Encapsulation Solutions For TOPCon Modules

TOPCon is currently the mainstream technology with the largest production base. The technology also presents unique challenges in encapsulation. Leading encapsulation materials supplier HANGZHOU FIRST emphasizes that TOPCon technology suffers from 2 degradation mechanisms – moisture-induced degradation (MID) and potential induced degradation (PID). MID occurs when moisture penetrates the module, particularly at the edges, leading to severe performance degradation, as observed in reliability tests. PID, on the other hand, is an electrochemical effect that degrades module performance but, in certain cases, can be reversed through sunlight exposure.

Coming to the encapsulation part, the choice is between POE, EPE and optimized EVA. Tests conducted by several materials suppliers and module makers indicate that POE demonstrates the highest reliability, followed by EPE, with EVA performing the least effectively. Beyond moisture resistance, POE also provides excellent anti-PID performance without requiring light-induced recovery. Performance is one thing, but costs are equally important in solar, especially in today’s context of low module prices. Thus, companies have been developing different solutions and promoting various combinations to strike the right balance between cost and reliability.

POE: HANGZHOU FIRST has developed a POE-based encapsulant series called TF4N, featuring a blocking ion mobility function. The details were presented by Stephen Tang, senior engineer at HANGZHOU FIRST during the TaiyangNews Cell & Module Production Equipment & Processing Materials Conference (watch presentation here). In addition to being effective for glass-glass modules, the company further emphasizes its products as also suitable for glass-backsheet configuration. When TF4N is used as the front encapsulant, the choice of rear encapsulation material becomes less critical, allowing even EVA to be used, according to the company. Additionally, the use of TF4N POE on the front eliminates the need for low WVTR backsheets. At the TaiyangNews Solar Technology Conference India 2025, InYoung Suh, Director of Business Development at Hangzhou First, will deliver a presentation on encapsulant materials and solutions for advanced solar cells and modules.

EPE: The majority of TOPCon producers are, however, increasingly adopting EPE encapsulants on both sides of the module. In addition to its cost effectiveness, EPE offers performance comparable to POE while providing superior processability. Unlike pure POE, which has certain drawbacks such as longer processing times and surface slipperiness, EPE supports higher productivity. Every leading encapsulant supplier is offering an EPE configuration for TOPCon. HIUV is one of the early developers of EPE. Jitin Rai Khanna, global sales director for HIUV, presented the company’s comprehensive solutions for TOPCon technology at the TaiyangNews High Efficiency Solar Technologies Virtual Conference. Khanna says the company’s EPE film is designed to meet the encapsulation requirements of all TOPCon cell architectures. The company optimizes the formulation of encapsulant additives to enhance the product's anti-PID polarization performance. The POE layer in the EPE structure is strengthened to prevent lamination bubbles effectively. The mixed sealing process of POE with EVA requires no additional padding on the edges, achieving a lamination yield of up to 100%. Already in mass production, this product has been validated by customers for its superior reliability, says Khanna. He adds that the product’s reliability is further demonstrated by passing industry tests, including PID 192 and DH2000.

Alongside its EPE film, HIUV has introduced a new product called P507S, which offers similar performance to pure POE films while reducing the amount of POE resin used. This co-extruded so-called EXP film, consisting of a structural strengthening layer between the POE and EVA layers, is designed to lower production costs and improve manufacturing efficiency, providing a cost-effective alternative to pure POE encapsulants without compromising performance. Endurans emphasizes that EPE still carries forward a part of the cost aspects of POE and is still prone to acid formation. It has developed a proprietary EPE configuration to replace the POE core layer with a low-cost and higher barrier and high melting PO film.

Imco Goudswaard, Commercial Manager & Sustainability Lead at Endurans Solar, presented the product details at the TaiyangNews Reliable Solar PV Module Design 2024 Conference. The film has superior moisture and electrical barrier properties, along with reduced acid formation properties. The film itself is much stiffer and has a lower shrinkage rate which eases handling and processing. In addition to lowering the costs, the film also supports sustainability, as the core layer is not crosslinked, making it easier to recycle at the end of a module’s life. Goudswaard showed the results of different testing protocols for the company’s EPE product, which showed a 40% reduction in water vapor transmission compared to conventional encapsulants, apart from reduced acid formation. Its improved moisture barrier properties have also been shown to reduce PID. The film also displayed good adhesion retention despite having a non-crosslinking core. Optical testing under prolonged UV exposure confirmed the encapsulant’s stability, with no significant loss in transmission after 5,000 hours of UV exposure (see Cost-effective & Reliable Coextruded Polyolefin-Based Encapsulation Solutions).

As India aims to strengthen its solar PV manufacturing industry, the TaiyangNews Solar Technology Conference India 2025 will provide a platform for experts to discuss cutting-edge advancements. To be held on April 10-11, 2025, in New Delhi, the event will feature technologists, scientists, and engineers driving innovation in the sector.

The text is an excerpt from the latest TaiyangNews Market Survey on Backsheets & Encapsulation Materials 2024/25, which can be downloaded for free here.