EVA remains the most cost-effective encapsulant, but it has an inherent issue as it forms acetic acid, which can lead to corrosion of the electrical circuit. To address this, several leading encapsulation material suppliers have developed and commercialized low acid-forming EVA. It reduces acetic acid formation, mitigating corrosion risks while retaining EVA’s cost advantage (see Encapsulation Solutions For TOPCon Modules).
HANGZHOU FIRST, for instance, offers a specialized acid-resistant EVA called EBISU, originally developed by Japan’s Kyocera. EBISU significantly reduces acetic acid release from EVA, and HANGZHOU FIRST holds exclusive licensing rights for this technology. Additionally, the company is promoting an EPE configuration based on EBISU, where the 2 layers of standard EVA are replaced with this special acid-resistant EVA.
HIUV also offers dual-EVA solutions for glass-glass modules, available in both transparent and white variants. These encapsulants provide superior moisture barrier protection, ultra-low acid content, and enhanced anti-PID performance. To improve the PID resistance of the films, the company has incorporated special additives for capturing ions to block them from penetrating. A specialized cation exchange and complexation network is implemented to trap or absorb metal ions such as sodium and potassium. Through a crosslinked resin matrix, these low-acid EVA films create a dense barrier that effectively also blocks ion penetration. Moisture resistance is improved by adding hydrophobic additives and using specialized crosslinking processes, reducing the risk of moisture ingress. Furthermore, the reduction of acetic acid content in EVA minimizes the risk of electrochemical corrosion, particularly for cell metallization layers composed of aluminum and copper.
To validate the effectiveness of low-acid EVA, HIUV conducted highly accelerated stress tests (HAST) over 48 and 96 hours. EL imaging comparisons between standard EVA and low-acid EVA revealed that modules using low-acid encapsulants exhibited minimal degradation and uniform brightness across cells. In contrast, standard EVA showed visible dark areas due to acid reactions in humid environments, leading to microcracks, discoloration, busbar corrosion, and delamination. These findings highlight the importance of using low-acid EVA to enhance module durability under extreme conditions. To further evaluate encapsulant performance, HIUV conducted EL imaging studies comparing different encapsulant-cell combinations under stress conditions. The results showed that the encapsulation system of HIUV’s dual EVA in combination with dual glass has shown good resistance against PID for standard TOPCon as well as LECO-based TOPCon cells. However, the testing revealed that LECO cells are more light-sensitive compared to non-LECO cells; thus, power recovery was quicker under light with LECO. HIUV also evaluated the glass-backsheet configuration based on dual EVA, but with white EVA on the rear side. The company’s evaluation of 2 TOPCon modules based on LECO from 2 different manufacturers indicated varying levels of moisture resistance. These results emphasize the importance of selecting the right encapsulant-cell combination for long-term module reliability (see Advancements In TOPCon Technology: HIUV’s Encapsulants).
UVID of TOPCon: Another important topic with respect to TOPCon in this context is UVID. The well-known phenomenon seen in HJT is not usually associated with TOPCon. However, similar cases are emerging in TOPCon technology where UVID negatively affects module efficiency and reliability. It can be addressed by optimizing the upstream processes, especially at the cell level, with the optimization of passivation layers. It can also be tackled at the encapsulation level with a method that’s not different from the one used for HJT – light conversion film, also known as down-conversion film .
Cybrid has started promoting its well-known UV conversion solution called RayBo and presented the details at the TaiyangNews High Efficiency Solar Technologies Virtual Conference. Anurag Mishra, Senior Marketing Manager at Cybrid, demonstrated in his presentation that RayBo has increased energy output by up to 0.53% for TOPCon modules. Through extensive UV reliability testing, RayBo has been shown to last 3 times longer than IEC standards, ensuring long-term durability and protecting modules from UVID. The encapsulant also underwent damp heat testing under 2,000 hours of exposure, where it exhibited the same output decay percentage as UV cut-off films. Cybrid emphasizes that the current RayBo film offers UV-cut performance comparable to traditional UV-cut films while simultaneously enhancing blue light transmission. Adapting to down-conversion encapsulation film on the front side is already mainstream. EPE with down conversion on the front and standard EPE on the rear are standard in today’s TOPCon production, emphasizes Alishan’s Khushbu Patel. At the upcoming TaiyangNews Solar Technology Conference India 2025, Dr. Khushbu Patel, AGM of Business Development at Alishan Green Energy, will present on encapsulation solutions for emerging technologies and their current status in India. Registrations are open here.
The text is an excerpt from the latest TaiyangNews Market Survey on Backsheets & Encapsulation Materials 2024/25, which can be downloaded for free here.
