**2.1 Experimental details**

Serial of porous silicon samples were prepared of *p*-type (100)-oriented silicon substrate with a resistivity of 0.001–0.02 Ω cm.

The experimental set-up consists first of all of a pulsed laser, the emission wavelength of which can be changed. The laser we have allows us to take measurements with an excitation of 447 nm. The laser beam is then conveyed to the sample by sets of mirrors. The sample is on a sample holder that can be placed in a cryostat (for low temperature studies) (**Figure 1**).

**111**

**Table 1.**

*different etching time and current density of 15 mA/cm2*

**Figure 2.**

*Optical Study of Porous Silicon Layers Produced Electrochemically for Photovoltaic Application*

*2.2.1 Evolution of photoluminescence spectra of P-type porous silicon prepared at* 

All of the PS samples showed a visible PL at a room temperature. **Figure 2** illustrates the PL spectra of samples of p-type elaborated at different etching times (60, 120, 180, and 240 s) as well as an etching current density of 15 mA/cm<sup>2</sup>

**Figure 2** shows that the observed large band, that ranges from 550 to 780 nm, decreases in time with a peak of 668 nm, and a decreased full width at half maximum (FWHM) from 226 to 112 is obtained along with an increase of PL intensity

The width of this PL band is attributed to the wide size distribution of the silicon nanocrystallites which constitute the porous layer. The intense spectrum is characterized by a maximum at the energy of 1.86 eV and a width at mid-height of

In addition, we noticed a second less intense band compared to the first. This may be due to an oxide layer located in a band between 780 and 900 nm (**Table 1**).

**Samples Etching time (s) λPic (nm) FWHM (meV) IPLMax (u,a) Eg (eV)** S1 60 628 226 0.07 1.96 S2 120 666 189 0.89 1.86 S3 180 652 122 6.81 1.91 S4 240 668 112 21.06 1.86

*Optimized fitting parameters corresponding to the theoretical curves of porous silicon samples prepared at* 

*.*

*Evolution of photoluminescence spectra of P-type porous silicon prepared at different etching times.*

.

*DOI: http://dx.doi.org/10.5772/intechopen.93720*

*different etching time*

from 0.07 to 21.06.

the order of 112 meV.

**2.2 Photoluminescence of porous silicon layers**

**Figure 1.** *Experimental device used for the measurement of photoluminescence.* *Optical Study of Porous Silicon Layers Produced Electrochemically for Photovoltaic Application DOI: http://dx.doi.org/10.5772/intechopen.93720*
