The Preparation And Performance Research Of Silver Powder And Organic Medium In Back- Side Silver Pastes Of Polycrystalline Silicon Solar Cells

The human energy supply is at a turning point. In recent decades, the reserves of the fossil energy is on the brink of exhaustion because of large-scale use. At the beginning of 21st century, the energy structure began to absorb wind energy, solar thermal, solar photovoltaic, biomass and geothermal energy and other renewable energy sources. Among them, solar photovoltaic cells which use solar photovoltaic bring to the attention of the people and has been widely applied because of many advantages, such as clean, convenient application and not be subject to regional restriction. With the vigorous development of the domestic photovoltaic industry, the demand of people on the silver paste, which is the conductive of the solar photovoltaic battery electrode, is higher and higher. It can not only improve the efficiency of solar cells, but also try to reduce the production cost of solar cells. This article mainly wants to select a kind of silver powder and a kind of organic medium which have a better performance through the system research on the silver powder and organic medium of the back-side silver electrode of polycrystalline silicon solar cells. And the back-side silver electrode paste was prepared by adjusting the content of the silver powder and organic medium. After the silver paste was screen printed and high temperature sintered, the impact of the related performance parameters on battery performance were tested.First, using the method of chemical reduction (among them, the silver nitrate serves as oxidant, ascorbic acid serves as reducing agent, polyvinyl alcohol serves as dispersing agent), micron spherical silver powders with different size and high dispersion were prepared. Then the silver powders and homemade glass powder and organic medium were mixed respectively. After they were rolled, screen printed, high temperature sintered and tested, a kind of spherical silver powders with D90≤1.0 um which was found having the optimal performance was gotten. The experiment method is simple and easy to implement and is an implementation scheme of currently industrialized production of the micron scale spherical silver powders.Second, the optimal combination and ratio of solvents in organic mediums of the back-side silver electrode paste has been optimized in the experiment as butyl butyrate 5.00 wt%, diethyl ethanedioate 20.00 wt%, terpineol 32.00 wt%, tributyl citrate 25.00 wt%. On this basis, the optimal composition of several common solid substances in the organic medium is that acrylic resin 3.50 wt%, phenoxy resin 2.30 wt% and ethyl cellulose 2.40 wt%. Under this condition, then a kind of organic medium with the viscosity of 4.36 pa·s and the volatile quantity of 53.02 wt% at 150 ℃ has gotten with a better performance, which can satisfy the demand of the back-side silver paste for organic mediums. The research about the material proportioning of organic mediums in this experiment has provided the theoretical research foundation for improving the performance of the back-side silver paste.Last, spherical silver powders D90≤ 1.0 um prepared in this experiment used as conductive phase, the glass system of Bi2O3-SiO2-B2O3-Al2O3 used as glass phase and the organic medium with the viscosity of 4.36 pa·s and the volatile quantity of 53.02 wt% at 150 ℃ were mixed up with each other. Then by changing the content of silver powders and organic medium, different kinds of back-side silver pastes have been prepared. The influence of the content of silver powder on the burn conjunctival surface morphology and the welding tension of the back-side silver electrode, and the influence of the content of organic medium on the viscosity and drying performance of the back-side silver paste, and the influence of different back-side silver pastes with different kinds of silver powders and organic mediums on the electrical performance of the solar cell all have been studied. It was found that the photoelectric conversion efficiency of the solar cell is highest when the content of silver powder is 54.72 wt% and the content of organic medium is 43.00 wt%. At the same time, it is also confirmed that the burn conjunctival surface morphology is smooth and dense, the weldability is good and the welding tension is big of the back-side silver electrode printed by the above mentioned silver paste in this experiment, which means that this silver paste has the optimum properties.