EPFL does extensive perovskite R&D work and is responsible for many publications and advancements in the field.
The latest EPFL perovskite news:
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.
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.
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.
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.
EPFL the CSEM PV-center researchers have combined silicon and perovskite to create solar cells with the resulting efficiency of 25.2%, in what is regarded as a record for this type of tandem cell. Their innovative yet simple manufacturing technique could be directly integrated into existing production lines, and efficiency could eventually rise above 30%.
The researchers explain that creating an effective tandem structure by superposing two materials is no easy task. "Silicon's surface consists of a series of pyramids measuring around 5 microns, which trap light and prevent it from being reflected. However, the surface texture makes it hard to deposit a homogeneous film of perovskite," explains Quentin Jeangros, who co-authored the paper. A common problem in such cells arises from the fact that when the perovskite is deposited in liquid form, it accumulates in the valleys between the pyramids while leaving the peaks uncovered, leading to short circuits. The team tackled this problem by using evaporation methods to form an inorganic base layer that fully covers the pyramids. That layer is porous, enabling it to retain the liquid organic solution that is then added using a thin-film deposition technique called spin-coating. The researchers subsequently heat the substrate to a relatively low temperature of 150°C to crystallize a homogeneous film of perovskite on top of the silicon pyramids.