Optical properties of electrochemically etched N-type
silicon wafers for solar cell applications

Martin Králik – Matej Goraus – Emil Pinčík

   The presented experiments and studies are intended for photovoltaic applications of crystalline silicon this work deals with chemical treatment of the surface of n-type silicon wafers with different resistivity to reduce their reflectivity. Chemical surface treatment of silicon is an alternative method to using the antireflection layer. Optical losses caused by the reflection of light from the surface of the solar cells significantly reduce their efficiency. The investigated samples were prepared by the electrochemical etching method in the solution based on hydrofluoric acid and ethanol. The analysis of the prepared samples is divided into two parts, namely experimental measurements, and theoretical modeling. Experimental measurements are performed using UV-VIS spectroscopy, spectroscopic ellipsometry and SEM microscopy. Theoretical modeling is based on the construction and optimization of theoretical model of optical response (reflectivity and ellipsometric parameters) to determine the effective refractive index and thickness of formed structure. Effective refractive index of studied samples in theoretical model of optical response is based on Looyenga effective medium approximation and Tauc-Lorentz dispersion model.

Keywords: electrochemical etching, effective medium approximation, Looyenga EMA, modified Fresnel coefficients, reflectivity, Tauc-Lorentz dispersion model

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