Preparation Of TeO₂-Bi₂O₃-B₂O₃ Based Glass Frit On Front Silver Paste Of Solar Cell

The conductive silver paste for most of solar cells usually contain lead,and green product is the primary requirements of social development,and various countries in the world have introduced the corresponding rules for lead-free conductive paste,so the research and development of lead-free silver paste for solar cells,which has great significance and practical value in solving the shortage of resources and environmental pollution.This paper focused on the glass frit glass frit for front contact electrodes of solar cells,TeO₂,Bi₂O₃,B₂O₃,Zn O and La₂O₃ was used to raw materials,Te O₂-Bi₂O₃-B₂O₃ based glasses were synthesized by the melting quenching method.Its glass frit was prepared by ball milling process.The nature of glasses,glass frit were studied by means of XRD,FESEM,IR and DSC-TG analysis and so on.During the whole process,the influence of oxide content on phase composition,structure,thermal properties and chemical durability of Te O₂-Bi₂O₃-B₂O₃ based glass was investigated;the milling process of glass frit was also investigated.These results show that the number of [Te O₄] and[BO₄] decreased and Te O₃] and [BO₃] increased,thermal expansion coefficient increased when the Bi₂O₃ content increased from 10 to 27.5mol%,however,the soften temperature decreased from 433oC to 413.5oC.the weight loss of glass specimen increased from 8×10-2mg/cm² to 43×10-2mg/cm².With the content of B₂O₃ increased from 10.5mol% to 40mol%,the thermal expansion coefficient decreased from 11.4 to 9.9×10-6/oC when the B₂O₃ content increased from 10.5 to 40mol%,and the soften temperature also linearly increased;the weight loss of glass specimen decreased from 8.48×10-2mg/cm²to2.78×10-2mg/cm².The thermal expansion coefficient decreased firstly when the Te O₂ content reached 60mol%,then increased with further increasing Te O₂ content.The glass transition temperatures are 400⁴50°C and melting temperature was as low as 800oC.The weight loss of surface area value is0.28×10-3mg/cm² as the content of Te O₂ reached 60 mol%,improving the chemical durability of the Bi₂O₃-Te O₂ glass system.The optimum milling process parameters for glass frit: milling time 5h,the ratio of grinding ball andglass powder 5:1,the speed of grinding machine 350r/min,the D50,D90 and volume average particle size of glass frit by the process conditions is 2.33μm,4.19μm and 3.07μm,respectively.The silver pastes were coated by spin coating method,and the effect of Te O₂-based glass frit content in Ag paste and sintering temperature and holding time on phase composition,micro-structure and specific resistances were also studied.The results of the study show that the content of glass frit has a great influence for silver films.The best content front sliver paste is3wt%,the optimum formula of silver paste contains 77wt% silver powder,3wt% glass frit and 20wt% organic carrier.The better sintering process of Ag paste with TeO₂-Bi₂O₃-B₂O₃ based glass frit is 750oC and holding time 8min.the specific resistances of silver film at this process is 3.1μΩ cm.