Solliance has developed a perovskite solar cell that combines good cell efficiency with a very high near infrared transparency of 93 percent. ECN showed that when this perovskite cell is mechanically stacked on a 6 inch silicon bottom cell with its proprietary MWT-SHJ (metal-wrap-through silicon heterojunction) design, 26.3 percent efficiency is achieved, an increase of 3.6 percentage points over the efficiency of the directly illuminated silicon cell laminate. The companies announced their findings at the Silicon PV/nPV conference, in Lausanne, Switzerland on 19th March 2018.
“By optimising 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” said 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 percent. This is significantly higher than the state of the art, which is below 85 percent. 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 percent”.
Sjoerd Veenstra, programme manager Perovskite Solar Cells at Solliance Zhang added that the active area of the tested small semi-transparent perovskite cell is 0.09 cm2 and the power conversion efficiency is 16.4 percent. The performance measurement of the four-terminal hybrid tandem was conducted according to the generally accepted procedure described by J. Werner in 2016.
Scaling up from a laboratory scale to an industrial process is one major barrier for a successful implementation of a new promising development. For this reason, Solliance employed different scales in development. Once the device was proven with spin coated layers, the company used pilot scale equipment provided by its industrial partners to scale it to a viable industrial production process. The expertise of industrial partners of Solliance in sheet-to-sheet spatial ALD and laser interconnection of thin film cells was used to scale-up the technology to 30x30 square centimetre demonstration modules.
Image: Solar PV 2016, Chambery, France
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