Encapsulant Stacks For Glass-Glass And Glass-Backsheet LECO TOPCon Modules

Key takeaways: 

• The EVA and POE films are tailored for LECO-based TOPCon bifacial modules in both glass-glass and glass-backsheet configurations 

• The encapsulant stacks have passed extended PCT and PID testing 

• Comparative PID and DH test data were presented to demonstrate the performance of different encapsulant combinations

Hangzhou First, a global leader in encapsulating solutions, showcased its latest combination of encapsulation stacks for both glass-glass (G2G) and glass-backsheet (G2B) modules at Intersolar Europe 2025. Considering the majority market share of TOPCon products, Hangzhou First has designed S406(P), an EVA film, specifically for low-aluminum or aluminum-free LECO (laser enhanced contact optimization) technology bifacial G2G modules. The company also presented TF4(N), a thermosetting POE film developed for G2B TOPCon bifacial modules. 

The company stated that S406(P) can be used on both front and rear sides or in combination with EP304, its EPE-based series film, on the rear side. According to Hangzhou First, a combination of both stacks has passed the PCT (pressure cooker test) at 121°C, 100% RH, and 0.2 MPa for 192 hours on a TOPCon module. The company claims that the product possesses anti-PID (potential induced degradation) properties and is able to pass the PID 192h test of the new IEC standard. Hangzhou First highlights that the module was built with special acid-resistant EVA called ‘EBISU’, a patented technology from Kyocera, which has been exclusively licensed by Hangzhou First. This, according to Hangzhou First, improves the weather resistance of the cell and the overall reliability of the module in hot and humid environments (see Low-Acid EVA & UV Films Address Corrosion & UVID In PV Modules). 

The company also showcased PID results of the LECO-based TOPCon module with S406(P) EVA encapsulation after 3 cycles of 96 h at 85°C, 85% RH, -1,500 Vdc. The overall module power degradation after the end of the testing sequence was 0.6% in comparison to 9.09% power degradation under the same conditions for an equivalent module with an unnamed competitor’s EVA film. 

For the G2B LECO TOPCon configuration, the encapsulant supplier also claimed to have performed PCT and DH tests on the modules with POE on the front and EVA on the rear (TF4(N) + F806W). Hangzhou First stated that the stack has passed a 92 h PCT. The overall power degradation after DH (damp heat test) for 2,000 h at 85 °C and 85% RH was 3.78% in comparison to 10.82% of the same module with a competitor’s POE + EVA stack, under the same test conditions.