Implantation d’une sonde d’absorption photo-induite dans une expérience de spectroscopie bidimensionnelle d’excitation sur le système polymérique modèle PCDBT:PCBM
This master’s thesis present the implemantation of a photo-induced absorption probe to a collinear phase modulated two-dimensionnal excitation spectroscopy experiment. This type of spectroscopy studies the correlations between different elctronic states of a material on an ultrafast timescale to know better about the system’s dynamics. This new probe, combined to this experiment gives insight on materials where a coupling prevents from understandin the dynamic of the system. If there is such coupling between two states, it is impossible to probe the relaxation directly with light. Studying the correlations between the states, is it possible to learn more about this coupling. To prove that this new technique brings valid information on a studied material, we want to compare the results obtained with the photoinduced absorption probe to those obtained with a photoluminescence one for a system where we expect these results to be the same, PCDTBT:PCBM. Since the two-dimensionnal spectroscopy experiment enlightens the correlations between the excited states and the final products, if we probe the same final products with different probes, we should obtain the same results. Even though it was impossible to compare the results with the photoluminescence probe since the emitted signal was too low to be detected, the validity of the new probe was shown by comparing with data already known in the litterature and by making sure that the sample’s response was linear when it was expected to be. Also, the signal obtained with the new probe came from the excited states of the PCDTBT:PCBM, hence of the absorption. Finally, these results were compared to the ones obtained by a photocurrent probe. The quantum efficiency of the obtained results by the both probes was almost identical, proving the validity of this new probe to study correlations in different materials.
PCDTBT:PCBM Photoluminescence Non-linear spectroscopy Photo-induced absorption Linearity