The Research On The Fabrication And The Properties Of Diamond Wire Saw Multi-crystalline Black Silicon

Crystalline silicon solar cells still account for the more than 80% share of the global photovoltaic market,and multi-crystalline silicon has been the mainstream of crystalline products for many years.As the development of the technology,a new slicing method called diamond-wire-saw technology,which can reduce the wafer cost by ?0.4-0.6/piece,has been the mainstream slicing method.However,the diamond-wire-saw technology cannot be popularized in multi-crystalline silicon,for the amorphous silicon existing on the surface hinder the etching process of HF/HNO3 system,making the much higher reflectance and diminishing the cell performance.But the diamond-wire-saw technology has been widely used in mono-crystalline silicon.Therefore,a new method must be incorporated to effectively solve the texturing problem of diamond-wire-saw multi-crystalline silicon.And the best method is black silicon fabricated with metal catalyzed chemical etching method.Because of the low selectivity for substrates?low reflectance,the black silicon has become the focus.In this paper,the black silicon technology fabricated with metal catalyzed chemical etching(MCCE)method as well as its optical properties has been studied systematically.First of all,the mechanism of fabricating black silicon in HF/AgNO3/H2O2 system has been studied: the electrochemical deposition of Ag-nanoparticles and the oxidation of Si by H2O2 catalyzed with Ag-nanoparticles as well as the etching process by HF.Then,we research the relationship between the black silicon structures and the concentration ratio of HF/AgNO3/H2O2 solution,and a black silicon structure which used to fabricate solar cells has been established through optimizing the solution conditions.Additionally,it should be noticed that the black silicon structure is very rough,leading to the much high surface recombination.Consequently,the black silicon structure has to be modified to make the structure smooth and large-open.So,the second work is the structure modification of black silicon using KOH/IPA mixture solutions.By controlling the concentration ratio,temperature and reaction time,we have obtained a series of modified structures,such as nano-inverted-pyramid,nano-pyramid,nano-square-hole and nano-round-hole.These structures have the very smooth surface,and can suppress the reflectance below 15%.After the mechanism and the modification of black silicon have been studied,the pre-treated diamond-wire-saw multi-crystalline silicon wafers,whose size is 156.75*156.75mm2,have been textured to form black silicon.Then,we modify the black silicon to make the surface smooth.Finally,these wafers have been fabricated into solar cells.Surprisingly,compared with the conventional slurry-saw solar cells,the diamond-wire-saw black silicon solar cells have the excellent electrical properties: the short circuit current ISC,the fill factor FF are increased by 114.9mA,0.74%,respectively,and the conversion efficiency is promoted by 0.32%.The outstanding performance of diamond-wire-saw black silicon solar cells testifies that the black silicon fabricated by metal catalyzed chemical etching combining with the modification has a great advantage in solving the texturing problems of diamond-wire-saw multi-crystalline silicon as well as promoting the cell performance.Besides,this set of technology is very simple and compatible with the current production line,making it suits for the commercial product.