Imec’s development of a 23.9% efficient tandem stacked module represents the latest in a long line of incremental improvements to its perovskite technology.
The semi-transparent perovskite module stacked on top of an interdigitated back contact (IBC) solar cell was first unveiled by Imec in 2016 as part of its collaboration with solar research organization Solliance, when it achieved an efficiency of 20.2% on a 4 square centimeter aperture area. Researchers at the association have now increased this efficiency on the same size module/cell stack.
“Two innovations are key to this achievement,” explains Tom Aernouts, group leader for thin-film PV at imec and perovskite program manager at Solliance. “First, a different perovskite material (CsFAPbIBr) was used, improving the stability and efficiency of the perovskite module to 15.3%.” Second, the architecture of the stack was optimized for minimal optical losses by adding an anti-reflection texture on top of the module and a refractive index matching liquid between the perovskite module and the Si solar cell.”
Cell configurations such as this have the potential to achieve efficiencies in excess of 30%, however, much of the research to date has only yielded cells of a very small size – Back in April scientists at Australia National University achieved 26.4% conversion efficiency on a tandem cell measuring 0.18 square centimeters.
Imec’s use of much larger cells represents a step forward in scaling the technology toward commercial application, however this is a still a long way off, and the team was able to achieve higher efficiency using smaller perovskite cells. “Having matched areas of this size makes the fabrication technology more attractive to the solar cell industry,” continues Aernouts. “We have also fabricated a stack of a small perovskite cell (0.13cm2) on top of an IBC c-Si cell (4cm2). Although less attractive from an industrial point of view, the overall power conversion efficiency of this stack is as high as 25.3%.”