Molybdenum Disulphide Heterointerfaces as Potential Materials for Solar Cells, Energy Storage, and Hydrogen Evolution

Molybdenum disulphide (MoS₂), an ideal semiconductor, belongs to the group of 40 well-identified transition metal dichalcogenides. These have unique chemical bonding; in an ideal case they do not feature dangling bonds and hence possess a layered-like atomic structure, such that strong intraplane and weak interplane bondings exist. Hence, MoS₂ can be peeled into a precisely controlled number of layers; the bulk with E_g = 1.2 eV can be reduced to a unit cell-thick layer (monolayer) with E_g = 1.89 eV. However, in reality, both bulk and monolayers possess many types of atomic defects associated with in-plane, edge, grain boundaries, etc. As a result, MoS₂ exhibits many interesting and tunable optoelectronic properties suitable for a wide range of applications. Interestingly, its basic polyhedral form (MoS₆) undergoes a structural change that leads to many polymorphic phases, the three in bulk and the five in monolayer. Theoretical predictions and experimental observations clearly confirm that MoS₂ and its interfaces with other materials can be significantly important for energy conversion and storage applications, which are emerging and critically important topics of modern science and society. This Review provides an overview of the past few years of research and developments on these topics.