Preparation Of The Lead-free Silver Conducting Paste For Silicon Solar Cells

The conductive silver paste for silicon solar cells usually contain lead, and lead-free electronic products is the mandatory requirements of our country, the European Union, the United States, Japan and other countries, so the research and development of lead-free electrode materials for silicon solar cells, which has great significance and practical value in solving the shortage of resources and environmental pollution. In this paper, the lead-free conductive silver paste for silicon solar cells was prepared by the development of organic carrier and lead-free low-melting glass frits.The volatility of the organic carrier used as the conductive silver paste for silicon solar cells was studied.the drying curve of mixing organic solution was simulated. The effect of different solvents on volatility of carrier was investigated.A kind of carrier having gradual volatility was prepared. When proper additives were added into the organic carrier,the proprieties of the organic carrier became more excellent.The better flowability of the glass was selected by orthogonal test method. A series of Bi₂O₃-B₂O₃-SiO₂-ZnO-D(metal oxide) glass were prepared by melting mixture of Bi₂O₃, B₂O₃, SiO₂, ZnO and D(metal oxide) powder at 1200℃,and the flowability of the lead-free low-melting glass frits was measured. The flowability of lead-free low-melting glass frits was optimal in compositions of 67(wt%)Bi₂O₃·20(wt%)B₂O₃·3(wt%)SiO₂·2(wt%)ZnO·8(wt%)D metal oxide.According to the screening results of orthogonal test,the effects of the components, such as Bi₂O₃/B₂O₃ ratio, ZnO(wt%), SiO₂ (wt%) and D metal oxide(wt%) on the flowability and the transition temperature(tg) have been studied by single-factor experimentation. The results demonstrated lead-free low-melting glass frits have higher flowability and lower transition temperature(tg) in the compositions of 62.7(wt%)Bi₂O₃·18.8(wt%)B₂O₃·6(wt%)SiO₂·1.5(wt%)ZnO·8(wt%)D metal oxide.The silver conducting pastes, composed of the lead-free glass frits,silver powders and organic vehicle, exhibited excellent conductive and processing properties and the pastes can be used for thick film conductor pastes on the polysilicon. After fired,the appearance of the films were bright and flat, the sheet resistance and binder force of the film at thickness of (15±3)μm was 4.2×10^-3Ω/mm² and 4N, respectively.