期刊
SCIENCE ADVANCES
卷 2, 期 5, 页码 -出版社
AMER ASSOC ADVANCEMENT SCIENCE
DOI: 10.1126/sciadv.1600002
关键词
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资金
- NSF [DMR-1150719]
- Air Force Office of Scientific Research [FA9550-14-1-0277]
- NSF Cooperative Agreement [DMR-1157490]
- state of Florida
- User Collaboration Grant Program at NHMFL
- Office of Naval Research [N00014-13-1-0662]
- Institute for Nanoelectronics Discovery and Exploration (Nano Electronics Research Corporation) [2013-NE-2399]
- Boeing Distinguished Professorship
- Clean Energy Institute - state of Washington
- Direct For Mathematical & Physical Scien
- Division Of Materials Research [1150719] Funding Source: National Science Foundation
In conventional light-harvesting devices, the absorption of a single photon only excites one electron, which sets the standard limit of power-conversion efficiency, such as the Shockley-Queisser limit. In principle, generating and harnessing multiple carriers per absorbed photon can improve efficiency and possibly overcome this limit. We report the observation of multiple hot-carrier collection in graphene/boron-nitride Moire superlattice structures. A record-high zero-bias photoresponsivity of 0.3 A/W (equivalently, an external quantum efficiency exceeding 50%) is achieved using graphene's photo-Nernst effect, which demonstrates a collection of at least five carriers per absorbed photon. We reveal that this effect arises from the enhanced Nernst coefficient through Lifshtiz transition at low-energy Van Hove singularities, which is an emergent phenomenon due to the formation of Moire minibands. Our observation points to a new means for extremely efficient and flexible optoelectronics based on van der Waals heterostructures.
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