Chemical bath deposition for 21.7%-efficient perovskite solar cell based on tin oxide films

Researchers at the Okinawa Institute of Science and Technology Graduate University (OIST) in Japan have fabricated a perovskite solar cell with an electron transport layer (ETL) based on high-quality large-area tin oxide (SnO₂) films by using a chemical bath deposition (CBD) process with the addition of potassium permanganate (KMnO).

The scientists explained that potassium (K) ions present in KMnO are able to diffuse into the perovskite material to both enlarge grain size and passivate the grain boundaries. Manganese (Mn) doping, meanwhile, improves both its crystallinity and stability.”In addition to the K and Mn ions diffusing into perovskites, several previous works also demonstrated that the direct incorporation of K and Mn ions into perovskite precursors can improve the perovskite grain size, reduce the hysteresis in resultant solar cells and enhance the thermal stability,” the Japanese group explained, noting that potassium is key in reducing the ionic migration and hysteresis – both known to cause defects and performance issues in the material.

The cell was built by depositing the SnO₂ film, the perovskite layer, the spiro-OMeTAD film and a gold electrode via CBD. According to the group, the proposed multifunctional interface engineering resulted in a solar cell with a power conversion efficiency of 21.7%, The cell was then used to produce a 7-cell perovskite module with a size of 5×5 cm and an efficiency of 15.62%, as well as a 14-cell module with a site of 10×10 cm and an efficiency of 11.80%. The academics are convinced that building a module with an area of 22.4 cm² and the same configuration of the 5x5cm panel could provide result in an efficiency of up to 13.62%.

“This precursor solution passivation in CBD method was demonstrated as a compatible technique for upscalable fabrication of solar modules,” the scientists concluded.

The manufacturing process is presented in the paper Up-Scalable Fabrication of SnO₂ with Multifunctional Interface for High Performance Perovskite Solar Modules, published in Nano Micro-Letters.