This is an important breakthrough because it combines a bi-facial design with state-of-the-art tandem technology to produce a 30+% equivalent light-to-electricity conversion efficiency, about one third better than state-of-the-art industrial solar cells which have an efficiency of around 22%.
ECN and the Solliance partners have expertise on various solar cell technologies suitable for tandem applications. The high performance offered by tandem solar technology contributes to reducing the overall solar system costs and is an essential factor increasing the energy yield. Both these aspects will support the transition to a society using primarily renewable energy to reduce CO2 emission.
The combination of different types of solar cells in a tandem module enables a better power conversion efficiency than what is achievable with one cell type only. With one cell optimized for high energy photons in blue light and the other for low energy photons in red colored light, more electrical energy can be extracted from sunlight. In addition, the newly developed device collects the available light simultaneously from both sides of the solar module.
Common silicon solar cells have typical efficiencies in the range of 19% to 22%, with close to 25% for best-in-class technologies. The theoretical limit for silicon solar cells is 29.4%.
Bifacial solar modules are already commercially available in the Netherlands. In freestanding applications, such as large solar power plants, reflected and diffuse light from surroundings, increase the annual electricity output typically by 10% to 30% using bifacial solar technology, compared to common solar modules. As the incident light on the front and the rear sides of the module is naturally varying during the day and from season to season, bifacial tandem devices need to be able to respond to this variability through their electronic design. The tandem device proposed here uses a four-terminal configuration.
“Reaching the 30% threshold is the first major milestone of this device architecture,” said Gianluca Coletti – program manager tandem technology at ECN. “Our next target is to work on the scalability, integration and reliability of this technology. We want to shorten the time to market and therefore we work together with our partners to make this technology ready for mass production.”
Partners that contributed to this work are Choshu Industry Co., Forschungszentrum Jülich, imec, and the Eindhoven University of Technology.