A Study Of Oxygen-Free Diffusion Technology For N-Type Crystalline Silicon Solar Cells

The main content of this article is an extension of the preliminary work of our research group,to verify the oxygen-free diffusion technology.First,this article describes the oxygen-free diffusion route and its key steps:boron-doped amorphous silicon source layer deposition,high temperature boron diffusion,residual source layer etching.Then,use oxygen-free diffusion technology to prepare p⁺emitter,and discuss the effects of diffusion temperature,diffusion time,source layer thickness on diffusion layer resistance and boron doping concentration curve.The difference between the square resistance and boron doping concentration curve obtained by two low-pressure oxygen-free diffusion is compared,so a preliminary understanding of oxygen-free diffusion technology is obtained.Furthermore,on the basis of previous experiments,the surface passivation samples of boron diffusion layer and TOPCon solar cells were prepared based on oxygen-free diffusion technology.Use WCT-120to characterize and analyze the lifetime and implied V_oc(i V_oc)of surface passivation samples of boron diffusion layer,use IV tester to characterize and analyze conversion efficiency(E_ff),short circuit current(I_sc),open circuit voltage(V_oc),fill factor（FF）of solar cells,use quantum efficiency tester to characterize and analyze internal quantum efficiency（IQE）and reflctivity（R）,analyze the above-mentioned electrical and optical properties change with the flux of borane doping.The main conclusion are as follows:（1）From the boron doping concentration curve of diffusion layer（prepared by oxygen-free diffusion technology）tested by SIMS,it can be seen that there is no introduction of oxygen during the preparation of boron diffusion layer by the oxygen-free technology.（2）Compared with conventional BBr₃diffusion,the p⁺emitter prepared by oxygen-free technology has lower square resistance,better conductivity and better boron doping concentration curve in diffusion layer.（3）As the source layer borane doping flux decreases,the I_scand V_ocof TOPCon solar cells gradually increase,the short-wavelength（300-500nm）spectral response becomes better,and the FF gradually decreases;When the borane doping flux is13sccm,the TOPCon solar cell has the highest efficiency of 22.29%,at this time,V_ocis 699.4m V,I_scis 9.711A,FF is 80.16%.