HANGZHOU FIRST offers reliable and economical encapsulation solutions, including POE, EVA, and EPE, for TOPCon and HJT modules
The company recommends HZ POE (TF4) as the most reliable encapsulant for Glass-Glass TOPCon modules to mitigate the risk of MID and PID
It also recommends PIB + EVA combination compared to PIB + POE for superior moisture barrier performance in HJT Glass-Glass module
The company offers UV-down conversion film to mitigate the risk of UVID and boost power generation in HJT module
The nature of PV module degradation is evolving alongside advancements in cell technologies, bill of materials (BOM), and module design. Encapsulation materials, a vital component of the module BOM, are laminated to protect the cell matrix from external stresses such as mechanical forces, moisture, and heat. Among the mainstream encapsulant technologies are EVA, EPE, and POE, while backsheets feature various multilayer structures.
Stephen Tang, Senior Engineer at HANGZHOU FIRST – a leading Chinese company with over 20 years of experience in encapsulant and backsheet manufacturing – delivered an insightful presentation on the primary degradation modes in TOPCon and HJT modules and the optimal packaging solutions at the TaiyangNews Reliable PV Module Design Conference 2024 (see Hangzhou First's presentation here). With 6 production bases spanning Thailand, Vietnam, and China, the company boasts an impressive annual production capacity of over 380 GW for encapsulants and 50 GW for backsheets.
TOPCon Encapsulation
Moisture-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.
HJT Encapsulation
Heterojunction (HJT) cell technology, which is susceptible to ultraviolet-induced degradation (UVID), employs various encapsulants with UV-through, UV-cutoff, and UV-down conversion characteristics. HANGZHOU FIRST's UV-down conversion film transforms high-energy UV photons (320–380 nm) into low-energy photons (425 nm), achieving up to a 1.35% initial efficiency gain compared to UV-cutoff films and less than 1% power loss within the first year.
Furthermore, the PIB sealant, specifically developed for edge sealing in HJT modules, offers the lowest water vapor transmission rate (WVTR) among major encapsulants, including backsheet, EVA, POE, and EPE. Mr. Tang noted that HANGZHOU FIRST's PIB-401 series sealant, with a moisture vapor transmission rate (MVTR) of less than 0.1 g/m² at a 0.7 mm thickness, demonstrated superior moisture barrier performance when used in combination with PIB + EVA compared to PIB + POE.
The company also offers a wide range of backsheets, including white, black, HR black, transparent, and grid transparent types.