What is 0 Busbar (0BB) solar Cell Technology?

After adopting 0BB technology, the silver paste cost for PERC can be reduced to 0.03 yuan per watt, TOPCon to 0.01 yuan per watt, and HJT to 0.04-0.06 yuan per watt. Additionally, if 0BB technology is combined with 30% silver-coated copper paste, the final silver paste cost for HJT is expected to drop to 0.03-0.04 yuan per watt.

3.Enhanced Efficiency:

0BB technology decreases electrical resistance within the solar cell, resulting in more efficient electron movement and increased energy conversion efficiency. This leads to higher energy output from the same amount of sunlight, making 0BB solar cells more productive.

4.Improved Shading Tolerance:

The presence of multiple thin connections in 0BB cells creates multiple pathways for electrical current, reducing the risk of power loss due to partial shading. This is particularly advantageous in installations where shading from objects like trees or buildings can affect performance.

5.Reduced Hotspots:

0BB technology evenly distributes electrical current over the cell surface, minimizing the occurrence of hotspots caused by high resistance. This helps prevent efficiency drops and long-term degradation of the cell.

6.Higher Quality:

With smaller and more numerous solder points, stress distribution in the cells is more uniform, reducing cell breakage, gridline breakage, and microcracks, thereby improving production yield. Additionally, the uniform stress distribution allows 0BB technology to use thinner silicon wafers, which can be as thin as 100μm according to experts.

By incorporating these advantages, 0BB technology significantly enhances the performance, durability, and efficiency of photovoltaic modules, positioning it as a key advancement in the solar energy industry.

Disadvantages of 0 Busbar (0BB) Technology

Despite its significant advantages, 0BB technology still faces several challenges, including ensuring welding consistency and efficiency testing. The most pressing issue is reliability. The fingers and solder points are a combination of silver and glass, making the structure loose and unstable. Since the solder ribbons are made of copper, the differing properties of silver and copper make it difficult to achieve a solid weld, leading to potential detachment and affecting the normal operation of photovoltaic cells.

0 Busbar (0BB) Solar Cells Interconnection

1.First Method: SmartWire Connection Technology

The core component of SmartWire Connection Technology is the copper wire composite film. This film is composed of an electrically insulating, optically transparent layer, an adhesive layer on the film’s surface, and multiple parallel copper wires (tabbing ribbons) embedded within the adhesive layer. These copper wires, bonded to the film via the adhesive, protrude with a low-melting-point alloy coating.

During the lamination process, the copper wire composite film connects the solar cells in series. The film is overlaid with an encapsulation film, backsheet, or glass, creating a stable electrical connection between the tabbing ribbons and the grid during the heating process.

The copper wire composite film is laminated on the surfaces of adjacent solar cells to form a series connection. Unlike conventional solar cell packaging, this method uses a new stringer machine to place the copper wire composite film on both the front and back surfaces of two cells, enabling their series connection. Once interconnected, the cells are arranged and stacked. Under specific lamination temperatures and pressures, the copper wires and solar cell grids are pressed together to form an ohmic contact.

2.Second Method: Dispensation

(1)Dispensing: Apply adhesive droplets on the surface of each solar cell.

(2)Tabbing: Evenly space multiple tabbing ribbons perpendicular to the grid lines on each solar cell.

(3)Fixing: Use UV light to cure the adhesive, bonding each tabbing ribbon to its corresponding solar cell, ensuring direct contact with the surface grid lines.

(4)Lamination: Heat and laminate the solar cell assembly to form alloy connections between the tabbing ribbons and grid lines.

This method differs from traditional stringing in two main ways:

(1)Dispensing: Adhesive droplets bond the tabbing ribbons to the solar cells, allowing for series connection and immobilization of the ribbons for subsequent module encapsulation.

(2)Alloying through Lamination: Achieve ohmic contact during the lamination process.

Advantages of this method include simple equipment and high stability. However, potential shadows during EL testing under the tabbing ribbons and insufficient bonding strength between the ribbons and solar cells are disadvantages.

3.Third Method: Soldering Dispensation

(1)Soldering: Use infrared heating to melt the surface of the solder ribbon, creating a preliminary connection with the solar cell surface and grid lines.

(2)Dispensing: Apply adhesive droplets at specified locations on the soldered solar cell-ribbon assembly. The number of adhesive droplets is carefully controlled to balance process complexity and bonding strength requirements. Typically, 3-8 rows of adhesive droplets are applied based on shadowing area and mechanical performance needs.

(3)Curing: Solidify the adhesive droplets on the front side of the soldered cell string. Transfer the cell string to the next station, flip it under controlled temperature conditions, and apply and cure adhesive droplets on the backside, forming the final cell string.

Compared to adhesive bonding, this method involves a preliminary soldering step followed by adhesive application for reinforcement. The initial connection between the solder ribbon and the grid lines is established through infrared heating. Adhesive is then applied and cured to enhance the stability of the solder ribbon-cell connection.

Advantages of this method include strong bonding between the solder ribbon and the solar cell, reducing the risk of ribbon detachment. However, there is a risk of grid breakage during soldering, and the dispensing process requires high precision, making it challenging and relatively slow.

By implementing 0BB technology in HJT solar cells, the photovoltaic industry can achieve significant cost reductions and efficiency improvements, driving the future of solar energy innovation.

Market Prospects for 0 Busbar (0BB) Technology

Although challenging, mastering 0BB technology could significantly reduce costs, enhance efficiency, and improve quality in photovoltaic cells, thus giving companies a technological edge. The enthusiasm for 0BB technology is high among various companies.

JinkoSolar: JinkoSolar has made the latest progress in 0BB technology, having completed development and pilot testing, and has begun applying it on a small-scale production line. The company expects to save approximately 10% of silver paste using 0BB technology. Currently, silver paste consumption is over 90 milligrams, but it is anticipated to drop to 80 milligrams in the future. The company projects that by the end of 2024, the efficiency of regular production line cells could reach over 26.5%, with the best production lines achieving 26.6-26.7%.

Canadian Solar: After more than a year of dedicated research, Canadian Solar has compared the pros and cons of various 0BB technology solutions and has identified the most suitable approach for them. The company believes that as photovoltaic technology continues to evolve and market demand changes, 0BB technology is likely to become mainstream in the photovoltaic industry.

Risen Energy: In 2023, Risen Energy utilized its proprietary 0BB cell technology, 210 ultra-thin wafer technology, pure silver usage of less than 7mg/W, and stress-free cell interconnection technology to establish a seamless production process from heterojunction silicon wafers to cells and modules. This achievement made it the first company in the industry to achieve large-scale production of heterojunction cells and modules.

Aiko Solar: Combining 0BB technology with the high conversion efficiency of ABC, Aiko Solar expects to increase the power of its ABC series products by 5W.

In summary, the application and development of 0BB technology in the market are advancing rapidly. Many companies are investing in research and trial production, and large-scale production is expected to be realized in the coming years. This will significantly reduce the cost of photovoltaic modules, improve power generation efficiency, and further drive the development of the photovoltaic industry.