Because of the reduced dielectric screening and enhanced Coulomb interactions, two-dimensional (2D) materials like phosphorene and transition metal dichalcogenides (TMDs) exhibit strong excitonic effects, resulting in fascinating many-particle phenomena covering both intralayer and interlayer excitons. Their intrinsic band gaps and strong excitonic emissions allow the possibility to tune the inherent optical, electrical, and optoelectronic properties of 2D materials via a variety of external stimuli, making them potential candidates for novel optoelectronic applications. In this review, we summarize exciton physics and devices in 2D semiconductors and insulators, especially in phosphorene, TMDs, and their van der Waals heterostructures (vdWHs). In the first part, we discuss the remarkably versatile excitonic landscape, including bright and dark excitons, trions, biexcitons, and interlayer excitons. In the second part, we examine common control methods to tune excitonic effects via electrical, magnetic, optical, and mechanical means. In the next stage, we provide recent advances on the optoelectronic device applications, such as electroluminescent devices, photovoltaic solar cells, and photodetectors. We conclude with a brief discussion on their potential to exploit vdWHs toward unique exciton physics and devices.
Part of the book: Advances in Condensed-Matter and Materials Physics
In recent years, a scientific shift has been observed that the use of carbon-based nanomaterials in different composite materials can improve their mechanical, thermal, and electrical properties. Different carbon-based nanomaterials have various structures and mechanical, electrical, and thermal conductivity characteristics. By combining with different material composite methods, carbon composite materials with different structures can be prepared. Through the optimization of material structure, carbon composite materials with high performance can be obtained. SP2 hybrid carbon materials, such as carbon nanotubes (CNTs), carbon fiber (CF), and graphene, have excellent electrical, thermal, and mechanical properties due to their regular carbon six-membered ring structure, so they are the main low-dimensional carbon materials and are widely used in composite research. In this chapter, the research progress of carbon nanotubes, carbon fibers, and graphene-based fibers (GBFs) in composite materials are introduced, respectively, and the preparation method, molding process, performance, and application in industry are summarized. Finally, the existing problems and future development trend of carbon-based composites are prospected.
Part of the book: Composite and Nanocomposite Materials