What is solar busbar

Conventional silicon solar cells are metallized with thin rectangular-shape strips printed on front and rear of a solar cell. These front and rear contact strips are referred to as busbars, or bus bars.

Solar busbars conduct the direct current produced by the solar cell from the incoming photons.Commonly, solar cell busbars are made of copper plated with silver.

Development trends and future

The most common solar cell design involves 3 or 4 full-line busbars printed onto the cell. You will nowadays still find the majority of all PV modules using such 4 busbar (4BB) cells as they are commonly abbreviated.

Since work on the improvement of existing solar cell technologies is becoming increasingly harder as researchers struggle to squeeze out more from conventional cells, and breathtaking, stable new solar cell technologies are still not in mainstream sight, an increasing trend in the industry is to re-think cell design and manufacturing to further increase efficiency and reliability.

At the center of these endeveaours: the classic busbar. The approaches are manifold and not only geared to cell performance and reliability, but also significantly towards reduction of material costs – especially regarding thesilver paste used in making conventional busbars – as well as aesthetical improvements.

5 busbar solar cells

Multi busbar cells, noticably 5 busbar (5BB) cells, are currently one of the major trends in solar cell and module design.

Many large PV module manufacturers, such as Solarworld and Trina Solar, increasingly focus their production on solar PV modules using Passivated Emitter Rear Contact (PERC) solar cells with 5BB frontside contacts.

This increased number of busbars reduces the internal resistance losses, which is due to the lesser distance between the busbars.We Bluesun Solar are one of the top manufacturer of 5BB high efficiency solar panels.

Even though the higher quantity of busbars increases the shading of the solar cell, yet overall performance of multi busbar cells is much better than that of conventional 3BB cells. Key aspects are the reduction of the effective finger length between the busbars, which reduces finger resistance losses, as well as the lesser impacts of micro cracks.Also, on the cost-side, the multi busbar design with thinner busbars allows for an overall reduction of the expensive silver paste.

Busbar-less solar cells

Contrary to the multi busbar approach, other companies are going an entire busbar-less way, spearheaded by California-based Solaria.

Solaria’s proprietary zero busbar and zero wire design uses overlapping solar cell segments that are directly electrically connected with each other.

The advantages of busbar-less cells are obvious:

*much better power production-to-space ratio

*more flexible module size design – conventional module design is limited by cell size and spacing requirements

*significantly reduced shading

*less potential cell-inherent defects such as micro cracks, often caused by cell soldering

*saving of busbar material costs