|
In recent years, silicon solar cell has been developing rapidly, and there are also lots of studies on silicon cell materials. Aluminum back field has important influence on the photoelectric conversion efficiency of solar cells. As the raw material of aluminum paste, the formula, preparation process, sintering process and so on have great influences on the performance of the aluminum paste. There also have a lot of requirements for solar cell aluminum paste in industry:good printing performance, high photoelectric conversion efficiency, good adhesion, low warp, small deformation, smooth and flat on aluminum membrane surface, without aluminum beads and ash, etc. Thus, in this paper, based on the technical problems of aluminum paste, slurry ratio of ingredients and the influence factors were studied:The experimental characterization for volatilization performance of three kinds of solvents and mixed solvents were carried out by constant temperature volatilization experiment. Organic solvents with levels of volatile were gotten by using solvents with different boiling points according to certain proportion, and experiment showed that the proportion of three solvents could be adjusted in62:20:18. And the influences of ethocel, thixotropic agent and two kinds of surfactant on viscosity, rheology and thixotropy of organic vehicle were studied. The thixotropy of organic vehicle was changed by polyamide, when the content of polyamide was0.4wt%, thixotropy was the best; With the content of sodium dodecyl benzene sulfonate (SDBS) increasing, solution viscosity increased firstly and then decreased, and the Span-85had little influence on the viscosity of organic vehicle. Through the experiments above, the best formula of organic vehicle was determined finally:mixed solvent90.6wt%, ethocel7wt%, polyamide0.4wt%and SDBS2wt%.The glass forming ability of Lead-free glass SiO2-Bi2O3-B2O3system was studied. The structure and properties of glasses were analyzed by IR, XRD, DSC. Glass powder with low glass transition temperature and relatively stable structure were prepared.The influences of raw material such as aluminum powder, glass powder, organic vehicle and additives on the properties of aluminum paste and the influence of sintering temperature on the back field structure were discussed. The influence of three different particle size of aluminum powder with different content on the particle size, appearance and photoelectric conversion efficiency of the aluminum paste were compared. When the aluminum powder with2microns,5microns and8microns had a proportion of10:15:75, the effect was the best. At the same time, using KH-550for surface modification of aluminium powder had a good improvement on phenomenon of the settlement of aluminum paste and the stability of aluminium powder. The influences of glass powder content and organic vehicle on the electrical property and adhesion of aluminum slurry after sintering were discussed. The most suitable for organic vehicle was obtained, which glass powder content was15.2%and glass powder4.5%. Finally, aluminum slurry formula was determined that aluminium powder was79.5%, organic vehicle is15.2%, glass powder was4.5%, additives was0.8%and sintering temperature was850℃.
|