Naughty Paul

The optical energy gap of as-grown MoS₂ flakes from chemical vapor deposition can be modulated from 1.86 eV (667 nm) to 1.57 eV (790 nm) by a vapor phase selenization process. This approach, replacing one chalcogen by another in the gas phase, is promising in modulating the optical and electronic properties of other transition metal dichalcogenide monolayers.

The surface plasmon resonance of Au nanoparticle on MoS₂ nanosheet is successfully measured by the electron energy-loss spectroscopy. Furthermore, Au-MoS₂ composite is developed as the photoanode material in the photo­electronchemical cell (PEC) for water splitting. Compared to the pure MoS₂-based PEC, Au-MoS₂ based PEC shows the enhanced performance in the photocatalytic water splitting.

A facile and efficient synthesis of a solution-processable MoO₃/MoS₂ featuring uniformly decorated MoO₃ nanoparticles onto exfoliated MoS₂ nanosheets is realized via a one-step oxidation and spontaneous exfoliation method using hydrogen peroxide. By using MoO₃/MoS₂ as a hole extraction layer in organic solar cells, high efficiencies, regardless of annealing conditions of the interfacial layer, and excellent long-term stability are demonstrated.

Highly photosensitive nanocrystal (NC) skins based on exciton funneling are proposed and demonstrated using a graded bandgap profile across which no external bias is applied in operation for light-sensing. Four types of gradient NC skin devices (GNS) made of NC monolayers of distinct sizes with photovoltage readout are fabricated and comparatively studied. In all structures, polyelectrolyte polymers separating CdTe NC monolayers set the interparticle distances between the monolayers of ligand-free NCs to <1 nm. In this photosensitive GNS platform, excitons funnel along the gradually decreasing bandgap gradient of cascaded NC monolayers, and are finally captured by the NC monolayer with the smallest bandgap interfacing the metal electrode. Time-resolved measurements of the cascaded NC skins are conducted at the donor and acceptor wavelengths, and the exciton transfer process is confirmed in these active structures. These findings are expected to enable large-area GNS-based photosensing with highly efficient full-spectrum conversion.

Photosensitive gradient nanocrystal skins rely on accumulating dissociated excitons after photogenerating and funneling. Excitons funnel along a gradually decreasing band gap gradient of the cascaded nanocrystal monolayers to enhance photosensitivity of the device platform. Substantial improvements are observed in the photosensitivity over a broadband spectral range (350–600 nm), with an approximately twofold enhancement factor along the entire operating wavelength range.

It is not often that the scientific community is blessed with a material, which brings enormous hopes and receives special attention. When it does, it expands at a rapid pace and its every dimension creates curiosity. One such material is perovskite, which has triggered the development of new device architectures in energy conversion. Perovskites are of great interest in photovoltaic devices due to their panchromatic light absorption and ambipolar behavior. Power conversion efficiencies have been doubled in less than a year and over 15 % is being now measured in labs. Every digit increment in efficiency is being celebrated widely in the scientific community and is being discussed in industry. Here we provide a summary on the use of perovskite for inexpensive solar cells fabrication. It will not be unrealistic to speculate that one day perovskite-based solar cells can match the capability and capacity of existing technologies.

Wonder material: The use of perovskites as light absorber in photovoltaic cells has revolutionized the field. Light-to-electricity conversion efficiencies of 15 % have already been achieved, and even without additional hole transport layers efficiencies up to 8 % can be measured. The unique combination of high extinction coefficient along with their ambipolar nature gives perovskites an advantage over quantum-dot- and dye-sensitized solar cells.

The structure and electronic structure of layered noble-transition-metal dichalcogenides MX₂ (M=Pt and Pd, and chalcogenides X=S, Se, and Te) have been investigated by periodic density functional theory (DFT) calculations. The MS₂ monolayers are indirect band-gap semiconductors whereas the MSe₂ and MTe₂ analogues show significantly smaller band gap and can even become semimetallic or metallic materials. Under mechanical strain these MX₂ materials become quasi-direct band-gap semiconductors. The mechanical-deformation and electron-transport properties of these materials indicate their potential application in flexible nanoelectronics.

Show you're metal: The structure and electronic structure of layered noble-transition-metal dichalcogenides MX₂ with metals M (Pt and Pd) and chalcogenides X (S, Se, and Te) have been investigated with periodic density functional theory calculations. The MS₂ monolayers are indirect band-gap semiconductors whereas the MSe₂ and MTe₂ analogues show a significant decrease in their band-gaps and can even become semimetallic or metallic materials.

The quantum-dot sensitization of a commercial TiO₂ photoelectrode with maximized light harvesting capacity leads to the realization of hydrogen generation under visible light irradiation. The greatly improved performance of an electrode with light-harvesting capability suggests the proposed route is an effective strategy for electrode materials in photoconversion systems.

Two MoS₂ field-effect transistors are compared using graphene and Au/Ti source-drain contacts in respects of their Ohmic and OFF behavior on an identical MoS₂ nanosheet. As a result, graphene-contact appears not only to show superior ohmic behavior to those of Au/Ti but also more enhanced OFF state behavior. Such results are attributed to the electric-field-induced work function tuning of exfoliated graphene.

Being confronted with the energy crisis and environmental problems, the exploration of clean and renewable energy materials as well as their devices are urgently demanded. Two-dimensional (2D) atomically-thick materials, graphene and grpahene-like layered transition metal dichalcogenides (TMDs), have showed vast potential as novel energy materials due to their unique physicochemical properties. In this Review, we outline the typical application of graphene and grpahene-like TMDs in energy conversion and storage fields, and hope to promote the development of 2D TMDs in this field through the analysis and comparisons with the relatively natural graphene. First, a brief introduction of electronic structures and basic properties of graphene and TMDs are presented. Then, we summarize the exciting progress of these materials made in both energy conversion and storage field including solar cells, electrocatalysis, supercapacitors and lithium ions batteries. Finally, the prospects and further developments in these exciting fields of graphene and graphene-like TMDs materials are also suggested.

This review summarizes recent progress of graphene and graphene-like layered transition metal dichalcogenide in energy conversion and storage application, including solar cells, electrocatalysis, supercapacitors, and lithium-ion batteries. Prospects and further developments in this exciting field are also discussed.