By manipulating excitons, researchers come up with a new approach to energy-efficient electronics
Researchers have developed a transistor based on excitons, a type of particle that is able to function at room temperature. To achieve this, they used two 2D materials as semiconductors.
This breakthrough sets the stage for optoelectronic devices that consume less energy and are both smaller and faster than current devices. With this, it will be possible to integrate optical transmission and electronic data-processing systems into the same device. Further, it will reduce the number of operations needed and make the systems more efficient.
Exciton to photon
Excitons are actually quasiparticles and it consists of an electron and an electron hole. The two are bound together when the electron absorbs a photon and achieves a higher level of energy.
The process follows the principle of Valence bond where the excited electron leaves behind a hole in the previous level of energy. This hole is a quasiparticle which is an indication of the missing electron in this band.
Since the electron is negatively charged and the hole is positively charged, the two particles remain bound by an electrostatic force. This bond between the electron and the hole, called Coulomb attraction. And this state of tension and balance forms an exciton.
When the electron finally falls back into the hole, it emits a photon. And with that, the exciton ceases to exist.
2D material used as the semiconductor
The lifespan of excitons is short and the energy it contained is considered to be fragile. In addition, excitons could only be produced and controlled in circuits at extremely low temperatures (around -173 ºC).
To deal with such a situation the researchers used two 2D materials: tungsten diselenide (WSe2) and molybdenum disulfide (MoS2). The excitons in these materials exhibit a particularly strong electrostatic bond and are not quickly destroyed at room temperature.
Hence, they created a special type of exciton where the two sides are farther apart than in the conventional particle. This delays the process in which the electron returns to the hole and light is produced. It’s at this point when the excitons remain in dipole form for slightly longer that they can be controlled and moved around using an electric field.