Novel Processing of Solar Cells with Porous Silicon Texturing
Damiani, Benjamin Mark
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A simple porous silicon texturing technique that is applicable to various kinds of silicon material, including multicrystalline and ribbon Si, of any doping type and level is used to fabricate solar cells. Acidic etching of Si leads to a homogeneous porous silicon (PS) surface layer with reflectance as low as 9 %. Phosphorus diffusion and thermal oxidation are shown to produce very low emitter saturation current density, 128 fA/cm(2), which is only slightly higher than values obtained on planar surfaces, but still capable of giving open-circuit voltages in excess of 650 mV. The dopant oxide solid source (DOSS) solar cell process with its simultaneous formation of phosphorus emitter and in-situ surface oxide leads to an excellent surface passivation, while maintaining low reflectance on P8-textured wafers. The fabricated solar cells show efficiencies of up to 14.9% using the PS layer as an anti-reflection coating (ARC) and surface passivation. This is the highest reported value with this kind of texturing and without any additional ARC. The simplicity of the process makes it a very promising technology and easily transferable into industrial production.