KAUST, Helmholtz-Zentrum Berlin present 31.2%-efficient blade-coated perovskite-silicon tandem solar cell

A group of researchers from the King Abdullah University of Science and Technology (KAUST) in Saudi Arabia and Helmholtz-Zentrum Berlin (HZB) in Germany have fabricated a perovskite-silicon tandem solar cell that reportedly achieves efficient charge extraction and interface passivation.

“Perovskite-silicon tandems have convincingly proven their high-performance potential with many groups now achieving efficiencies higher than 30%,” the research's lead author, Stefaan De Wolf, told pv magazine. “However, translating these results from a lab-scale environment towards techniques that are relevant to the industry requires attention, especially for solution processing techniques. Here, we show certified efficiencies above 31% using blade-coated perovskites. The devices show improved performances thanks to contact passivation using 2D perovskites.”

In the study “Efficient blade-coated perovskite/silicon tandems via interface engineering,” which was recently published in Joule, the academics explained that they used blade coating instead of spin coating, as the latter currently faces scalability issues due to limited throughput. It was used, in particular, to deposit the 3D perovskite onto a 2D perovskite layer in the perovskite top device, which had a p-i-n inverted device configuration.

“By tuning the targeted dimensionality (n) of the 2D perovskite film, which is made prior to the 3D perovskite, we minimize the energy level mismatch at the bottom interface, achieve efficient hole extraction, and reduce performance losses in our blade-coated p-i-n devices,” the scientists said, noting that this configuration helped the top perovskite device achieve a power conversion efficiency of 22.6%, an open-circuit voltage of 1.23V, and a fill factor (FF) of 82%.

With this device, the research group built a 1 cm2 encapsulated tandem device based on a substrate made of indium tin oxide (ITO), several layers of amorphous silicon (a-Si), a crystalline silicon absorber, a transparent back contact made of indium zinc oxide (IZO), the 2D perovskite layer, the blade-coated 3D perovskite layer, a p-phenylenediaminium iodide (PDAI) layer, an electron transport layer (ETL) made of thermally evaporated buckminsterfullerene (C60), a tin oxide (SnO₂) layer, another IZO layer, an anti-reflective coating based on magnesium fluoride (MgF2), and a silver (Ag) metal contact.

Tested under standard illumination conditions, this tandem cell also showed it can retain around 80% of its initial efficiency for 1,700 h under 1-sun. “Our overall strategy, with robust perovskite composition and bottom 2D interface, enabled blade-coated tandems to be certified for the first time in literature, with an efficiency of 31.2% measured at Fraunhofer Institute for Solar Energy (ISE) Systems,” the scientists stated.

KAUST announced in August it achieved an efficiency of 33.7% for a perovskite-silicon tandem device using a new perovskite additive known as tetrahydrotriazinium. In 2021, HZB announced it fabricated a perovskite-silicon tandem cell with an efficiency of 29.80%, which at the time was a world record for this cell architecture.

The most efficient tandem device to date is a 34.6% efficient cell presented by Chinese manufacturer Longi in September.

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