Technical / research - Page 29

Researchers from Texas A&M University, Northwestern University, University of South Florida and University of Illinois Urbana-Champaign have studied the fatigue behavior of 2D hybrid organic-inorganic perovskites (HOIPs) in practical applications.

The application of repeated or fluctuating stresses below the material's strength, known as fatigue loading, often leads to failure in 2D hybrid materials. However, the fatigue properties of HOIP materials have remained elusive despite their widespread use in various applications. The research group demonstrated how fatigue loading conditions, wearing different components, would affect the lifetime and failure behavior of the materials. Their results provide insights into designing and engineering 2D HOIPs and other hybrid organic-inorganic materials for long-term mechanical durability.

A collaborative project involving over 10 laboratories and research institutes from Surrey, Oxford, Cambridge, Bath, Warwick, UCL, EMPA and UESTC, has investigated how to release high-speed photonic sources using metal-halide perovskites. 

The team reported a holistic approach for realizing fast perovskite photonic sources on silicon based on tailoring alkylammonium cations in perovskite systems. The scientists revealed the recombination behavior of charged species at various carrier density regimes relevant for their modulation performance. They demonstrated perovskite devices with efficient light outcoupling and achieved device modulation bandwidths of up to 42.6 MHz and data rates above 50 Mbps, with further analysis suggesting that the bandwidth may exceed gigahertz levels. The principles developed in this work have the potential to support the development of perovskite light sources for next-generation data-communication architectures. The demonstration of solution-processed perovskite emitters on silicon substrates also opens up the possibility of integration with micro-electronics platforms.

Researchers from North Carolina State University, National Synchrotron Light Source II at Brookhaven National Laboratory and Rey Juan Carlos University have created a novel materials acceleration platform (MAP), essentially a robot capable of conducting experiments more efficiently and sustainably to develop a range of new semiconductor materials with desirable attributes. The researchers have demonstrated that the new technology, called RoboMapper, can rapidly identify new perovskite materials with favorable properties and improved potential for creating stable and efficient solar cells.

“RoboMapper allows us to conduct materials testing more quickly, while also reducing both cost and energy overhead – making the entire process more sustainable,” says Aram Amassian, corresponding author of a paper on the work and a professor of materials science and engineering at North Carolina State University.

Researchers from Rice University, National Renewable Energy Laboratory (NREL), Lawrence Berkeley National Laboratory, CNRS and HZB have designed a conductive adhesive-barrier (CAB) that translates >99% of photoelectric power to chemical reactions. The device combines halide perovskites with electrocatalysts and could serve as a platform for a wide range of chemical reactions that use solar-harvested electricity to convert feedstocks into fuels.

The CAB enables halide perovskite-based photoelectrochemical cells with two different architectures that exhibit record solar-to-hydrogen (STH) efficiencies. 

Sweat is less invasive to collect than blood, and can tell a lot about a person's health. This is the premise behind the wearable sweat sensors developed by Wei Gao, assistant professor of medical engineering at the California Institute of Technology (Caltech). Over the past five years, Gao has steadily added features to his wearables, making them capable of reading out levels of salts, sugars, uric acid, amino acids, and vitamins as well as more complex molecules like C-reactive protein that can provide timely assessment of certain health risks. Most recently, in collaboration with Martin Kaltenbrunner's group at Johannes Kepler University Linz in Austria, Gao has powered these wearable biosensors with a flexible perovskite solar cell (FPSC).

Perovskite is as much as 1,000 times thinner than silicon solar cell layers, making them "quasi-2D" in Gao's terms. Perovskites can also be tuned to the spectra of different lighting, from outdoor sunlight to various forms of indoor lighting. Importantly, perovskite solar cells can achieve a higher power conversion efficiency (PCE) than silicon, which means they can convert a greater proportion of the light they receive into usable electricity. The flexible perovskite solar cell (FPSC) on Gao's wearable sweat sensor has a record-breaking PCE exceeding 31 percent under indoor light illumination. 

Researchers from The University of Sydney, CSIRO Energy and Australia's Nuclear Science and Technology Organization have shown that perovskite solar cells damaged by proton radiation in low-Earth orbit can recover up to 100% of their original efficiency via annealing in thermal vacuum.

This is achieved through careful design of the hole transport material (HTM), which is used to transport photo-generated positive charges to the electrode in the cell.

Researchers from Switzerland's Ecole Polytechnique Fédérale de Lausanne (EPFL), Chinese Academy of Sciences (CAS) and Peking University have developed a perovskite solar cell with a 2D/3D heterojunction architecture.

The cell uses a 2D perovskite layer at the interface between the perovskite and the hole transport layer, which the researchers said can improve charge-carrier transport/extraction while suppressing ion migration. Cells with this architecture usually exhibit large exciton binding energies and are generally more stable than conventional 3D devices due to the protection provided by the organic ligands.

Researchers at the Indian Institute of Science Education and Research (IISER) have developed new LEDs which emit light simultaneously in two different wavelength ranges, for a simpler and more comprehensive way to monitor the freshness of fruit and vegetables.

 The team explains that modifying the LEDs with perovskite materials causes them to emit in both the near-infrared range and the visible range, a significant development in the contact-free monitoring of food. Angshuman Nag and his team at the Indian Institute of Science Education and Research (IISER) are proposing a perovskite application in LED technology that could simplify the quality control of fresh fruit and vegetables.

Researchers at Huazhong University of Science and Technology, Russian Academy of Sciences, Okinawa Institute of Science and Technology Graduate University (OIST) and Shanghai Jiao Tong University have developed a design strategy that could reduce defects in FAPbI₃-based solar cells, improving their power efficiency. This strategy involves the application of an additive and a coating agent to the perovskite films integrated in the solar cells.

"Power conversion efficiencies of inverted perovskite solar cells (PSCs) based on methylammonium- and bromide-free formamidinium lead triiodide (FAPbI₃) perovskites still lag behind PSCs with a regular configuration," Rui Chen, Jinan Wang, and their colleagues wrote in their paper. "We improve the quality of both the bulk and surface of FA_0.98Cs_0.02PbI₃ perovskite films to reduce the efficiency gap."

Researchers from the University of Toronto, the University of Kentucky, EPFL, North Carolina State University and Northwestern University have designed a perovskite solar cell that can stand up to high temperatures for more than 1,500 hours — an important achievement on the to commercialization. 

“Perovskite solar cells offer new pathways to overcome some of the efficiency limitations of silicon-based technology, which is the industrial standard today,” said Ted Sargent, professor of electrical and computer engineering at the McCormick School of Engineering, professor of chemistry in the Weinberg College of Arts and Sciences, and a former professor at the University of Toronto. “But due to its multi-decade head start, silicon still has an advantage in some areas, including stability. This study shows how we can close that gap.”