Yusheng Li

Synthesis and characterization of tin oxide nanoparticles dispersed in monolithic mesoporous silica

Tin oxide nanocrystalline uniformly dispersed in mesoporous silica has been prepared by decomposing coordinated complex of Sn 4+ with acetyl acetone. Structural analysis indicates that the Sn 4+ coordinated complex decomposes and tin oxide nanocrystalline begins to form at about 300 ◦ C and completes at about 600 ◦ C. With the increase of the annealing temperature from 300 ◦ C to 600 ◦ C, tin oxide nanocrystalline in mesoporous silica slightly grows. Tin oxide nanoparticles or nanochains may be obtained depending on the concentration of precursor solution. The obtained nanocomposite remains large specific surface area. uf6d9 2003 Editions scientifiques et medicales Elsevier SAS. All rights reserved.

Synthetic Molecular Rectifier of a Langmuir–Blodgett Film Based on a Novel Asymmetrically Substituted Dicyano-tri-tert-butylphthalocyanine

A novel asymmetrically substituted dicyano-tri-tert-butylphthalocyanine ((CN)2BuPc) with rectifying behavior has been synthesized. The morphology and conductive properties of (CN)2BuPc Langmuir–Blodgett (LB) films on mica and highly ordered pyrolytic graphite (HOPG) substrates were studied by atomic force microscopy (AFM) and scanning tunneling microscopy (STM), in air at 22 °C. The average area of each (CN)2BuPc molecule obtained from the AFM topography in situ is ca. 73.6 A2, which is in good agreement with the result of ca. 74 A2 obtained from the π–A isotherm curve of a LB film. This indicates that the molecules are standing edge-on, tilted by 38° against the surface normal of the substrate. The conductive properties for the 7-layer LB films of (CN)2BuPc were studied by STM with a tungsten tip. The asymmetric I–V curve revealed a type of rectifying behavior for a negative and a positive bias. A feature model of the intramolecular and intermolecular charge transfer is presented. It not only interprets electron transfer from electron-donor to electron-acceptor molecules via a molecular “bridge”, but also the tunneling effect through intermolecular charge transfer.

Preparation of the SnO2/SiO2 xerogel with a large specific surface area

SnO2/SiO2 nanocomposite xerogel was synthesized by using the about-to-gel silica sol as “nanoglue”. Tin oxide uniformly dispersed within the three-dimension network of the silica in the form of nanoparticles. The SnO2/SiO2 nanocomposite xerogel has a large specific surface area (SSA), which depends on the deposition time of the silica sol.

Fluorinated fused nonacyclic interfacial materials for efficient and stable perovskite solar cells

Three fused-ring n-type semiconductors based on 6,6,12,12-tetrakis(4-hexylphenyl)-indacenobis(dithieno[3,2-b;2,3-d]thiophene) end-capped with 1,1-dicyanomethylene-3-indanone substituted by different numbers of fluorine atoms (INIC series) are employed as interfacial materials to modify the surface of the perovskite film in inverted planar perovskite solar cells (PSCs). Due to fast interfacial charge extraction and efficient trap passivation, PSCs based on INIC series exhibit a maximum power conversion efficiency of 19.3% without any hysteresis, which is superior to control devices without INIC series (16.6%). Moreover, the strong water-resistance ability of fluorinated INIC significantly enhances the ambient stability of the PSCs. The effects of fluorine atom number on the device performance are discussed.

Magnetostriction in twin-free single crystals TbyDy1−yFe2 with the addition of aluminum or manganese

Magnetostriction at room temperature under various conditions of compressive prestress and applied fields of TbyDy1−y(Fe1−xTx)2 (T=Al,u2009Mn) twin-free single crystals was investigated. The substitution of Al or Mn for Fe lowers the magnetostriction under ordinary temperature and pressure, and decreases the saturation field, which enables these materials with potential benefits for applications. Moreover, Tb0.5Dy0.5(Fe0.9Mn0.1)2 shows negative magnetostriction at room temperature under zero prestress, due to the rotation of domains 109.5° away from 〈111〉. Under appropriate compressive stress, a quite large magnetostriction of 2160 ppm with a saturation field of 900 Oe and high d33 of 4.8 ppm/Oe can be obtained.

