Band Edge Tailoring in Few-Layer Two-Dimensional Molybdenum Sulfide/Selenide Alloys

Abstract

Chemical alloying is a powerful approach to tune the electronic structure of semiconductors, 36 and has led to the synthesis of ternary and quaternary two-dimensional (2D) dichalcogenide 37 semiconductor alloys (e.g. MoSSe 2 , WSSe 2 etc.). To date, most studies have been focused on 38 determining the chemical composition by evaluating the optical properties, primarily via 39 photoluminescence and reflection spectroscopy of these materials in the 2D monolayer limit.However, a comprehensive study of alloying in multilayer films with direct measurement of 41 electronic structure, combined with first principles theory, is required for a complete understanding 42 of this promising class of semiconductors. We have combined first-principles density functional 43 theory calculations with experimental characterization of MoS 2(1-x) Se 2x (where x ranges from 0 to 44 1) alloys using X-ray photoelectron spectroscopy to evaluate the valence and conduction band 45 edge positions in each alloy. Moreover, our observations reveal that the valence band edge energies 46 for molybdenum sulfide/selenide alloys increase as a function of increasing selenium 47 concentration. These experimental results agree well with the results of density functional theory 48 calculations showing a similar trend in calculated valence band edges. Our studies suggest that 49 alloying is an effective technique for tuning the band edges of transition-metal dichalcogenides, 50 with implications for applications such as solar cells and photoelectrochemical devices.

Flexible Substrate‐Structured Sb2S3 Solar Cells with Back Interface Selenization

“…The heterojunction composed of Sb 2 S 3 and CdS films can realize efficient separation and transfer of electron-hole pairs. The energy band alignments among the various layers of the device extracted from the literature [36][37][38] are shown in Figure 1b. The photo-generated electrons in the Sb 2 S 3 film can be extracted by the Ag electrode, and the holes can be extracted by the Mo foil.…”

Electronic structure of strain-tunable Janus WSSe–ZnO heterostructures from first-principles

“…Leveraging control over the CB energies has been studied as a means of attempting to tune product selectivity amongst the various competing CO 2 RR products and HER. 6 Nonetheless, it is still informative to consider the band edges of the Janus TMD-ZnO heterostructures relative to both the OER and HER, knowing that the CO 2 RR potentials are in the neighborhood of the HER potentials. 1,2 The redox potentials for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) at pH = 0 are plotted on the band edge plots in Fig.…”

“…For example, pristine MoS 2 , which has been demonstrated to catalyze the hydrogen evolution reaction (HER) and CO 2 RR, exhibits rapid carrier recombination, has band edge energies that do not inherently align well with those of the relevant redox potentials requiring an applied bias, and tends to denature under aqueous operating conditions. [3][4][5][6] This motivates the search for novel methods of tuning the electronic and structural properties of TMDs for improved photocatalytic performance.…”

“…Examples that have been probed experimentally include changing the element used for the second type of cation in ternary metal vanadate photoanodes or producing alloys of TMDs with controllable fractions of mixed chalcogens or transition metals. 6,7 An alternative method is introducing a polar material in proximity to the photocatalyst whose dipole moment can rigidly shi the band edges of the photocatalyst. Examples of this approach in past work include generating a heterostructure of a monolayer TMD on top of the polar surface of the bulk ferroelectric BiFeO 3 or passivating the surface of a bulk semiconductor, like CdSe, with polar surface ligands.…”

Chalcogen···Chalcogen Bonding in Molybdenum Disulfide, Molybdenum Diselenide and Molybdenum Ditelluride Dimers as Prototypes for a Basic Understanding of the Local Interfacial Chemical Bonding Environment in 2D Layered Transition Metal Dichalcogenides

“…Transition metal dichalcogenides (TMDCs or TMDs), MCh 2 (M = a transition metal; Ch = a chalcogen, an element of group 16) are a special class of exotic 2D layered materials well known to the chemistry and physics community for decades [1][2][3][4]. Formally, in MCh 2 , the metal cation is in its +4-oxidation state, and the chalcogenide anion carries a −2 charge.…”