Optoelectronic devices play an essential role in the modern world by converting an electric current to light (as exemplified by the ubiquitous LED lights), or conversely, by capturing light to produce electricity (as in solar cells). A class of materials offering significant potential for highly cost-effective optoelectronics are the so-called hybrid perovskites. In practice, the use of hybrid perovskites faces several challenges, including rapid changes in output in response to a voltage. Previous experiments were unable to directly observe the chemical origin of these changes. Using nanoprobe x-ray fluorescence at the U.S. Department of Energy’s Advanced Photon Source, researchers have for the first time directly measured nanoscale changes in the chemical composition of crystals of methylammonium lead bromide, a leading hybrid perovskite candidate for optoelectronic devices. The experiments revealed how the presence of an applied voltage depleted the bromine within regions of the material, degrading its optoelectronic performance. The researchers contend that limiting bromine migration within methylammonium lead bromide, and in similar hybrid perovskites, should stabilize these compounds, thereby enhancing their outstanding optoelectronic properties and promoting their use for inexpensive, yet highly-efficient, solar cells, photonic lasers, photodetectors, and light-emitting diodes
Researchers using the U.S. Department of Energy’s Advanced Photon Source have been able to decipher a key aspect of the behavior of perovskites made with different formulations: With certain additives there is a kind of “sweet spot” where sufficient amounts will enhance performance and beyond which further amounts begin to degrade it.
A team of researchers from Argonne National Laboratory has developed a new device for quickly acquiring high-resolution x-ray images over large sample areas. Dubbed the Velociprobe, the new instrument utilizes a technique called “x-ray ptychography.”
To better understand amorphous-amorphous phase separation that can reduce or even halting active drug release, researchers used high-brightness x-rays at the U.S. Department of Energy’s Advanced Photon Source, opening the way to some promising opportunities for the development and design of new and improved systems.
Work is based on research at two U.S. Department of Energy x-ray light sources including the Advanced Photon Source is part of a new study that solves a key, fundamental barrier in the electrochemical water splitting process and demonstrates a new technique to reassemble, revivify, and reuse a catalyst that allows for energy-efficient water splitting.
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A team of researchers used a combination of high-resolution structural imaging, magnetic domain imaging, and dichroic spectroscopy on three separate x-ray beamlines at the U.S. Department of Energy’s Advanced Photon Source to shed light on coupled structural and magnetic phase transitions. Through this combination of three individually powerful x-ray techniques, the team was able to provide added insights into the phase transition process and the nature of the coupling between the magnetic and structural order.
Retrieving phase information from hard (high-energy) x-ray diffraction patterns is one way to improve sample imaging. One such phase-retrieval technique uses multiple overlapping diffraction patterns derived from a coherent x-ray beam. Using this scheme, highly-detailed three-dimensional (3-D) images of a sample's nanostructure have been obtained, along with additional information such as variations in the local strain field. However, phase-retrieval techniques face certain limitations, such as the need to rotate the sample. In this study, researchers implemented a new phase-retrieval technique called 3-D Bragg projection ptychography (3DBPP). A major advantage of this method is that the sample remains fixed. Utilizing a specially-tailored micro-electronic prototype device, the researchers used the 3DBPP technique to create a nanoscale 3-D reconstruction of the device's lattice distortions, thereby revealing its internal strains. Employing the highly-intense and coherent x-rays of the U.S. Department of Energy’s Advanced Photon Source was essential to the experiment. The comparative simplicity of 3DBPP, coupled with its powerful 3-D imaging and strain field capabilities, is expected to find application in a wide variety of experimental settings for improved 3-D x-ray microscopy of crystalline materials.
Researchers used the U.S. Department of Energy’s Advanced Photon Source to help them invent an innovative way for different types of quantum technology to “talk” to each other using sound. The study is an important step in bringing quantum technology closer to reality.
A team of engineers has created hardware made of hydrogen-doped nickelate perovskite that can learn skills using a type of AI that currently runs on software platforms. They used two U.S. Department of Energy x-ray light sources and a DOE nanoscale science research center to understand the microscopic origins of tree-like memory in the hydrogen-doped material.
Ferroelectric Domain Wall Movement in a Complex Oxide Thin Film: Research at the U.S. Department of Energy’s Advanced Photon Source and Center for Nanoscale Materials demonstrate the feasibility of transferring thin-film lead zirconium titanate and other complex oxides to silicon, thereby promoting their use for applications including non-volatile computer memory and quantum computing.
Hydrogen fuel cells can be used for portable technologies that must function for long periods without recharging. Such fuel cells often use metal hydrides to store hydrogen, and work much the same way as lithium-ion battery cathodes that store lithium. They have the same problems, too: charging and draining the metal hydride stresses the material and causes tiny defects to form, defects that degrade the material’s ability to store hydrogen. Eventually the storage material can only hold a fraction of the hydrogen it could originally, much like an old lithium battery in a cell phone that ceases to hold a charge. Materials scientists have known that the strain on the storage material is the primary reason for degradation, but they didn’t know the details. Now, for the first time, researchers working at the U.S. Department of Energy’s Advanced Photon Source (APS) have obtained detailed images of strain defects caused by repeated charge/discharge cycles in hydrogen. Their work shows the optimal size for a particle of metal hydride in a palladium-hydride storage system, and it could ultimately help engineer storage materials that take strain in controlled ways that do not damage, but rather improve them.
Scientists using two synchrotron x-ray light sources including the U.S. Department of Energy’s Advanced Photon Source have an explanation for the cause of performance-reducing “voltage fade” that currently plagues a promising class of cathode materials called lithium-rich NMC (nickel magnesium cobalt) layered oxides.
New research at the U.S. Department of Energy’s Advanced Photon Source promises new insights for the optimization of high-performance materials for aerospace and power generation.
Results obtained at the U.S. Department of Energy’s APS promise unprecedented imaging of complex crystalline materials and polycrystalline interfaces and will encourage broader use of coherent x-ray diffraction imaging experiments at fourth-generation x-ray light sources.
Nanoscale Defects Could Boost Energy Storage Materials: Some imperfections pay big dividends. X-ray nanoimaging at the U.S. Department of Energy’s Advanced Photon Source yields an unprecedented view into solid-state electrolytes, revealing previously undetected crystal defects and dislocations that may now be leveraged to create superior energy storage materials.
Better-Educated Neural Networks for Nanoscale 3-D Coherent X-ray Imaging: One of the inescapable realities of various imaging techniques is called the phase problem: the loss of phase information in imaging methods such as x-ray diffraction. Researchers working at the U.S. Department of Energy’s Advanced Photon Source have demonstrated a new approach to this perennial obstacle: a deep-learning neural network with enhanced accuracy to perform fast 3-D nanoscale imaging from coherent x-ray data.
Materials Properties for Longer-Lasting, More Efficient Solar Cells: The designers of solar cells know the cells must contend with a wide range of temperatures and weather conditions that can impact efficiency and useful lifetime. Researchers using the U.S. Department of Energy’s Advanced Photon Source found that small tweaks to the chemical makeup of perovskites and the magnitude of the electrical field it is exposed to can greatly affect overall material stability.
In recent work carried out at two U.S. Department of Energy x-ray light sources, including the Advanced Photon Source, a novel tool was developed to obtain impressive spatial resolutions (e.g., 36 nanometers) in intact cells. which may allow for previously inaccessible structures and molecules to be imaged at a high resolution.