Optimization Of Anti - Reflective Microstructure Of Monocrystalline Silicon Surface

The monocrystalline silicon solar cells as an important component of the photovoltaic industry, has gradually become a hot research topic. By chemical etching technique texturing structures on the surface of silicon wafers can greatly reduce the surface reflectivity of solar cells, increase photo generated charge, improve the short-circuit current and other indicators, with the result to improve the performance of solar cells in a large extent and reduce the production cost. At present, most of the studies both at home and abroad are NaOH, KOH and other alkaline solution with adding surfactant of isopropyl alcohol（IPA） for anisotropic etching of silicon wafers.However, the IPA added in the system is not only expensive, but also has toxicity,which does great harm to the human body. Therefore, the traditional alkaline solution is not good for industrial production. This paper aims to explore a kind of texturization technology, which prepares low reflectivity and uniform textured microstructure with low cost. It can optimize the preparation process of traditional alkaline solution.We used the single component of Na₂CO₃ and the system composed of Na₂CO₃ and NaHCO₃ with a self-made equipment to fabricate monocrystalline silicon microstructure under different conditions of set in advance respectively. Scanning electron microscope（SEM） and metallographic microscope observed the morphology of textured surface and ultraviolet visible spectrophotometer with an integrating sphere tested the samples surface reflectivity. After the comprehensive comparative analysis of the experimental results, we concluded that the size of the microstructure is relatively large and pyramids can not completely cover the entire surface of the silicon wafers when used the single reagent of Na₂CO₃ solution. Add appropriate amount of NaHCO₃ can significantly improve the morphology of texturing structure.In the Na₂CO₃/NaHCO₃ mixed solution, OH- plays a key role in etching the silicon wafers and HCO₃-has the same utility of IPA used in the traditional alkaline solution.The experiment has eventually shown that our optimized process lasted for 30 min at90 °C using the mixed solution containing 24 wt% Na₂CO₃ and 4 wt% NaHCO₃.After texturing, we can obtain high quality microstructure, which coverage rate reached 100% and the reflectivity was also reduced to a minimum value of 12.34%.