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Adv Mater. 2017 Sep;29(33). doi: 10.1002/adma.201701512. Epub 2017 Jul 3.

Tunneling Photocurrent Assisted by Interlayer Excitons in Staggered van der Waals Hetero-Bilayers.

Luong DH1,2, Lee HS1,2, Neupane GP1,2, Roy S1,2, Ghimire G1,2, Lee JH1,2, Vu QA1,2, Lee YH1,2.

Author information

1
Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS), Suwon, 16419, Republic of Korea.
2
Department of Energy Science, Sungkyunkwan University, Suwon, 16419, Repulic of Korea.

Abstract

Vertically stacked van der Waals (vdW) heterostructures have been suggested as a robust platform for studying interfacial phenomena and related electric/optoelectronic devices. While the interlayer Coulomb interaction mediated by the vdW coupling has been extensively studied for carrier recombination processes in a diode transport, its correlation with the interlayer tunneling transport has not been elucidated. Here, a contrast is reported between tunneling and drift photocurrents tailored by the interlayer coupling strength in MoSe2 /MoS2 hetero-bilayers (HBs). The interfacial coupling modulated by thermal annealing is identified by the interlayer phonon coupling in Raman spectra and the emerging interlayer exciton peak in photoluminescence spectra. In strongly coupled HBs, positive photocurrents are observed owing to the inelastic band-to-band tunneling assisted by interlayer excitons that prevail over exciton recombinations. By contrast, weakly coupled HBs exhibit a negative photovoltaic diode behavior, manifested as a drift current without interlayer excitonic emissions. This study sheds light on tailoring the tunneling transport for numerous optoelectronic HB devices.

KEYWORDS:

interlayer excitons; photovoltaics; transition metal dichalcogenides; tunneling; van der Waals hetero-bilayers

PMID:
28671724
DOI:
10.1002/adma.201701512

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