Classification of solar cell pastes
发布时间：
2022-05-27 17:42
Classification of solar cell paste:
Backside silver paste From the perspective of the effects of the three pastes, the functionality of backside silver is the smallest, so the technical threshold is relatively low. The previous back silver is usually called silver-aluminum paste. As the name suggests, the paste contains silver and aluminum. We all know that silver and aluminum are difficult to form alloys, and silver paste containing aluminum will affect welding, but why add aluminum?
I think there are two main points. First, I hope that the aluminum in the silver aluminum paste can form a similar BSF layer between the back electrode and the battery like the aluminum paste during the sintering process. (Indeed, the previous battery back electrodes were two or three relatively wide.) The second is to reduce the cost of back silver. After all, the prices of silver and aluminum are very different. At that time, the solid content of back silver was still about 78%. Since the back silver has little effect on the performance of the battery, the requirements of the battery cell factory for the back silver are mainly unit consumption, welding performance, etc., so everyone took basically the same route, removing aluminum and reducing the solid content, whether it is DuPont, Heraeus or Flow, the current solid content of back silver is less than 70%, and the silver content is even lower.
Therefore, the obvious development direction of back silver is to reduce the silver content, reduce the unit consumption, and ultimately reduce the cost while maintaining or improving the welding performance. Backside aluminum paste The function of aluminum paste is mainly to form an aluminum backfield on the back of the cell during the sintering process to improve the electrical performance of the cell. There are two mechanisms of action of the aluminum back field, one is aluminum gettering; the other is the formation of the so-called P+ layer. From the perspective of the battery itself, the requirements for aluminum paste are as follows: electrical properties, appearance, warpage, adhesion, etc., among which electrical properties are the key. There are many related patents at home and abroad that can be consulted, and combined with the current requirements of cell and component factories, it can be seen that its future development direction must be high electrical performance, low warpage, uniform appearance, and adhesion. Front silver paste The function of front silver (photovoltaic auxiliary material net) is to collect current. It looks very simple, but it is actually the most difficult of the three pastes. So far, no domestic enterprise has successfully launched a front silver. The basic requirements of front silver Z are good printing performance, high aspect ratio, and at the same time, it can form a good ohmic contact with the silicon wafer and reduce the contact resistance, so that the cell has a high photoelectric conversion efficiency. Printing and aspect ratio are not difficult for many developers. Of course, the current blank of available domestic raw materials is also an insurmountable obstacle. In fact, it is more important to control the corrosion of the slurry to the anti-reflection film and the silicon wafer so as to form a uniform and good ohmic contact. Some information shows that high square resistance is one of the development trends. High square resistance corresponds to low concentration diffusion, and it is more difficult to control the formation of good ohmic contact by sintering. Therefore, it can be speculated that one of the development directions of front silver is good brush performance, high width and width. The ratio is high, the contact can be heavily doped and a uniform and good ohmic contact can be formed.
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