Perovskite-Info: the perovskite experts

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.

A team of researchers at the French National Solar Energy Institute (INES) at the country’s Alternative Energies and Atomic Energy Commission (CEA) has announced achieving 18% power conversion efficiency of perovskite solar modules.

They were able to achieve this level on an active surface area of 10 cm² under illumination of 1 STC sun, using a coating step carried out in air followed by a gas quenching conversion step to form the desired perovskite material. This material was developed without methyl ammonium comprising multi-cations and a mix of halogens.

A team of researchers at MIT (along with colleagues from South Korea and Georgia) has developed a new approach to the design of perovskite cells by adding a specially treated conductive layer of tin dioxide bonded to the perovskite material, which provides an improved path for the charge carriers in the cell. By also modifying the perovskite formula, the researchers have reportedly boosted its overall efficiency as a solar cell to an impressive 25.2%.

On top of many other attractive properties, perovskites have a higher bandgap than silicon, which means they absorb a different part of the light spectrum and thus can complement silicon cells to provide even greater combined efficiencies. But even using only perovskite, MIT's Jason Yoo says, “what we’re demonstrating is that even with a single active layer, we can make efficiencies that threaten silicon, and hopefully within punching distance of gallium arsenide. And both of those technologies have been around for much longer than perovskites have.”

Scientists at the Helmholtz-Zentrum Berlin have improved a process for vertically depositing a solution made from an inexpensive perovskite solute onto a moving substrate placed below. Not only have they discovered the crucial role played by one of the solvents used, but they have also taken a closer look at the aging and storage properties of the solution.

The liquid solution of perovskite precursor, solvent, and additive flows from a slit-shaped nozzle onto the glass substrate being conveyed below. Credit: Jinzhao Li / HZB

The perovskite solar cells that Prof. Eva Unger and her team at the Helmholtz-Zentrum Berlin (HZB) are researching seem to be extremely promising. “These are the best solar cells to date that can be made using a 2D ink”, the researcher explains. “And now their efficiencies are approaching those for cells made of crystalline silicon.”

Five Wrocław University of Science and Technology researchers have been awarded over than 12 million PLN (around USD$3.2 million) for research projects under the Maestro and Sonata Bis competitions organized by the National Centre for Science. Among the research area are perovskites, active enzymes, and artificial intelligence.

Targeting experienced scientists, Maestro is a competition for research projects aimed at carrying out pioneering, and also interdisciplinary, research that is important for the development of science and reaching beyond the current state of knowledge, which may result in scientific discoveries.