Ligong Yang

Design of Cu8Zr5-based bulk metallic glasses

Basic polyhedral clusters have been derived from intermetallic compounds at near-eutectic composition by considering a dense packing and random arrangement of atoms at shell sites. Using such building units, bulk metallic glasses can be formed. This strategy was verified in the Cu–Zr binary system, where we have demonstrated the existence of Cu8Zr5 icosahedral clusters in Cu61.8Zr38.2, Cu64Zr36, and Cu64.5Zr35.5 amorphous alloys. Furthermore, ternary bulk metallic glasses can be developed by doping the basic Cu–Zr alloy with a minority element. This hypothesis was confirmed in systems (Cu0.618Zr0.382)100−xNbx, where x=1.5 and 2.5at.%, and (Cu0.618Zr0.382)98Sn2. The present results may open a route to prepare amorphous alloys with improved glass forming ability.

ZnO/poly(9,9-dihexylfluorene) based inorganic/organic hybrid ultraviolet photodetector

Solution processed inorganic/organic hybrid films of ZnO nanoparticles and poly(9,9-dihexylfluorene) (PFH) are sandwiched between two electrodes to form bulk heterojunction in this letter. The devices obtained show high ultraviolet photo-to-dark current ratio of about three orders of magnitude for −1V bias with a relatively fast response speed of less than 200ms after aging in air for enough time. The spectral response covers 300–420nm, with its peak locating around 335nm. Those results indicate that the ZnO/PFH hybrid devices might be used as low-cost UV optical switches or photodetectors.

Atomic structure in Zr70Cu29Pd1 metallic glass

Local atomic structures of Pd, Cu, and Zr atoms in an as-prepared Zr70Cu29Pd1 glassy alloy and the annealed samples containing icosahedral quasicrystal have been investigated by Pd, Cu, and Zr K-edge extended x-ray absorption fine structure (EXAFS) measurements. It is found that Cu and Zr atoms have an icosahedral atomic surrounding. Cu atoms could locate at both center position and shell sites while Zr atoms most likely occupy the shell sites of icosahedron. Pd atoms neither substitute Zr atoms nor Cu atoms. They sit at octahedral interstices, which link up icosahedron and promote the growth of icosahedron into long-range-order icosahedral quasicrystal in the ternary Zr70Cu29Pd1 glassy alloy during annealing treatment.

Short-range structure of Zr41Ti14Cu12.5Ni10Be22.5 glass prepared by shock wave

Short-range structure of a Zr41Ti14Cu12.5Ni10Be22.5 bulk metallic glass prepared by shock-wave treatment was investigated by x-ray diffraction using synchrotron radiation with a wavelength of 0.112 71 A. The radial distribution function was obtained from S(Q) with a large Q value up to 20 A−1. The oscillation in S(Q) of the glass definitely persists up to Q∼14 A−1. The shoulder on the high Q side of the second peak is observed in the bulk glass. It is found that the glass has higher coordination numbers in the range of r∼2.4–5.6 A and lower numbers in the range of r∼5.6–9.5 A than those for a water-quenched glass while the shell distances are similar in both glasses prepared by shock-wave and water-quenching methods. In the shock-waved glass, atomic configurations in the first, fourth, or fifth coordination shells are modified, i.e., atoms are packed denser in the first two coordination shells and less (or more free volume) in the third and fourth coordination shells as compared to those for the water-que...

Sb2O3 anode buffer induced morphology improvement in small molecule organic solar cells

We report that a very thin n-type Sb2O3 anode buffer layer in copper phthalocyanine (CuPc)/fullerene (C60) organic solar cells (OSCs) increases the power conversion efficiency by a factor of ∼34%. The enhancement is mostly attributed to the preferred orientation of CuPc layer and the increased contact area of CuPc/C60 interface, induced by the Sb2O3 layer rather than commonly regarded energy level alignment achieved by other metal oxides such as MoO3. Our study provides an insight to understand effect of the metal oxide buffer layers on the morphological influence in organic solar cells.

