Photoelectric current generation in a monolayer MoSe₂–WS₂ lateral heterojunction

Abstract

Based on density functional theory calculations and non-equilibrium Green's function method, we study the photovoltaic effect of monolayer MoSe2-WS2 lateral heterojunction under vertical irradiation. Combined with the differential charge density, it predicts the stability of the MoSe2-WS2 heterojunction and the high possibility of charge transfer from MoSe2 to WS2. As a result, such MoSe2-WS2 lateral heterojunction breaks the spatial inversion symmetry thus leading to a photocurrent. The resultant photocurrent increases from close to zero to a maximum value in the range of photon energy of 1.7 eV to 2.8 eV. The photocurrent response fits the cosine function with respect to the polarization angle. The peak photocurrent is obtained when the photon energy is 2.8 eV, and can be attributable to the large density state peaks near -1.3 eV in the valence band and 1.5 eV in the conduction band. Meanwhile, the single-layer MoSe2-WS2 lateral heterojunction exhibits higher polarization sensitivity that is characterized by an extinction ratio of up to 9.6. These results suggest possible applications of the single-layer MoSe2-WS2 lateral heterojunction in next generation optoelectronic devices.

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