Front Cover Image

Abstract

The easy transferability and feasible epitaxial growth of two‐dimensional semiconductors pave a promising way to further tune their optoelectronic properties by constructing van der Waals heterostructures. The authors herein performed a high‐throughput first‐principles study of electronic structure and optical properties of the layer‐by‐layer stacking heterostructing superlattices of two‐dimensional transition metal dichalcogenides. The indirect‐to‐direct band‐gap transition or even semiconductor‐to‐metal transition can be realized by varying component compositions of superlattices. The results provide useful guidance for engineering optoelectronic properties by forming heterostructures and superlattices in two‐dimensional semiconductors. (DOI: https://doi.org/10.1002/inf2.12155)

Funnel Devices Based on Asymmetrically Strained Transition Metal Dichalcogenides

“…[45] According to theoretical calculations, the conduction band minimum is reduced by the tensile strain, whereas the valence band maximum is less affected by the strain compared to the conduction band minimum. [40,46,47] Thus, in the case of WS 2 or MoS 2 flake transferred on the fork-shaped microstructure, the conduction band minimum in the strained regions tilts in the direction opposite to the direction of strain increase. The photogenerated excitons then move toward a more strained region, resulting in a funnel effect (Figure 4a).…”

Bright and Efficient Light‐Emitting Devices Based on 2D Transition Metal Dichalcogenides

“…As mentioned earlier, TMDCs fall within the range of materials proved suitable for building LEDs and other optoelectronic applications owing to their direct bandgap at monolayer limit, [60,65,158,159] exciton dominant optical properties, [160][161][162] and easy van der Waals heterostructure construction. [54,71,[163][164][165] The next consideration regarding the appropriateness of any material for light emission is to determine how efficiently it can emit light in response to the excitation. The luminescent efficiency of an optical material is dictated by its PL QY, defined by Equation (3), where R r and R nr denote the radiative and the nonradiative recombination rates, respectively.…”

Electronic property modulation in two-dimensional lateral superlattices of monolayer transition metal dichalcogenides

“…Conversely, in the vertical SLs, changes in the stacking sequence will significantly affect the electronic band structure owing to the changes in the symmetry and QCE. 18,[74][75][76] Thus, it suggests that constructing 2D lateral TMD-SLs is an excellent strategy to tune the target physical properties without changing the basic electronic band structure.…”

“…For van der Waals HSs, the selected constituent sub-lattices can be combined freely to design new materials and functionalities owing to their high in-plane stability imparted by strong covalent bonds and high assemblability benefiting from weak interlayer van der Waals interaction. 9,[13][14][15][16][17][18][19][20][21][22][23][24] However, these vertical HSs have no apparent charge transfer between layers due to weak interlayer coupling, and the electronic states of the constituent sub-lattices are not significantly changed, limiting the amplitude of property modulation. Conversely, the constituent sub-lattices of 2D lateral SLs are joined via covalent bonds.…”