Study On The Textured Surface Microstructure Of MC-SI Wafers Etched By Nitrousacid Solutions

Mc-Sisolarcell is low-cost, high-efficiency, wide-application and will remainthe mainstream status for a long time in the future. Atpresent, the PV-market isovercapacity and falling prices, The PV manufacturers are actively adopt measures toimprove the efficiency of the Mc-Si solar cell through a variety of processimprovement method.At present,the technique for optimizating Mc-Si solar cellsurface is one of the effective ways to improve the cell efficiency, andlow-cost.Therefore, this paper has studied the textured of Mc-Si wafers which etchedthrough adjusting acid solution, optimized the surface structure，get the goal ofimproving the reflectivity of mc-Si wafers.Mc-Si solar cell surface texturing is usually achieved by acid solutions due toacidic etching is isotropic,that is to say the different crystallographic plane in Mc-Sihas the same etching speed.This paper has studied etching by HF-HNO₃solution inthe production line of SNNED, and found traditional acidic etching leading Mc-Sisolar cell surface texture structure is not ideal, have the space to improve the lighttrapping effect.Through the analysis of the SEM images of existing Mc-Si solar cellsamples,we find the pits on the of Mc-Si solar cell is shallow and large withtraditional acid,the cell surface is not conducive to the light collection, surfacereflectivity up to over31.8%.So we improved the traditional acid HF-HNO₃etchingprocess, Using NaNO₂as oxidant instead of HNO₃.We finded the new etchingprocess omparable improvements in surface microstructure, and the pits likeearthworms depth and density is relatively large, uniform, surface reflectancedecreased to23.8%, compared with the traditional of low of about8%.So the resultsshow that NaNO₂instead of HNO₃in the etching process of Mc-Si solar cell, can getlow surface reflectivity texturing.