Research On The Fabrication Of Monocrystallion Sillicon With Ultra Low Surface Reflectance

The energy sources are becoming the bottleneck of controlling international community development when the electricity, coal, oil and other non-renewable energy are in emergency. More and more countries have begun to implement the plan of Sunshine to explore solar energy, however, solar cells are the most optoelectronic devices which can transfer sunlight to electricity energy.How to reduce the cost and increase the efficiencies of monocrystallion silicon solar cells have been hot topics for many years. From the development process of solar cells, the light loss is still one of the most important factors when the light shines to the cell surface. The ideal light trapping structure can increase the absorption in order to achieve higher energy conversion. Now, the common method is using alkaline solution for etching to obtain the texturization structures. NaOH, as an etching solution using with a surfactant isopropyl alcohol (IPA), is widely used as a common solution. However, under the high temperature, IPA need continue to be added because of volatilization, so the cost of texturization will be high and the surface reflectance can only be reduced to 14%.Silicon nanowire is a new one dimensional nano-material and is an important part for researching because of its unique optical, electrical properties, excellent anti-reflectance, electrical transport properties. So far, compared with the above trapping structures, SiNWs has lower reflectance, but only up to 3%.In this paper, a structure combining pyramids with nanowires arrays was fabricated to reduce the reflectance of monocrystalline silicon surface. Scanning electronic Microscope (SEM) and reflectance measurement set-up consisting of a spectrophotometer and an integrating sphere were used to estimate the sample. The influence factors on reflectance were discussed, and the surface reflectance can be reduced to 0.9% under the optimized conditions.First of all, we obtained the good pyramid structure using NaOH and IPA solution under the optimized condition with the average reflectance of 14%. In order to further reduce reflectance, the sputtering system and chemical etching were used. The lowest reflectance was obtained using this binary structure. In this paper, the influences of silver particle morphology, size and etching time on binary structure were discussed. And we obtained the optimized condition is the sputtering time is 3min, the etching time is also 3min. Under the optimized condition, the reflectance of 0.9% was obtained. The size of pyramids is uniform, the height is 2-6μ, and the length of SiNWs is about 1 p., the width is less than 100nm. Most important of all, the surface of a sample is very uniform. Using this new method, not only we can obtain the lowest reflectance of silicon, but also it is a new way to fabricate high-efficiency silicon solar cells.