Multiple hot-carrier collection in photo-excited graphene Moiré superlattices

Sanfeng Wu, Lei Wang, You Lai, Wen Yu Shan, Grant Aivazian, Xian Zhang, Takashi Taniguchi, Kenji Watanabe, Di Xiao, Cory Dean, James Hone, Zhiqiang Li, Xiaodong Xu

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Abstract

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 Moiré 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 Moiré minibands. Our observation points to a new means for extremely efficient and flexible optoelectronics based on van der Waals heterostructures.

Original languageEnglish (US)
Article numbere1600002
JournalScience Advances
Volume2
Issue number5
DOIs
StatePublished - May 2016

All Science Journal Classification (ASJC) codes

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    Wu, S., Wang, L., Lai, Y., Shan, W. Y., Aivazian, G., Zhang, X., Taniguchi, T., Watanabe, K., Xiao, D., Dean, C., Hone, J., Li, Z., & Xu, X. (2016). Multiple hot-carrier collection in photo-excited graphene Moiré superlattices. Science Advances, 2(5), [e1600002]. https://doi.org/10.1126/sciadv.1600002