Perovskite-Info: the perovskite experts

Researchers at Linköping University and Shenzhen University have shown how inorganic perovskites can be used to produce low-cost and efficient photodetectors that transfer both text and music. "It's a promising material for future rapid optical communication," says Feng Gao, researcher at Linköping University.

"Perovskites of inorganic materials have a huge potential to influence the development of optical communication. These materials have rapid response times, are simple to manufacture, and are extremely stable." says Feng Gao.

A next-generation optical material based on perovskite nanoparticles can achieve vivid colors even on very large screens. Due to their high color purity and low cost advantages, it has also gained much interests in industry. A recent study including researchers with UNIST has introduced a simple technique to extract the three primary colors (red, blue, green) from this material.

This innovative work was led by Professor Jin Young Kim in the School of Energy and Chemical Engineering at UNIST. In the study, the research team introduced a simple technique that freely controls light emitting spectra by adjusting the anion halides in perovskite materials. The key is to adjust the anion halides by dissolving them in solvents to achieve red, blue and green lights. Application of this technique to LEDs can result in crystal-clear picture quality.

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 at UvA-IoP have shown that certain perovskites possess the desirable property of carrier multiplication – an effect that makes materials more efficient in converting light into electricity.

Research leaders Dr. Chris de Weerd and Dr. Leyre Gomez explain this property, which had so far not been shown to exist in perovskites. When semiconductors – in solar cells, for example – convert the energy of light into electricity, this is usually done one particle at a time: a single infalling photon results in a single excited electron (and the corresponding ‘hole’ where the electron used to be) that can carry an electrical current. However, in certain materials, if the infalling light is energetic enough, further electron-hole pairs can be excited as a result; it is this process that is known as carrier multiplication.

Researchers at Duke University computationally predicted the electrical and optical properties of layered hybrid organic-inorganic perovskites (or HOIPs) - popular materials for light-based devices such as solar cells and light-emitting diodes (LEDs). The ability to build accurate models of these materials atom-by-atom will allow researchers to explore new material designs for next-generation devices.

“Ideally we would like to be able to manipulate the organic and inorganic components of these types of materials independently and create semiconductors with new, predictable properties,” said David Mitzi, Professor of Mechanical Engineering and Materials Science at Duke. “This study shows that we are able to match and explain the experimental properties of these materials through complex supercomputer simulations, which is quite exciting.”

Researchers from Nazarbayev University in Kazakhstan and Hong Kong Polytechnic University have demonstrated a new 4-step process including (i) spin-coating of the precursors; (ii) cryogenic treatment; (iii) blow-dry process for the removal of the solvent; and (iv) thermal annealing. This process is a straightforward and effective technique which can yield homogenous perovskite films without the use of anti-solvents and regardless of the complexity of the precursor compositions.

When mixed perovskite precursor solutions are evaporated, usually non-uniform films with poor morphology are obtained due to coalescence of perovskite crystallites during rapid solvent removal. Therefore, anti-solvents are usually used to preapare mixed perovskite thin films. However, this technique is not convenient for large-scale manufacturing in industry since the final perovskite film quality critically depends on multiple parameters while adding the anti-solvent. Inaccurate control of the mixing process will cause gradients in over-saturation of the precursor solution, leading to spatially inhomogeneous nucleation of the perovskite and deterioration of the resultant film quality. Furthermore, commonly used anti-solvents such as chlorobenzene or toluene are environmentally harmful and highly toxic. The team's new method circumvents these issues and offers an improved alternative that enhances the control over the perovskite growth process, decoupling the nucleation and crystallization phases.

Swansea University researchers have declared a perovskite solar module the size of an A4 sheet of paper, (nearly six times bigger than 10x10 cm² modules of that type reported before), developed by using simple and low-cost printing techniques. The accomplishment shows that the technology works at a larger scale, not just in the lab, which is crucial for commercial use.

The team works for the SPECIFIC Innovation and Knowledge Center led by Swansea University. The researchers used an existing type of cell, a Carbon Perovskite Solar Cell (C-PSC), made of different layers - titania, zirconia and carbon on top - which are all printable. Though their efficiency is lower than other perovskite cell types, C-PSCs do not degrade as quickly, which has been established through 1 year of stable operation under illumination.