Researchers at the École Polytechnique fédérale de Lausanne (EPFL) and Sungkyunkwan University in South Korea have identified the cause behind the degradation of perovskite solar cells and developed a technique to improve its stability.

Perovskite solar cells (PSCs) utilize low-cost materials and are efficient. Further, they can surpass traditional silicon solar cells and potentially revolutionize clean energy.

But PSCs’ response to external stimuli such as heat or moisture negatively impacts stability.

The researchers said their new method brings us closer to the widespread adoption of these cost-effective and efficient solar cells.

‘Facet engineering’ to improve stability

The team looked at two specific crystal facets or the crystal’s flat surface, characterized by a particular arrangement of atoms.

The arrangement of atoms on these facets affects the crystal’s properties and behavior, such as its stability and response to external stimuli like moisture or heat.

The researchers looked at two facets of perovskite crystals — represented as (100) and (111) facets.

The (100) facet is a plane that is perpendicular to a crystal’s c-axis, with its atoms arranged in a repeating pattern in the form of a square grid, and in the (111) facet, the atoms are arranged in a triangular grid.

The researchers found that the (100) facet is particularly prone to degradation as it can quickly transition to an unstable, inactive phase when exposed to moisture. In contrast, the (111) facet was found to be much more stable and resistant to degradation.

The researchers also identified the cause of the degradation. They found that it was due to a strong bond between the perovskite and water molecules, which caused the transition from the stable to unstable phase.

The team used their findings to develop a “facet engineering strategy,” in which they used a special substance called ligand molecules to grow the more stable (111) facet.

This resulted in perovskite films that were exceptionally stable and resistant to moisture and heat.

The researchers said their study represents an important step forward in developing PSCs, as stability is a major hurdle to their commercialization.

A team of researchers from EPFL in December 2022, developed a method that improves both power conversion efficiency and stability of solar cells based on pure iodide and mixed-halide perovskites.

Earlier in the month, researchers from the Indian Institute of Technology (IIT), Roorkee, said they had successfully developed a prototype of a low-cost, high-quality perovskite solar cell that achieved a stable power conversion efficiency (PCE) of 17.05%.