Abstract
Van der Waals heterostructures based on the heteroassembly of 2D materials represent a recently developed class of materials with promising properties especially for optoelectronic applications. The alignment of electronic energy bands between consecutive layers of these heterostructures crucially determines their functionality. In the present paper, relying on dispersion-corrected density-functional theory calculations, we present electrostatic design as a promising tool for manipulating this band alignment. The latter is achieved by inserting a layer of aligned polar molecules between consecutive transition-metal dichalcogenide (TMD) sheets. As a consequence, collective electrostatic effects induce a shift of as much as 0.3 eV in the band edges of successive TMD layers. Building on that, the proposed approach can be used to design electronically more complex systems, like quantum cascades or quantum wells, or to change the type of band lineup between type II and type I.
Highlights
Research on two-dimensional (2D) materials has been growing rapidly since the successful exfoliation of graphene [1]
This problem can, be overcome by realizing a kinetically trapped configuration where first a TiOPc layer is deposited onto a MoS2 surface and, subsequently, the transition-metal dichalcogenide (TMD) layer is covered with a second MoS2 flake [33, 34]
Electronic structure of the MoS2|TiOPc|MoS2 system To characterize the electronic structure of the investigated systems, it is useful to discuss densities of states projected onto either individual TMD layers or onto the intercalated molecules (PDOSs); the corresponding band-structures can be found in the supporting information
Summary
Research on two-dimensional (2D) materials has been growing rapidly since the successful exfoliation of graphene [1]. Amongst them, semiconducting transitionmetal dichalcogenides (TMDs) have proven to be especially interesting, on the one hand, for gaining fundamental physical insights and, on the other hand, for optoelectronic applications. This is associated with the emergence of spin and valley physics [2,3,4] and strong light–matter interactions [5,6,7] observed in these systems. The latter result in large absorption coefficients and, for properly designed band-offsets, either in significant electron–hole pair creation or exciton recombination, two properties highly relevant for optoelectronics. Of particular interest in this context is the combination of semiconducting organic molecules with 2D materials to change their characteristics either via doping [8, 9] or by the exploitation of dielectric effects [10]
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