Tailoring the structural and electronic properties of an SnSe2/MoS2 van der Waals heterostructure with an electric field and the insertion of a graphene sheet.

van der Waals heterostructures (vdWHs), obtained by vertically stacking different two-dimensional (2D) layered materials are being considered intensively as potential materials for nanoelectronic and optoelectronic devices because they can show the most potential advantages of individual 2D materials. Here, we construct the SnSe2/MoS2 vdWH and investigate its electronic and optical properties using first-principles calculations. We find that the band structures of both MoS2 and SnSe2 monolayers are well kept in the SnSe2/MoS2 vdWH because of their weakly interacting features via vdW interaction. The SnSe2/MoS2 vdWH forms a type-I band alignment and exhibits an indirect semiconductor band gap of 0.45 eV. The type-I band alignment makes the SnSe2/MoS2 vdWH a promising material for optoelectronic nanodevices, such as light emitting diodes because of ultra-fast recombination of electrons and holes. Moreover, the band gap and band alignment of the SnSe2/MoS2 vdWH can be tailored by the electric field and the insertion of a graphene sheet. After applying an electric field, type-I to type-II and semiconductor to metal transitions can be achieved in the SnSe2/MoS2 vdWH. Besides, when a graphene sheet is inserted into the SnSe2/MoS2 vdWH to form three stacking types of G/SnSe2/MoS2, SnSe2/G/MoS2 and SnSe2/MoS2/G, the p-type semiconductor of the SnSe2/MoS2 vdWH is converted to an n-type Ohmic contact. These findings provide theoretical guidance for designing future nanoelectronic and optoelectronic devices based on the SnSe2/MoS2 vdWH.

First-principles investigation of a type-II BP/Sc2CF2 van der Waals heterostructure for photovoltaic solar cells.

Constructing heterostructures has proven to be an effective strategy to manipulate the electronic properties and enlarge the application possibilities of two-dimensional (2D) materials. In this work, we perform first-principles calculations to generate the heterostructure between boron phosphide (BP) and Sc2CF2 materials. The electronic characteristics and band alignment of the combined BP/Sc2CF2 heterostructure, as well as the effects of an applied electric field and interlayer coupling, are examined. Our results predict that the BP/Sc2CF2 heterostructure is energetically, thermally and dynamically stable. All considered stacking patterns of the BP/Sc2CF2 heterostructure possess semiconducting behavior. Furthermore, the formation of the BP/Sc2CF2 heterostructure gives rise to the generation of type-II band alignment, which causes photogenerated electrons and holes to move in opposite ways. Therefore, the type-II BP/Sc2CF2 heterostructure could be a promising candidate for photovoltaic solar cells. More interestingly, the electronic properties and band alignment in the BP/Sc2CF2 heterostructure can be tuned by applying an electric field and modifying the interlayer coupling. Applying an electric field not only causes modulation of the band gap, but also leads to the transition from a semiconductor to a gapless semiconductor and from type-II to type-I band alignment of the BP/Sc2CF2 heterostructure. In addition, changing the interlayer coupling gives rise to modulation of the band gap of the BP/Sc2CF2 heterostructure. Our findings suggest that the BP/Sc2CF2 heterostructure is a promising candidate for photovoltaic solar cells.