Heterojunction batteries are high-efficiency technologies that have aroused great attention in the industry in recent years. Due to their advantages of high conversion efficiency and double-sidedness, high efficiency potential, large cost reduction space, short process flow, etc., they have become the industry’s most recognized future battery technology. One of cost-effective solutions. Therefore, various schemes to improve efficiency and reduce costs have been successively proposed. As shown in TaiyangNews 2019, among the battery efficiency published by various heterojunction manufacturers, those currently in the ramping and trial production stage are still mainstream. Among them, the average efficiency of most trial production is above 23%, the highest efficiency of the production line or the R & D test line (R & D) is even more than 24.5%, and it is expected to reach 25% in the future. It is exciting to be the world leader in advanced photovoltaic technology solutions. The supplier Meyer Burger has successfully provided its customer REC with the only 600MW global mass production heterojunction production line with an average efficiency of more than 24%. At the same time, the cost of the module end is close to PERC technology. Competitive. Demonstrates the high potential of heterojunction battery technology.

In addition to the high conversion efficiency of heterojunction battery technology, the consideration of production cost is the industry’s most concerned. This article will explain and analyze the main cost reduction projects of heterojunction batteries, hoping to give readers corresponding inspiration:

Wafer thinning

N-type silicon wafer is one of the cost centers with the highest proportion in the production cost of heterojunction cells, so using thinned silicon wafers to reduce material costs has become a necessary way to reduce costs. Due to the symmetrical structure of the heterojunction battery and the maximum temperature of the battery process not exceeding 200 ° C, it is easier to use thinned silicon wafers in mass production, such as the content of Meyer Burger in the 2018 CSPV, The thickness of the silicon wafer is reduced from 180um to 120um. Although the short-circuit current (Isc) decreases as the thickness of the battery becomes thinner, the open circuit voltage increases. Therefore, even using thinned silicon wafers can maintain the same battery efficiency. With Smart Grid Technology (SWCT ), the output of wattage of about 5W can be added to the component. Therefore, for the use of N-type silicon wafer heterojunction batteries, it is possible to achieve the function of improving efficiency and reducing costs by gradually using thinned silicon wafers.

Simple process

Another advantage of the heterojunction battery is that the process steps are relatively simple. The HELiA PECVD developed by Meyer Burger integrates the deposition of amorphous silicon films on the front and back sides and the HELiA deposits a transparent oxide conductive film (TCO) on the front and back sides of the battery. For PVD equipment, four main equipments are used to complete eight process steps, which greatly simplifies the process flow and greatly reduces the production site.

01, velvet washing machine:

Battery front and back texturing

02. Plasma enhanced chemical vapor (PECVD)

Depositing a frontal intrinsic amorphous silicon film (i-a-Si: H) and an n-type amorphous silicon film (n-a-Si: H),

An intrinsic amorphous silicon film (i-a-Si: H) and a p-type amorphous silicon film (p-a-Si: H) are deposited on the reverse side of the deposition.

03. Physical Vapor Deposition (PVD)

A transparent oxide conductive film (TCO) deposited on the front and back of the battery

04 、 Screen printing machine

Front metal electrode preparation

Reverse metal electrode preparation

annealing

Testing and binning

Through Mayerberg’s mass production practice, due to the short process flow of the heterojunction battery, the workshop space requirement is reduced by 25% compared with the traditional mass production line, and the low temperature process can also reduce the consumption of electrical energy, which will build large-scale quantities in the future Production lines can reduce the cost of factory services and facilities. The gradual increase in the future production capacity of equipment is also an important part of reducing production costs. The heterojunction electricity can also be perfectly matched to make a perovskite silicon heterojunction stacked battery, showing the high potential of future heterojunction battery technology to improve efficiency and reduce costs.

Reduced silver paste usage

The material of low-temperature silver paste in the preparation of metal electrodes of heterojunction battery technology accounts for the highest proportion of the entire non-silicon cost. The single-chip consumption of low-temperature silver paste required for screen printing 5BB battery structure exceeds 300 mg, which is about the average 3-4 times the PERC silver paste, even if using a multi-busbar (MBB) structure, its low-temperature silver paste single-chip consumption is more than 150 mg, and it needs to face the challenge of using low-temperature string welding processes in components. In this part, the main grid-free smart grid technology (SWCT ) used by Meyer Burger in the 2018 PV Cell tech published its low-temperature silver paste consumption of less than 100 mg, and further optimization after mass production is expected It achieves a consumption of less than 100 milligrams, and the overall shielding rate after the cells are connected in series is also lower than the 5.5% of 5BB to only 4.3%. Coupled with the thinning of grid lines in the future and the optimization of SWCT components, there is a very high potential for cost reduction. This is why Mayerberg’s heterojunction mass production technology can become the world’s first success, and it is also a major reason for the only successful case so far.

Driving the cost of heterogeneous single-watt power generation to decline, making heterojunction batteries more economical than single-crystal PERC batteries has become the most important issue for all heterojunction manufacturers. For Meyer Burger, the company has long been committed to the R & D and industrialization of innovative systems and production equipment solutions in the photovoltaic industry. It not only integrates heterojunction cell process technology and matched automation equipment, but also provides intelligent networks. Grid technology (SWCT ) is used with heterojunction batteries to successfully integrate battery technology and component technology to improve battery efficiency while reducing single-watt power generation costs. The only supplier of total heterogeneous technology solutions that achieves mass production in a true sense and has both efficiency and cost reduction. We are full of hope that in the near future, heterojunction technology will be accepted by more manufacturers and markets, and will quickly become the next-generation mainstream manufacturing technology of photovoltaic cells and modules.