#TeddersRecommends

A solution-based passivation scheme is developed featuring the use of molecular iodine and PbS colloidal quantum dots (CQDs). The improved passivation translates into a longer carrier diffusion length in the solid film. This allows thicker solar-cell devices to be built while preserving efficient charge collection, leading to a certified power conversion efficiency of 9.9%, which is a new record in CQD solar cells.

Phonon-assisted anti-Stokes emission and its stimulated emission in polar semiconductor ZnTe are demonstrated via the annihilation of phonons as a result of strong exciton–phonon coupling. The findings are not only important for developing high-power radiation-balanced lasers, but are also promising for manufacturing ultraefficient solid-state laser coolers.

Research on van der Waals heterostructures based on stacked 2D atomic crystals is intense due to their prominent properties and potential applications for flexible transparent electronics and optoelectronics. Here, nonvolatile memory devices based on floating-gate field-effect transistors that are stacked with 2D materials are reported, where few-layer black phosphorus acts as channel layer, hexagonal boron nitride as tunnel barrier layer, and MoS₂ as charge trapping layer. Because of the ambipolar behavior of black phosphorus, electrons and holes can be stored in the MoS₂ charge trapping layer. The heterostructures exhibit remarkable erase/program ratio and endurance performance, and can be developed for high-performance type-switching memories and reconfigurable inverter logic circuits, indicating that it is promising for application in memory devices completely based on 2D atomic crystals.

Nonvolatile ambipolar memory devices are developed based on stacked black phosphorus–boron nitride–molybdenum disulphide heterostructure floating-gate field-effect transistors. The memory device exhibits a fairly large memory window with a width (ΔV) of ≈60 V for a maximum control gate voltage of 40 V and can be switched well between the erase and program state.

High-quality ultrathin single-crystalline SnSe₂ flakes are synthesized under atmospheric-pressure chemical vapor deposition for the first time. A high-performance photodetector based on the individual SnSe₂ flake demonstrates a high photoresponsivity of 1.1 × 10³ A W⁻¹, a high EQE of 2.61 × 10⁵%, and superb detectivity of 1.01 × 10¹⁰ Jones, combined with fast rise and decay times of 14.5 and 8.1 ms, respectively.

Layer-by-layer assembled 2D montmorillonite nanosheets are shown to be high-performance, solution-processed dielectrics. These scalable and spatially uniform sub-10 nm thick dielectrics yield high areal capacitances of ≈600 nF cm⁻² and low leakage currents down to 6 × 10⁻⁹A cm⁻² that enable low voltage operation of p-type semiconducting single-walled carbon nanotube and n-type indium gallium zinc oxide field-effect transistors.

Two-dimensional boron materials have recently attracted extensive theoretical interest because of their exceptional structural complexity and remarkable physical and chemical properties. However, such 2D boron monolayers have still not been synthesized. In this report, the synthesis of atomically thin 2D γ-boron films on copper foils is achieved by chemical vapor deposition using a mixture of pure boron and boron oxide powders as the boron source and hydrogen gas as the carrier gas. Strikingly, the optical band gap of the boron film was measured to be around 2.25 eV, which is close to the value (2.07 eV) determined by first-principles calculations, suggesting that the γ-B₂₈ monolayer is a fascinating direct band gap semiconductor. Furthermore, a strong photoluminescence emission band was observed at approximately 626 nm, which is again due to the direct band gap. This study could pave the way for applications of two-dimensional boron materials in electronic and photonic devices.

Atomically thin two-dimensional γ-boron films were synthesized on copper foils by a scalable chemical vapor deposition method. The experimentally obtained optical band gap of around 2.25 eV is close to that determined by first-principles calculations (2.07 eV). The strong photoluminescence of the material suggests that the monolayer is a direct band gap semiconductor.

High-quality organic and inorganic van der Waals (vdW) solids are realized using methylammonium lead halide (CH₃NH₃PbI₃) as the organic part (organic perovskite) and 2D inorganic monolayers as counterparts. By stacking on various 2D monolayers, the vdW solids exhibit dramatically different light emissions. Futhermore, organic/h-BN vdW solid arrays are patterned for red-light emission.

The detailed understanding of the physical and reaction chemistry of engineering lubricants is key to new developments in the future. Here, we draw together the main chemical/engineering literature in the first systematic review of the standard anti-wear additive used as an aviation lubricant, tricresyl phosphate (TCP), focusing on understanding the links between the surface chemistry, tribology and decomposition of TCP. While there is still debate concerning the mechanism of TCP, it is clear that it is activated by moisture, oxygen or oxidised metal surfaces. Its anti-wear properties arise from the resulting formation of iron phosphate or polyphosphate on the contact surfaces. Evidence stresses the importance of chemistry at the boundary layer and a mechanism involving pre-coordination of TCP at the surface, resulting in activation at the P-centre and subsequent attack by residual H₂O or surface O²⁻. This perspective provides a potential baseline for the development of future phosphorus-based high-performance additives. Copyright © 2015 John Wiley & Sons, Ltd.

Although phosphorene has attracted much attention in electronics and optoelectronics as a new type of two-dimensional material, in-depth investigations and applications have been limited by the current synthesis techniques. Herein, a basic N-methyl-2-pyrrolidone (NMP) liquid exfoliation method is described to produce phosphorene with excellent water stability, controllable size and layer number, as well as in high yield. Phosphorene samples composed of one to four layers exhibit layer-dependent Raman scattering characteristics thus providing a fast and efficient means for the in situ determination of the thickness (layer number) of phosphorene. The linear and nonlinear ultrafast absorption behavior of the as-exfoliated phosphorene is investigated systematically by UV–vis–NIR absorption and Z-scan measurements. By taking advantage of their unique nonlinear absorption, ultrashort pulse generation applicable to optical saturable absorbers is demonstrated. In addition to a unique fabrication technique, our work also reveals the large potential of phosphorene in ultrafast photonics.

A basic N-methyl-2-pyrrolidone liquid exfoliation method is described to produce phosphorene with an excellent water stability, controllable size and layer number, as well as in a high yield. Phosphorene with one to four layers exhibits layer-dependent Raman scattering characteristics thus providing a fast and efficient means for the in situ determination of the thickness of phosphorene.