. This is the first example of intermolecular exciplex formation between two π-conjugated polymers. Exciton diffusion lengths in the polyquinolines were estimated to be 17−22 nm. These results suggest that nanolayered polythiophene/polyquinoline heterojunctions are promising new material systems for the development of photovoltaic devices and for model studies of the photophysics of multicomponent conjugated polymers.
Alam et al. (Sat,) studied this question.