Antireflective porous-silicon coatings for multicrystalline solar cells:: the effects of chemical etching and rapid thermal processing

In this paper, the emitter of multicrystalline silicon solar cells has been chemically etched in order to form porous silicon (PS) layers, usually known as stain-etched PS, to be used at the same time as a selective emitter and as an efficient antireflective layer. The optical behaviour of the solar cells in the 250-850 nm wavelength range (5-1.45 eV range) was determined before and after PS formation, resulting in a notable reduction of reflectance after PS formation and a corresponding increase in cell efficiency. The different morphologies of the silicon emitter and metallic contacts, before and after PS formation, were analysed by scanning electron microscopy and atomic force microscopy. Furthermore, the electrical properties of both the emitter region and the contacts were investigated, as well as the most significant solar cell parameters before and after PS formation. Finally, the effect of rapid thermal processing in nitrogen and oxygen atmospheres on both the surface morphology and the optical behaviour of PS was studied.