Surface Treatment Of Polycrystalline Silicon And Study On Heterojunction Solar Cell

The surface pattern of polysilicon will affect the utilization rate of the incident light seriously,and the lower reflectivity can increase absorption of incident light,thereby improving the efficiency of solar cells.There are many ways to reduce the surface reflection of polysilicon,such as wet etching,grooving and ion etching.Among them,wet corrosion is common particularly.The corrosion of the surface of polycrystalline silicon will produce different structures,which can significantly increase the absorption of incident light,and achieve the desired results.At present,the wet etching of crystalline silicon is mainly composed of acid etching and alkali etching,and the former uses various kinds of acid corrosion,moreover the latter is based on alkali corrosion.The main advantages of wet etching are mature technology,low price,high selectivity and easy to mass production.In this paper,the literature on wet etching at home and abroad was studied,and the effects of the two methods on the surface morphology of polysilicon were investigated.Firstly,The influence of alkaline etching time and alkali etching concentration on the surface reflectivity of polycrystalline silicon was studied.The results shows that the alkali corrosion concentration is 15%,a temperature 80?and the corrosion time15 min,and the average reflectivity of polysilicon is 24.37%,which is lower than the original silicon reflectivity of 35.43%.Secondly,The influence of acid etching time,acid ratio and additives on the reflectivity of polysilicon surface is studied.The results shows that the optimum conditions are acidity ratio of HNO₃:HF:H₂O:CH₃COOH=5:1:3:1.5,and the etching time is 225 s,and the reflectivity is about 19.05%,which can effectively increase the utilization of light energy.Then the optimum design of the AZO film is also studied.The results show that under the conditions of target distance of 45 mm,vacuum of 2.0×10^-4 Pa,argon flow rate of 50 sccm and sputtering time of10 min,at the same time,the sputtering power is 200 W and the substrate temperature is 300?,and the average resistivity is 5.7×10^-4??cm,and the average mobility is34.76 cm²?v^-1?s^-1,moreover the average transmittance is 89.51%.Finally,we utilize simulation software AFORS-HET to analysis the feasibility of using the polycrystalline silicon in HIT solar cell,and then we conclude that the doping concentration of 1×10¹⁷ cm^-3,intrinsic layer thickness of 5 nm,doped layer thickness of 10 nm,and then we can get 16.52%photoelectric conversion efficiency of the HIT solar cell.