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While numerous works deal with the properties and applications of porous silicon (PS), some of the related topics are not complete or could be investigated from different aspects. The main objective of this paper is to provide novel information associated with the optical properties of nano-and meso-PS by studying the variation of the effective refractive index (n eff ) and the relative dielectric constant (ε r,eff ) as a function of porosity. For this purpose various PS samples were prepared by electrochemical etching of p and p + -type silicon wafers in order to form silicon supported nano-PS and free-standing meso-PS layers, respectively. The experimental effective optical parameters (n eff , ε r,eff ) of the meso-PS films, were determined from the transmission spectra and the Bragg law. While, in the case of nano-PS layers, we applied the Goodman method, and deduced the values of n eff and ε r,eff from the Bruggeman's effective medium approximation (EMA). In the EMA calculation, the PS structure was considered as being a physical combination of three distinct phases formed by silicon, silicon dioxide and voids with a convenient volume fraction. A good agreement between theory and experiment was found in the case of silicon-supported nano-PS for all porosities. However, for free-standing meso-PS, the theory does not well fit the experimental results for porosities lower than 50% and higher than 70%.

In this work, we report the structural, morphological, and optical properties of TiO2 thin films synthesized by the electro phoretic deposition technique. The TiO2 film was formed on a doped fluorine tin oxide (SnO2:F, i.e., FTO) layer and used as a photo electrode in a dye solar cell (DSC). Using spectroscopic ellipsometry measurements in the 200 to 800 nm wavelengths domain, we obtain a thickness of the TiO2 film in the range of 70 to 80 nm. Characterizations by X-ray diffraction and atomic force microscopy (AFM) show a polycrystalline film. In addition, AFM investigation shows no cracks in the formed layer. Using an ultraviolet–visible near-infrared spectrophotometer, we found that the transmittance of the TiO2 film in the visible domain reaches 75%. From the measured current–voltage or I-V characteristic under AM1.5 illumination of the formed DSC, we obtain an open circuit voltage Voc = 628 mV and a short circuit current Isc = 22.6 μA, where the surface of the formed cell is 3.14 cm2.

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