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Grid line optimization and upgrading multi-line parallel

Metallization is one of the key processes in PV cell preparation, which can affect cell cost and photoelectric conversion efficiency. The conductive paste is printed on the front and back of the wafer through screen printing technology, and after low temperature baking and high temperature sintering operation, the electrode and the cell form an ohmic contact electrode, thus deriving the internal current of the cell.

At present, the optimization and upgrading of the metallization link has the following two main technical paths.

Both MBB and SMBB are designed to increase the number of main grids, reduce the width of the grids, reduce the shading loss and shorten the current collection route, thus reducing the cell silver paste consumption while increasing the power generation efficiency.

0BB (no main grid technology) only screen-printed thin grids, using polymer films with embedded copper wires instead of main grids, and optimizing the width and spacing of thin grids, reducing the shading area and resistance loss of the cell, resulting in improved cell efficiency and savings in paste consumption.

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Laser transfer technology innovation upgrade

Laser pattern transfer technology is an emerging alternative technology for metallization of PV electrodes. By filling the grooves of the flexible light-transmitting material with paste and scanning it with a high-speed laser pattern, the paste is transferred from the flexible light-transmitting material to the surface of the wafer to form the grid lines. The technology can be applied to a wide range of cell technology routes and can be matched to low-temperature pastes for HJT's low-temperature process. Due to the non-contact printing mode, laser printing can reduce the risk of hidden cracks, fragmentation, contamination, and scratches, and is suitable for thin wafer, flexible heterojunction cells. Compared with traditional screen printing, laser transfer printing technology can significantly reduce the HJT grid line width, to achieve a reduction in silver paste consumption, and good printing performance, the height of the printed grid line is consistent, uniform width, improve the use of silver paste, efficiency and cost reduction advantages.

Low temperature silver paste localization is the right time

As the heterojunction cell uses amorphous silicon thin film, the whole process needs to be prepared at low temperature, so low temperature silver paste must be used. Compared with the traditional high temperature silver paste, the silver content in low temperature silver paste is higher and more difficult to prepare. In the early development of the photovoltaic industry, the global low-temperature silver paste market has been monopolized by Japanese enterprises, low-temperature silver paste relies heavily on overseas imports. Under the huge pressure of cost reduction, domestic silver paste enterprises to domestic replacement as the goal, and constantly increase investment in independent research and development of domestic silver paste, and gradually achieve the independent replacement of silver paste rate. With the localization of low-temperature silver paste replacement process to speed up, paste cost reduction will be just around the corner.

Silver-clad copper technology has a bright future

Silver paste composed of high purity silver powder, glass oxide and organic materials is the core auxiliary material in the production process of heterojunction battery, accounting for more than half of the non-silicon materials, while silver powder accounts for a very high proportion of the total cost of silver paste, meaning that the price of silver paste is closely related to the price of precious metal silver. Silver clad copper technology through chemical plating, in the ultra-fine copper powder surface to form different thicknesses of silver plating, adjust the ratio of silver and copper paste to improve the antioxidant capacity, to achieve the low-cost metal instead of high-priced metal cost reduction goals. At present, Akcome keeps increasing investment in R&D and actively exploring the technology route of silver-coated copper slurry, with the goal of achieving a lower silver consumption per unit of HJT cells than PERC silver consumption in the next few years, leading HJT into the era of low-cost mass production.

Copper plating technology is ready for development

Copper plating technology is a cost-reducing technology based on the development of silver-clad copper technology, which is based on the electrolytic principle of depositing metallic copper on the surface of the cell to make copper grid lines to collect the carriers generated by the photovoltaic effect and export the cells by means of current. As the copper powder replaces the precious metal silver powder, the cost reduction of HJT cells is achieved. Compared with the traditional screen printing technology, the wire width and pitch of the grid lines printed with copper plating technology are significantly lower, which further reduces the resistivity and brings higher power generation efficiency to the heterojunction cells. However, copper plating technology is still facing problems such as high cost of equipment and consumables, low capacity, and many pollutants, which need to be gradually solved by manufacturers through technology upgrade in the future.


Post time: Sep-28-2022