The research partners noted that the tandem perovskite solar cell combines good cell efficiency with a very high near infrared transparency of 93%, an increase of 3.6 percentage points over the efficiency of the directly illuminated silicon cell laminate.

“By optimizing the ITO (indium tin oxide) composition and deposition conditions as well as careful design of the anti-reflection coating (ARC), an extremely high transparency is achieved for the top electrode, despite the low temperature process window,” noted Dong Zhang, researcher at Solliance “Using this ITO, with a sheet resistance as low as 40 Ohm per square, a perovskite photovoltaic cell was made with an average transmittance in the relevant near infrared wavelength range (800 – 1200 nm) of 93 %. This is significantly higher than the state of the art, which is below 85%. To put this into perspective, the same glass sheet without ARC but with perovskite cell has a transparency in this wavelength range of around 92%.

Sjoerd Veenstra, program manager Perovskite Solar Cells at Solliance added, “Scaling up from a laboratory scale to an industrial process is one major barrier for a successful implementation of a new promising development. Therefore Solliance employs different scales in development. Now that the device was proven with spin coated layers, we use pilot scale equipment provided by our industrial partners to scale it to a viable industrial production process. Also the expertise of industrial partners of Solliance in sheet-to-sheet spatial ALD and laser interconnection of thin film cells is used to scale-up the technology to 30x30 cm2 demonstration modules.”

ECN also said that it was working to further optimize the bottom cells and the module integration to obtain higher conversion efficiency as well as reliability. Using conventional cells ECN said it would also be working to lower production cost to match the market requirements for tandem applications.