Bandgap engineering of high mobility two-dimensional semiconductors toward optoelectronic devices

Over the last few years, great advances have been achieved in exploration of high-mobility two-dimensional (2D) semiconductors such as metal chalcogenide InSe and noble-transition-metal dichalcogenide PdSe₂. These materials are competitive candidates for constructing next-generation optoelectronic devices owing to their unique crystalline and electronic structures. Moreover, the optical and electronic properties of 2D materials can be efficiently modified via precisely engineering their band structures, which is critical for widening specific applications ranging from high-performance optoelectronics to catalysis and energy harvesting. In this review, we focus on the progress in bandgaps engineering of newly emerging high-mobility 2D semiconductors and their applications in optoelectronic devices, incorporating our recent study in the InSe and PdSe₂ systems. First of all, we discuss the structure-property relationship of typical high-mobility 2D semiconductors (InSe and PdSe₂). Next, we analyze several viable strategies for bandgap engineering, including thickness, strain or pressure, alloying, heterostructure, surface modification, intercalation, and so on. Furthermore, we summarize the optoelectronic devices fabricated with such high-mobility 2D semiconductors. The conclusion and outlook in this topic are finally presented. This review aims to provide valuable insights in bandgap engineering of newly emerging 2D semiconductors and explore their potential in future optoelectronic applications.