Tandem technology combines a lower HJT silicon cell with an upper perovskite cell, enabling different portions of the solar spectrum to be exploited in a synergistic and complementary way. The perovskite portion increases light capture by absorbing high-energy photons in the ultraviolet and visible spectrum, while the lower HJT silicon cell converts the lower-energy photons that pass through the upper layer, enabling light to be exploited more completely and surpassing the 29% theoretical efficiency limit characteristic of conventional silicon-only technologies.
This approach represents the natural successor to current solutions, capable of delivering up to +20% more electricity generation or, for the same amount of energy generated, a 20% reduction in land use and in the CO₂ footprint of solar plants.
3SUN modules based on HJT technology represent one of the most advanced evolutions in photovoltaics. The innovative cell architecture, combined with the intrinsic advantages of HJT technology, ensures stability, durability, and excellent performance even under high-temperature and low-irradiance conditions. In addition to delivering top-tier performance, heterojunction provides the ideal technological infrastructure and enabling platform selected by 3SUN to develop the solar systems of the future, starting with Tandem technology (perovskite on silicon), which stacks a perovskite cell on an HJT silicon cell to capture the solar spectrum in an integrated way and exceed the theoretical 29% efficiency limit of conventional silicon technology. Confirming this vision, in January 2025 the collaboration between 3SUN and CEA (at the National Institute for Solar Energy, INES) set a new efficiency record of 30.8% on a 9 cm² Tandem cell. Achieved on a surface area significantly larger than the standard 1 cm² laboratory test cells, this milestone marks a decisive step toward overcoming technical barriers and accelerating industrialization and mass-scale production in the coming years.