Growth of segmented ZnS nanocones induced by regular occurrence of twins structure

Segmented ZnS nanocones have been prepared at 1200 degrees C by thermal evaporation of zinc sulfide powders and catalyst metal tin. The as-synthesized products have been studied by energy-dispersive x-ray spectroscopy, selected-area electron diffraction, and high-resolution transmission electron microscopy. Microstructure characterization indicates that the formation of segmented nanocones can be attributed to the effects of regular twins structure. Theoretical analysis reveals that the nonuniform cross sections of nanocones are related to the continuous change of Sn-ZnS liquid droplets scale resulting from the supply of Sn atoms during the evaporation. According to microstructure characterization and dimension analysis, the potential formation mechanism of the segmented ZnS nanocones was discussed

Photocharge accumulation and recombination in perovskite solar cells regarding device performance and stability

Photocharge accumulation and recombination in perovskite solar cells have been systematically investigated in this paper by electrochemical spectroscopy and transient photocurrent/photovoltage methods. It is found that the non-equilibrium photocharges stored in the selective charge transport layers follow a backward recombination mechanism. That is, the photocharges are first captured by the interface defects corresponding to the fast photovoltage decay, while the bulk charge recombination instead of the diffusion process dominates the slow photovoltage decay process. Further investigation reveals that the device degradation preferentially takes place at the interface under working conditions, which thus can confirm the importance of interface engineering to enhance the device stability.

Morphology controlled growth of large area ordered porous film

Abstract The morphology controlled growth of large area ordered porous film presents a number of challenges. This paper reports work on a universal route, solution dipping template strategy, for such structured films. The morphologies of the porous film can easily be controlled by concentration of the precursor solution and treatment conditions. By decreasing concentration from a high to a very low level, nanostructured complex (pore–hole, and pore–particle) arrays, through pore arrays, and even ring arrays can, in turn, be acquired. The pore size is adjustable over a range up to two orders of magnitude using the diameter of latex spheres. This new synthesis route is universal and can be used for metals, semiconductors, and compounds on any substrate. Such structures may be useful in applications in energy storage or conversion, especially in next generation integrated nanophotonics devices, biomolecular labelling and identification.

Growth of iron-based Laves phase containing Pr and Nd magnetostrictive materials

The synthesis and magnetostriction of R(1-x)Ce(x)Fe(2) (R = Pr, Nd) have been investigated. The pesudobinary compounds of Laves phase with high-Pr and Nd concentration can be obtained due to the strong Ce 4f bonding. Oriented polycrystalline materials can be produced by means of Czochralski method with cold crucible system. The measurement of magnetostriction reveals that the materials possess large magnetostriction at room temperature

Application of Cesium on the Restriction of Precursor Crystallization for Highly Reproducible Perovskite Solar Cells Exceeding 20% Efficiency

In this study, we systematically explored the mixed-cation perovskite Cs x(MA0.4FA0.6)1- xPbI3 fabricated via sequential introduction of cations. The details of the effects of Cs+ on the fabrication and performance of inorganic-organic mixed-cation perovskite solar cells examined in detail in this study are beyond the normal understanding of the adjusting band gap. It is found that a combined intercalation of Cs+ and dimethyl sulfoxide (DMSO) in PbI2-DMSO precursor film formed a strong and steady coordinated intermediate phase to retard PbI2 crystallization, suppress yellow nonperovskite δ-phase, and obtain a highly reproducible perovskite film with less defects and larger grains. The Cs-contained triple-cation-mixed perovskite Cs0.1(MA0.4FA0.6)0.9PbI3 devices yield over 20% reproducible efficiencies, superior stabilities, and fill factors of around 0.8 with a very narrow distribution.