Structural and electronic properties of defective 2D transition metal dichalcogenide heterostructures.
We present a first-principles study on the structure-property relationships in MoS2 and WS2 monolayers and their vertically stacked hetero-bilayer, with and without Sulfur vacancies, in order to dissect the electronic features behind their photocatalytic water splitting capabilities. We also benchmark the accuracy of three different exchange-correlation density functionals for both minimum-energy geometries and electronic structure. The best compromise between computational cost and qualitative accuracy is achieved with the HSE06 density functional on top of Perdew-Burke-Ernzerhof minima, including dispersion with Grimme's D3 scheme. This computational approach predicts the presence of mid-gap states for defective monolayers, in accordance with the present literature. For the heterojunction, we find unexpected vacancy-position dependent electronic features: the location of the defects leads either to mid-gap trap states, detrimental for photocatalyst or to a modification of characteristic type II band alignment behavior, responsible for interlayer charge separation and low recombination rates.
['Pecoraro|Adriana|A|', 'Schiavo|Eduardo|E|', 'Maddalena|Pasqualino|P|', 'Muñoz-García|Ana B|AB|', 'Pavone|Michele|M|https://orcid.org/0000-0001-7549-631X']
defect electronic structure heterojunction DFT transition-metal dicalchogenides