TaiyangNews Market Survey on Backsheets And Encapslutaion lists various encapsulation solutions and technologies related to Heterojunction Technology (HJT) solar cells. In our previous article we explained encapsulation solutions in context of TOPCon (see Various Packaging Options For Both The Front And Rear Sides Of TOPCon Cells In Solar Module Production)
For HJT, given the hydrophobic nature of the deposited amorphous silicon layers, the encapsulation material needs to be carefully selected to have high water vapor barrier properties. The optimization of encapsulation materials from a TCO compatibility standpoint is equally important. Encapsulation solutions supporting busbar-less interconnection with integrated film is also top of the agenda for major suppliers.
According to Cybrid's International Marketing Director Eric Yang, a reliable encapsulation solution is only available with the glass-glass structure, while not yet for the glass-backsheet configuration, and the choice could be between POE and EPE on the front and rear sides. However, HIUV's Peng says that EPE can meet the requirements of the HJT, and thus is the most widely used solution.
Encapsulation material makers have developed a somewhat disruptive solution specifically for HJT. The UV also causes degradation in TCO layers of HJT cells. One way to overcome this issue is to use UB cutting film, but this reduces the efficiency. To mitigate these losses, 2 leading encapsulation material suppliers, Cybrid and Hangzhou First in a cooperative effort, have developed a wavelength transfer film that improves the optical absorption of the module. It is a photoelectric conversion film that converts UV light with a low photon response for HJT solar cells into blue light or red light with a higher photon response. The film increases the power of a 60-cell M6 HJT solar module by more than 5W, and with larger modules, it can go up to 7W. The power gain is about 1.5%, according to Stephen Gong, Senior Product Manager at Cybrid (see Stephen Gong's presentation: Innovations In Solar Module Wraps).Cybrid signed a supply agreement for huge volumes with leading HJT makers including Huasun. The next interesting thing is that the technology can be implemented on any polymer base – EVA, POE or EPV. However, since only HJT can benefit from the technology (not beneficial for TOPCon and PERC) and EPE is the most widely used encapsulation configuration, Cybrid is offering this technology implemented on EPE. "We are already selling in the range of 10,000 m2 to our partner HJT makers," says Yang, "We are planning to build 1 million m2/month capacity for the technology around March to May of 2023." Answering the question on reliability, Yang says it is the same as the base material on which the technology is implemented – in this case, identical to EPE. The technology currently doubles the price of the encapsulation material; however, when it is implemented in mass production, costs can be reduced by 50%, according to Yang.
Needless to say, Hangzhou First is also offering such light conversion film technology, as both Cybrid and Hangzhou First jointly hold the patents on the technology while sharing it with 2 more companies. HIUV is one among them as it is also commercializing a similar product.
Light conversion: Encapsulation material suppliers are offering a unique UV light conversion film technology for HJT that increase the power output of the module and it can be implemented on any kind of film – EVA, POE or EPE. (Source: HIUV)
Another topic of interest in HJT segment is supporting busbar less technology, which is much similar to Meyer Burger's SWCT. It requires special encapsulation film. Here the ribbons are not bonded to the cell by means of soldering but via ECA or tape. Thus, the connection between the ribbon and the cell is not complete. A good contact is only established after the lamination. However, during the lamination, as the encapsulation film is melting, there is a possibility of film following under ribbon, creating a thin insulation between the cell and ribbon, explains HIUV's Senior Marketing Manager Peter Peng. To overcome this issue, HIUV is developed a a new encapsulation film with low following rates. Even Cybrid is offering special encapsulation solutions for busbar-less interconnection technology (see: Peter Peng's presentation: Reliable Encapsulation Of TOPcon & HJT Modules).
The article is an excerpt from the TaiyangNews Market Survey on Backsheets and Encapsulation 2022-23, which can be accessed free of charge here.