Researchers discover new method to control excitons


Scientists working with two-dimensional semiconductor materials have made a discovery which they say could eventually lead to the development of unique new materials for solar cells.

The team was working with a two-dimensional material named molybdenum disulfide (MoS2), which comprises a one atom layer of molybdenum between two layers of sulfur.

In their paper ‘Momentum-space indirect interlayer excitons in transition metal dichalcogenide van der Waals heterostructures’, published in the journal Nature Physics, the team outlines how it developed a multilayered ‘heterostructure’ consisting of layers of MoS2  and wolframite diselenide (WSe2).

The structure placed mono layers of the materials on top of each other, and led to the appearance of a new type of exciton (described as tightly bound electron-hole pairs, quasiparticles that act as a carrier of positive charge). In this type of exciton the electron and hole are spatially divided between the different layers.

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“Thanks to the use of spectroscopic methods and quantum-chemical calculations from the first principles, we have revealed a partially charged electron-hole in MoS2/WSe2 heterostructures, as well as [the electron-hole’s] location,” explained NUST Scientist Gotthard Seifert. “We have managed to control the radiation energy of this new exciton by changing the relative orientation of the layers”

The team states that it will now focus on further understanding and controlling the exciton effects observed here, and the effects of layer rotations on different materials electronic properties. “In the future,” says NUST’s press release, this will allow for the creation of unique new materials for solar panels or electronics.”

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