Experimental Research On Direct Ink Writing Of Ag Fingers Of Solar Cell

Higher photoelectric conversion efficiency and lower cost are the everlasting goals of the solar cell industry.On the one hand,thinner,higher and more uniform front contact Ag fingers of solar cell are crucial to achieve the higher photoelectric conversion efficiency.On the other hand,Direct Ink Writing(DIW)technique can help to reduce the waste of silver paste and the consumption of silicon material.Thus,this paper provides two kinds of DIW technique,Electrohydrodynamic Jet(E-Jet)Printing and Extrusion-Based Printing,to fabricate micro Ag fingers of solar cells.Favorable Ag fingers were written and showed better morphology than those made via traditional technique,which shows good market application prospect.The research details are as follows:Firstly,Nano silver ink was used to fabricated micro Ag structures based on E-Jet printing technique.A cooling structure of the printing nozzle was designed to avoid nozzle blockage.The printing process parameters of nozzle height,voltage,flow rate,temperature,speed and number of layers were investigated.Appropriate parameters were confirmed and micro Ag structures with approximate width of 46?m,height of 22?m and aspect ratio of 0.5 were printed.Secondly,this paper tried to use the Extrusion-Based Printing technique and silver paste to further enhance the aspect ratio of the Ag fingers.A set of cost-effective and reliable fluid connectors were designed.A stirring system was designed for the real-time dispersion of the silver paste inside the nozzle to avoid nozzle blockage.An Extrusion-Based printing system was established.Finally,the Extrusion-Based printing process was investigated.The influence of nozzle height and printing speed to the printing results was studied.When appropriate parameters were applied in the printing process with various nozzle inner diameters,Ag fingers with smaller line width than the nozzle inner diameter were fabricated.These Ag fingers were sintered later,and after the heat treatment,the line width of Ag fingers became smaller.Finally,Ag fingers with approximate line width of 39?m,aspect ratio of 0.9,uniform morphology and good bonding character with the substrate were fabricated.