Gradual oxidation of stain etched porous silicon nanostructures applied to silicon-based solar cells

This work describes the photoluminescence (PL) and morphology of stain etched porous silicon nanostructures (PSN) submitted to a gradual oxidation by immersion in a HNO3 boiling point solution and applied to solar cells. The gradual oxidation passivates the extremely reactant fresh porous surface and softens the porous structure for ail adequate placement of the metallic contact on top. The pore size and the porosity of the samples have been evaluated by means of the Brunauer, Emmett and Teller (BET) technique. The surface morphology has been analyzed by atomic forces microscopy. The oxidation process of the layers has been evaluated using a Fourier transform infrared spectrometer (MR), analyzing the evolution of the Si-O, Si-H and Si-OH absorption bands. It is found a blueshift in the PI-spectra attributed to the oxidation process which increases the photoconversion properties of the nanostructures. An efficiency of 15.2% and fill factor (FF) of 80.5% were found. (C) 2008 Elsevier B.V. All rights reserved.