TOPCon EncapsulationMoisture-induced degradation (MID) and subsequent corrosion – common challenges in Glass-Glass and Glass-Backsheet TOPCon modules – can be mitigated through several strategies. These include eliminating the active aluminum electrode via the LECO process, creating a robust moisture barrier with low water vapor transmission rate (WVTR) protection, and reducing ion transportation, emphasized Mr. Tang.For Glass-Glass TOPCon module configurations, which are particularly prone to horizontal moisture ingress at the module edges, HANGZHOU FIRST conducted in-house pressure cooker tests (PCT) using various encapsulant combinations on the front and rear sides, including POE-POE, EPE-EPE, and EVA-EVA. Under testing conditions of 121°C and 100% relative humidity (RH), TOPCon cells engineered with the LECO process showed signs of corrosion after 200 hours. Among the tested combinations, POE-POE modules exhibited the highest resistance to moisture ingress, followed by EPE-EPE and EVA-EVA, respectively.The superior performance of POE is attributed to its low WVTR, measured at 3–5 g/m² per 24 hours, compared to EPE's WVTR of 7–12 g/m² per 24 hours and EVA's significantly higher WVTR of 25–35 g/m² per 24 hours. Additionally, HANGZHOU FIRST's POE encapsulant demonstrated strong long-term anti-PID properties in Glass-Glass TOPCon modules, with less than 5% power loss observed after an in-house PID test lasting 576 hours. Based on these results, the company recommends HZ POE (TF4) as the most reliable encapsulant for Glass-Glass TOPCon modules, applied to both the front and rear sides. For more cost-effective alternatives, HZ EPE or HZ EVA is suggested for both sides.For Glass-Backsheet TOPCon modules, which face dual vulnerabilities to moisture ingress from both the module edges and the backsheet, POE's low WVTR alone is insufficient to fully block moisture, particularly from the rear side. The moisture ingress creates an electrolyte-rich environment within the cell matrix, compounded by factors such as sodium (Na⁺) and calcium (Ca⁺) ions from glass, residual metal ions and additives in POE, and organic acids and chlorides from flux. To address these challenges, HANGZHOU FIRST developed its TF4N series POE, featuring enhanced low WVTR and anti-electrochemical properties. The company recommends using TF4N series POE on both the front and rear sides for optimal reliability in Glass-Backsheet TOPCon modules. For a more economical alternative, a combination of TF4N on the front side and S806 or F806W series white EVA on the rear side is suggested.
