In this work, we present the measurements of reflectance, luminescence and photocarriers lifetime for monocrystalline Si substrates covered with a polycrystalline undoped Si 1− x Ge x thin film made porous by stain etching. The reflectance of the samples decreases from ∼39 to ∼8% when the Si 1− x Ge x thin film is made porous. The porous films are photoluminescent, showing a slight redshift when the Ge amount of the film increases. Nevertheless, the growth of the Si 1− x Ge x thin film diminishes the lifetime values, which does not vary after the Si 1− x Ge x surface is passivated with a SiN x thin film. However, when the Si 1− x Ge x thin film is made porous, a slight increase of the lifetime is observed. These results are discussed in terms of application of these thin films in solar cells and photodetectors.