Formation and characterization of porous silicon layers for application inmulticrystalline silicon solar cells

The electrochemical formation of porous silicon (PS) layers in the n(+) emi tter of silicon p-n(+) homojunctions for solar energy conversion has been i nvestigated. During the electrochemical process under constant polarization , a variation of the current density occurs. This effect is explained by co nsidering the doping impurity gradient in the emitter and by TEM characteri zation of the PS layer structure. Optical transmission measurements indicat e that modifications of the refractive index and absorption coefficient of PS are mainly related to the porosity value. Reflectivity measurements, spe ctral response and I-V characteristics show that PS acts as an efficient an tireflection coating layer. However, beyond a critical layer thickness, i.e . when PS reaches the p-n(+) interface, the junction properties are degrade d. (C) 1999 Elsevier Science B.V. All rights reserved.