The Controllable Preparation And Application Explore In Solar Cell Conductive Paste Of Silver Powder

Conductive silver paste is widely used in the front side metallization of silicon solar cells due to its facile synthesis process.Silver particles play a very important role on the major component within silver paste.The properties of silver paste are dominated by the different morphologies,size distribution and tap density of silver particles.Hence,in this work,liquid phase reduction method was utilized to obtain silver particles with different morphologies and size distribution.Meanwhile,we conducted an investigation on the shape-controlled synthesis.Various chemical agents and reducing agents were utilized in order to produce silver particles with different sizes and dimensions.The chemical composition was characterized by X-ray Diffraction(XRD),the morphologies were observed by Scanning Electronic Microscopy(SEM),and the diameter of particles was detected by Laser Particle Size Analyzer.The results indicated that different reducing agents and capping agents played an important role on synthesis of different morphologies of the silver particles.By controlling these factors,nanosized silver,silver wires,plate like silver and silver spheres are produced successfully.Then,the silver pastes are prepared by using these different silver particles and the conductivity is investigated.Sodium borohydride,silver nitrate,Arabic gum was used to prepare nanosized silver particles.The final powders are in spherical shape but appear in aggregated status,and the size of the powders should be around 100nm.In order to produce silver wires,dodecylamine was used herein.With the increases of dodecylamine molar concentration,morphology of silver particles shows irregular shape.Nevertheless,with the help of oxidative etching power of Cl-on twinning boundaries and dislocation,silver wires can be produced by fast growing(100)facets.When the molar ratio of Cl-and Ag+ is 1:2,the yield of silver wires can be 90%with tens micron long.In order to produce silver plate,sodium citrate worked as capping agent,and ascorbic acid were used to reduce silver nitrite.It was believed that when the reaction rate is slow and under thermodynamic control,the growth of silver product will proceed along the path to minimize the total surface free energy of the system.In this case,silver will be grow along the[100]direction and eventually form plate like structure.Regarding to spherical silvers,when the ascorbic acid was utilized,the final products showed flower like structure.It is believed that the reducing ability of ascorbic acid was not strong enough and the residual reducing agent and Ag+were under the thermodynamic control leading to anisotropic growth.When ferrous sulfate was used,the silver nucleates very fast and everywhere and formed basic nano clusters.Final spherical silver balls were formed by aggregation of these basic silver clusters.Finally,SiO2@Ag composites were introduced into this work.The monodispersed SiO2 microballs were synthesized via Stober method beforehand.The XRD was used to identify the Ag and SiO2.It is observed that SiO2 is amorphous.The whole composites were in 300?400 nm.Via HAADF-TEM techniques,the shell of Ag was in thickness of 30 nm.Substitution of glass powder by SiO2@Ag within silver paste showed reasonable property of conductivity.On the other hand,when the silver spheres with the high tap density are introduced,the conductivity of silver paste increase firstly and then decrease.