Scotch tape contraption crafted to improve LED resolution

A cover story appearing in the peer-reviewed journal Nanoscale Horizons reports a new bilayer material, with each layer measuring less than one nanometer in thickness that someday could lead to more efficient and versatile light emission. Researchers working at the Ultrafast Laser Lab at the University of Kansas successfully created the material by combining atomically thin layers of molybdenum disulfide and rhenium disulfide.

“Both absorb light very well as semiconductors, and they’re both very flexible can be stretched or compressed,” said Hui Zhao, associate professor of physics and astronomy at KU, who co-authored the paper. “The goal of this whole direction of research is to produce light-emitting devices, such as LEDs that are ultrathin just a few nanometers thick and flexible enough that you can bend it. We showed through this bilayer material, it can be achieved.”

To explain the breakthrough, Zhao likens the behavior of electrons in the new material to a classroom. “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 KU researcher said that 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,” he said. Previous studies by several groups, including Zhao’s, have produced various bilayer materials by stacking different types of atomic sheets.