When Photovoltaic BC Tech Meets 0BB: What's the Impact?

What is BC cell?

BC cell is back contact cell. BC cell technology moves the PN junction and metal contact to the back of the cell, so that the front is not blocked by the electrode, and the cell absorbs a larger area of sunlight, thereby improving the conversion efficiency and emitting more power.

BC cell does not refer to a specific type of cell, but a general platform technology that can be combined with PREC, TOPCon, and HJT to improve photovoltaic cell efficiency. For example, TOPCon+BC=TBC cell, HJT+BC=HBC.

What is 0BB technology?

There are many metal electrodes on the front and back of photovoltaic cells for conducting electricity. These electrodes are divided into two types: thick and thin. The current from the thin electrodes will eventually flow to the thick electrodes, a bit like the relationship between the main trunk and branches of a river. The thin electrode is called the auxiliary grid, and the thick electrode is called the main grid (Busbar), or BB for short.

The development direction of the entire grid line is to make the main grids thinner and thinner, from 4BB (i.e. 4 main grids) to 5BB, and then to MBB and SMBB (16 main grids). This can reduce shading loss, reduce silver paste consumption, and have better conductivity.

The current market is striving to eliminate the need for main grids in the cell process and use copper solder ribbon to conduct current in the module process. In this way, there is almost no silver consumption on the cells and the light-shielding area is smaller. Without main grid, it is 0 (zero) BB.

Photovoltaic 0BB technology means removing the main grid and directly connecting the soldering ribbon and the fine grid. After removing the main grid, the light-receiving area of the cell increases, improving power generation efficiency. In addition, the amount of silver paste used is reduced thereby reducing costs.

BC technology superimposed on 0BB technology

From a manufacturing perspective, the superposition of BC technology and 0BB technology means that after all the main grids and fine grids on the front are moved to the back of the photovoltaic module, the number of solder joints on the back of the photovoltaic module will be at least 25% more than that of 0BB with other technologies. With the same area, there are 25% more solder joints, and the process difficulty is greatly increased.

In addition, 0BB technology adopts a silver-free metal coating process and uses copper electrodes. Under external force or harsh thermal expansion and contraction environment, the soldering ribbon and electrode are not easy to separate, which can solve problems such as heating warpage of photovoltaic BC cells, soldering uniformity, and cell crack rate. Compared with the current mainstream SMBB technology, 0BB can reduce silver consumption by more than 10% by eliminating the main grid. While reducing module costs, module power is increased by more than 5W.