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2D transition metal dichalcogenide (TMD) nanosheets, including MoS₂, WS₂, and TaS₂, are used as hole injection layers (HILs) in organic light-emitting diodes (OLEDs). MoS₂, WS₂, and TaS₂ nanosheets are prepared using an exfoliation by ultrasonication method. The thicknesses and sizes of the TMD nanosheets are measured to be 3.1–4.3 nm and more than 100 nm, respectively. The work functions of the TMD nanosheets increase from 4.4–4.9 to 4.9–5.1 eV following ultraviolet/ozone (UVO) treatment. The turn-on voltages at 10 cd m⁻² for UVO-treated TMD-based devices decrease from 7.3–12.8 to 4.3–4.4 V and maximum luminance efficiencies increase from 5.74–9.04 to 12.01–12.66 cd A⁻¹. In addition, this study confirms that the stabilities of the devices in air can be prolonged by using UVO-treated TMDs as HILs in OLEDs. These results demonstrate the great potential of liquid-exfoliated TMD nanosheets for use as HILs in OLEDs.

2D transition metal dichalcogenide (TMD) nanosheets, including MoS₂, WS₂, and TaS₂, are used as hole injection layers (HILs) in organic light-emitting diodes (OLEDs). MoS₂, WS₂, and TaS₂ nanosheets are prepared using an exfoliation by an ultrasonication method. It is shown that the stability of the devices in air can be prolonged by using UV/ozone-treated TMDs as HILs in OLEDs.

Oxford University Press, Oxford 2014. 432 pp., softcover, £ 32.99.—ISBN 978-0199668212

A 3D catalyst electrode is fabricated by layer-by-layer assembly of 2D WS₂ nano­layers and P, N, O-doped graphene sheets into a heterostructured film. The film exhibits remarkable hydrogen evolution performance, benefitting from the utmost exposed active centers on 2D nanolayers, highly expanded surface, and continuous conductive network, as well as strong synergistic effects between the components.

A 3D catalyst electrode is fabricated by layer-by-layer assembly of 2D WS₂ nano­layers and P, N, O-doped graphene sheets into a heterostructured film. The film exhibits remarkable hydrogen evolution performance, benefitting from the utmost exposed active centers on 2D nanolayers, highly expanded surface, and continuous conductive network, as well as strong synergistic effects between the components.

This work reports on the preparation of semitransparent perovskite solar cells. The cells transparency is achieved through a unique wet deposition technique that creates perovskite grids with various dimensions. The perovskite grid is deposited on a mesoporous TiO₂ layer, followed by hole transport material deposition and evaporation of a semitransparent gold film. Control of the transparency of the solar cells is achieved by changing the perovskite solution concentration and the mesh openings. The semitransparent cells demonstrate 20–70% transparency with a power conversion efficiency of 5% at 20% transparency. This is the first demonstration of the possibility to create a controlled perovskite pattern using a direct mesh-assisted assembly deposition method for fabrication of a semitransparent perovskite-based solar cell.

Semitransparent perovskite solar cells are presented. Cell transparency is achieved through a unique wet deposition technique that creates perovskite grids with various dimensions. This unique technique enables control of the transparency of the solar cells. The semitransparent cells demonstrate 20–70% transparency with a power conversion efficiency of 5% at 20% transparency.

Grain boundaries in as-grown polycrystalline MoS₂ monolayers are revealed by second-harmonic-generation microscopy. Through the anisotropic polarization pattern and phase interference at the grain boundary, grain edge termination and boundary types are identified. Statistical analysis on hundreds of grains shows that grain-boundary formation is driven by kinetics and can be nicely described by the edge attachment growth model.

A new topological crystalline insulator material, SnSe in the rock-salt structure, is obtained using molecular beam epitaxy. The thermodynamically unstable rock-salt SnSe phase is stabilized in epitaxial films up to 20 nm by a Bi₂Se₃ substrate. Dirac surface states are observed at both the and the points using angle-resolved photoemission spectroscopy; this confirms the topological crystalline insulator phase of the films.

The creation of self-aligned MoS₂ and WS₂ wire arrays and their stacked hetero structures with controlled sizes and properties by a novel and facile method is presented. The thicknesses and periodicities of the aligned wires can be precisely controlled by adjusting certain parameters. These transition metal dichalcogenide wires are used as 1D semiconducting materials in the construction of flexible and transparent electronic devices. In addition, WS₂/MoS₂ heterostructures display clear optical and structural modulation.

A thiol–amine solvent mixture is used to dissolve ten inexpensive bulk oxides (Cu₂O, ZnO, GeO₂, As₂O₃, Ag₂O, CdO, SnO, Sb₂O₃, PbO, and Bi₂O₃) under ambient conditions. Dissolved oxides can be converted to the corresponding sulfides using the thiol as the sulfur source, while selenides and tellurides can be accessed upon mixing with a stoichiometric amount of dissolved selenium or tellurium. The practicality of this method is illustrated by solution depositing Sb₂Se₃ thin films from compound inks of dissolved Sb₂O₃ and selenium that give high photoelectrochemical current response. The direct band gap of the resulting material can be tuned from 1.2–1.6 eV by modulating the ink formulation to give compositionally controlled Sb₂Se_3−xS_x alloys.

It's in the mix: Conversion of bulk oxides to chalcogenides by ambient solution processing is demonstrated. Sulfides are recovered by low-temperature annealing of inks of bulk oxides dissolved in thiol–amine mixtures, while selenides and tellurides are synthesized from compound inks comprised of a dissolved oxide with Se or Te. The procedure was used to produce photoresponsive thin films and alloys with tunable band gaps.