Recently, the U.S. Department of Energy (DOE) at the Argonne National Laboratory in Lemont, Illinois led the development of an important LED material.
The researchers of the reform laboratory team said: “LEDs are highly efficient, emit less heat, and last for a long time.” “Scientists are studying new materials to make LEDs more efficient and longer-lasting, and are used in consumer electronics, medicine, and Security field."
Researchers and partners from Brookhaven National Laboratory, Los Alamos National Laboratory, and SLAC National Accelerator Laboratory reported that they have prepared stable perovskite nanocrystals for this LED.
"Nature Photonics" published a paper describing the work of the group. "Our research shows that this method allows us to greatly improve the brightness and stability of luminescent nanocrystals," commented Xuedan Ma, a scientist at the Argonne Nanomaterials Center.
Perovskite nanocrystals are the main candidates for a new type of LED material. But for a long time, it proved to be unstable in testing.
The research team stabilized the nanocrystals in a porous structure called a metal-organic framework (MOF).
Based on the abundant materials on the earth and manufactured at room temperature, these LEDs may one day enable lower-cost TVs and consumer electronics, as well as better gamma-ray imaging equipment, even for medicine, security scanning, and science. Researched self-powered X-ray detector.
"We solved the stability problem by encapsulating the perovskite material in the MOF structure," said a scientist at the Argonne Center for Nanomaterials (CNM), Office of Scientific User Facilities, Department of Energy. "Our research shows that this method can help greatly improve the brightness and stability of luminescent nanocrystals."
"The operating concept of combining perovskite nanocrystals in MOF has been proven in powder form, but this is the first time we have successfully integrated it into the emission layer of an LED."
Previous attempts to manufacture nanocrystalline LEDs were hindered by the degradation of nanocrystals back to an unwanted volume phase, losing the advantages of nanocrystals and weakening their potential as practical LEDs.
Bulk matter usually consists of billions of atoms. Materials such as perovskites are composed of a few to a few thousand atoms in the nanometer stage, so they behave differently.
In their new method, the research team stabilized the nanocrystals by making nanocrystals in a matrix of MOF. They described MOF as "like a tennis ball caught by a barbed wire." They use lead nodes in the framework as metal precursors and halide salts as organic materials.
The halide salt solution contains methyl ammonium bromide, which reacts with the lead in the framework to assemble nanocrystals around the lead core in the matrix.
The matrix keeps the nanocrystals separated, so they do not interact and degrade. This method is based on a solution coating method, which is much cheaper than the widely used vacuum process for manufacturing inorganic LEDs.
MOF stable LEDs can produce bright red, blue, and green light, as well as different shades of each light.
Wani Nie, a scientist at the Center for Comprehensive Nanotechnology at Los Alamos National Laboratory, said: “In this work, we have demonstrated for the first time that perovskite nanocrystals that are stable in MOF will create bright and stable colors of various colors. LED." "We can create different colors, improve color purity, and increase photoluminescence quantum yield. This is a measure of the luminous ability of materials."
The research team used Advanced Photon Source (APS) for time-resolved X-ray absorption spectroscopy, a technique that allowed them to discover changes in perovskite materials over time. Researchers can track the movement of electric charges in the material and understand important information that occurs when light is emitted.
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