Magnetic and electronic properties of two-dimensional metal-organic frameworks TM_(3)(C_(2)NH)_(12)

The ferromagnetism of two-dimensional(2D)materials has aroused great interest in recent years,which may play an important role in the next-generation magnetic devices.Herein,a series of 2D transition metal-organic framework materials(TM-NH MOF,TM=Sc-Zn)are designed,and their electronic and magnetic characters are systematically studied by means of first-principles calculations.Their structural stabilities are examined through binding energies and ab-initio molecular dynamics simulations.Their optimized lattice constants are correlated to the central TM atoms.These 2D TM-NH MOF nanosheets exhibit various electronic and magnetic performances owing to the effective charge transfer and interaction between TM atoms and graphene linkers.Interestingly,Ni-and Zn-NH MOFs are nonmagnetic semiconductors(SM)with band gaps of 0.41 eV and 0.61 eV,respectively.Co-and Cu-NH MOFs are bipolar magnetic semiconductors(BMS),while Fe-NH MOF monolayer is a half-semiconductor(HSM).Furthermore,the elastic strain could tune their magnetic behaviors and transformation,which ascribes to the charge redistribution of TM-3d states.This work predicts several new 2D magnetic MOF materials,which are promising for applications in spintronics and nanoelectronics.

Electronic and optical properties of 3N-doped graphdiyne/MoS_(2) heterostructures tuned by biaxial strain and external electric field

The construction of van der Waals(vdW)heterostructures by stacking different two-dimensional layered materials have been recognised as an effective strategy to obtain the desired properties.The 3N-doped graphdiyne(N-GY)has been successfully synthesized in the laboratory.It could be assembled into a supercapacitor and can be used for tensile energy storage.However,the flat band and wide forbidden bands could hinder its application of N-GY layer in optoelectronic and nanoelectronic devices.In order to extend the application of N-GY layer in electronic devices,MoS_(2) was selected to construct an N-GY/MoS_(2) heterostructure due to its good electronic and optical properties.The N-GY/MoS_(2) heterostructure has an optical absorption range from the visible to ultraviolet with a absorption coefficient of 10^(5) cm^(-1).The N-GY/MoS_(2) heterostructure exhibits a type-II band alignment allows the electron–hole to be located on N-GY and MoS_(2) respectively,which can further reduce the electron–hole complexation to increase exciton lifetime.The power conversion efficiency of N-GY/MoS_(2) heterostructure is up to 17.77%,indicating it is a promising candidate material for solar cells.In addition,the external electric field and biaxial strain could effectively tune the electronic structure.Our results provide a theoretical support for the design and application of N-GY/MoS_(2) vdW heterostructures in semiconductor sensors and photovoltaic devices.

Hexagonal boron phosphide and boron arsenide van der Waals heterostructure as high-efficiency solar cell

The rapid development of two-dimensional(2D)materials offers new opportunities for 2D ultra-thin excitonic solar cells(XSCs).The construction of van der Waals heterostructure(vdWH)is a recognised and effective method of integrating the properties of single-layer 2D materials,creating particularly superior performance.Here,the prospects of h-BP/h-BAs vdW heterostructures in 2D excitonic solar cells are assessed.We systematically investigate the electronic properties and optical properties of heterogeneous structures by using the density functional theory(DFT)and first-principles calculations.The results indicate that the heterogeneous structure has good optoelectronic properties,such as a suitable direct bandgap and excellent optical absorption properties.The calculation of the phonon spectrum also confirms the well-defined kinetic stability of the heterstructure.We design the heterogeneous structure as a model for solar cells,and calculate its solar cell power conversion efficiency which reaches up to 16.51%and is higher than the highest efficiency reported in organic solar cells(11.7%).Our work illustrates the potential of h-BP/h-BAs heterostructure as a candidate for high-efficiency 2D excitonic solar cells.