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A new approach for the texturing of monocrystalline silicon solar wafers was developed. By using a spray etching process with aqueous HF-HCl-Cl2 mixtures, textured wafers were generated and processed to PERC solar cells and compared to cells textured by a conventional alkaline texturing process. Also, a novel saw damage removal (SDR) process using aqueous HF-Cl2 mixtures was tested against the typical NaOH SDR. A possible dependency of cell parameters on the wafer reflectivity is discussed. The etch rates of the spray etching process are compared to other chlorine-containing hydrofluoric acid-based processes and alkaline potassium hydroxide-based mixtures. Computational fluid dynamic analyses were performed to identify possible reasons for marks occurring on the spray textured wafers. The influence of the marks on the electrical properties were examined with electroluminescence measurements. As cell performance data show promising results, we discuss whether the spray etching process with HF-HCl-Cl2 mixtures is a viable way for the implementation of an inline texturing process for solar cell production.

The wet-chemical acidic treatment of silicon wafer surfaces is very important in photovoltaic, microelectronic and further industries. Recent works report on new mixtures for acidic anisotropic etching mixtures based on hydrofluoric acid HF and hydrochloric acid HCl with an added oxidant. The aim of this work was to get an insight into the reactions during the etching process of silicon in the system HF-HCl-Cl2. The etching mixtures, gaseous reaction products, as well as the generated silicon surfaces were investigated by 19F, 29Si, and 35Cl NMR, ion chromatography (IC), iodometric titration, FT-IR spectroscopy, diffuse reflectance FT-IR spectroscopy (DRIFT) as well as scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM-EDX). A reaction scheme for the anisotropic dissolution of silicon in chlorine containing aqueous HF-solutions is proposed, which involves dissolved Cl2 as the oxidizing agent, coordination of fluoride/chloride ions and formation of a hydrophilic surface. These steps are similar to the well known alkaline anisotropic etching of silicon.