Electrochemical oxidation pre-treatment for wet texturing of monocrystalline silicon solar cells

Abstract

To improve the textured structure uniformity of monocrystalline silicon solar cells, an electrochemical anodic oxidation pretreatment technology was implemented to the silicon surface before the alkali texturing process. The effects of pretreatment on the textured structure were investigated at different oxidation conditions (voltage and duration) in three typical aqueous electrolytes with different pH values. The structure and thickness of the silicon oxide layer on the silicon wafer surface were analyzed by X-ray photoelectron spectroscopy. It was found that the uniform oxide layer of 1.5–2 nm formed on the Si surface can promote the uniform growth of pyramidal nuclei in the initial texturing stage, while the excessive thicker oxide layer will reduce their density and uniformity. The average pyramid sizes were 1.4 ± 0.7 μm and 1.6 ± 1.7 μm with and without electrochemical oxidation pretreatment, respectively. The distribution of pyramid size became more uniform because the fraction of extremely large pyramids was greatly reduced. Compared with the traditional texturing process, the average reflectivity of the textured surface decreased from 13.1 % to 10.4 %. This technique is expected to be a suitable substitute for the H2O2 pre-cleaning process in the Si texturization for the industrial production of solar cells.