Comparison of MBB and 0BB technologies for solar cells

What is multi-busbar (MBB) technology for solar cells?

Photovoltaic multi-busbar technology (MBB) is a method to improve the design and manufacturing of solar cells. It improves the performance and efficiency of cells by adding more busbars on the surface of the cell. Traditional solar cells usually use 2 to 5 busbars, while multi-busbar technology can use 9 or even more busbars.

Characteristics and main advantages of multi-busbar technology

More busbars: Multi-busbar technology evenly distributes more busbars on the surface of the cell, usually 9 or more. These busbars are used to collect and conduct photogenerated current. More busbars disperse the current and reduce the current density of each busbar, thereby reducing ohmic losses (resistance losses) and improving the fill factor and overall efficiency of the cell.

Improve mechanical strength: More busbars enhance the mechanical strength of the cell to a certain extent, reducing the risk of damage caused by stress during manufacturing, transportation and installation.

Improve hot-spot effect: The multi-busbar structure helps to evenly distribute current and reduce the hot-spot effect, thereby improving the long-term reliability and performance of the module.

Fine grid line design: When the number of main grid lines increases, the width of a single grid line can be reduced. Due to the fine grid line design, multi-busbar technology reduces the shading area on the surface of the solar  cell, allowing more light to reach the surface of the silicon wafer, increasing the photoelectric conversion efficiency.

Manufacturing process: The application of multi-busbar technology requires precise screen printing process and advanced electroplating technology to ensure high precision and consistency of multiple fine grid lines.

The implementation of multi-busbar technology usually requires corresponding process improvements and equipment upgrades in the cells manufacturing process. At present, multi-busbar technology has been widely used in the field of crystalline silicon solar cells and has become one of the important means to improve cell  performance and reduce costs.

What is Busbar-less (0BB) technology?

Busbarless Technology is an emerging photovoltaic cell manufacturing technology that improves the efficiency of solar cells and reduces costs. In crystalline silicon solar cells, the busbars are metal lines used to collect current, and there are usually multiple busbars. Busbarless technology eliminates these busbars and uses thinner metal lines or conductive materials to collect current.

The busbar-free (0BB) process eliminates the main grid and sub-grid in the metal electrode screen printing process, and optimizes the width and spacing of the sub-grid. The advantages of busbar-free (0BB) are cost reduction, silver reduction and efficiency improvement.

In the cell segment, compared with SMBB, 0BB can save about 30% of silver paste, adhesive film and 10% of soldering ribbons; in the component segment, 0BB uses low-temperature welding technology and ultra-fine and ultra-flexible soldering ribbons, which helps to improve the component welding yield. The use of ultra-fine and ultra-flexible soldering ribbons can collect more current, shorten the current transmission distance, and increase the solar panel  power.

Advantages of Busbar-less (0BB) Technology 

Reduce shading: Busbar-less technology reduces shading of light by the grid lines and improves the efficiency of solar cells.

Increased current collection: Busbar-less technology can use thinner metal lines or conductive materials, thereby increasing the current collection area and further improving the efficiency of the solar cells.

Reduce costs: Busbar-free technology can reduce the number and complexity of busbars and reduce the production cost of solar cells.

Improve reliability: Busbar-free technology can reduce the risk of solar cell failure due to busbar breakage or other problems, thus improving solar cells  reliability to a certain extent.