Charge transport at hybrid bulk heterojunction based on CdS nanopillar arrays embedded in a conducting polymer

Charge transport in hybrid devices based on a quasiordered heterojunction consisting of a CdS film with nanopillarlike nanostructures embedded in a poly[2-methoxy-5-(20ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) layer was investigated. Temperature-dependent photoluminescence spectra indicate that there exist two kinds of defects (sulfur vacancy and sulfur interstitial) in this CdS film, which act as electron and hole traps, respectively. Current (I)-voltage (V) characteristics in dark show that charge recombination is the main mechanism at the hybrid interface when Ohmic contacts are formed at CdS/indium tin oxide and MEH-PPV/Au interfaces. Photocurrent action spectra and I-V performance under illumination indicate that the recombination was enhanced at the interface due to the participation of the defects. In view of these realities, the light intensity dependence of the photocurrent and the photovoltage of the hybrid devices could be understood by a quantitative model including trap-assistant recomb...

Origin of the pre-peak in Zr70Cu29Pd1 metallic glass

High-resolution x-ray diffraction experiments were performed for Zr70Cu30?xPdx (x = 0, 1, 5, 10, 20 and 30?at.%) metallic glasses together with reverse Monte Carlo. A pre-peak arising in the low-Q range of S(Q) in Zr70Cu29Pd1 metallic glass was detected whereas no pre-peak was observed in the other samples. The origin of the pre-peak is identified to be the medium-range order around Pd atoms occupying an octahedral-like cluster in the metallic glass. When a pre-peak in S(Q) exists for metallic glasses containing heavy metal elements at a low concentration (such as noble metal or rare earth elements), medium-range order, centered with these heavy atoms, might occur in metallic glasses.

Crystallization of Zr41Ti14Cu12.5Ni10Be22.5 bulk metallic glass under high pressure examined by in situ synchrotron radiation x-ray diffraction

Crystallization of Zr41Ti14Cu12.5Ni10Be22.5 bulk metallic glass under high temperature and high pressure has been investigated by in situ synchrotron radiation x-ray diffraction. The onset temperature of crystallization was found to increase with pressure, but with a sudden drop at about 5.6GPa. Though the primarily precipitated phase is the same at different pressures, the sequences of the following phase precipitation are different.

A facile nanotemplate preparation method for [60]fullerene nanofibres : surface-wetting

Highly-ordered and well-aligned fullerene nanofibre arrays were fabricated via a nanotemplate preparation method and surface-wetting technique. The as-prepared fullerene nanofibre arrays were characterized by field-emission scanning electron microscopy, transmission electron microscopy, ultraviolet-visible absorption spectra and X-ray diffraction analysis. The dual-layered photoreceptors containing the fullerene nanofibre arrays or bulk fullerene films as the charge-generation layer (CGL) were fabricated. The photosensitivity of photoreceptors with fullerene nanoarrays as CGL was improved by one order of magnitude compared to that of their bulk films. The effect of the diameter and the length of the fullerene nanofibres on the photosensitivity of the photoreceptors was also investigated.

Reduced contact resistance in solution-processed phenylenevinylene-based copolymer thin-film transistors using annealing-induced morphological variation

A significant (about 10-fold) reduction in contact resistance in top-contact poly[divinyl-bis(hexyloxy)benzene-alt-diketopyrrolopyrrole] thin-film transistors was realized by changing the microscopic morphology of Au/polymer interface through thermal annealing. An enhancement of roughness was caused by the variation of molecular stacking, as confirmed by x-ray diffraction spectra. The influences of roughness variation on the mobility-dependent contact resistances were compared, and a more than 10-fold increase in linear field-effect mobility was obtained in annealed devices, approaching 10?3?cm2?V?1?s?1. Further analysis showed that the increased density of local states and better bulk transport near the contact interface, which resulted from the enhanced surface roughness, should be responsible for this improvement.