Porous silicon is one of the spongy materials, capable of absorbing gaseous or liquid substances without deteriorating. Thanks to this property, the matrix of the material reacts with the environment; the optical, electrical, mechanical and thermal properties can change. Thin films of porous silicon are used in the field of chemical sensors [1] (liquid, gas and biological material), and also in the field of solar cells as antireflection layers on the surface of silicon [2] or as heterojunction PS / c- Si [3] that offer an additional absorption zone to the solar cell. In our work thin films of porous silicon are developed using two inexpensive methods: chemical etching and electrochemical etching using solutions based on hydrofluoric acid [4]. In order to study the morphological, optical and electrical properties of these thin films of porous silicon, we have used several characterization techniques such as: SEM and AFM that show the formation of dense and homogenous porous layer of thickness 1.2 µm with nano-pores of size of 12 nm. The Raman spectra of porous layer show a peak at 530 cm^-1 with different intensities depending on crystallite size. The XRD results confirm that porous silicon has the same crystallographic orientation as silicon substrates.  The electrical resistivity of the porous layers was measured with four-point probe method. The UV-Visible spectroscopy showed the considerable improvement in the porous silicon absorption in the visible. The reflectivity of PS/c-Si heterojunction was reduced from 35% to 6%. The optical band gap of porous silicon was found to be 1,85 eV. These results show the great potential of porous silicon as intersecting material for improving the performances of high efficiency solar cells.

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References

[1] F. Rahimi , A. Iraji zad & F. Razi. Synthesis and Reactivity in Inorganic, Metal-Organic and Nano-Metal Chemistry, (2007)37:377–380,

[2] Mukhlis M. Ismail et Al, International Journal for light and Electron optics (2017).

[3] Bechiri, F., Zerdali, M., Rahmoun, I., Hamzaoui, S. The European Physical Journal-Applied Physics,

(2013) 61(3).

[4] A. Moussi, D. Bouhafas, N. Benreguia. Surface Review and Letters, Vol. 15, No. 3 (2008) 261–264