In order to obtain the optimal photoelectric properties of vertical stacked MoS2/Si heterostructure solar cells, we propose a theoretical model to address the relationship among film thickness, atomic bond identities and related physical quantities in terms of bond relaxation mechanism and detailed balance principle. We find that the vertical stacked MoS2/Si can form type II band alignment, and its photoelectric conversion efficiency (PCE) enhances with increasing MoS2 thickness. Moreover, the optimal PCE in MoS2/Si can reach 24.76%, inferring that a possible design way can be achieved based on the layered transition metal dichalcogenides and silicon.

Recent advances in the fabrication of monolayer black phosphorus (MBP) call for a detailed understanding of the physics underlying the electronic structure and related modulation by the method of strain engineering. Here, we present an analytic study to explore the uniaxial strain effect of band structure in MBP based on the first-principles calculations and atomic-bond-relaxation correlation mechanism. It was found that the stress responses of MBP show evident anisotropy due to different edge type structures. The electronic band structure of MBP can be tuned by the applied strain. Moreover, we propose an analytic expression for the variation of the bandgap induced by the uniaxial strain from the perspective of atomistic origin, which suggests an effective bridge between the measurable quantities and the atomic bond identities of MBP. The underlying mechanism on the strain-dependent band offset can be attributed to the variation of crystal potential induced by the changes of bond length, strength, and angle, providing a better understanding of the modulation of electronic properties with strain engineering.

Two-dimensional molybdenum disulfide (MoS 2 ) attracts a great deal of interest owing to its potential application in the next generation of electronic devices in recent years. However, the physical mechanism on the strain engineering for the band offset in single-layer MoS 2 from the atomistic origin is still a challenge. Herein, we propose an analytical model to address the band offset in single-layer MoS 2 modulated by the uniaxial tensile strain based on atomic-bond-relaxation consideration. It was found that the bandgap of single-layer MoS 2 shows an approximately linearly red shift with a rate of ∼53.4 meV/% strain under uniaxial tensile strain. The underlying mechanism can be attributed to the variation of crystal potential induced by the changes of bond identities such as bond length, strength, and angle. The results were validated by comparing them with the available evidence, suggesting that the proposed model can be an effective method to clarify the modulation mechanism of relevant electronic properties in two-dimensional semiconductor nanostructures.

In order to explore the theoretical relationship between interlayer spacing, interaction and band offset at the atomic level in vertically stacked two-dimensional (2D) van der Waals (vdW) structures, we propose an analytical model to address the evolution of interlayer vdW coupling with random stacking configurations in MoS 2 bilayers based on the atomic-bondrelaxation correlation mechanism. We found that interlayer spacing changes substantially with respect to the orientations, and the bandgap increases from 1.53 eV (AB stacking) to 1.68 eV (AA stacking). Our results reveal that the evolution of interlayer vdW coupling originates from the interlayer interaction, leading to interlayer separations and electronic properties changing with stacking configurations. Our predictions constitute a demonstration of twist engineering the band shift in the emergent class of 2D crystals, transition-metal dichalcogenides.

Inserting an insulator at the interface in vdW heterostructure solar cell unit can improve the photoelectric conversion efficiency, and the insulator has an optimal thickness.