Optimization Of Textured Multicrystalline Silicon Wafers For Solar Cells

Energy is the base for human society development.And environment is the necessary condition of continuable development.People have to search new clean energy as common energies are being used up.All kinds of new energies have their advantages and disadvantages.Photovoltaic as one kind of new energies are being cared by more and more people.The yield of solar cells increased greatly in recent years.Crystalline silicon solar cells are market mainstream all the same and the multicrystalline silicon cell occupies fifty-three percent of all the markets.Acid etching technology is more and more used in multicrystalline silicon solar cell industry.However,the auto-catalyzing character led to uncontrolled and un-repeating problems when common acid solutions are used.Then some assistant apparatuses have to be used to maintain large-scale production,which enhances the product cost.According to these ideas,this paper studies some rules about multicrystalline silicon texturization via HF/HNO₃.The influences of different mixture ratio of etching solution on the etching rate,the etching surfaces and their reflectance characters of different etching moment,were researched.The results showed that the etching rate measure up the manufacture grade if HF(40%):HNO₃(70%) in the range of 99:1 to 94:6 or in the range of 10:90 to 5:95 or add DIW in 0-20℃.This solution can form surface texture of multicrystalline silicon in order to reduce the reflectance, achieve 12%,of the surface and the etching rate,10μm/min,apply the multicrystalline silicon texturing for solar cell fabrication.Secondly,the new method,which is based on acidic texturing and using ultrasonic,was applied to optimize the HF/HNO₃ to form surface texture of multicrystalline silicon in order to reduce the reflectance of the surface.The influences about using ultrasonic on etching rate,surface and reflectance characters were researched.The results shows that the etching rate decreased by using this method,5μm/min,which is more up to the mustard of solar cell fabrication.Besides these,this method advantage to created micro-rough surface which reduced the reflectance at 3.5%of surface effectively. Thirdly,the new method,which is based on HF/HBr texturing and using ultraviolet radiation,was applied to form surface texture of multicrystalline silicon in order to reduce the reflectance of the surface.Orthogonal test method was used to find the influences of all components in the new etching solution on the etching rate. It was found that HF ratio was most important factor to the influences of other reagents on etching rate.The etching surfaces and their reflectance characters of different etching moment via this new method were researched.The results show that this new method can form low reflectance at 5%,etching rate at 12μm/h,low cost textured-surface,the experiment conditions were easy-control as well.At last,some other experiments to be done were brought forward.We hoped that the optimization of the new etching solution could be used in crystalline solar cell production line as early as possible.