February 2020

KAIST researchers have designed a method to make perovskite crystals at lower temperatures, that could lead the way towards lower-cost solar cells by eliminating defects that reduce efficiency.

Most current work on perovskite solar cells focuses on polycrystalline versions, where the efficiency record is 25%, say Omar Mohammed and Osman Bakr, materials scientists at King Abdullah University of Science and Technology. But polycrystalline films are only a few hundred nm thick, whereas single crystals can be grown to approximately 20 µm. The thicker films can absorb more light so single-crystal solar cells could prove to be superior. The problem is that so far, single-crystal lead perovskite solar cells don't reach 20% efficiency.

Scientists from Hasselt University, imec, VITO, EnergyVille and international partners within the PERCISTAND consortium have announced that they achieved an energy efficiency of 25% with a thin-film solar cell.

Bart Vermang, coordinator within the PERCISTAND consortium, describes the development of thin-film solar cells as 'Pioneering'. The consortium, which partly consists of the collaborations within EnergyVille and Solliance, has succeeded in achieving a record energy efficiency with thin film solar cells. 'We've achieved an energy efficiency of 25 percent for the first time, which is just as much energy as a traditional solar cell can generate on a day-to-day basis. And we haven't yet reached the upper limit of our thin-film solar cells.'

Researchers at the Pohang University of Science & Technology (POSTECH) have developed eco-friendly-solvent processable hole transport polymers by using peppermint oil and walnut aroma food additives and the polymer can prevent lead leakage.

The POSTECH research team consisted of Prof. Taiho Park and Junwoo Lee, that developed Alkoxy-PTEG - hole transport polymers that could be dissolved in peppermint oil, by applying ethylene glycol side chains when producing perovskite solar cells. Also, the team confirmed that this polymer captured leaking lead in aging perovskite solar cells.

A team of scientists from the NUST MISIS Laboratory of Advanced Solar Energy has proposed a new approach that uses the two-dimensional inorganic material zirconium trisulfide as the electron transport layer of a perovskite LED. In the future, this may allow the mass production of a new type of light-emitting diodes, as well as solving the problem of LED displays degradation, for example, in smartphones and TVs.

The screens of many modern smartphones and TVs "suffer" from pixel burnout. Due to the presence of an organic component in OLED-type matrices (and their derivatives), pixels begin to degrade when the same icons on the screen are lit for a long time. So far, manufacturers advise users to periodically change the screen interface, rearrange the icons in places and regularly update the screen saver. In fact, the problem could be solved by minimizing the use of organic components in the screen matrix. Perovskite diodes are proposed as a way to make a revolution in designing screens.

Researchers at China's Xi'an Jiaotong University have developed a solar cell based on multiple-cation lead mixed-halide perovskite (MLMP), which reportedly has a stronger moisture resistance compared to cells based on single-halide perovskites.

The team says that mixed halides offer the chance to manufacture more reproducible, thermally stable films with higher crystal qualities. However, these halides also suffer from stability issues due to abundant point defects and dangling bonds at the grain boundary and film surface. In order to address this problem, the scientists turned to interface engineering. They used phosphorus-containing Lewis acid and base molecules such as triphenylphosphine oxide (TPPO), tetraisopropyl methylenediphosphonate (TMPP), and tris (pentafluorophenyl) phosphine (TPFP) in the surface passivation process.

Researchers at Northern Illinois University and the U.S. Department of Energy's (DOE) National Renewable Energy Laboratory (NREL) in Colorado have reported on a potential breakthrough in the development of hybrid perovskite solar cells.

Led by Tao Xu of NIU and Kai Zhu of NREL, the scientists have developed a technique to sequester the lead used to make perovskite solar cells and minimize potential toxic leakage by applying lead-absorbing films to the front and back of the solar cell.

Research by EPFL shows that a new engineered passivator, 4'tert'butyl'benzylammonium iodide (tBBAI), has bulky tert'butyl groups that prevent unwanted aggregation by steric repulsion. It was found that simple surface treatment with tBBAI significantly accelerates the charge extraction from the perovskite into the spiro'OMeTAD hole'transporter, while retarding the nonradiative charge carrier recombination.

This boosts the power conversion efficiency (PCE) of the PSC from '20% to 23.5%, reducing the hysteresis to barely detectable levels.

Researchers in Australia's University of Sydney have found a way to manipulate laser light at a fraction of the cost of current technology. The discovery could help drive down costs in industries as diverse as telecommunications, medical diagnostics and consumer optoelectronics.

The polarization of transmitted light is rotated by a crystal immersed in a magnetic field (top). The perovskite crystal (bottom right) rotates light very effectively, due to the atomic configuration of its crystal structure (bottom left)

The research team, led by Dr Girish Lakhwani from the University of Sydney Nano Institute and School of Chemistry, has used inexpensive perovskite crystals to make Faraday rotators. These manipulate light in a range of devices across industry and science by altering a fundamental property of light ' its polarization. This gives scientists and engineers the ability to stabilize, block or steer light on demand.

University of Central Florida researchers are helping to close the gap separating human and machine minds, using a technology based on perovskite quantum dots. In a recent study, a UCF research team showed that by combining two promising nanomaterials into a new superstructure, they could create a nanoscale device that mimics the neural pathways of brain cells used for human vision.

"This is a baby step toward developing neuromorphic computers, which are computer processors that can simultaneously process and memorize information," said Jayan Thomas, an associate professor in UCF's NanoScience Technology Center and Department of Materials Science and Engineering. "This can reduce the processing time as well as the energy required for processing. At some time in the future, this invention may help to make robots that can think like humans."

Researchers at Spain's Charles III University of Madrid claim to have significantly reduced optical losses in a monolithic, nano-structured perovskite silicon tandem solar cell by using a new design.

Such two-terminal tandem cell devices are said to offer high conversion efficiency, due to a large number of layers, but to also suffer significant optical losses because of the high number of interfaces.