To a flourishing list of two-dimensional semiconductors, such as graphene, boron nitride, and molybdenum disulfide, whose singular electronic properties make them intensity successors to silicon in destiny devices, we can now supplement hybrid organic-inorganic perovskites. However, distinct a other contenders, that are covalent semiconductors, these 2D hybrid perovskites are ionic materials, that gives them special properties of their own.
Researchers during a U.S. Department of Energy (DOE)’s Lawrence Berkeley National Laboratory (Berkeley Lab) have successfully grown atomically skinny 2D sheets of organic-inorganic hybrid perovskites from solution. The ultrathin sheets are of high quality, vast in area, and square-shaped. They also exhibited fit photoluminescence, color-tunability, and a singular constructional decrease not found in covalent semiconductor sheets.
“We trust this is a initial instance of 2D atomically skinny nanostructures done from ionic materials,” says Peidong Yang, a chemist with Berkeley Lab’s Materials Sciences Division and universe management on nanostructures, who initial came adult with a thought for this investigate some 20 years ago. “The formula of a investigate open adult opportunities for elemental investigate on a singularity and characterization of atomically skinny 2D hybrid perovskites and introduces a new family of 2D solution-processed semiconductors for nanoscale optoelectronic devices, such as field outcome transistors and photodetectors.”
Yang, who also binds appointments with a University of California (UC) Berkeley and is a co-director of a Kavli Energy NanoScience Institute (Kavli-ENSI), is a analogous author of a paper describing this investigate in a biography Science. The paper is patrician “Atomically skinny two-dimensional organic-inorganic hybrid perovskites.” The lead authors are Letian Dou, Andrew Wong and Yi Yu, all members of Yang’s investigate group. Other authors are Minliang Lai, Nikolay Kornienko, Samuel Eaton, Anthony Fu, Connor Bischak, Jie Ma, Tina Ding, Naomi Ginsberg, Lin-Wang Wang and Paul Alivisatos.
Traditional perovskites are typically metal-oxide materials that arrangement a far-reaching operation of fascinating electromagnetic properties, including ferroelectricity and piezoelectricity, superconductivity and gigantic magnetoresistance. In a past integrate of years, organic-inorganic hybrid perovskites have been solution-processed into skinny films or bulk crystals for photovoltaic inclination that have reached a 20-percent energy acclimatisation efficiency. Separating these hybrid materials into individual, free-standing 2D sheets by such techniques as spin-coating, chemical fog deposition, and automatic exfoliation has met with singular success.
In 1994, while a PhD tyro during Harvard University, Yang due a process for scheming 2D hybrid perovskite nanostructures and tuning their electronic properties though never acted on it. This past year, while scheming to pierce his office, he came on a offer and upheld it on to co-lead author Dou, a post-doctoral tyro in his investigate group. Dou, operative especially with a other lead authors Wong and Yu, used Yang’s offer to harmonize free-standing 2D sheets of CH3NH3PbI3, a hybrid perovskite done from a mix of lead, bromine, nitrogen, CO and hydrogen atoms.
“Unlike exfoliation and chemical fog deposition methods, that routinely furnish comparatively thick perovskite plates, we were means to grow uniform square-shaped 2D crystals on a prosaic substrate with high produce and glorious reproducibility,” says Dou. “We characterized a structure and combination of particular 2D crystals regulating a accumulation of techniques and found they have a somewhat shifted band-edge glimmer that could be attributed to constructional relaxation. A rough photoluminescence investigate indicates a band-edge glimmer during 453 nanometers, that is red-shifted somewhat as compared to bulk crystals. This suggests that color-tuning could be achieved in these 2D hybrid perovskites by changing piece density as good as combination around a singularity of associated materials.”
The well-defined geometry of these square-shaped 2D crystals is a symbol of high peculiarity crystallinity, and their vast distance should promote their formation into destiny devices.
“With a technique, straight and parallel heterostructures can also be achieved,” Yang says. “This opens adult new possibilities for a pattern of materials/devices on an atomic/molecular scale with particular new properties.”