Transient absorption of copper selenide nanowires of different stoichiometry

Copper selenide nanowires of different stoichiometric compositions and having different density of defects that form intra-band states embedded in a porous alumina layer have been investigated by means of a femtosecond absorption pump-probe technique. Depending on the formation conditions, different samples have different absorption spectra in the near-infrared spectral range, but all of them show bleaching of the most intense absorption bands, which competes with the induced absorption of free charge carriers. A transient absorption relaxation takes place in two steps, with time constants of about 1 ps and several tens of ps. Relative contribution of the fast relaxation component increases in samples with the higher density of defect states forming the recombination centres.