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Janus monolayers and their van der Waals heterostuctures are investigated by hybrid density functional theory calculations.

The stacking of monolayers in the form of van der Waals heterostructures is a useful strategy for band gap engineering and the control of dynamics of excitons for potential nano-electronic devices. We performed first-principles calculations to investigate the structural, electronic, optical and photocatalytic properties of the SiC-MX (M = Mo, W and X = S, Se) van der Waals heterostructures. The stability of most favorable stacking is confirmed by calculating the binding energy and phonon spectrum. SiC-MoS is found to be a direct band gap type-II semiconducting heterostructure. Moderate in-plane tensile strain is used to achieve a direct band gap with type-II alignment in the SiC-WS, SiC-MoSe and SiC-WSe heterostructures. A difference in the ionization potential of the corresponding monolayers and interlayer charge transfer further confirmed the type-II band alignment in these heterostructures. Furthermore, the optical behaviour is investigated by calculation of the absorption spectra in terms of ε(ω) of the heterostructures and the corresponding monolayers. The photocatalytic response shows that the SiC-Mo(W)S heterostructures can oxidize HO to O. An enhanced photocatalytic performance with respect to the parent monolayers makes the SiC-Mo(W)Se heterostructures promising candidates for water splitting.

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Based on (hybrid) first-principles calculations, material properties (structural, electronic, vibrational, optical, and photocatalytic) of van der Waals heterostructures and their corresponding monolayers (transition metal dichalcogenides and MXenes) are investigated.

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Stacked layers in the form of van der Waals (vdW) heterostructures can significantly extend the applications of its building materials. In this study, based on hybrid functional (HSE06) with vdW corrections, we systematically investigated the electronic structure and optical properties of BlueP/Sc2CX2 (X=O,F,OH) vdW heterostructures and their corresponding monolayers. All three heterostructures are indirect bandgap semiconductors with type-II band alignment. The calculated bandgap of BlueP/Sc2CF2 is found to be 1.528 eV. A small amount of charge transfers from BlueP to Sc2CF2 and from Sc2CO2 [Sc2C(OH)2] to BlueP, rendering it p- and n-doped, respectively. The formation of heterostructures enhanced the optical absorption in the visible light region as compared to their parent monolayer, particularly in BlueP/Sc2CF2 and BlueP/Sc2C(OH)2. Heterostructures show excellent device absorption efficiencies (70%–80%) from infrared to ultraviolet spectrum of light. These results suggest that BlueP/Sc2CX2 heterostructures are potential for nanoelectronics, optoelectronics, and photovoltaic device applications.