Flexible perovskite solar cell-driven photo-rechargeable lithium-ion capacitor for self-powered wearable strain sensors

Two-dimensional crystals have emerged as a class of materials that may impact future electronic technologies. Experimentally identifying and characterizing new functional two-dimensional materials is challenging, but also potentially rewarding. Here, we fabricate field-effect transistors based on few-layer black phosphorus crystals with thickness down to a few nanometres. Reliable transistor performance is achieved at room temperature in samples thinner than 7.5 nm, with drain current modulation on the order of 10(5) and well-developed current saturation in the I-V characteristics. The charge-carrier mobility is found to be thickness-dependent, with the highest values up to ∼ 1,000 cm(2) V(-1) s(-1) obtained for a thickness of ∼ 10 nm. Our results demonstrate the potential of black phosphorus thin crystals as a new two-dimensional material for applications in nanoelectronic devices.

http://absimage.aps.org/image/MAR14/MWS_MAR14-2013-005031.pdf

Black Phosphorus Field-effect Transistors

Band Alignment Engineering in Two‐Dimensional Transition Metal Dichalcogenide‐Based Heterostructures for Photodetectors

A grand family of two-dimensional (2D) materials and their heterostructures have been discovered through the extensive experimental and theoretical efforts of chemists, material scientists, physicists, and technologists. These pioneering works contribute to realizing the fundamental platforms to explore and analyze new physical/chemical properties and technological phenomena at the micro-nano-pico scales. Engineering 2D van der Waals (vdW) materials and their heterostructures via chemical and physical methods with a suitable choice of stacking order, thickness, and interlayer interactions enable exotic carrier dynamics, showing potential in high-frequency electronics, broadband optoelectronics, low-power neuromorphic computing, and ubiquitous electronics. This comprehensive review addresses recent advances in terms of representative 2D materials, the general fabrication methods, and characterization techniques and the vital role of the physical parameters affecting the quality of 2D heterostructures. The main emphasis is on 2D heterostructures and 3D-bulk (3D) hybrid systems exhibiting intrinsic quantum mechanical responses in the optical, valley, and topological states. Finally, we discuss the universality of 2D heterostructures with representative applications and trends for future electronics and optoelectronics (FEO) under the challenges and opportunities from physical, nanotechnological, and material synthesis perspectives.

2D Heterostructures for Ubiquitous Electronics and Optoelectronics: Principles, Opportunities, and Challenges.

Van der Waals Integration Based on Two-Dimensional Materials for High-Performance Infrared Photodetectors

Strain Engineering in 2D Material-Based Flexible Optoelectronics

The applications of any two-dimensional (2D) semiconductor devices cannot bypass the control of metal-semiconductor interfaces, which can be severely affected by complex Fermi pinning effects and defect states. Here, we report a near-ideal rectifier in the all-2D Schottky junctions composed of the 2D metal 1 T′-MoTe2 and the semiconducting monolayer MoS2. We show that the van der Waals integration of the two 2D materials can efficiently address the severe Fermi pinning effect generated by conventional metals, leading to increased Schottky barrier height. Furthermore, by healing original atom-vacancies and reducing the intrinsic defect doping in MoS2, the Schottky barrier width can be effectively enlarged by 59%. The 1 T′-MoTe2/healed-MoS2 rectifier exhibits a near-unity ideality factor of ~1.6, a rectifying ratio of >5 × 105, and high external quantum efficiency exceeding 20%. Finally, we generalize the barrier optimization strategy to other Schottky junctions, defining an alternative solution to enhance the performance of 2D-material-based electronic devices. Here, a defect healing method is used to tune the height and width of the Schottky barrier at the interface between 2D metals and 2D semiconductors, leading to the realization of van der Waals rectifiers with enhanced performance.

/pdf/near-ideal-van-der-waals-rectifiers-based-on-all-two-3l4dh0ticu.pdf

Near-ideal van der Waals rectifiers based on all-two-dimensional Schottky junctions.

Piezotronic effect on interfacial charge modulation in mixed-dimensional Van der Waals heterostructure for ultrasensitive flexible photodetectors

Monolayer 2D semiconductors (e.g., MoS2 ) are of considerable interest for atomically thin transistors but generally limited by insufficient carrier mobility or driving current. Minimizing the lattice defects in 2D semiconductors represents a common strategy to improve their electronic properties, but has met with limited success to date. Herein, a hidden benefit of the atomic vacancies in monolayer 2D semiconductors to push their performance limit is reported. By purposely tailoring the sulfur vacancies (SVs) to an optimum density of 4.7% in monolayer MoS2 , an unusual mobility enhancement is obtained and a record-high carrier mobility (>115 cm2 V-1 s-1 ) is achieved, realizing monolayer MoS2 transistors with an exceptional current density (>0.60 mA µm-1 ) and a record-high on/off ratio >1010 , and enabling a logic inverter with an ultrahigh voltage gain >100. The systematic transport studies reveal that the counterintuitive vacancy-enhanced transport originates from a nearest-neighbor hopping conduction model, in which an optimum SV density is essential for maximizing the charge hopping probability. Lastly, the vacancy benefit into other monolayer 2D semiconductors is further generalized; thus, a general strategy for tailoring the charge transport properties of monolayer materials is defined.

Huihui Yu

Papers

Strain Engineering in 2D Material-Based Flexible Optoelectronics

Near-ideal van der Waals rectifiers based on all-two-dimensional Schottky junctions.

Piezotronic effect on interfacial charge modulation in mixed-dimensional Van der Waals heterostructure for ultrasensitive flexible photodetectors

Hidden Vacancy Benefit in Monolayer 2D Semiconductors

Gate‐Controlled Polarity‐Reversible Photodiodes with Ambipolar 2D Semiconductors