Swiss researchers improve stability of perovskite solar cells

A group of researchers from Switzerland’s Ecole Polytechnique Fédérale de Lausanne (EPFL) has achieved a higher level of operational stability for cuprous thiocyanate-based (CuSCN) perovskite solar cells.

Progress in the development of the durability of the cells was realized after they were exposed to accelerated aging tests. With a thin layer of reduced graphene oxide, performance fell by less than 5% when the cells were placed under 60°C sunlight for more than 1000 hours.

The researchers claim to have achieved the highest stability levels for CuSCN perovskite to date. The cells retained 95% of their initial stability, with an efficiency level of 20%.

The EPFL scientists have conducted research on cheap and stable hole transporters for perovskite solar cells and have concluded that CuSCN stands out as a stable, efficient and cheap option. However, earlier research has produced only moderate efficiency and stability improvements.

In order to resolve these issues, researchers at Michael Grätzel’s lab at EPFL have developed a simple dynamic solution-based method for depositing highly conformal, 60-nm thick CuSCN layers. This facilitates the construction of perovskite cells with stabilized power-conversion efficiencies above 20%.

The introduction of a thin spacer layer of reduced graphene oxide between the CuSCN and gold layers also allows the PSCs to achieve high levels of operational stability, so they can retain 95% of their initial efficiency while operating at a maximum power point for 100 hours under 605 degrees of sun.

The researchers also discovered that the root cause of PSC instability originates from the degradation of CuSCN/gold contact as a solar cell operates.

“This is a major breakthrough in perovskite solar-cell research and will pave the way for large-scale commercial deployment of this very promising new photovoltaic technology,” said researcher Michael Grätzel.

Another researcher, M. Ibrahim Dar, also hailed the importance of the discovery. “It will benefit the numerous scientists in the field that have been intensively searching for a material that could replace the currently used, prohibitively expensive organic hole-transporters.”