Technical / research - Page 9

Researchers at Hong Kong Baptist University, The Hong Kong University of Science and Technology (HKUST) and Yale University have revealed the existence of surface concavities on individual crystal grains that are the fundamental blocks of perovskite thin films, and examined their significant effects on the film properties and reliability. 

Based on this discovery, the team designed a new way of making perovskite solar cells (PSCs) more efficient and stable via a chemo-elimination of these grain surface concavities.

Researchers from China's Shaanxi Normal University, Zhejiang Normal University, China Institute of Radiation Protection and Chinese Academy of Sciences have developed lead-free photoferroelectric hybrid metal halide perovskite flexible membranes for wearable detectors, that offer excellent X-ray response with high sensitivities, low detection limit and impressive imaging capabilities. 

Demonstration and application potential for lead-free photoferroelectric perovskite membrane (LFPPM). a) Optical images of the LFPPM. b) Schematic diagram of LFPPM wearable X-ray dosimeter. c) Schematic diagram of the working principle of wearable X-ray dosimeter. (Image credit: Nanowerk)

High-sensitivity wearable radiation detectors are important for personnel protection in radiation environments such as defense, nuclear facilities, and medical fields. Traditional detectors using bulk crystals tend to lack flexibility. Hybrid metal halide perovskites have shown promise for next-generation radiation detection as they can efficiently absorb high-energy radiation and convert it into electrical signals. However, there are concerns of lead toxicity. More recent efforts have explored lead-free alternatives, but these have generally suffered from poor charge transport properties, reducing their effectiveness as radiation detectors.

Researchers at the National Renewable Energy Laboratory (NREL) and University of North Carolina at Chapel Hill have reported a systematic study on the degradation mechanisms of p–i–n structure perovskite solar cells (PSCs) under reverse bias. Reverse bias is a phenomenon that can occur when, for example, an individual cell is shaded and other cells in the module try to push a higher current through it, increasing the temperature and potential damage to the cells. These conditions make solar cells unstable and deteriorate their performance over time.

The team's new strategy could improve the stability of PSCs under reverse bias conditions and facilitate the future deployment of perovskite-based photovoltaics (PVs) in real-world settings.

Yayoi Takamura, professor and chair of materials science and engineering at the University of California, Davis, and researchers at Lawrence Livermore National Laboratory (LLNL) have designed deep-learning model ensembles, a method in machine learning involving multiple neural networks, to investigate the magnetic behavior of perovskite oxide multilayers.

Perovskite oxides are gaining attention for use in next-generation magnetic and ferroelectric devices due to their exceptional charge transport properties and the opportunity to tune the different properties of electrons and atoms, including charge, spin, lattice and orbital degrees of freedom. While the materials may offer a pathway for innovative designs in perovskite oxide-based devices, the atomic-level compositions of the interfaces between perovskite oxides are unknown, therefore hindering the establishment of design principles using these materials. With this new model, the researchers investigated the effects of composition and process parameters on the magnetic behavior of perovskite oxide multilayers.

Researchers at The University of Toledo (UToledo), Northwestern University and University of Washington have focused on the stability of perovskite solar cells, and reported an adjustment to the chemical structure of a key component of a tandem cell that allows it to continuously generate electricity for more than 1,000 hours.

Image from Joule

“State-of-the-art all-perovskite tandem cells with a conventional hole-transfer layer can only continuously operate for hundreds of hours,” said Dr. Zhaoning Song, a co-author and assistant professor in the Department of Physics and Astronomy at UToledo. “Our innovation prolongs the stability of these devices, advancing all-perovskite tandem technology and bringing it closer to practical application.”

As silicon-based transistors approach their limits, researchers are exploring alternative materials to continue progress in semiconductor technology. Carbon nanotubes (CNTs) are considered promising candidates for next-generation electronics due to their exceptional electrical properties and nanoscale dimensions. Yet, the challenge of precisely controlling the electronic characteristics of CNTs has hindered their widespread adoption in practical applications.

Researchers at China's Peking University, Zhejiang University and Chinese Academy of Science (CAS) have developed an inner doping method by filling CNTs with 1D halide perovskites to form a coaxial heterojunction, which enables a stable n-type field-effect transistor for constructing complementary metal–oxide–semiconductor electronics.

A team of researchers, led by the Fudan University in China, has developed a p-i-n structure inverted perovskite solar cell that uses a synergistic bimolecular interlayer (SBI) and achieves what the team says is the smallest nonradiative recombination induced open-circuit voltage loss ever reported. 

Schematic illustration of p-i-n PSC using MPA/PEAI as SBI. Image from Nature Communications

The researchers' SBI strategy consisted of depositing 4-methoxyphenylphosphonic acid (MPA) and 2-phenylethylammonium iodide (PEAI) as modulators to functionalize the perovskite surface.

Researchers at Tokyo Institute of Technology and Tohoku University have reported hexagonal perovskite-related oxides with exceptionally high proton conductivity and thermal stability. 

The team explained that these materials' unique crystal structure and large number of oxygen vacancies enable full hydration and high proton diffusion, making them ideal candidates as electrolytes for next-generation protonic ceramic fuel cells that can operate at intermediate temperatures without degradation.

Researchers from Northwestern University, University of Toronto and KAUST have hypothesized that perovskitoids, with robust organic-inorganic networks enabled by edge- and face-sharing, could impede ion migration. This addresses the issue of the migration of cations between 2D and 3D layers which results in the disruption of octahedral networks that leads to degradation in performance over time

The scientists explored a set of perovskitoids of varying dimensionality, and found that cation migration within perovskitoid/perovskite heterostructures was suppressed compared to the 2D/3D perovskite case. Increasing the dimensionality of perovskitoids improves charge transport when they are interfaced with 3D perovskite surfaces – the result of enhanced octahedral connectivity and out-of-plane orientation. 

Researchers at India's Chitkara University Institute of Engineering and Technology have developed 2D perovskite solar cells with MXene materials to build a PV device with remarkable efficiency and open-circuit voltage. The scientists claim the new cell architecture can help charge carriers move smoothly through the cell layers and reduce recombination losses.

The team's 2D DJ perovskite solar cell implemented bandgap grading techniques and use contacts based on a functionalized two-dimensional titanium carbide known as MXene. MXenes are compounds that take their name from their graphene-like morphology and are made via selective etching of certain atomic layers from a bulk crystal known as MAX. Recently, MXenes materials have shown promise for use in PV technology due to their unique optoelectronic properties, such as their large charge carrier mobility, excellent metallic conductivity, high optical transmittance, and tunable work function (WF).