Making encapsulation solutions for HJT is not straightforward. Given the hydrophobic nature of the deposited amorphous silicon layers of HJT, the encapsulation material needs to be carefully selected to have high water vapor barrier properties. An even more important point to consider is the technology’s sensitivity to UVID. The TCO and amorphous silicon layers absorb UV light; thus, the typical HJT structure suffers from low currents. UV also causes degradation in the TCO layers of HJT cells. One way to overcome this issue is to use encapsulation films that cut off UV light. While this saves the modules from degradation, it also lowers efficiency (see Encapsulation Sector Balancing Innovation And Cost Pressures In Solar).
To meet both ends, encapsulation material suppliers innovated the light conversion film described above. This has turned the known challenge of UVID into an opportunity to boost efficiency by converting the UV light into blue-band radiation.
Cybrid is at the forefront of this technology development with its RayBo brand name. The underlying mechanism works through an orbital electron transition process, where UV light is absorbed and converted into visible light. In addition to protecting the module by reducing UV damage, it also contributes to increased energy yield, offering the dual benefit of improved durability and enhanced efficiency.
The UV-conversion technology was invented by Dr. Hisanari Onouchi in 2013 while he was at Nitto Denko, which patented the technology in multiple countries, including China and the USA. In 2014, with Nitto Denko's support, Cybrid began developing RayBo based on EVA and POE, and the 2 companies jointly explored global markets. By 2015, Nitto Denko had begun selling UV conversion POE film to CHOSHU INDUSTRY CO., LTD. in Japan. A couple of years later, in 2017, Nitto Denko sold the patents to CHOSHU, which then independently took over the production of UV conversion agents and POE films in Japan. Since 2020, with CHOSHU's support, Cybrid has been producing and promoting RayBo worldwide. In 2023, under an exclusive license from CHOSHU, Cybrid began commercial production of UV conversion agents in China.
Anurag Mishra, Senior Marketing Manager at Cybrid, presented the results of stability tests during the TaiyangNews High Efficiency Solar Technologies Virtual Conference (watch presentation here). Under extensive testing, RayBo’s light conversion agent showed excellent durability even under prolonged exposure to harsh UV conditions. After simulated exposure equivalent to 50 years, only 2% of the light conversion agent is lost, ensuring that the encapsulant continues to deliver high efficiency and durability even under extreme environmental conditions. Further tests indicate that due to the proper concentration of UV conversion agents, there is nearly no decay in UV band transmission, even after exposure to 1,200 kWh/m² radiation under a 60 W/m² sun lamp.
Moving to damp heat testing, Mishra explained that RayBo has been rigorously evaluated under high humidity conditions. After more than 2,500 hours of exposure, the film exhibited less than 10% degradation in its light conversion ability, proving its resilience in challenging environments, particularly in coastal areas where high humidity can accelerate material degradation. The effectiveness of RayBo has also been verified through independent testing conducted on Tier 1 TOPCon modules by TÜV Nord and Shanghai Jiao Tong University, along with Cybrid. In the end, RayBo has already proven its effectiveness in addressing this issue in HJT modules, where it provides an average power gain of 1.5% per module, according to Mishra. Apart from Cybrid, many other leading encapsulation suppliers are also promoting similar light conversion films.
