Doping of solution-processed two-dimensional transition metal dichalcogenides

Semiconducting transition metal dichalcogenides (TMDs) such as MoS2, WSe2 or WS2 have attracted a lot of interest in recent years because of their outstanding optoelectronic properties including tunable bandgap or strong light absorption in the visible range, even at sub-micrometer thickness. Furthermore, doping these materials with transition metal atoms is an approach which can additionally modify a TMDs’ optoelectronic properties and therefore could enable these TMDs to take part in new applications. Indeed, one method to exfoliate TMD materials is the electrochemical intercalation of TMDs with THA+ molecules. Recently this method was altered to make it more scalable, using annealed pellets made from commercially available powder. This method is readily adaptable such that bulk TMDs are doped in the annealing phase before being exfoliated into doped 2D TMD nanoflakes. In this work we present an extensive study regarding p-type doping of MoS2 with Niobium (Nb) for different atomic concentrations. We confirm the incorporation of the dopant agent to the TMD crystal lattice and observe consequential changes in the optoelectronic properties of the resulting nanoflakes. Besides, from 0.75% Nb doping the intrinsic n-type MoS2 displays ambipolar due to the p-type behavior added by Nb atoms. Consequently, NbMoS2 shows promise as a building block of ultra-thin ambipolar field effect transistors (FETs). We follow up with the incorporation of n-type dopant agent Rhenium (Re) as preliminary story. Here, Re is also confirmed to enter at MoS2 crystal structure. However, as it stands 0.5% and 1% Re doping to MoS2 are not beneficial for PEC performance of this material. Finally, we show that this method can also be used for other TMDs such as p-type WSe2 and n-type WS2, showcasing the universality of this method. Here, dopant agent incorporation to the TMDs crystal lattices is also confirmed and therefore optoelectronic properties of WSe2 and WS2 are also demonstrated to change because of Nb addition. In summary, we successfully dope 2D TMD materials using a scalable, solution-processable method and we show that these doped materials have potential in future ultrathin optoelectronic devices.Outgoin