Researchers at the Department of Energy's Oak Ridge National Laboratory (ORNL) and the University of Tennessee have proposed a way to automate the search for new materials, with a focus on metal halide perovskites (MHPs), to advance solar energy technologies. The study, part of an ORNL-UT Science Alliance collaboration, aims to identify the most stable MHP materials for device integration.

The automated workflow combines chemical robotics and machine learning to speed the search for stable perovskites. Credit: Jaimee Janiga/ORNL, U.S. Dept of Energy

The team has developed a novel workflow that combines robotics and machine learning to study metal halide perovskites. 'Our approach speeds exploration of perovskite materials, making it exponentially faster to synthesize and characterize many material compositions at once and identify areas of interest,' said ORNL's Sergei Kalinin.

A research team, led by Dr. Luigi Angelo Castriotta at the at University of Rome Tor Vergata's CHOSE Center for Hybrid and Organic Solar Energy, has reported impressive results on methylammonium free perovskites processed in air, using a scalable technique based on infrared annealing and potassium doped graphene oxide as an interlayer.

The team reached efficiencies of 18.3% and 16.10% on 0.1cm² cell and on 16cm² module respectively, with enhanced stability compares to the standard multi cation reference.

Various dangerous chemicals are currently used for agriculture and industry, including fumigants like methyl iodide, which is used to control insects and fungi. The wrong amounts or incorrect use of these fumigants can be harmful to people and degrade the ozone layer. As it’s invisible and doesn’t smell, it’s hard to tell whether there are dangerous amounts of methyl iodide present, and until now the best way to test for it was in a laboratory using expensive, complicated equipment, which isn’t practical in many real-world settings. Some cheaper, lightweight detection methods have been tried, but they didn’t have enough sensitivity and took too long to deliver results.

Now, a research team led by the ARC Centre of Excellence in Exciton Science, along with Australia’s national science agency CSIRO and the Department of Defense, has found a perovskite-based way to detect methyl iodide, with the accuracy, flexibility and speed necessary for practical use. This new sensing mechanism is also versatile enough for use in detecting a wide range of fumigants and chemical warfare agents.

Scientists from the University of North Carolina have developed a perovskite solar cell with an efficiency of 23.2% by adding benzylhydrazine hydrochloride (BHC) as an iodine (I) reductant agent in precursor solutions such as methylammonium iodide (MAI) and formamidinium iodide (FAI).

'Preventing the degradation of perovskite precursor solutions is equally important compared to post-fabrication device encapsulation, because large-area perovskite modules are generally manufactured in air and perovskite precursor inks are generally prepared in large quantity and stored for days or months,' the scientists said.

Scientists in Italy have devised a way to fine-tune the optical emission and robustness of a new set of Ruddlesden'Popper metal'halide layered perovskites. It is shown that the type of molecule regulates the number of hydrogen bonds that it forms with the edge'sharing [PbBr₆]^4' octahedra layers, leading to strong differences in the material emission and tunability of the color coordinates, from deep'blue to pure'white. In addition, the emission intensity strongly depends on the length of the molecules, thereby providing an additional parameter to optimize their emission efficiency.

The combined experimental and computational study provides a detailed understanding of the impact of lattice distortions, compositional defects, and the anisotropic crystal structure on the emission of such layered materials.

King Abdullah University of Science and Technology (KAUST) researchers have shown how fluid injection of perovskite semiconductors creates microwires to build different optoelectronic devices on a single silicon chip. They have developed a microfluidic pumping technology that can help perovskites be more readily incorporated into silicon-based semiconducting platforms.

The "lab on a chip" designed at KAUST consists of several perovskite-based optoelectronic devices on one silicon chip, embodying a photodetector, transistor, light-emitting diode and a solar cell, for example. Credit: KAUST and Techxplore

Compared to traditional semiconductors, perovskites are soft and unstable. "This makes it difficult to pattern them using standard lithography methods," says materials scientist Iman Roqan at KAUST. The challenge tackled by Roqan and her colleagues was to adapt microfluidic technologies to manipulate solutions carrying perovskites to create semiconducting microscale wires.

An international research team, which included researchers from Pakistan, China and Saudi Arabia, has developed a perovskite solar cell with strong thermal stability and enhanced electron injection by using special nanotubes made of cesium-titanium dioxide (Cs-TiO₂).

The scientists used titanium sheets with 99.4% purity, 1 mm thickness, and a length of 50 mm. The cell was fabricated with a two-step electrochemical anodization process and was then encapsulated with Cs nanoparticles, after being doped with a Cs-based solution. The C2-TiO₂ nanotubes were then annealed at 450 C. The solar cell is based on methylammonium lead triiodide (CH₃NH₃PbI₃), which is a perovskite with high photoluminescence quantum yield.

A group of researchers at Germany's Karlsruhe Institute of Technology (KIT), the University of Heidelberg and the Technical University of Dresden have developed a new model to reliably and precisely determine the photoluminescence quantum yield of perovskite layers.

In their new paper, the research team shows how the novel method they developed can determine the photoluminescence quantum yield under solar irradiation conditions more precisely than previously assumed. 'It depends on the photon recycling, that is, the proportion of the photons emitted by the perovskite that is reabsorbed within the thin layers and re-emitted again, KIT scientist Paul Fassl explained.