New Class of Flexible Photodetectors

Artistic view of the photo-thermionic effect in a graphene-WSe2-graphene heterostructure (Source: ICFO)

Artistic view of the photo-thermionic effect in a graphene-WSe2-graphene heterostructure (Source: ICFO)

A research group led by Frank Koppens at the Institute of Photonic Sciences  ICFO in Barcelona demonstrate a novel way to detect low-energy photons using vertical hetero­structures made by stacking graphene and other 2D semi­conducting materials. By studying the photo­response of these atomi­cally thin sandwiches, the researchers have shown that it is possible to generate a current by heating electrons in graphene with infrared light and extracting the hottest electrons over a vertical energy barrier.

This ingenious mechanism, named photo-thermio­nic effect, takes advantage of the unique optical properties of graphene such as its broadband absorption, ultrafast response and gate-tuna­bility. Moreover, owing to their vertical geometry, devices relying on this effect make use of the entire surface of graphene and can be poten­tially scaled up and integrated with flexible or rigid platforms.

More generally, this study reveals once again the amazing pro­perties of these man-made hetero­structures. According to Prof. Frank Koppens “this is just the tip of the iceberg, these 2D sandwiches still have a lot to reveal”. ICFO researcher Mathieu Massi­cotte, first author of this study, emphasizes the new possi­bilities opened up by these new materials: “Everyone knows it is possible to detect light with graphene using in-plane geo­metries, but what about the out-of-plane direction? To answer, you need to think outside the 2D box!”

The results obtained from this study have shown that hetero­structures made of 2D materials and graphene can be used to detect low-energy photons which could lead to new, fast and efficient opto­electronic applic­ations, such as high-speed integrated commu­nication systems and infrared energy harvesting. In addition, it demonstrates the compa­tibility of 2D materials with the digital chips currently utilized in cameras, paving the way for low cost infrared spectro­meters and imaging systems. (Source: ICFO)

Reference: M. Massicotte et al.: Photo-thermionic effect in vertical graphene heterostructures, Nat. Comm. 7, 12174; DOI: 10.1038/ncomms12174

Link: Institute of Photonic Sciences ICFO, Barcelona, Spain

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