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Resolving the ultrafast dynamics of charge carriers in nanocomposites

Here we describe an optical method to determine the dynamics of optically excited carriers in nanostructured composite samples. By combining pump-probe time-resolved reflectivity with scattering measurements, we extract the characteristic times for charge carrier evolution. We use the 3D Maxwell-Garnett formulae, modified to include the Drude optical response, to model the results. The method, applied to hydrogenated amorphous silicon containing crystalline silicon nanoparticles, showed that the recombination times in the nanocrystals and in the matrix were ~4.9 ps and ~22 ps, respectively. The charge transfer time between the crystals and the matrix was ~4 ps.