Abstract
Conventional acidic etching cannot form low reflectance surfaces from multi-crystalline silicon (multi-Si) wafers sawn by fixed abrasive (FXA) machining technology, which makes it difficult to replace the time- and cost-consuming free abrasive (FRA) machining method. In the present work, a nanocrystalline Si (nc-Si) layer is formed by use of the surface structure chemical transfer (SSCT) method, and the layer is used as a starting point of alkaline etching to fabricate low reflectance submicron texture on FXA multi-Si wafers. Although the nc-Si layer cannot be passivated by deposition of a silicon nitride (SiN) layer, the submicron textured surface formed from the nc-Si layer by alkaline etching can effectively be passivated by the SiN layer. Using the developed method, the SiN passivated submicron textured FXA multi-Si wafers possess both high minority carrier lifetime and lower reflectance than that of acidic textured FRA multi-Si wafers. The excellent passivation effect of the SiN layer on the low reflectance textured surface is attributed to the low interface state density of 1.2×1011 cm-2eV-1.
Highlights
Multi-crystalline silicon solar cells account for the largest part of commercial photovoltaics
We have developed a surface passivation method for the nanocrystalline Si (nc-Si) layer with extremely large surface area using phosphosilicate glass (PSG)
After the surface structure chemical transfer (SSCT) treatment followed by 1% KOH etching for 30 s, the nc-Si layer was etched away and the submicron texture was formed on the surface (Fig. 1c)
Summary
Multi-crystalline silicon (multi-Si) solar cells account for the largest part of commercial photovoltaics. We have applied the SSCT method to promote alkaline etching of FXA multi-Si wafers and achieved both the low reflectance and the high minority carrier lifetime.
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