Big changes in photovoltaic technology and how it develops
- The expansion of N-type production is accelerating
- Wafer thinning
- Metallization process and low-cost metal paste
The expansion of N-type production is accelerating. It is estimated that the production capacity of TOPCon22 will exceed 90GW this year, and the production capacity of heterojunction will be nearly 6GW.
The production capacity planning and production progress of TOPCon photovoltaic technology and HJT photovoltaic technology, which belong to photovoltaic technology, have exceeded expectations.
At present, TOPCon photovoltaic technology plans to have a production capacity of nearly 230GW, and it is expected that more than 90GW will be completed and commissioned. HJT photovoltaic technology planned production capacity exceeds 170GW, and it is expected to mass produce nearly 6GW this year.
The expansion of N-type production is accelerating
TOPCon production capacity will exceed 90GW
TOPCon, one photovoltaic technology, plans to have a production capacity of nearly 230GW, and over 90GW will be built/put into operation. TOPCon photovoltaic technology is the N-type battery route that is the first to land, has the most plans, and is under construction and put into production with the most production capacity.
Industry leaders such as JinkoSolar, Jolywood, Junda, and Trina Solar, which is one of photovoltaic module manufacturers in the world all have layouts on the TOPCon photovoltaic technology route.
Among them, JinkoSolar is currently in full production of 16GW, and the first phase of Junda is expected to be mass-produced in the second half of 2022. Taizhou’s 3.6GW is in full production and Shanxi’s 4GW is in the process of climbing. It is estimated that by the end of this year, the production capacity of TOPCon photovoltaic technology will exceed 90GW.
HJT planned production capacity exceeds 170GW
The planned production capacity of heterojunction exceeds 170GW, and the mass production capacity this year is nearly 6GW. There are many Chinese heterojunction cell capacity plans, but currently only Huasheng, Aikang and Diamond Glass have mass production capacity. In 2022, Huasheng has put into production 2.7GW. In February this year, it entered the mass production preparation stage, with a total of 5.9GW of heterojunction in 2022.
As a leader in heterojunction cells, Huasheng has taken the lead in achieving 2.7GW cell and module production capacity. The third phase of 4.8GW production capacity is expected to be put into operation in 23 years. Planning 5GW heterojunction cell and module production capacity. Akcome Technology, Baoxin Technology, and Diamond Glass plan 24GW, 18GW, and 6GW heterojunction production capacity respectively.
The N-type inflection point has arrived
Silicon wafer cost accounted for 62%, and silver paste accounted for 16%. Thinning and reducing silver consumption are the main ways to reduce the cost of N-type batteries, which belong to photovoltaic technology. Cell costs include silicon costs and non-silicon costs. In terms of reducing the cost of silicon, it is mainly achieved through the thinning of silicon wafers. The proportion of silver paste in non-silicon cost is relatively high, and the cost of TOPCon photovoltaic technology silver paste accounts for 16%.
According to the data, in 2021, the front silver consumption of p-type batteries, a photovoltaic technology, is about 71.7mg/piece, the back silver consumption is about 24.7mg/piece, and the front silver and aluminum paste (95% silver) of TOPCon batteries consumes 75.1mg/piece.
The back silver consumption of some enterprises is about 70mg/piece. The double-sided low-temperature silver paste consumption of heterojunction cells is about 190mg/piece. The cost of N-type battery silver paste is much higher than that of P-type batteries, and the cost reduction of silver paste will become the main means of cost reduction.
Chinese manufacturers of photovoltaic technology silver powder include Suzhou SMT, Shandong Jianbang, and Ningbo Jingxin Electronic Materials. In 2021, China will import 3,240 tons of silver powder throughout the year, of which Japan, the United States, and South Korea account for 91.48%, 6.81%, and 0.86% respectively, and more than 50% of the imports are used for the production of photovoltaic technology silver paste.
The high price of silicon materials + the cost of N-type silicon wafers is higher than that of P-type silicon wafers. The mismatch between supply and demand of polysilicon has caused the price to continue to rise to 300 RMB/kg, and the price of polysilicon has been higher than 200 RMB/kg for more than a year. The price of silicon materials continues to rise, and the cost of silicon wafers is rising.
At the same time, the 22-year battery has entered the first year of N-type. Because N-type photovoltaic technology silicon wafers have higher requirements on the quality of silicon materials and impurity content in the production process, the cost is higher than that of P-type photovoltaic technology. The most direct measure to reduce the cost of silicon wafers is to thin silicon wafers. Nowadays, the thickness of silicon wafers has dropped by more than 15μm.
The thickness of silicon wafers decreases, and the number of single KG silicon rods increases, which directly dilutes the cost of silicon wafers. According to CPIA, in 2021, the output of P-type 158.75mm square rods per kilogram will be about 70 pieces, and the P-type 166mm size will be about 64 pieces per kilogram of single crystal square rods.
Wafer thinning needs to balance open circuit voltage (Voc), short circuit current (Jsc) and fill factor (FF). The conversion efficiency of crystalline silicon cells depends on the product of open circuit voltage (Voc), short circuit current density (Jsc) and fill factor (FF).
The silicon wafer is thinned, the open circuit voltage (Voc) and fill factor (FF) of the battery are increased, but the short-circuit current is reduced, and the conversion efficiency may also be reduced. According to relevant calculations by Zhonghuan, the efficiency of 160μm silicon wafer cells is 0.02% lower than that of 175μm.
