Missouri S & T researchers have discovered an unprecedented and cost-effective method for creating high-performance inorganic thin films, or "epitaxial", used in semiconductor fabrication for flexible electronics, LEDs and solar cells.
The research is published today in Science in the article entitled "Spit Coating Epitaxial Films".
"We have developed an extremely simple method that has never been implemented before to make these films from a commercially available spin coating solution," says Dr. Jay Switzer, professor at the discovery of the Donald L. Castleman Foundation / Chemical Research in Chemistry at Missouri S & T. "This is an inexpensive and easily accessible route to monocrystalline materials that are expected to have superior electronic and optical properties.
"Our work with the highly ordered epitaxial deposits of cesium bromide and lead, a perovskite material, is a new semiconductor used in energy-efficient photovoltaic solar cells, and aims to increase the efficiency of solar cells. produced with this material, "adds Switzer.
Epitaxy is the growth of crystals, or thin films, whose orientation is determined by the crystalline substrate on which they are laminated. When the atomic structure of these crystals aligns perfectly with their substrate, the result is a film with superior electronic and optical properties capable of competing with the more expensive single crystal attributes.
Until now, the spin coating was mainly used for the manufacture of lithographic polymer coatings or for the deposition of organic semiconductor films on substrates, but the films thus obtained were either polycrystalline or without crystalline structure. They were not epitaxial with the degree of perfection sought corresponding to the current state of the art electronics.
"We have learned to use spin coating to make highly oriented films and nanocrystals on a variety of inorganic substrates," says Switzer. "Up to now, atomically perfect epitaxial films have been manufactured according to several other methods, some of which are very expensive and require a very high vacuum."
These methods include molecular beam epitaxy (MBE), chemical vapor deposition, liquid phase epitaxy, hydrothermal treatment, chemical bath deposition and electroplating. According to SBIR (Small Business Innovation Research), MBE machines cost about $ 1 million and much more for larger production systems; and Switzer says, every MBE machine must be dedicated to a single material. Other epitaxial methods are limited by the high demands of temperature and pressure.
The research team showed that, over a two-year period, epitaxial films in inorganic materials such as the crystalline structures of lead iodide, zinc oxide, sodium chloride and perovskite could be deposited on single crystals or comparable substrates. materials.
Perovskite LED lights with photonic crystals
Epitaxial spin coating films. Science. DOI: 10.1126 / science.aaw6184
Researchers discover cost-effective way to produce high-performance thin films for electronics (April 12, 2019)
recovered on April 12, 2019
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