Preparation and formation mechanism of the highly dispersive silver powders used for the front paste of the solar cell

摘要

The preparation of highly dispersive silver particles of average particle size of 1～2μm used for the front paste of the solar cell were carried out by rapid addition of ascorbic acid solution into the aqueous AgNO_3 solution at room temperature. The dispersive quasi-spherical silver particles were obtained with the AgNO_3 concentration of 0.1 M, AgNO_3/Ascorbic acid mass ratio of 1:0.8 without controlling the pH value of the system. Elevating the concentrations of the AgNO_3 solution resulted in the formation of flowerlike structures. The formation mechanism was investigated, it was concluded that the growth process of the highly dispersive silver particles include three stages, first, the formation of the precursor, followed by the nuclei burst and the diffusive growth process due to formation of H~+ ions adsorbed on the negative charged Ag nuclei as well as the steric effect of the ascorbic acid molecule, finally, when the pH value decreased dramatically to approaching the isoelectric point, the adsorbed H~+ was released and the resulting primary particles in turn aggregated to form secondary particles.