Abstract:Inserting an insulator at the interface in vdW heterostructure solar cell unit can improve the photoelectric conversion efficiency, and the insulator has an optimal thickness.
“…[ 329 ] Further, researchers have used different thicknesses of h‐BN as a spacer to control the excitonic emission in TMDs such as bilayer MoS2, MoS 2 /WSe 2, etc. [ 322,323 ] In both cases it has been observed that the lifetime of interlayer excitons has significantly improved due to delay in the recombination of e–h pairs. Thus, h‐BN plays an important role in separating the e‐ and h‐ in different layers of TMDs; very useful in high‐efficiency solar cells.…”
Section: Doping Vdw Heterostructures and Nanocompositesmentioning
Hexagonal boron nitride (h-BN) has emerged as a strong candidate for twodimensional (2D) material owing to its exciting optoelectrical properties combined with mechanical robustness, thermal stability, and chemical inertness. Super-thin h-BN layers have gained significant attention from the scientific community for many applications, including nanoelectronics, photonics, biomedical, anti-corrosion, and catalysis, among others. This review provides a systematic elaboration of the structural, electrical, mechanical, optical, and thermal properties of h-BN followed by a comprehensive account of stateof-the-art synthesis strategies for 2D h-BN, including chemical exfoliation, chemical, and physical vapor deposition, and other methods that have been successfully developed in recent years. It further elaborates a wide variety of processing routes developed for doping, substitution, functionalization, and combination with other materials to form heterostructures. Based on the extraordinary properties and thermal-mechanical-chemical stability of 2D h-BN, various potential applications of these structures are described.The ORCID identification number(s) for the author(s) of this article can be found under
“…[ 329 ] Further, researchers have used different thicknesses of h‐BN as a spacer to control the excitonic emission in TMDs such as bilayer MoS2, MoS 2 /WSe 2, etc. [ 322,323 ] In both cases it has been observed that the lifetime of interlayer excitons has significantly improved due to delay in the recombination of e–h pairs. Thus, h‐BN plays an important role in separating the e‐ and h‐ in different layers of TMDs; very useful in high‐efficiency solar cells.…”
Section: Doping Vdw Heterostructures and Nanocompositesmentioning
Hexagonal boron nitride (h-BN) has emerged as a strong candidate for twodimensional (2D) material owing to its exciting optoelectrical properties combined with mechanical robustness, thermal stability, and chemical inertness. Super-thin h-BN layers have gained significant attention from the scientific community for many applications, including nanoelectronics, photonics, biomedical, anti-corrosion, and catalysis, among others. This review provides a systematic elaboration of the structural, electrical, mechanical, optical, and thermal properties of h-BN followed by a comprehensive account of stateof-the-art synthesis strategies for 2D h-BN, including chemical exfoliation, chemical, and physical vapor deposition, and other methods that have been successfully developed in recent years. It further elaborates a wide variety of processing routes developed for doping, substitution, functionalization, and combination with other materials to form heterostructures. Based on the extraordinary properties and thermal-mechanical-chemical stability of 2D h-BN, various potential applications of these structures are described.The ORCID identification number(s) for the author(s) of this article can be found under
“…Interestingly, Tan et al theoretically proposed that charge recombination can be suppressed by inserting a 2–3 nm thick hBN insulating layer between the MoS 2 and WSe 2 and that the photoelectric conversion efficiency (PCE) of MoS 2 /hBN/WSe 2 photovoltaic devices can be approximately doubled. They theoretically predicted that the PCE exceeding 23% could be obtained by increasing the TMDC thickness and optimizing the hBN thickness [ 178 ]. Figure 11.…”
The past decades of materials science discoveries are the basis of our present society – from the foundation of semiconductor devices to the recent development of internet of things (IoT) technologies. These materials science developments have depended mainly on control of rigid chemical bonds, such as covalent and ionic bonds, in organic molecules and polymers, inorganic crystals and thin films. The recent discovery of graphene and other two-dimensional (2D) materials offers a novel approach to synthesizing materials by controlling their weak out-of-plane van der Waals (vdW) interactions. Artificial stacks of different types of 2D materials are a novel concept in materials synthesis, with the stacks not limited by rigid chemical bonds nor by lattice constants. This offers plenty of opportunities to explore new physics, chemistry, and engineering. An often-overlooked characteristic of vdW stacks is the well-defined 2D nanospace between the layers, which provides unique physical phenomena and a rich field for synthesis of novel materials. Applying the science of intercalation compounds to 2D materials provides new insights and expectations about the use of the vdW nanospace. We call this nascent field of science ‘2.5 dimensional (2.5D) materials,’ to acknowledge the important extra degree of freedom beyond 2D materials. 2.5D materials not only offer a new field of scientific research, but also contribute to the development of practical applications, and will lead to future social innovation. In this paper, we introduce the new scientific concept of this science of ‘2.5D materials’ and review recent research developments based on this new scientific concept.
“…[13][14][15] Understanding the mechanism of photo carries relaxation in vdW HSs is a crucial step in the development of potential applications since it determines the response speed and efficiency of photo-electron conversion. [16,17] Ultrafast optical spectroscopy is an ideal technique for unveiling all of the mysterious processes. [18,19] In the past few years, a variety of studies have been carried out on photocarriers' relaxation in 2D vdW HSs.…”
Van der Waals (vdW) heterostructures (HSs) built on 2D materials provide an ideal platform for research of energy migration at the nanoscale. However, the underlying charge transfer mechanism in type II vdW HSs is still not well understood. Here, ultrafast exciton dynamics are investigated in trilayer-WS 2 -MoS 2 -WSe 2 and trilayer-MoS 2 -WSe 2 -WS 2 HSs by broadband pump-probe spectroscopy. A two-step process of exciton transfer in trilayer-WS 2 -MoS 2 -WSe 2 is directly observed when the band edge exciton of WSe 2 is excited. The electrons in WSe 2 are initially transferred to the high lying electronic state of MoS 2 -WS 2 on a time scale of tens of femtoseconds, and then electrons eventually relax into the conduction band minimum of MoS 2 within 1 ps. Furthermore, the transfer of interlayer excitons is observed for the first time in trilayer-MoS 2 -WSe 2 -WS 2 . Both transfer processes can be better understood by the Dexter charge exchange model. Due to the nature of Dexter type transfer that the exchange rate exponentially depends on the donor−acceptor distance, the interlayer exciton transfer rate is nearly a hundred times slower than that of exciton transition in bilayer HSs. The results deepen the understanding of charge transfer in 2D vdW HSs and also indicate that the exciton effect and orbital hybridization make HS a strong coupling system.
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