POROUS SILICON IN SOLAR-CELLS - A REVIEW AND A DESCRIPTION OF ITS APPLICATION AS AN AR COATING

In this paper, we first review the potential applications of porous Si in solar cell structures. Then we describe the fabrication of this material by both electrochemical and chemical etching methods, providing some guidelines for a better comprehension of the influence of each process parameter. After that, the properties of porous Si in terms of morphology, structure, photoluminescence, and electroluminescence emissions are summarized together with their actual photovoltaic applications. The results of our study specifically address the creation of an antireflection (AR) coating for polycrystalline Si based solar cells. We have demonstrated the feasibility of a very efficient porous Si AR layer, prepared by a simple, cost effective, chemical etching method. The formation of a porous Si layer about 0.5 mu m thick on the polycrystalline wafer results in an effective reflectance coefficient R(eff) lower than 5% in the wavelength region from 350 to 1150 nm. The drastic reduction of the optical losses is controllable by the process parameters and is almost independent of the starting substrate.