**3.2 Experimental device used**

**Figure 11** shows the "GES5" spectroscopic ellipsometer used in our work; this ellipsometer is assisted by a computer and controlled by the WinElli-II software.

#### **Figure 10.**

*The multilayer model of the PSL [31].*

**Figure 11.** *Real photo of the GES 5 Sopra Ellipsometry used in our work.*

This work was carried out at the techno pole photovoltaic laboratory of bordj çedria in Tunisia.

### **3.3 Thickness measurement**

We measured the thicknesses of the series A samples (see **Table 1**).

**Figures 12** and **13**, respectively, represent the ellipsometric spectra of samples S2 and S3.

The measure and the shape of the ellipsometrical spectra are presented in **Figures 12** and **13**.

The first serial allows us to determine ellipsometry. The adjustment parameters for the thickness of separated layers, using each sub-layer of the optical model are summarized in **Table 3**.

**Figure 6** shows an agreement between the PL measurement presented by the integral intensity of PL along with the SE measurement presented by the thickness of porous layers obtained through varying etching time.

#### **3.4 Porosity measurement**

The second serial of samples was obtained following an etching time of 180 s and a current density varying from 5 to 20 mA/cm2 . **Figures 14** and **15** show the measurement and the shape of ellipsomety spectra.

#### **Figure 12.**

*SE measurements of the PSL obtained by using 15 mA/cm<sup>2</sup> , 120 s, and the calculated spectra based on the best-fitted parameters [31].*

#### **Figure 13.**

*SE measurements of the PSL obtained by using 15 mA/cm<sup>2</sup> , 180 s, and the calculated spectra based on the best-fitted parameters [31].*

**119**

**Table 3**.

**Figure 15.**

**Figure 14.**

*best-fitted parameters [31].*

*best-fitted parameters [31].*

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

The second serial allows us to determine the porosity of separated layers, using ellipsometrical method. The adjustment parameters for each sub-layer of an optical

*, 180 s, and the calculated spectra based on the* 

*, 180 s, and the calculated spectra based on the* 

**Figures 14** and **15**, respectively, show the measurement and shape of the spectra obtained by ellipsometry, the porous layers (S5, S6) obtained by J = 5 mA/cm2 and

**Figure 7** shows an agreement between the PL measurement presented by the integral intensity of PL and SE measurements presented by the porosity of porous

The two produced curves using values obtained by ellipsometry show that the thickness is as an increased function following etching time; meanwhile the porosity

In this case, the PL comportment can be explained by the absence of the laser interference in the cleaned layer, as previously indicated. The contrary case was

Adjusting the parameters of the proposed model to the experimental measurements taken on the sample, allowed us to obtain the values presented in

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

*SE measurements of the PSL obtained in using 5 mA/cm<sup>2</sup>*

model are summarized in **Table 3**.

J = 10 mA/cm2, and an anodization time of 180 s.

*SE measurements of the PSL obtained in using 10 mA/cm<sup>2</sup>*

layers obtained following varying current density.

is as an increased function following the current density [39].

noticed in the thickness and the porous layer of silicon variations.

*Optical Study of Porous Silicon Layers Produced Electrochemically for Photovoltaic Application DOI: http://dx.doi.org/10.5772/intechopen.93720*

#### **Figure 14.**

*Solar Cells - Theory, Materials and Recent Advances*

çedria in Tunisia.

**Figures 12** and **13**.

summarized in **Table 3**.

**3.4 Porosity measurement**

**3.3 Thickness measurement**

This work was carried out at the techno pole photovoltaic laboratory of bordj

**Figures 12** and **13**, respectively, represent the ellipsometric spectra of samples S2 and S3. The measure and the shape of the ellipsometrical spectra are presented in

The first serial allows us to determine ellipsometry. The adjustment parameters for the thickness of separated layers, using each sub-layer of the optical model are

**Figure 6** shows an agreement between the PL measurement presented by the integral intensity of PL along with the SE measurement presented by the thickness

The second serial of samples was obtained following an etching time of 180 s

. **Figures 14** and **15** show the

*, 120 s, and the calculated spectra based on the* 

*, 180 s, and the calculated spectra based on the* 

We measured the thicknesses of the series A samples (see **Table 1**).

of porous layers obtained through varying etching time.

and a current density varying from 5 to 20 mA/cm2

measurement and the shape of ellipsomety spectra.

*SE measurements of the PSL obtained by using 15 mA/cm<sup>2</sup>*

*SE measurements of the PSL obtained by using 15 mA/cm<sup>2</sup>*

**118**

**Figure 13.**

*best-fitted parameters [31].*

**Figure 12.**

*best-fitted parameters [31].*

*SE measurements of the PSL obtained in using 5 mA/cm<sup>2</sup> , 180 s, and the calculated spectra based on the best-fitted parameters [31].*

#### **Figure 15.**

*SE measurements of the PSL obtained in using 10 mA/cm<sup>2</sup> , 180 s, and the calculated spectra based on the best-fitted parameters [31].*

The second serial allows us to determine the porosity of separated layers, using ellipsometrical method. The adjustment parameters for each sub-layer of an optical model are summarized in **Table 3**.

**Figures 14** and **15**, respectively, show the measurement and shape of the spectra obtained by ellipsometry, the porous layers (S5, S6) obtained by J = 5 mA/cm2 and J = 10 mA/cm2, and an anodization time of 180 s.

**Figure 7** shows an agreement between the PL measurement presented by the integral intensity of PL and SE measurements presented by the porosity of porous layers obtained following varying current density.

The two produced curves using values obtained by ellipsometry show that the thickness is as an increased function following etching time; meanwhile the porosity is as an increased function following the current density [39].

In this case, the PL comportment can be explained by the absence of the laser interference in the cleaned layer, as previously indicated. The contrary case was noticed in the thickness and the porous layer of silicon variations.

Adjusting the parameters of the proposed model to the experimental measurements taken on the sample, allowed us to obtain the values presented in **Table 3**.

**Figure 16.** *Variation of refractive index and extinction coefficient as a function of porosity [31].*

### **3.5 Calculation of the refractive index (n) and the extinction coefficient (k)**

The results illustrated in **Table 3** and **Figure 16** show that the refractive index and the extinction coefficient are as a decreased function along with the porosity.

In case of a porosity of 34%, we get n = 1.77 and k = 0.0035, while for porosity of 78%, we get n = 1.22 and k = 0.0014 [31].

This result shows that the remained porous layer is more proper, but less thick and gives us a best PL intensity. Hence, the laser diffuses in wells by confinement effect. This confinement means to confine the incident laser radiation in crystallites seals and therefore the laser reflection is reduced following the big values of thickness and the porous layers.
