Collaborative team focuses on MA to better understand perovskite PV stability issues

Researchers from the University of Fribourg and École Polytechnique Fédérale de Lausanne in Switzerland, Pandit Deendayal Petroleum University in India and Benemérita Universidad Autónoma de Puebla in Mexico have revealed new clues about the stability of perovskite thin films and solar cells.

“Our chief aim is to stabilize perovskite solar cells for many years and decades,” explains Michael Saliba, principal investigator at the Adolphe Merkle Institute, University of Fribourg. “Without long-term stability, any commercialization efforts will fail.”

EPFL researchers develop a new way to achieve to high-performance, stable perovskite solar cells

Some of the key challenges for hybrid organic-inorganic perovskite solar cells are their limited stability, scalability, and molecular level engineering. Researchers at the Laboratory of Photonics and Interfaces (LPI) and Laboratory of Magnetic Resonance (LMR) at EPFL show how molecular engineering of multifunctional molecular modulators (MMMs) and using solid-state nuclear magnetic resonance (NMR) to investigate their role in double-cation pure-iodide perovskites can lead to stable, scalable, and efficient perovskite solar cells.

The objective of the team lead by Professor Grätzel (LPI), in collaboration with the group of Professor Lyndon Emsley (LMR) was to tackle the above-mentioned challenges through rational molecular design in conjunction with solid-state NMR, as a unique technique for probing interactions within the perovskite material at the atomic level. The team designed a series of organic molecules equipped with specific functions that act as molecular modulators (MMs), which interact with the perovskite surface through noncovalent interactions, such as hydrogen bonding or metal coordination. While hydrogen bonding can affect the electronic quality of the material, coordination to the metal cation sites could ensure suppression of some of the structural defects, such as under-coordinated metal ions.

Research team develops a technique to prolong lifespan of perovskite solar cells

Researchers at Kaunas University of Technology (KTU), Lithuania, along with ones from Vilnius University and the Swiss Federal Institute of Technology, Lausanne (EPFL), have uncovered one of the possible reasons behind the short lifespan of perovskite solar cells and have offered solutions. The scientists have found that hole transporting materials used in perovskite solar cells are reacting with one of the most popular additives, tert-butylpyridine, which has a negative impact on overall device performance.

Professor Vytautas Getautis from the KTU Faculty of Chemical Technology says that so far, no attention has been paid to the possible interaction between the elements of the solar cell. For the first time, KTU chemists have uncovered the chemical reaction between the components of the hole transporting layer composition – the semiconductor and the additive used to improve the performance of the solar cell.

EPFL and AMI teams develop a method to replace one of the least stable components in perovskite solar cells

Researchers at the Adolphe Merkle Institute in Fribourg and the Ecole Polytechnique Fédérale de Lausanne have developed a new technique to replace one of the least stable components in perovskite solar cells, which could be a major step towards commercialization.

Perovskites are seen as promising thin-film solar-cell materials because they can absorb light over a broad range of solar spectrum wavelengths thanks to their tuneable bandgaps. Charge carriers (electrons and holes) can also diffuse through them quickly and over long lengths. The most efficient perovskite solar cells usually contain bromide and MA, which is thermally unstable. To overcome this problem, researchers tried replace MA with FA since it is not only more thermally stable but also has an optimal redshifted bandgap. Unfortunately, because of its large size, FA does distort the perovskite lattice and tends to produce a photoinactive “yellow” phase at room temperature. The other photoactive “black phase” can only be seen at high temperatures. However, the researchers in this new work have now found a way to stabilize the black phase of FA at room temperature.

International team created highly efficient waterproof perovskite solar cells

Researchers from Qatar, Switzerland and Italy have designed a composite perovskite material with a thin surface layer that repels water and protects against moisture-induced degradation. The team has managed to do this by allowing the self-assembly of two-dimensional perovskite on top of a three-dimensional perovskite in an inert atmosphere.

Waterproof perovskite solar cells image

The composite perovskite did not decompose when kept in highly humid air for three days. The top layer of the 2D perovskite blocked water penetration into the 3D perovskite beneath it, preventing its degradation. Bare 3D perovskite completely degrades at a similar humidity.