Giant exciton-enhanced shift currents and direct current conduction with subbandgap photo excitations produced by many-electron interactions

Shift current is a direct current generated from nonlinear light–matter interaction in a noncentrosymmetric crystal and is considered a promising candidate for next-generation photovoltaic devices. The mechanism for shift currents in real materials is, however, still not well understood, especially...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 2021-06, Vol.118 (25), p.1-5
Main Authors: Chan, Yang-Hao, Qiu, Diana Y., da Jornada, Felipe H., Louie, Steven G.
Format: Article
Language:English
Subjects:
Continuous radiation
Direct current
Electron-hole interaction
Energy gap
Excitation
Excitons
First principles
Photoelectric effect
Photoelectric emission
Photovoltaic cells
Photovoltaics
Physical Sciences
Two dimensional materials
Wave propagation
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Summary:Shift current is a direct current generated from nonlinear light–matter interaction in a noncentrosymmetric crystal and is considered a promising candidate for next-generation photovoltaic devices. The mechanism for shift currents in real materials is, however, still not well understood, especially if electron–hole interactions are included. Here, we employ a first-principles interacting Green’s-function approach on the Keldysh contour with real-time propagation to study photocurrents generated by nonlinear optical processes under continuous wave illumination in real materials. We demonstrate a strong direct current shift current at subbandgap excitation frequencies in monolayer GeS due to strongly bound excitons, as well as a giant excitonic enhancement in the shift current coefficients at above bandgap photon frequencies. Our results suggest that atomically thin two-dimensional materials may be promising building blocks for next-generation shift current devices.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.1906938118