Study On The Improvement Of The Grain Size Of CIGS Absorbers

Supttering Cu?In,Ga?Se₂?CIGS?quanternary target with subsequently selenization can obtain high-qualified absorbers,achieve good uniformity in large area,and be easily applied in the massive fabrication.However,the grain size of CIGS absorbers made by this method is not large enough which limits the further enhancement of the coversion effieciecy of CIGS solar cells.In order to enlarge the grain size of the CIGS absorbers,this work proposed three solutions.Method 1:introducing a Cu-rich stage.Cu-rich CIGS was firstly fabricated and then converted into Cu-poor one by deposting a thin layer of Cu-poor materials.Cu-Se phase existing in the Cu-rich CIGS thin films is good for the growth of the grain of CIGS,which can be absorbed by the Cu-poor materials and the grain size of CIGS thin films remains the same simutaneously.Method 2:fabricating the CIGS thin film via preparing sublayers with thickness less than 500 nm.Each sublayer was fabricated on top of the previously annealed quanternary CIGS precursors.Every sublayer consisted of large grains which result in the reduction of the small grains layers in the absorbers.This method can fabricate1600-nm-thick CIGS without small grains.Method 3:reducing the content of the selenium in the CIGS precursor.The results indicate that reducing the selenium content in CuInSe₂ precursors can enhance the grain size of CuInSe₂.The above three methods are unrelavent.Each of them can efficienctly improve the grain size of CIGS absorbers.