Influence Factors on the Size of Spherical Silver Powder Used for Solar Cell Top Electrode Paste

摘要

The ultra-fine silver powders were prepared by chemical reduction using nitric acid silver (AgNO_3) as raw material, ascorbic acid (C_6H_8O_6) as deoxidizer and adding polyvinylpyrrolidone (PVP) as dispersing agent. The influence factors, such as AgNO_3 solution concentration, ascorbic acid solution concentration, PVP dosage and reaction conditions such as temperature, PH etc. were studied. The morphology and particle size distribution were observed by Field Emission Scanning Electron Microscopy (FSEM) and laser particle analyzer. The composition was analyzed by Energy Dispersive Spectrometer (EDS).The crystal phase was tested by X-ray Diffraction (XRD). It indicates that the spherical ultra-fine silver powder is face-centered cubic structure, its diameter is about 1.0 um with homogeneous particle size distribution and smooth surface. It was prepared under the conditions as following: dropwise added 60 g/L AgNO_3 solution into 40g/L ascorbic acid solution, with the presence of PVP, and pH=3,45℃,360rpm. It meets the requirements of paste for solar cells' top electrode.