Liquid silicate additive for alkaline texturing of mono-Si wafers to improve process bath lifetime and reduce IPA consumption

An improved texturing process is reported for industrial monocrystalline silicon wafers, which uses a small amount of liquid potassium silicate as an additive to the conventional KOH/IPA texturing process. The new silicate additive does not require any other changes to the chemical components and thus can easily be integrated into the standard industrial process. Reflectivity and scanning electron microscope studies confirm that the new process yields smaller pyramidal structures of about 4–6 μm in height, with an improved uniformity across the entire Si surface resulting in a low solar weighted average reflectance (WAR) in the range 11.4–12.2%. Moreover a near three-fold decrease in IPA consumption and a six-fold increase in bath lifetime are achieved by the new texturing process compared to the standard texturing process. For 156 mm×156 mm pseudo-square CZ monocrystalline p-type silicon wafers cell efficiencies of over 18% are achieved with the new texturing process on industrial-grade, screen-printed solar cells fabricated on SERIS' industrial R&D pilot line. This process offers the potential for significant cost reduction in manufacturing of monocrystalline silicon wafer solar cells.

This paper reports an improved texturing process for monocrystalline silicon wafers. The potassium silicate additive improves process bath lifetime and reduces iso-propyl alcohol (IPA) consumption. The new texturing process yields smaller pyramids, ∼4–6 μm in height, with better uniformity across the Si surface resulting in low weighted average reflectance(11.4–12.2%). Compared to the standard process, the new process achieves an approximately three times decrease in IPA consumption, a three times increase in throughput and a six times increase in bath life. Using the new texturing process industrial screen printed silicon wafer solar cells with efficiencies of >18% were produced. Figure optionsDownload as PowerPoint slideHighlights
► A new alkaline texturing process for c-Si cells is reported with new additive potassium silicate.
► This additive improves pyramidal uniformity with WAR<2% after ARC deposition.
► The new process reduces IPA consumption, increases throughput and enhances bath lifetime.
► This process does not require major hardware variation in texturing tool.
► For screen-printed large-area cells this texturing process achieved efficiencies over 18%.