Surface texturing of single-crystalline silicon solar cells using low density SiO₂ films as an anisotropic etch mask

Abstract

Solar cells require surface texturing in order to reduce light reflectance, and to enhance light trapping. Anisotropic wet chemical etching is commonly used to form pyramids on the (1 0 0) silicon wafer surface by etching back to the (1 1 1) planes. In this paper, we used a low density silicon dioxide layer to allow etching in localized regions as an etch mask, forming inverted pyramid etch pits. Such an oxide can be deposited by plasma enhanced chemical vapor deposition using low deposition temperatures. The inverted pyramids are ideal for reducing surface reflectance, and are used in the highest efficiency silicon solar cells. Depending on the etch time and oxide quality, a variety of surface texture morphologies can be achieved. Due to the oxide mask, very little silicon is removed. This is an economical ideal method for texturing thin film single-crystalline silicon solar cells, as it combines the benefits of low reflectance with minimal thickness removed, while no photolithography is employed. © 2010 Elsevier B.V. All rights reserved.