Graphene, since its discovery in 2004, has stimulated considerable interest in two- dimensional layered materials research (2DLMs). Various applications have been investigated with the ever-expanding family of 2D materials, ranging from electronic, optoelectronic, sensing, energy storage and catalytic applications, etc. With weak van der Waals forces between layers, generally, 2DLMs can be exfoliated into atomically thin sheets and reassembled in a designed sequence for building artificial heterostructures, namely, van der Waals heterostructures (vdWHs). Except for the most common 2D material -- graphene, the building blocks for vdWHs also include semiconductors, insulators and even metallic materials. Such versatility has rendered vdWHs become a promising platform for high performance electronic and optoelectronic devices. Researchers have shown that the devices based vertically stacked vdWHs could be the candidates for transistors (barristors), photodetectors, light-emitting diodes and flexible electronics, etc. Particularly, the unique electronic properties of graphene have been playing very important roles in these vertically stacked vdWH devices. In addition to the transparency and extraordinary electrical conductivity of graphene, the work function of graphene can be modulated by varying the gate electric field, enabling a tunable electrical contact with other materials. With the experience we have built up with 2D materials, we further explored the possibilities of integrating a new category of materials - organic- inorganic hybrid perovskites. The hybrid perovskites are the newly emerging materials for high performance optoelectronic applications, which are mostly investigated for solar cell applications. The perovskite based solar cells have shown an astonishing improvement in power conversion efficiency from 3.8 to 22.1% in just few years. Such prominent performance has attracted tremendous research interests from different perspectives. However, these perovskite materials are generally not compatible with conventional nanodevice fabrication due to their considerable solubility in polar organic solvent and water. Despite such fabrication difficulties, we have proposed several approaches to fabricate electronic and optoelectronic devices based on the integration of perovskites and 2D materials. In this dissertation, I will show how we develop a universal water-free dry transfer method to solve the fabrication problems of perovskites and how we build new types of vdWHs with perovskites and 2D materials. We have realized the first van der Waals heterojunction devices based on perovskites and 2D materials, and achieved a high photo- responsivity (950 A/W) and a very high photoconductive gain (~2200) with graphene/perovskite/graphene vertical structure. Moreover, a unique and prominent gate-tunable photovoltaic effect has been observed in the vertically stacked perovskite/WSe2 heterojunction devices. Finally, we have investigated the doping effect induced by ionic solid and the ion migration in perovskites. A switchable p-n junction formation has been demonstrated on a monolayer WSe2 device by electrical poling, along with a very high external quantum efficiency up to 93% under the excitation of 532 nm laser. I believe that in the near future, such platform can enable more possibilities in both electronic and optoelectronic applications with the expanding 2D materials family and hybrid perovskites with compositional tunability.

The advent of graphene and, more recently, two-dimensional materials has opened new perspectives in electronics, optoelectronics, energy harvesting, and sensing applications. This book, based on a Special Issue published in Nanomaterials – MDPI covers experimental, simulation, and theoretical research on 2D materials and their van der Waals heterojunctions. The emphasis is the physical properties and the applications of 2D materials in state-of-the-art sensors and electronic or optoelectronic devices.

2D Nanoscale Heterostructured Materials: Synthesis, Properties, and Applications assesses the current status and future prospects for 2D materials other than graphene (e.g., BN nanosheets, MoS2, NbSe2, WS2, etc.) that have already been contemplated for both low-end and high-end technological applications. The book offers an overview of the different synthesis techniques for 2D materials and their heterostructures, with a detailed explanation of the many potential future applications. It provides an informed overview and fundamentals properties related to the 2D Transition metal dichalcogenide materials and their heterostructures. The book helps researchers to understand the progress of this field and points the way to future research in this area. Explores synthesis techniques of newly evolved 2D materials and their heterostructures with controlled properties Offers detailed analysis of the fundamental properties (via various experimental process and simulations techniques) of 2D heterostructures materials Discusses the applications of 2D heterostructured materials in various high-performance devices

Semiconductors and Semimetals series, highlights new advances in the field, with this new volume presenting interesting chapters. Each chapter is written by an international board of authors. Provides the latest information on cancer research Offers outstanding and original reviews on a range of cancer research topics Serves as an indispensable reference for researchers and students alike

This four-volume handbook gives a state-of-the-art overview of hybrid organic inorganic perovskites, both two dimensional (2D) and three dimensional (3D), from synthesis and characterization and simulation to optoelectronic devices (such as solar cells and light emitting diodes), spintronics devices and catalysis application. The editors, coming from academia and national laboratory, are known for their didactic skills as well as their technical expertise. Coordinating the efforts of 30 expert authors in 21 chapters, they construct the story of hybrid perovskite structural and optical properties, electronic and spintronic response, laser action, and catalysis from varied viewpoints: materials science, chemical engineering, and energy engineering. The four volumes are arranged according to the focus material properties. Volume 1 is focused on the material physical properties including structure, deposition characteristic and the structure of the electronic bands and excitons of these compounds. Volume 2 covers the hybrid perovskite optical properties including the ultrafast optical response, photoluminescence and laser action. Volume 3 contains the spin response of these compounds including application such as spin valves, photogalvanic effect, and magnetic response of light emitting diodes and solar cell devices. Finally, and highly relevant to tomorrow's energy challenges, volume 4 is focused on the physics and device properties of the most relevant applications of the hybrid perovskites, namely photovoltaic solar cells. The text contains many high-quality colorful illustrations and examples, as well as thousands of up-to-date references to peer-reviewed articles, reports and websites for further reading. This comprehensive and well-written handbook is a must-have reference for universities, research groups and companies working with the hybrid organic inorganic perovskites.

Real insight from leading experts in the field into the causes of the unique photovoltaic performance of perovskite solar cells, describing the fundamentals of perovskite materials and device architectures. The authors cover materials research and development, device fabrication and engineering methodologies, as well as current knowledge extending beyond perovskite photovoltaics, such as the novel spin physics and multiferroic properties of this family of materials. Aimed at a better and clearer understanding of the latest developments in the hybrid perovskite field, this is a must-have for material scientists, chemists, physicists and engineers entering or already working in this booming field.

Monoelemental 2D materials called Xenes have a graphene-like structure, intra-layer covalent bond, and weak van der Waals forces between layers. Materials composed of different groups of elements have different structures and rich properties, making Xenes materials a potential candidate for the next generation of 2D materials. 2D Monoelemental Materials (Xenes) and Related Technologies: Beyond Graphene describes the structure, properties, and applications of Xenes by classification and section. The first section covers the structure and classification of single-element 2D materials, according to the different main groups of monoelemental materials of different components and includes the properties and applications with detailed description. The second section discusses the structure, properties, and applications of advanced 2D Xenes materials, which are composed of heterogeneous structures, produced by defects, and regulated by the field. Features include: Systematically detailed single element materials according to the main groups of the constituent elements Classification of the most effective and widely studied 2D Xenes materials Expounding upon changes in properties and improvements in applications by different regulation mechanisms Discussion of the significance of 2D single-element materials where structural characteristics are closely combined with different preparation methods and the relevant theoretical properties complement each other with practical applications Aimed at researchers and advanced students in materials science and engineering, this book offers a broad view of current knowledge in the emerging and promising field of 2D monoelemental materials.