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The electronic structures and nonlinear optical (NLO) responses of eight triangle group‐VI transition metal dichalcogenides (TMDs) lateral‐core–shell heterostructures quantum dots (QDs) [MaX2MbX2 and MXa2MXb2; M (Ma, Mb) = Mo and W; X (Xa, Xb) = S and Se] have been explored by using quantum chemistry method. Frontier molecular orbital (FMOs) analyses indicate that the triangular frameworks with more active W and/or Se atoms at shell have smaller energy gaps than those with Mo and/or S atoms, and the active sites of the ultra‐small TMD heterostructures mainly locate at the edge and/or the corner of the frameworks. Generally speaking, active atoms at the shell are beneficial to the enhancement of the frequency‐dependent first hyperpolarizabilities compared with the active atoms in the cores. First hyperpolarizability density analyses show that the local contributions of the first hyperpolarizability in x direction is mainly located at the left and right corners, while that in y direction is mainly located at the bottom edge and top corner, confirming the important role that the shell of the TMDs lateral‐core–shell heterostructure QDs play in its NLO response. Further, the electronic transitions contributed to the SHG responses also occur at the shell of these triangular frameworks. [ABSTRACT FROM AUTHOR]

van der Waals heterostructures (vdWHs) based on two-dimensional (2D) materials have been extensively recognized as promising candidates for fabricating multi-functional novel devices. In this work, we investigated the structural and electronic properties of the InS–arsenene vdWH in some detail by using the first principles calculation method to explore its potential application in nanoelectronics. Numerical results show that the InS–arsenene vdWH possesses a stable structure, excellent flexibility, high carrier mobility and direct band gap semiconducting behavior. In particular, its electronic properties can be regulated effectively by vertical strain, in-plane strain and an external electric field. Vertical strain can tune the band gap of the semiconducting vdWH in a wide range with stable type-II band alignment. However, in-plane strain and an external electric field can even realize phase transitions from semiconducting to metallic behaviors, which implies great application potential of the InS–arsenene vdWH in multi-purpose nanoelectronic devices, optoelectronic devices and tunnel field-effect transistors (TFETs). This theoretical work would provide valuable guidance for fabricating the InS–arsenene vdWH and extending the application of InS and arsenene monolayers. [ABSTRACT FROM AUTHOR]

By first-principles calculations, we investigate the geometric stability, electronic and optical properties of the type-II PN-WSe2 and type-I PAs-WSe2 van der Waals heterostructures(vdWH). They are p-type semiconductors with indirect band gaps of 1.09 eV and 1.08 eV based on PBE functional respectively. By applying the external gate field, the PAs-WSe2 heterostructure would transform to the type-II band alignment from the type-I. With the increasing of magnitude of the electric field, two heterostructures turn into the n-type semiconductors and eventually into metal. Especially, PN/PAs-WSe2 vdWH are both high refractive index materials at low frequencies and show negative refractive index at high frequencies. Because of the steady absorption in ultraviolet region, the PAs-WSe2 heterostructure is a highly sensitive UV detector material with wide spectrum. The type-II PN-WSe2 heterostructure possesses giant and broadband absorption in the near-infrared and visible regions, and its solar power conversion efficiency of 13.8% is higher than the reported GaTe–InSe (9.1%), MoS2/p-Si (5.23%) and organic solar cells (11.7%). It does project PN-WSe2 heterostructure a potential for application in excitons-based solar cells. [ABSTRACT FROM AUTHOR]

The electro-optical properties of Indium Selenide/Black Arsenic Phosphorus (InSe/α-AsP) van der Waals heterojunction have been systematically investigated by using first-principles calculations. The presented two-dimensional (2D) heterojunction possesses a narrow direct bandgap (1.07 eV), with a high absorption coefficient in the infrared region and a cutoff wavelength of ~2 μm. Type-II band alignment is predicted which would lead to an efficient separation of electrons and holes. Charge carrier mobilities are calculated reaching up to 103 cm2V−1s−1 at room-temperature, which promises high-performance electron transport behavior. Lattice strain is revealed to tune the band structure but without changing the type-II band alignment of the InSe/α-AsP van der Waals heterojunction. These results suggest that InSe/α-AsP van der Waals heterojunction is a promising candidate for infrared photodetection devices. • We design a stable InSe/α-AsP vdW heterostructure with narrow direct band gap. • The InSe/α-AsP vdWH show a significant amount of optical absorption in the infrared region. • The InSe/α-AsP vdWH have higher efficiency of electron–hole separation and transfer because of its critical type-II band alignment. [ABSTRACT FROM AUTHOR]