Comprehensive solutionsAfter explaining the unique requirements of BC cell encapsulations, Jin proposed an optimized combination of front and rear encapsulations tailored to the specific characteristics of BC cell technology. The HPBC cell technology module, whether in a glass-glass or glass-backsheet configuration, faces PID issues on the front side and a high risk of corrosion on the back due to metal contacts on both polarities. The TBC cell technology (the BC version of TOPCon) glass-glass module is also susceptible to PID degradation on both sides and carries a risk of corrosion on the backside. Additionally, the HBC cell technology (the BC version of HJT) module, in a glass-glass configuration, requires high resilience against front-side UVID and rear-side water ingress to the TCO layers.Aligning with the specific encapsulation needs of different BC technologies, Jin recommended POE or EPE-based front-side encapsulation of less than 360 GSM for both HPBC and TBC modules, with EVA for the back-side of HPBC modules. However, for the back-side of TBC modules, POE or EPE should be used. For the HBC technology module, Jin suggested thin front-side EVA or POE or EPE-based encapsulants, with a GSM value of less than 360, and POE or EPE-based encapsulants for the back-side.For the front-side thin encapsulation films, HANGZHOU FIRST offers both POE and EPE encapsulants. The company began in 2012 with the launch of the TF series cross-linked POE and has since made periodic technological upgrades. In 2019, they developed the first co-extruded EPE film, followed by the TF4N series POE film and 360 GSM POE film for BC cells in 2022, noted Jin. This thin POE film, with high light transmittance, possesses key characteristics required for BC modules, including a thickness range of 280 µm to 360 µm, anti-PID properties, low shrinkage rate, good adhesion to glass, and no visual defects. However, the thin front-side EPE film, with a GSM value of between 280 and 360, can be customized with an EPE layer ranging from 90 to 150 GSM. Additionally, the EP304 series meets key property requirements, including excellent PID resistance, cross-linking, and adhesion performance, as well as process requirements such as uniformity, flatness, and low shrinkage rate, explained Jin. Internal test data, under extended PID stress test of up to 288 hours for a glass-glass TOPCon module, featuring front-side EP304 EPE and rear-side EVA, shows anti-PID requirement can be met with a 110 GSM POE layer. According to Jin, the anti-PID requirements of TBC cells are similar to those of TOPCon cells, suggesting that EP304 can also meet the anti-PID needs of TBC cells.Furthermore, the company has launched the FW806WH series of high-reflective black films, featuring 2 layers: a black layer (cell side) and a white layer (airside). With a reflectance of up to 75%, this film allows infrared wavelengths between 760 nm and 1,100 nm to pass through the black layer and be reflected to the cell or front glass from the white layer. This unique feature enhances the module’s aesthetic appeal and boosts power output, said Jin. The film also offers high color stability and migration stability.The insulating ink, a new material developed for BC cells, meets the insulation requirements between the positive and negative gridlines during the interconnection process. It is available in 2 main categories: thermal curing and UV curing, as well as either in colored or transparent formats, suitable for glass-glass and glass-backsheet configurations, added Jin. Additionally, the FT (thermal curing) and FURN (UV curing) series insulating inks, with visible light transmittance of up to 86.4% and 84.4%, respectively, demonstrated excellent reliability properties, such as good adhesion and a low yellowness index under in-house extended stress tests, noted Jin.The company also offers cover strips or PI strips for BC modules, designed to cover the wires between the cell matrices, further enhancing the module's aesthetic appeal. On the backsheet side, the company provides high-reflection (HR) black backsheets with an infrared light reflection rate of over 60%, says Jin.
