Fluorescence study of intrachain and interchain ultrafast processes in domain-structured polythiophene

Exciton dynamics of poly(3-dodecylthiophene) were studied by steady state and femtosecond time-resolved fluorescence spectroscopy. Comparing the solution and solid-state results intrachain and interchain exciton transfer processes were distinguished. The steady-state spectra revealed extra nonradiative relaxation channel in solid state and excitation wavelength-dependent fluorescence, suggesting non-trivial energy level structure. According to the observed wavelength dependent spectral splitting phenomena a domain model of the poly(3-dodecylthiophene) solid structure were suggested. The time-resolved results confirmed the domain concept unveiling two spectral areas with different fluorescence character. Moreover, the time-resolved study was able to differentiate between two poly(3-dodecylthiophene) samples with small change (13%) of their regioregularity. The obtained results are a demonstration of usefulness of fluorescence spectroscopy to analyze the interchain polymer structure in solid state.