Preparation And Characterization Of High Performance Crystalline Silver Powder And Its Application In Solar Photovoltaic Cell Silver Electrode Paste

With the increasingly importance of energy crisis,unprecedented development has been taken place in the solar cells field.Silver powder is widely used for the silicon solar cell front electrode paste because of its higher electric conductivity and better chemical stability than other metals.In this paper,a green and convenient processing technique was proposed for the preparation of crystalline silver powder,and its application in silicon solar cell electronic paste was investigated.First of all,monodisperse crystalline silver particles in microscale were prepared via chemical reduction method and the reaction conditions were systematically investigated.Gelatin was chosen as dispersion agent and oleic acid was used as surfactant to prevent the agglomeration of silver particles.The crystallized and mono-disperse silver particles were obtained at the optimal synthesis condition(1.2 mol/L silver nitrate,0.8 mol/L ascorbic acid,dosage of gelatin=0.025(gelatin/silver,w/w),oleic acid/silver=1 wt%,pH=1.5 and the reactive temperature=30?).The average particle size of the silver particles is 1-2 ?m and the tap density of silver particles is over 5.0 g/cm3.The pH value is a key factor for preparation of crystallized silver particles.When the pH value increases from 1.0 to 4.0,the morphology of silver particles changes from polyhedron crystalline to spherical particles.Next,we prepared silicon solar cell front electrode paste with glass powder system of PbO-SiO2-B2O3-TeO2.When the percentage of organic medium is 11%?13%,the height to width of front electrode is high because of the appropriate viscosity(280Pa·s?350Pa·s)and high thixotropic index(>3)of paste.Using the crystalline silver particles with high tap density,the solar cell grid electrode has excellent electrical performance,and the photoelectric conversion rate is more than 18.4%and the fill factor exceed 78.7 for monocrystalline silicon cells.A series of silver pastes are prepared to better understand the function of the TeO2 contents in the glass frits for the formation of Ag crystallites in glass phase.The Te02 is favorable to produce Ag crystallites in glass phase.The size and quantity of the Ag crystallites formed in glass phase influences the electrical properties of the solar cells.Finally,we prepared silicon solar cell back electrode silver paste with glass powder system of Bi2O3-SiO2-B2O3-Al2O3.When the size of crystalline silver particles is 0.4 ?m,and the percentage of glass powder is 5%,the back electrode grid of Si solar cells has low resistivity,good film forming property and high adhesion strength after soldering.