Two-dimensional/two-dimensional (2D/2D) heterostructures consisting of two or more 2D building blocks possess intriguing electronic features at the nanosized interfacial regions, endowing the possibility for effectively modulating the confinement, and transport of charge carriers, excitons, photons, phonons, etc. to bring about a wide range of extraordinary physical, chemical, thermal, and/or mechanical properties. By rational design and synthesis of 2D/2D heterostructures, electrochemical properties for advanced batteries and electrocatalysis can be well regulated to meet some practical requirements. In this review, a summary on the commonly employed synthetic strategies for 2D/2D heterostructures is first given, followed by a comprehensive review on recent progress for their applications in batteries and various electrocatalysis reactions. Finally, a critical outlook on the current challenges and promising solutions is presented, which is expected to offer some insightful ideas on the design principles of advanced 2D-based nanomaterials to address the current challenges in sustainable energy storages and green fuel generations.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/eem2.12184

2D/2D Heterostructures: Rational Design for Advanced Batteries and Electrocatalysis

Monolayer MoS2 is a direct band gap semiconductor with large exciton binding energy, which is a promising candidate for the application of ultrathin optoelectronic devices. However, the optoelectronic performance of monolayer MoS2 is seriously limited to its growth quality and carrier mobility. In this work, we report the direct vapor growth and the optoelectronic device of vertically-stacked MoS2/MoSe2 heterostructure, and further discuss the mechanism of improved device performance. The optical and high-resolution atomic characterizations demonstrate that the heterostructure interface is of high-quality without atomic alloying. Electrical transport measurements indicate that the heterostructure transistor exhibits a high mobility of 28.5 cm2/(V·s) and a high on/off ratio of 107. The optoelectronic characterizations prove that the heterostructure device presents an enhanced photoresponsivity of 36 A/W and a remarkable detectivity of 4.8 × 1011 Jones, which benefited from the interface induced built-in electric field and carrier dependent Coulomb screening effect. This work demonstrates that the construction of two-dimensional (2D) semiconductor heterostructures plays a significant role in modifying the optoelectronic device properties of 2D materials.

High-performance optoelectronic devices based on van der Waals vertical MoS 2 /MoSe 2 heterostructures

Compared with their bulk counterparts, 2D materials can sustain much higher elastic strain at which optical quantities such as bandgaps and absorption spectra governing optoelectronic device performance can be modified with relative ease. Using first-principles density functional theory and quasiparticle GW calculations, we demonstrate how uniaxial tensile strain can be utilized to optimize the electronic and optical properties of transition metal dichalcogenide lateral (in-plane) heterostructures such as MoX2/WX2 (X = S, Se, Te). We find that these lateral-type heterostructures may facilitate efficient electron–hole separation for light detection/harvesting and preserve their type II characteristic up to 12% of uniaxial strain. Based on the strain-dependent bandgap and band offset, we show that uniaxial tensile strain can significantly increase the power conversion efficiency of these lateral heterostructures. Our results suggest that these strain-engineered lateral heterostructures are promising for optimizing optoelectronic device performance by selectively tuning the energetics of the bandgap.

http://absimage.aps.org/image/MAR15/MWS_MAR15-2014-001993.pdf

Strain engineered optoelectronic properties of transition metal dichalcogenides lateral heterostructures

2D materials and their heterojunctions have been explored for gas sensing applications due to their tremendous surface-to-volume ratio, active edges with atomic thickness, and tunable electrical properties. Heterostructures of 2D materials exhibit absolutely novel physics and versatility with accelerated device performance by integrating the atomic scale properties of individual materials. Traditional gas sensors use homogeneous materials as the sensing interface in which the surface adsorbed oxygen ion species play an important role in its performance. But the performance of the sensors suffers greatly due to their selectivity and high working temperature leading to poor stability and short-term uses; the van der Waals 2D p-n heterojunction-based gas sensors hold several advantages since both the materials and the depletion layer formed at the junction can actively tune the sensing performance. By choosing 2D materials with different band structures, charge polarity, carrier concentration, and work function, band alignment at the interface can be precisely engineered to achieve the selective gas sensing performance with low operating temperature. Herein, we have reviewed the working principles, recent developments, and future perspectives of p-n heterojunctions of 2D materials for gas sensing applications.

A review on mechanisms and recent developments in p-n heterojunctions of 2D materials for gas sensing applications

In recent years, emerging two-dimensional (2D) platinum diselenide (PtSe2) has quickly attracted the attention of the research community due to its novel physical and chemical properties. For the past few years, increasing research achievements on 2D PtSe2 have been reported toward the fundamental science and various potential applications of PtSe2. In this review, the properties and structure characteristics of 2D PtSe2 are discussed at first. Then, the recent advances in synthesis of PtSe2 as well as their applications are reviewed. At last, potential perspectives in exploring the application of 2D PtSe2 are reviewed.

/pdf/two-dimensional-platinum-diselenide-synthesis-emerging-2xxb3jokd8.pdf

Two-Dimensional Platinum Diselenide: Synthesis, Emerging Applications, and Future Challenges

Recent developments in synthesis and nanofabrication technologies offer the tantalizing prospect of realizing various applications from two-dimensional (2D) materials. A revolutionary development is to flexibly construct many different kinds of heterostructures with a diversity of 2D materials. These 2D heterostructures play an important role in semiconductor and condensed matter physics studies and are promising candidates for new device designs in the fields of integrated circuits and quantum sciences. Theoretical and experimental studies have focused on both vertical and lateral 2D heterostructures; the lateral heterostructures are considered to be easier for planner integration and exhibit unique electronic and photoelectronic properties. In this review, we give a summary of the properties of lateral heterostructures with homogeneous junction and heterogeneous junction, where the homogeneous junctions have the same host materials and the heterogeneous junctions are combined with different materials. Afterward, we discuss the applications and experimental synthesis of lateral 2D heterostructures. Moreover, a perspective on lateral 2D heterostructures is given at the end.

/pdf/recent-advances-in-2d-lateral-heterostructures-597z1v65xd.pdf

Zhiqiang Li

Papers

Recent Advances in 2D Lateral Heterostructures.