|Taken from the cover of Nanoscale Horizons,|
Volume 2 Number 1 January 2017
“One can think of a material as a classroom full of students — which are the electrons — one on each seat,” he said. “Sitting on a seat, a student — or electron — can’t move freely to conduct electricity. Light can provide enough energy to stand up some of the students, who can now move freely and, as electrons, to conduct electricity. This process is the foundation for photovoltaic devices, where the energy of sunlight is captured and converted to electricity.” The emission of light involves the inverse process, in which a standing electron sits down in a seat, releasing its kinetic energy in the form of light. “To make a good material for light emission devices, one needs not only the electrons that carry energy, but also the ‘seats’ — called holes — for the electrons to sit down.”
Previous scientific studies, including some by Zhao, had already used the method of stacking different types of atomic sheets to create bilayer materials; however, those materials had the electrons and the “seats” located in different atomic layers. Because it is difficult for electrons to find "seats," light emission efficiency of prior bilayer materials was very low – more than 100 times lower than if both electrons and “seats” were located in one atomic layer. Within this newly produced bilayer material, the electrons and their seats will be located in their original layer, instead of separate layers. Thus, the new bilayer material will produce light emissions that are much stronger.
A cover story appearing in the January 2017 edition of the peer-reviewed journal Nanoscale Horizons by Zhao and his fellow researchers Matthew Bellus, Samuel Lane, Frank Ceballos and Qiannan Cui, all KU physics graduate students, and Ming Li and Xiao Cheng Zeng of the University of Nebraska-Lincoln, titled Type-I van derWaals heterostructure formed by MoS2 and ReS2 monolayers details the how the low tech “Scotch tape” method was used to create the new bilayer material.
Funding for this Research partially provided by the Kansas and Nebraska NSF EPSCoR Track 2 Grant #1430519 titled: "Imaging and Controlling Ultrafast Dynamics of Atoms, Molecules, and Nanostructures." The grant's educational objectives are designed to enhance STEM education in Kansas by supporting activities that will lead to an expanded STEM workforce or prepare a new generation for STEM careers in the areas of atomic/molecular/optical science.
For additional information on this discovery, go to KU Today article, Using 'Scotch tape' and laser beams, researchers craft new material that could improve LED screensat at https://goo.gl/w1HKyh