Resolving the ultrafast dynamics of charge carriers in nanocomposites

TL;DR

This paper introduces an optical pump-probe method combining reflectivity and scattering to measure ultrafast charge carrier dynamics in nanocomposites, revealing recombination and charge transfer times.

Contribution

It develops a novel experimental approach and modeling framework to accurately determine charge carrier dynamics in nanostructured composites.

Findings

Recombination time in nanocrystals is approximately 4.9 ps.

Recombination time in the matrix is approximately 22 ps.

Charge transfer time between nanocrystals and matrix is about 4 ps.

Abstract

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.