Fengxia Wei

Synthesis, characterization, self-assembly, and physical properties of 11-methylbenzo[d]pyreno[4,5-b]furan.

Synthesis, structure, and physical properties of a novel 11-methylbenzo[d]pyreno[4,5-b]furan (BPF) and its self-assembly in water have been reported. The performance of nanowire-based films in organic light-emitting diodes is much better than that of the thin film deposited by directly drop-coating BPF molecules in THF solution. SEM study indicates that the well-organized structure (nanowires) is an important factor in enhancing the performance of OLED devices.

The synthesis, structure and electronic properties of a lead-free hybrid inorganic–organic double perovskite (MA)2KBiCl6 (MA = methylammonium)

In a search for lead-free materials that could be used as alternatives to the hybrid perovskites, (MA)PbX3, in photovoltaic applications, we have discovered a hybrid double perovskite, (MA)2KBiCl6, which shows strong similarities to the lead analogues. Spectroscopic measurements and nanoindentation studies are combined with density functional calculations to reveal the properties of this interesting system.

Crystal structure and phototransistor behavior of N-substituted heptacence.

6,8,15,17-Tetraaza-1.18,4.5,9.10,13.14-tetrabenzoheptacene (TTH, 1) has been prepared and characterized by single-crystal X-ray structure analysis. A phototransistor device based on TTH single crystal demonstrated that TTH showed a good performance in signal amplification under the photoconductive effect as well as photocontrolled switches.

Exploring the properties of lead-free hybrid double perovskites using a combined computational-experimental approach

Density functional theory screening of the hybrid double perovskites (MA)2BIBiX6 (BI = K, Cu, Ag, Tl; X = Cl, Br, I) shows that systems with band gaps similar to those of the MAPbX3 lead compounds can be expected for BI = Cu, Ag, Tl. Motivated by these findings, (MA)2TlBiBr6, isoelectronic with MAPbBr3, was synthesised and found to have a band gap of ∼2.0 eV.

Liquid-gated electric-double-layer transistor on layered metal dichalcogenide, SnS2

With ionic liquid (IL) gating in electric-double-layer transistors (EDLTs), we report field effect operation and electronic state modulation in a layered material of SnS2, demonstrating that the EDLT is applicable to modifying the electronic properties of metal dichalcogenides. The IL-gated SnS2 EDLTs allow us to realize high performance transistor operation and to achieve interfacial carrier accumulation to a level as high as 5.4×1014 cm−2, as quantitatively estimated from the Hall effect. A considerable decrease of the activation energy in temperature-dependent sheet resistance implies that liquid gating is an effective way to tune the electronic states of metal dichalcogenides at EDL interfaces.

Fluorination of Metal Phthalocyanines: Single-Crystal Growth, Efficient N-Channel Organic Field-Effect Transistors, and Structure-Property Relationships

The fluorination of p-type metal phthalocyanines produces n-type semiconductors, allowing the design of organic electronic circuits that contain inexpensive heterojunctions made from chemically and thermally stable p- and n-type organic semiconductors. For the evaluation of close to intrinsic transport properties, high-quality centimeter-sized single crystals of F16CuPc, F16CoPc and F16ZnPc have been grown. New crystal structures of F16CuPc, F16CoPc and F16ZnPc have been determined. Organic single-crystal field-effect transistors have been fabricated to study the effects of the central metal atom on their charge transport properties. The F16ZnPc has the highest electron mobility (~1.1 cm2 V−1 s−1). Theoretical calculations indicate that the crystal structure and electronic structure of the central metal atom determine the transport properties of fluorinated metal phthalocyanines.

Synthesis, crystal structure, and optical properties of a three-dimensional quaternary Hg–In–S–Cl chalcohalide : Hg7InS6Cl5

A crystalline three-dimensional (3D) quaternary chalcohalide, Hg(7)InS(6)Cl(5) (1), has been synthesized through a solid-state reaction under medium temperature. It is the first example in the family of the Hg-IIIA-Q-X (Q = S, Se, Te; X = F, Cl, Br, I) systems. Compound 1 features a 3D network and has an optical band gap of 2.54 eV.

Atomically Flat, Large-Sized, Two-Dimensional Organic Nanocrystals

Large-sized, 2D single crystals of perylene are grown by both solution-cast and physical vapor transport methods. The crystals have a atomically flat parallelogram morphology and the aspect ratios of the lateral extension compared to the thickness are up to 10(3) . The atomically flat feature leads to good interface contact, making a single-crystal field-effect transistor with higher mobility. The mobility of atomically flat crystals can be 10(3) -10(4) times higher than rough crystals.

Five-Dimensional Incommensurate Structure of the Melilite Electrolyte [CaNd]2[Ga]2[Ga2O7]2

Melilite-type gallium oxides are potential intermediate temperature electrolytes for solid oxide fuel cells. Single crystals of [CaNd](2)[Ga](2)[Ga(2)O(7)](2) grown using an optical floating zone furnace have been investigated using transmission electron microscopy and powder and single-crystal X-ray diffraction. The anion array topologically conforms to a [(3.5.4.5)(2), 3.5.3.5] network that contains distorted pentagonal tunnels. The distortion is necessary to achieve space filling and accommodate structural misfit between the layers. Satisfactory bond lengths and angles are obtained through two-dimensional modulation in the tetragonal based plane, leading to five-dimensional symmetry in the superspace group P(4⁻)2(1)m(α,α,0)00s((a⁻)a,0)000, α = 0.2319(2), with modulation vectors q(1) = α(a* + b*) and q(2) = α(-a* + b*). Both displacive and occupational modulations are found. Through this mechanism, melilites are primed to accommodate mobile oxygen interstitials, suggesting a rational approach to crystallochemical tailoring that will enhance ionic diffusion and optimize electrolyte performance.

In situ formation of new organic ligands to construct two novel self-charge-transfer Pb( ii )-based frameworks

Employing in situ-formed new organic ligands, two Pb(II)-based metal–organic frameworks were synthesized. Compound 1 possesses a 3D framework while compound 2 has a layered structure. Solid state UV-visible absorptions indicate that the two compounds are semiconductors with band gaps of 1.70 and 1.78 eV. Magnetic properties reveal that they are temperature-independent diamagnetic.