Research On Te-based Lead-free Glass Powder For Front Silver Paste Of Silicon Solar Cells

At present,fossil resources are increasingly exhausted and the environment is deteriorating.In the face of this situation,people begin to pay attention to clean,environmental protection and renewable new energy.Among them,solar energy is an endless and widely distributed renewable energy.Silicon solar cell is the key device to convert solar energy into electric energy,in which silver paste is the key part of solar cell,and glass powder plays an important role in silver paste.At present,all countries in the world have made relevant regulations on conductive paste,the most important of which is not to contain lead.Therefore,the development of high-performance and environmentally friendly lead-free conductive silver paste is of great significance to the global energy shortage and environmental pollution.This article first takes the glass frit used in the front silver paste of solar cells as the research object,and takes TeO₂-Bi₂O₃-B₂O₃ glass as the starting point for the research.The content of each component is determined by DSC and infrared spectroscopy analysis.Subsequently,ZnO and Ge O₂ were added in sequence,and the final groups were determined by DSC and infrared spectroscopy:45wt%TeO₂-35wt%Bi₂O₃-6wt%Ge O₂-6wt%B₂O₃-6wt%ZnO.Due to the presence of Ge O₂,free oxygen is added to the glass,so that Zn⁺no longer robs the O^2-in the[TeO₄]double triangular pyramid,which weakens the tendency of the[TeO₄]double triangular pyramid to transform into the[TeO₃]triangular pyramid,The glass stability is better.XRD shows that the glass powder has a higher degree of non-crystallinity and good vitreous properties.A chemical stability test was performed on the glass powder,and the results showed that the glass frit had better chemical stability and less quality loss.The effects of different sintering processes on the square resistance,adhesion,surface morphology and cross section morphology of silver films were discussed.The optimum sintering process was determined as sintering temperature 800?and holding time 60s.The square resistance of silver film was 2.57 m?/(9),and the adhesion was 4.85N.In this sintering process,the liquid glass can effectively infiltrate the silver powder,the glass with silver particles dispersed evenly on the silicon substrate,the silver particles contacted and connected with each other to form a dense conductive network,and there were no deep holes on the cross section.When the sintering temperature is too high,the viscosity of liquid glass decreases,the silver powder can not be dissolved well,and the ohmic contact effect is poor.In addition,there is overburning phenomenon,too high temperature makes the silicon substrate strongly etched,which may damage the P-N junction.The influence of the relative content of glass powder on the sintering process of the sample is discussed.The effects of glass frit content in the silver paste on the square resistance,adhesion and cross-section morphology of the sintered silver film were studied.The optimal ratio was determined when the glass frit content was 3wt%.At this time,the square resistance of the silver film is the lowest,2.26 m?/(9),and the adhesion is 4.85N.The cross-sectional morphology shows that the silver film has good density,no deep holes,the anti-reflection layer(ARC)is completely etched,the thickness of the glass layer is uniform,and the ohmic contact effect between the silver film and the silicon emitter is better.The influence of the silver content in the glass frit on the cross-sectional morphology of the sample was studied.When the glass frit is doped with 6wt%Ag NO₃ particles,the lowest contact resistivity is obtained.The cross-sectional SEM morphology showed that a relatively uniform size of nano-silver particles were deposited on the interface between the glass layer and the silicon emitter,which was conducive to the transmission of electrons and improved conductivity.In addition,compared with doping silver powder in glass powder oxide raw materials,EDS shows that the silver content of the silver powder-doped glass frit is less,and the SEM morphology shows that the sample made of the glass powder has less silver crystallites at the Ag-Si interface.