Excitons Could Make Electronic Devices More Energy Efficient

EPFL researchers have developed a new method that they believe may make electronic devices of the future more energy efficient. The team says that excitons are quasiparticles formed when electrons absorb light. These particles have the potential to revolutionize the building blocks of circuits.The team has been studying the properties of excitons to design more energy-efficient electronic systems and have found a way to control them better when they are moving in a semiconductor. Quasiparticles are a temporary phenomenon that results from the interaction between two particles within solid matter. Excitons are created when an electron absorbs a photon and moves into a higher energy state, leaving behind a hole in its previous energy state.

The electron and electron-hole are bound together via attractive forces, and the two together form what is called an exciton. When the electron falls back into the hole, it emits a photon, and the exciton ceases to exist. Last year the team was able to make a transistor that runs on excitons rather than electrons at room temperature.

To make the excitons last longer, the scientist layers two different 2D materials on top of each other. The materials were tungsten diselenide and diselenide. The material created had a shimmering texture that influenced how the quasiparticles were distributed. Within the materials, the excitons tended to group together in specific places and prevent current from flowing.

To prevent that from happening this time, the team added a middle layer of hexagonal form boron nitride that let them see the excitons and their energy levels more clearly. The group also figured out how to polarize the exciton currents so the quasiparticles could eventually be used to encode data. The team says this opens the door to more future applications in coding and data processing on a nanoscopic level.