At present, the mainstream silicon wafer thickness of PERC is maintained at about 150 μm, while TOPCon photovoltaic technology and heterojunction both use silicon wafers with a thickness of 130 μm. The mass production thickness of heterojunction silicon wafers has been switched to 130 microns. Akcome expects to introduce 120 μm thick silicon wafers in the second half of 22.
It is estimated that the target of heterojunction silicon wafers will be reduced to 90 μm by 2026. Huasheng New Energy has completed the small-scale production of 120μm batteries, and the test data A product rate of large-size 98μm silicon wafers under development is also stable at more than 90%. The current cell thickness of Junda TOPCon photovoltaic technology is about 130μm.
Metallization process and low-cost metal paste
Less silver, ultra-fine, dense, and high aspect ratio are the main development directions of grid lines for crystalline silicon cells. The battery grid lines will block part of the light from entering, so the thinner the grid lines, the higher the battery conversion efficiency.
However, if the grid lines are thin, the resistance loss will be large and the fill factor will be reduced. Therefore, the core of the grid line development is to balance the relationship between shading and conductivity.
The silver paste cost reduction path mainly includes two directions:
- On the premise of not affecting the battery conversion efficiency, reduce the grid line area and reduce the consumption of silver paste. At present, it mainly includes multi-busbar photovoltaic technology (MBB), SMBB, 0BB, laser transfer printing and copper plating.
- Use low-cost metal paste to reduce the use of silver. Use lower-priced metals to partially or completely replace silver, and the measures mainly include silver-clad copper.
Contact metallization process
Metal electrodes mainly include main grids and fine grids. Increasing the number of main grids and reducing the width of the fine grids can effectively reduce the consumption of silver paste. The main grid is used for confluence and series connection, and the fine grid is used for collecting photogenerated carriers. As the number of busbars increases, the current passing through each busbar line decreases, and the resistance loss decreases.
At the same time, the number of busbars increases, the carrier transmission distance through the fine grids is shortened, the carrying current of the fine grids is reduced, and the ohmic loss is significantly reduced. While increasing the number of busbars and reducing the width of the busbars and fine grids, it is possible to reduce the amount of silver paste without sacrificing the conversion efficiency of the battery and increasing the reliability of the photovoltaic technology components.
Non contact metallization process-laser transfer printing
Laser pattern transfer printing technology (PTP) is a non-contact printing technology that coats the required slurry on a specific flexible light-transmitting material, uses a high-power laser beam to scan at high speed, and transfers the slurry from the flexible light-transmitting material transfer to the surface of the battery to form grid lines. Laser transfer printing has no selectivity for the type of paste (silver paste, silver-coated copper), and is not limited to the battery structure, and can be applied in PERC, TOPCon photovoltaic technology and HJT photovoltaic technology batteries.
Non contact metallization process-copper electroplating
Electroplating photovoltaic technology uses electrochemical methods to deposit a thin layer of metals, alloys and composite materials on the surface of conductive solids. After the electroplating solution is energized, the metal cations move to the surface of the battery due to the potential difference, and deposit to form a metal coating, that is, an electrode.
The copper plating process is similar to the photolithography process in semiconductors.
After the silicon wafer is cleaned by texturing, amorphous silicon deposition, and TCO film deposition, a layer of insulating anti-reflection film is deposited on the surface of the TCO film. The insulating anti-reflection film is used as a mask layer, and the designed The insulating anti-reflection film at the electrode pattern, after cleaning, exposes the TCO film below, which is the place where the electroplating copper is attached.
Prepare copper electrodes at the target pattern by electroplating, then remove the mask and seed layer, and the front and back of the battery. This operation needs to be repeated. This process is similar to the glue coating, exposure, development, etching/ion implantation, and glue removal processes of the photolithography process in semiconductors.
Copper electroplating can replace silver paste, while shortening the line width, increasing the illuminated area, and improving conversion efficiency. The screen printing line width can reach 20 μm, and the copper electroplating can achieve a line width of about 10 μm.
During the electrode preparation process, the width and height of the grid line can be controlled, which can effectively improve the aspect ratio of the grid line, reduce the shadow loss caused by the grid line, and effectively reduce the contact resistance between the electrode and the PN junction, the volume resistance of the electrode itself and the battery resistance.
The internal resistance of a battery improves the photoelectric conversion efficiency of the battery. Electroplating photovoltaic technology can be applied to the production of battery electrodes such as TOPCon, HJT, PERC, and IBC, and all of which belongs to photovoltaic technology.
Low cost metal paste-silver clad copper
Silver powder accounts for 95% of the cost of silver paste, and the reduction in the amount of silver powder will reduce the overall paste cost. Silver-clad copper paste replaces silver partially by base metal copper, covers copper with silver, and improves photoelectric conversion efficiency by adjusting the doping ratio of silver and copper, which not only retains the advantages of silver but also prevents copper oxidation and composite production.
Silver-coated copper powder is prepared on the basis of ultra-fine copper powder products, and the quality of ultra-fine copper powder directly affects the performance of silver-coated copper. Silver-coated copper powder can only be used in low-temperature HJT photovoltaic technology routes. Because silver-coated copper loses its activity in high-temperature environments, silver-coated copper powder can only be used in low-temperature heterojunction routes.
Silver-clad copper can reduce battery costs by 30%. Experiments have proved that when using silver-coated copper paste to prepare heterojunction cells, the cell efficiency only loses 0.4%, but the cost can be saved by 30%.