With the global energy crisis and environmental pollution becoming more and more serious,solar energy as a renewable energy has been attracted more attention.Photovoltaic is a very important way for the utilization of solar energy.In the photovoltaic industry,crystalline silicon solar cells account for more than 90%of the share.In the current industrial production of multicrystalline silicon solar cell,the emerging cutting technology in recent years is the diamond wire sawing(DWS)technique.There are many advantages,such as the fast cutting speed,high precision,less waste of high-purity silicon,easy to recycle the cutting waste and less pollution.And the DWS has already replaced the traditional multi-wire slurry sawing(MWSS)technique.However,there is a damage layer on the surface of multicrystalline silicon by DWS,the traditional method of making texture surface can not effectively obtain the proper texture surface,so as to obtain the optimal solar cell performance.In addition,the influence of damage layer on making texture surface and solar cell performance is not clear,the correlation between the texture structure,reflectivity and solar cell performance is not clear yet.In this paper,the basic characters and the formation mechanism of damage layer of DWS multicrystalline silicon wafer were studied,and the influence of damage layer on making texture surface and performance of solar cell was analyzed.On this basis,acid etching method and metal-catalyzed chemical etching method were used to make texture surface,and study the properties.The relationship between the depth-to-width ratio,reflectivity and solar cell performance was clarified.The results show that,there are parallel saw marks and randomly distributive pits on the surface of silicon wafer by DWS,which is due to the reciprocating movement of diamond wire and grinding of grains,respectively.The amorphous phase layer,with the thickness of approximately 40-130nm,was found on the silicon wafer surface.Numerous defects,including twins,stacking faults and dislocations emerged under the amorphous layer,which the thickness is approximately 1 μm.During the cutting process,the crystalline structure of silicon changed from crystal to nanocrystalline to amorphous.The amorphous layer and defect layer can be removed effectively by 20 wt.%NaOH solution under 80℃ for 20s.After removing damage layer,the etching rate can be increased,and reflectivity of silicon wafer can be reduced by the same conditions of making texture surface.As acid etching method has the advantage of extremely low equipment modification price,the lowest reflectivity of silicon wafer obtained by two-step acid etching method is 32.48%,which is about 4.24%lower than that by one-step etching method.In order to decrease the etching rate,improve the surface wettability,and change the gas fugacity.The structure of texture surface can be modified and the efficiency of making texture can be improved.A mixed additive consisting of dodecyl benzene sulfonic acid solution,polyvinyl alcohol,polyethylene glycol,NaNO2,and sodium citrate was added to the acid etching solution to making texture surface.The minimum e reflectivity of the optimized multicrystalline silicon wafer is 16.66%lower than that without additives.The average photovoltaic conversion efficiency of solar cell obtained is 1 8.38%.By using the Ag as catalyst to make texture surface on DWS multicrystalline silicon wafer,the texture surface can be adjusted to have a wide range of depth-to-width ratio and a very low reflectivity.In this paper,the depth-to-width ratio and reflectivity obtained are 0.63~5.31 and 3.14~18.15%,respectively,and the reflectivity decreases exponentially with the increase of depth-width ratio.With the structure of silicon wafer surface with depth-to-width ratio of 1.58,the photovoltaic conversion efficiency of the solar cell is the highest,which is 18.53%.In addition,the mixed solution of H2O2 and NH3·H2O can completely remove the residual Ag particles on the surface of multicrystalline silicon wafer after making texture surface.Ag is a kind of precious metal,and waste liquid containing Ag is difficult to be treated.In this paper,texture surface is made by using Cu catalyst with lower cost and better catalytic activity.A dense Cu film was formed on the surface of silicon by Cu catalyzed chemical etching,which significantly restrict the etching process.There are partial polished area on the surface after removing Cu particles,and the reflectivity is 34.18%.By adding the oxidants with different oxidizing capacities and dissolved states in the solution of Cu catalyzed chemical etching,the silicon can be etched continuously,in addition,the composite structure can be obtained.The wedge-shaped etching pits,which the size ranges approximately 2~3μm,was formed when adding FeCl3 into etching solution,which the reflectivity is 22.85%.A composite structure with the shallow pits and nanopores was formed when adding MnO2 into solution,which the reflectivity is 23.17%.An inverted pyramid structure,which the size is approximately 1μm,was formed when adding H2O2 into solution,which the reflectivity is 18.16%.The average photoelectric conversion efficiency of solar cells when adding H2O2 is 18.92%.To sum up,by making texture surface on DWS multicrystalline silicon wafer by different methods,the influence of depth-to-width ratio of texture surface on reflectivity and solar cell performance was studied.And the relationship between the performance of the solar cell and depth-to-width ratio of texture structure is described in this paper.By using acid etching method to make texture surface,when the range of depth-to-width ratio is 0.54~1.60,the highest photoelectric conversion efficiency is 18.69%.By using MCCE to make texture surface,when the range of depth-to-width ratio is 1.33~1.76,the highest photoelectric conversion efficiency is 19.00%. |