Technical / research - Page 37

Researchers from The Hebrew University of Jerusalem in Israel have reported the fabrication of flexible and semitransparent perovskite-based solar cells.

Much of the research in the field of building-integrated photovoltaics is focused on semitransparent perovskite solar cells on glass substrates, which can be utilized as glass windows during the construction of the buildings. In their recent study, the team chose to develop cells that can be used in existing windows through a retrofitting process.

Scientists from the University of Konstanz in Germany, Quaid-i-Azam University and Kohsar University Murree in Pakistan and Huazhong University of Science and Technology in China have fabricated an inverted perovskite solar cell with a passivation technique utilizing a mixed solvent vapor annealing method based on ethylenediamine (EDA).

The team managed to show how simple passivation can improve both the performance and operational stability of a perovskite solar cell. The scientists said EDA has been used in previous research projects to suppress the defect states in different kinds of perovskite. However, the exact way that EDA contributes to the morphology, defect passivation and optoelectronic properties of perovskite films was unclear.

Researchers from Nanyang Technological University, Singapore (NTU Singapore) and the Institute of Materials Research and Engineering (IMRE) at the Agency for Science, Technology and Research (A*STAR) in Singapore have developed a method for capping materials based on non-toxic metals being used in the manufacture of perovskite solar cells.

(Left) A diagram showing the different layers of the perovskite solar cell capped with the zinc-based capping material fabricated by the researchers. (Right) The dotted green rectangle indicates the active region of the perovskite solar cell that captures sunlight and converts it to electricity. Image: NTU Singapore / Nature Energy

Perovskite solar cells are made of several layers of materials, including a perovskite layer that harvests light and a capping layer. The capping layer is coated onto the perovskite layer to protect the solar cell from environmental stresses such as heat and moisture and to boost the performance of the cell. To ensure that the capping layer is compatible with the underlying perovskite layer, researchers typically use an approach called the half precursor (HP) method to fabricate the capping layer. One of the precursor chemicals is first deposited on top of the perovskite layer which provides the other precursor. Through a process known as cation exchange reaction, the deposited precursor then reacts with lead ions present in the perovskite layer beneath to form a lead-based chemical compound that makes up the capping layer. As a result of the HP method, lead is also present in the protective capping layer. A method that enables non-toxic metals to be used in the capping layer could be a game-changer for perovskite solar cells.

Researchers from Penn State and the U.S. Army Combat Capabilities Development Command Aviation & Missile Center have created a new process to fabricate large perovskite devices that is more cost- and time-effective than previously possible and that might accelerate future materials discovery.

“This method we developed allows us to easily create very large bulk samples within several minutes, rather than days or weeks using traditional methods,” said Luyao Zheng, a postdoctoral researcher in the Department of Materials Science at Penn State and lead author on the study. “And our materials are high quality — their properties can compete with single-crystal perovskites.”

Researchers from Eindhoven University of Technology and TNO at Holst Centre have developed a sensor that converts light into an electrical signal at an astonishing 200% efficiency – a seemingly impossible figure that was achieved through the exceptional nature of quantum physics.

SA schematic of the photodiode architecture

The team of scientists sees its invention potentially used in technology that monitors a person's vital signs (including heartbeat or respiration rate) from afar, without the need for anything to be inserted or even attached to the body.

Researchers from Korea's Institute for Basic Science (IBS), Chinese Academy of Sciences, the University of Rochester in the U.S, and The Australian National University have increased the photoresponsivity of a lead-halide perovskite for solar cell applications by 250%. They created a perovskite film with a plasmonic substrate made of hyperbolic metamaterial and characterized it with transition dipole orientation.

The team has considerably reduced electron recombination processes in lead-halide perovskites (LHPs) used for solar cell applications. Recombination can have a significant impact on electrical performance in perovskite cells, with implications for open-circuit voltage, short-circuit current, fill factor, and ultimately, power conversion efficiency.

Researchers from Purdue University, Florida State University, University of Kentucky,  Lawrence Berkeley National Laboratory, University of Houston, Rice University, China's Qilu University of Technology (Shandong Academy of Sciences) and Taiwan's National Cheng Kung University have found that LEDs based on halide perovskites can produce more vivid, colorful and brighter images. The recent research presents extremely efficient perovskite LED devices in the red color region.

Perovskite materials often tend to be less stable and can degrade quickly. Further, device efficiency has not been fully optimized to compete with conventional LEDs. “Our work aims to resolve these critical issues,” said Purdue's Letian Dou, who conceived the idea, supervised the project and provided funding support.

Scientists from The University of Toledo, University of Washington, Northwestern University, University of Toronto and Empa–Swiss Federal Laboratories for Materials Science and Technology, have addressed a major challenge standing in the way of the commercialization of halide perovskite solar cells - their durability - by discovering an ingredient that enhances adhesion and mechanical toughness.

“Perovskite solar cells offer a route to lowering the cost of solar electricity given their high power conversion efficiencies and low manufacturing cost,” said Dr. Yanfa Yan, UToledo Distinguished University Professor of physics and a member of the UToledo Wright Center for Photovoltaics Innovation and Commercialization. “However, we needed to strengthen the emerging solar cell technology’s endurance during outdoor operation”. The technology needs to survive for decades outdoors in all kinds of weather and temperatures without corroding or breaking down.

Researchers from the Institute of Chemical Research of Catalonia-The Barcelona Institute of Science and Technology (ICIQ-BIST), Centre Tecnològic de Catalunya EURECAT, Istituto Italiano di Tecnologia (IIT), ICREA and Universitat Rovira i Virgili have reported the application of two carbazole-based self-assembled molecules (SAMs) as hole injecting materials in perovskite-based LEDs.

Their structures differ in one phenyl ring in the bridge; however, the extra ring provides more stability to the devices, even surpassing the one obtained with the widely used polymer PTAA. In addition, due to the structural and electronic characteristics of the SAMs, the efficiency of the devices is also increased.

A team of researchers from the X-ray Cancer Imaging and Therapy Experimental (XCITE) Lab at the University of Victoria in Canada set out to examine the potential of perovskite-based X-ray detectors. To do this, the team performed virtual clinical trials on next-generation perovskite detectors integrated into common X-ray imaging devices.

The team investigated the perovskite crystal methylammonium lead bromide (MAPbBr₃), which combines high charge carrier mobility and long carrier lifetimes, making it extremely sensitive to incident X-ray photons. Indeed, some MAPbBr₃ crystals show equivalent performance to that of cadmium zinc telluride (CZT), a promising material used in cutting edge medical imaging techniques such as photon-counting CT.