Study On Anti-reflective Structures For Crystalline Silicon Solar Cells

Searching new kinds of energy is an effective way to solve the energy crisis. Solar energy is a kind of inexhaustible and reproducible green energy, photovoltaic power generation is an important way to utilize the solar energy. In recent years, the photovoltaic industry developed rapidly under the supporting of the favorable policies around the world. The crystalline silicon solar cells share the main PV market for its low-cost and high conversion efficiency. Decreasing the thickness of crystalline silicon solar cells is the key technique to further reduce the cost of the cells. In order to use the energy of sunlight effectively, antireflective structure on the surface of the crystalline silicon solar cells become very critical. So we focuse on the antireflective structure on the surface of crystalline silicon cells in this article,we have developed a new kind of alkaline texturing additive, the additive can completely replace the use of isopropanol during the reaction and obtained uniform antireflective structure, which can reduce the cost effectively. On the basis of this work, we fabricated a series of pyramid size from200nm to10urn by using alkaline texture, the pyramid size is not the main factor to affect the reflectivity of the silicon wafer. The reflectivity between the structure of1,5and10microns do not make much difference if they have the similar uniformity situation. We did a simulation based on geometrical optics.which shows the same result with our experiments. The structure with1micron pyramid have the highest efficiency among our samples, which is mainly due to the better uniformity of this structure and the electrode can contact silicon wafer more completely.Micro-projection-like structure can be obtained in the rich hydrofluoric system, when the concentration of HF is increased, the density of micro-projection is increased while the depth become shallow. As the time increases, the micro-projections at the ceter of the ditch spread to the entire wafer.The bubble-like structure can be obtained when the concentration of nitric acid is high in the rich nitric acid system, which has a poor antireflective fuction. Ditch-like structure can be formed when the concentration of nitric acid is low.We fabricated inverted pyramid structure at the suface of silicon wafer by using metal-assisted etching and alkaline etching. Comparing the morphology and reflectance characteristics of the inverted pyramid under different reaction conditions.we have grown well-aligned ZnO nanowhisker (NW) arrays on Czochralski silicon solar cells by a seeding-growth two-step process. It is found that the ZnO NWs have a great effect on the macroscopic antireflection effect and, therefore, improves the solar cell performance. The ZnO NW array-coated solar cells display a broadband reflection suppression from500to1,100nm. it has been confirmed that an increase of3%relatively in the solar cell efficiency can be obtained.