The widespread adoption of bifacial technologies like TOPCon and HJT has made glass the dominant rear cover, replacing backsheets in mainstream modules
The price of 2 mm glass fell by 50% in early 2024, making it a more cost-effective rear cover option and increasing its appeal amid falling module prices
In India, companies report full backsheet capacity utilization for specialty applications such as agrivoltaics, BIPV, and government projects, even as glass dominates mainstream module production
Backsheets have ceded their exclusive position as the preferred rear cover material. Historically, the market size for backsheets reflected the module production, as these polymers were the universal choice for rear covers, with glass playing only a niche role until 2019. In a role reversal, glass is now increasingly becoming the prime choice for rear covers, apart from being the de facto choice for a module’s front cover to protect the cell laminate from environmental damage. Several factors have contributed to this shift, with the increased adoption of bifacial products being a major driver.
The use of bifacial technology, particularly in utility applications, is on the rise. It has also made glass the predominant choice for a module’s rear cover. The growing popularity of bifacial technology is fueled by various factors. All cell technologies, from PERC to TOPCon and HJT, are naturally bifacial, and some companies are even optimizing back contact cells specifically for this purpose (see Advanced Solar Technologies Drive Changes In Module Materials).
At the module level, the main requirement is a transparent rear cover to allow light to pass through. Although transparent backsheets are available, glass-glass configurations are gaining favor among customers. This design has enabled manufacturers to offer extended 30-year power warranties with glass-glass modules, compared to the typically promoted 25 years for polymer variants. Additionally, during periods of high PVDF prices, some companies switched from PVDF backsheets to glass, moving away from backsheets entirely.
Another driving force for glass-glass modules is that the 2 current mainstream technologies, TOPCon and HJT, are intrinsically hydrophobic, which raises the standard for water vapor transmission rate (WVTR). While carefully engineered backsheets can also achieve very low levels of WVTR, the use of glass is a low-hanging fruit. In reality, TOPCon’s growing adoption rates have meant that backsheets are losing ground, with glass-glass configurations favored over glass-backsheet.
In addition, falling glass prices have also made them cost-effective. According to the TaiyangNews PV Price Index for Calendar Week 5, the price of 3.2 mm glass was 19.5 RMB/m², while the 2 mm variant was 12 RMB/m², both dropping significantly by about 30% and 50%, respectively, from the start of 2024. The 2 mm glass, typically used for glass-glass structures and a main contender for rear covers, has seen a substantial price reduction. These falling prices have also lured module makers, who are reeling under severe cost pressure with module prices hitting rock bottom. All this has led manufacturers to replace the backsheet with glass as the rear cover. According to the 15th edition of International Technology Roadmap for Photovoltaics (ITRPV), glass-backsheet modules had a share of 60% in 2023, dropping to less than 50% in 2024, expected to be less than 40% by 2026, and finally to decline to 23% in the next 10 years. However, several companies we spoke to estimate that the glass-backsheet configuration accounts for only 15% to 20%. The flip side of using glass-glass modules is that they require longer lamination times, which can reduce the productivity of module fabs, are susceptible to damage during handling, and are notably heavier.
Sharing the Indian context, Alishan and RenewSys emphasize that backsheets are still in demand, though not in the mainstream. According to Khushbu Patel, AGM at Alishan, the company's backsheet capacity is mostly occupied, primarily supplying module makers catering to specialty applications, such as agrivoltaics and building-integrated photovoltaics (BIPV), and a few government projects. RenewSys’ encapsulation and backsheets business wing CEO Rakesh Singh also emphasizes that the company's backsheet capacity is fully utilized, while no new capacity has been added. In February 2025, RenewSys introduced its anti-acid property EVA for high-efficiency PV module manufacturing (see RenewSys: Anti Acid EVA Technology For Reliable PV Module).
Jolywood notes that glass-glass modules, although preferred, face challenges related to thickness and cost reduction. While some manufacturers are experimenting with thinner glass (e.g., 1.8 mm or 1.6 mm), these alternatives are still considered risky due to the increasing size of PV modules, which raises reliability concerns. The size of the module plays a crucial role in determining the required glass thickness. A compromise on thickness could also affect reliability. Nevertheless, the backsheet segment as a whole is going through tough times and has seen a significant decline since 2022.
Summarizing the discussion with leading backsheet suppliers, the majority agrees that the production of glass-backsheet modules accounted for about 160 GW in 2022 using a total of about 800 million m2 of backsheets. For 2023, total backsheet shipments were close to 600 million m2. However, the total backsheet market reduced by nearly 50% in 2024 to about 310 million m2, indicating a glass-backsheet module volume of about 60 GW. It is further expected to decline to between 200 and 300 million m2 in 2025. During SNEC 2024, the Chinese backsheet & module maker Jolywood showcased its transparent meshed & reflective black backsheet and the latest windproof module (see Jolywood Displays Latest Offerings At SNEC 2024).
As India aims to strengthen its solar PV manufacturing industry, 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. Day 2 will feature a session on "Advancing Solar Module Performance and Reliability Through the Right Bill of Materials." InYoung Suh, Director of Business Development, Hangzhou First, and Dr. Khushbu Patel, AGM, Business Development ALISHAN GREEN ENERGY, will discuss innovations in encapsulants and back sheets. Early-bird registrations are on 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.