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As mono-Si product prices continue to decline, multi-Si products have slowly lost the price advantage, leading to lower market share. The industry is eager to find solutions, which makes diamond-wire cutting with black silicon the new focus. Recently, researchers at Fraunhofer ISE, Germany, successfully produced multi-Si cells with efficiency of 21.9%, even higher than the efficiency of mono-Si PERC cells.
Researchers at Fraunhofer ISE indicated that the quality of multi-Si cell silicon material can be controlled through managing the production processes of polysilicon, ingot, wafers, and cells. For cell-end, they use TOPCon technology, adding a passivation layer without patterning at the back-side of a cell. Not only simplify the manufacturing process, but also effectively improve the conversion efficiency.
The conversion efficiency has reached 21.9% through the use of N-type technologies like TOPCon, much higher than the efficiency of following cells: 18.2-18.4% for mainstream multi-Si cells, more than 18.4% for high-efficiency cells, 19.6-19.8% for mainstream mono-Si cells, and mono-Si PERC cells.
Fraunhofer ISE has also applied the same TOPCon technology in mono-Si cells in 2016, adding passivation layers at the front and back-side of the cell and increasing the conversion efficiency to 25.3%. From production process point of view, TOPCon technology belongs to next-generation technology, which is not yet entering the mass production stage.
However, Chinese manufacturers like Jinneng, Jolywood, GCL-Si as well as NSP of Taiwan and Tesla of the US have started the capacity configuration and technology planning for N-type cells (such as heterojunction). Although N-type technology has not matured, it’s worth paying attention to in the future.
In July 2016, Trina Solar announced that they have reached a conversion efficiency of 20.16% for multi-Si PERC cell and it was developed based on mass production equipment. But according to EnergyTrend’s cost and efficiency analysis, multi-Si PERC cell is not as cost-effective as mono-Si PERC cell. As a result, multi-Si PERC cell will be more difficult to get orders. If manufacturers can produce multi-Si cells using diamond-wire cutting with black silicon and PERC technologies this year, perhaps they can get more orders through lower cost and higher efficiency.
(Photo Credit: Fraunhofer ISE)