**2. Photoluminescence study**

The PL measurements were carried out by a solid laser 447 nm and detected through a Jobin Yvon 250-mm HR mono-chromator, with a GaAs photomultiplier associated to standard lock-in technique. Of note, the laser power of 7.66 mW was applied on the surface of the sample.

The optical characterization used in our work is based on "the radiationmatter interaction"; it tells us about the optical properties of the material. Photoluminescence spectroscopy is widely used to study the electronic structure of materials and the processes of radiative recombinations. It is a nondestructive optical characterization technique for nanomaterials.

In this part, using photoluminescence (PL) spectroscopy, we will determine the optical properties of porous silicon samples produced by electrochemical anodization. First, we analyze the PL spectra of SiP at room temperature. Second, we study the variation of the intensity, and the integrated intensity of PL in the temperature range [10–300 K].
