The increasing demand for high efficiency PV modules at lower costs of production leads to new designs of solar cells. For enhanced module efficiency, the cell efficiency must be optimized first to guarantee later operation under module conditions. Therefore the interconnection of solar cell structure has to be assessed instead of the common way of separately optimizing the single solar cells.
The number of busbars can be varied so as to decrease the total series resistance of the interconnected Solar cells. Also, a device with multiple busbars has a high cost saving potential due to the reduction in the metal consumption for front side metallization process. This led to the development of Multi Busbars for the PV module industry.
Benefits of Multi Busbar
A big cost element is the screen printed silver (Ag) front side metallization process. In recent years the 3 busbar cell design was optimized by adding extra busbars to the device.The variation in number and geometry of the busbars lead to a significant decrease in Ag paste consumption while boosting the module efficiency in the same time.
An extra silver reduction can also be achieved by replacing the rear side pads of Ag/Al with tin pads for the soldering process. These changes make the Multi Busbar use in solar cell design lead to significant reductions in cost of the metallization process and in increase the efficiency of the Solar modules at the same time.
Growth of Multi Busbar in recent years
The industry is currently moving in the direction of the 6 busbar module architectures.In recent years, the 3 busbar was a staple in solar module industry. After some time, the 4 busbar became mainstream. The 5 busbar is gaining steam and quickly will become mainstream and beyond the 6 busbar, the multi ribbon and wire busbar are becoming the trend.
For improvement of the cell metallization interconnection, multi ribbon and multi wire busbars are used to decrease the gap between cells and increase the efficiency of solar cell performance. This leads to decrease in silver (Ag) paste consumption and can be significantly reduced (nearly 2.4 g for the 60 cell module) and also decrease in the electrical and optical losses due to the shorter finger length and improved light in-coupling than the usual ribbon technologies.