In nature, there is a kind of silver-white metal "indium" with light blue, which is soft, ductile, low resistance, corrosion resistance, good light permeability and strong conductivity. ITO (Indium Tin Oxide) made of indium is widely used in the production of liquid crystal displays, flat screens, touch screens, optical coatings and other products as a target.
In addition, it is also used in the third step of the heterojunction battery process, that is, through PVD equipment, using the principle of magnetron sputtering, the target material (ITO) is deposited on the surface of the silicon wafer to prepare a double-sided transparent conductive film (TCO).
However, as a rare metal, the price of indium is relatively high. Therefore, in order to promote the industrialization development of heterojunction technology to reduce costs and increase efficiency, Maiwei shares continue to promote the low indium scheme of heterojunction TCO from the aspects of equipment and process, and strive to reduce the dependence of heterojunction batteries on indium, so as to avoid the manufacturing side being constrained by it. The following is an introduction to Maiwei's "Indium Reduction Trilogy":
Equipment Optimization and Indium
Reduction For PVD equipment of heterojunction batteries, Maiwei has attached great importance to the reduction of unit consumption of target materials from the beginning of R & D and design. Through continuous optimization of the sputtering unit, the theoretical unit consumption of Maiwei's latest equipment for 100% indium-based target has been reduced from nearly 20 mg/W to 13.5 mg/W, and the old equipment can also be upgraded.
In the process of optimizing the unit consumption of target materials, thanks to the deep accumulation of a large number of test data and improvement schemes, a clear and effective technical path for reducing unit consumption has been formed. It is expected that by the end of 2023, the theoretical unit consumption of 100% indium-based target materials will be reduced to about 12 mg/W in the overall solution of heterojunction battery manufacturing provided by Maiwei. The theoretical unit consumption of the indium-based target material can be reduced to about 6mg/W by combining the low-indium
laminated film scheme (50% free of indium) with the above equipment improvement scheme. Through continuous process research and development, Maiwei uses 50% indium-based + 50% non-indium-based stacked TCO to prepare heterojunction batteries, whose conversion efficiency is equal to that of all-indium-based TCO batteries. At the same time, the low indium-based scheme has good reliability and stability, and can be perfectly combined with low-cost schemes such as copper electroplating and silver-clad copper.
For such low indium solutions, Maiwei's PVD equipment is compatible and can be easily imported by simply adjusting the target material and target position. Considering that there are many kinds of non-indium-based targets and their resistivity span is very large, Maiwei's PVD equipment uses a variety of input modes, which can make the sputtering of non-indium-based targets more stable. The scale of
large-scale indium recovery
heterojunction industry is expanding day by day, and the recovery of indium materials can be further realized. Combined with the gradual deepening of indium-free targets, the consumption of indium in gigawatt (GW) heterojunction battery factories is expected to be reduced to 1mg/W.
Through unremitting equipment optimization and technological innovation, Maiwei shares focus on heterojunction technology, constantly broaden its path of cost reduction, and bravely climb its peak of efficiency. In August last year, the company adopted the TCO process with low indium (50%) content combined with copper plating grid line, and obtained the ISFH certification of 25.94% heterojunction cell efficiency, which is consistent with the cell efficiency under the all-indium-based scheme. Promoted by the "Indium Reduction Trilogy", Maiwei shares will help the heterojunction industry usher in a brighter and broader future.
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