Fabrication of organic photovoltaic devices by the layer-by-layer polyelectrolyte deposition method

Organic photovoltaic cells were fabricated by the layer-by-layer polyelectrolyte deposition process by which the film thickness can be controlled accurately. Ruthenium/rhenium complexes containing poly(p-phenylenevinylene) and sulfonated polyaniline were used in the process. This new method provides flexibility in the fabrication of multilayer polymeric devices with well-defined structure. © 2005 IEEE.published_or_final_versio

Cordless printed circuit board transformers for power transfer in neuroprosthesis

Author name used in this publication: K. W. E. ChengAuthor name used in this publication: K. Y. TongRefereed conference paper2006-2007 > Academic research: refereed > Refereed conference paperVersion of RecordPublishe

Development of a circuit for functional electrical stimulation

Author name used in this publication: Kai-Yu Tong2003-2004 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Fabrication of bulk heterojunction photovoltaic devices using sublimable rhenium diimine complexes as photosensitizers

A series of chlorotricarbonyl rhenium (I) bis(phenylimino)acenaphthene (Re-DIAN-X) complexes were used as the photosensitizers for photovoltaic cells. Unlike other transition-metal-based photovoltaic sensitizers that can only be prepared by solution method, these complexes are sublimable. Compared to other rhenium diimine complexes based on bipyridine or 1,4-diaza-1,3-butadiene ligands, these complexes have lower band gaps, which can be modified easily by changing the structure of the ligand. It allows the preparation of blend of metal complexes in order to broaden the sensitization region in UV-vis absorption spectrum. One of the complexes also shows bipolar charge transport character with relatively high charge carrier mobilities in the order of 10 -3 cm2V-1s-1. Multilayer heterojunction and bulk heterojunction devices with fullerene as the electron accepting molecule were prepared. For the bulk heterojunction devices, the fill factor and power conversion efficiency under AM 1.5 simulated solar light illumination were 0.51 and 1.29 %, respectively. The effects of changing the Re-DIAN/C60 film thickness, Re-DIAN/C60 ratio and variation of ligand structures in the bulk heterojunction devices were studied. The amount of photosensitizer and electron transport molecules may strongly affect the balance between the photon absorption, exciton formation, dissociation, and charge transport processes. Atomic force microscopic images showed that the complex dispersed evenly with fullerene molecules in solid state.published_or_final_versio

Terpenoid, benzenoid and phenylpropanoid compounds in the floral scent of vanda mimi palmer.

Vanda Mimi Palmer is the product of a cross between Vanda Tan Chay Yan and Vanda tessellata. The flower of this hybrid produces a sweet-smelling fragrance during day time at the open-flower stage. This study aimed to investigate the floral scent constituents in Vanda Mimi Palmer. Scent emission analysis of this orchid was carried out at different time points in a 24-h cycle and also at different floral developmental stages. A comparison was also made on the volatiles emitted by Vanda Mimi Palmer and both of its parents. Gas chromatography-mass spectrometry (GC-MS) analysis showed that the scent of Vanda Mimi Palmer was dominated by terpenoid, benzenoid, and phenylpropanoid compounds. The identified terpenoids were ocimene, linalool oxide, linalool, and nerolidol; while the benzenoid and phenylpropanoid compounds were methylbenzoate, benzyl acetate, phenylethanol, and phenylethyl acetate. The emission of terpenoid, benzenoid, and phenylpropanoid compounds was developmentally and temporally regulated. Comparison of the volatiles emitted by both of its parents showed that the scent of Vanda Mimi Palmer is dissimilar to that of its fragrant parent, V. tessellata

Low-band-gap, sublimable rhenium(I) diimine complex for efficient bulk heterojunction photovoltaic devices

The fabrication of efficient bulk heterojunction photovoltaic cells using the chlorotricarbonyl rhenium(I) diimine complex as photosensitizer was discussed. The complex has a lower band gap, which can be adjusted easily by changing the structure of the ligand. The electric properties of the complex were studied using time-of-flight analysis. It was observed that the rhenium complex showed bipolar charge transport character with relatively high electron and hole mobilities.published_or_final_versio

Siam-weeb based gelatin electrospun scaffolds

Siam weed (Chromolaena odorata) is a traditional herb used to soothe burns and scars and potentially improve dressing and tissue-engineered construct healing ability. The use of Siam weed is mainly in the form of extract. The state of liquid extract limits the use of Siam weed compared to the state of gels and membrane. However, the development of the hybrid of Siam weed in gel and membrane form is lacking. In this study, Siam weed was harvested and made into aqua extracts. The biocompatibility of the aqua extract with various concentrations was tested using Cell Proliferation Assay. The aqua extract was then incorporated into the gelatin solution and spun into nanofibers using an electrospinning technique. The cell proliferation study shows maximum cell proliferation at the 25 μg/ml concentration. The scanning electron microscope images of the electrospun scaffolds show fibrous networks’ microstructures without beads. The concentration of the hybrid solution was found to affect the morphology of the nanofibers by having diameters in the range of 160 ± 90 to 250 ± 150 nm. The Siam-weed-based gelatin electrospun scaffolds provide a native-like microenvironment and potentially improve wound healing ability for biomedical application

Fabrication of Photovoltaic Cell from Ruthenium Containing Polymer Using Layer by Layer Polyelectrolytes Adsorption Technique

Multilayer photovoltaic devices were fabricated by the sequence adsorption of different polyelectrolytes. A ruthenium terpyridine complex containing poly(p-phenylenevinylene) was used as the polycation layer. This polymer has been shown to exhibit large photo-sensitivity due to the presence of the ruthenium complex, which has relatively long-lived excited state. This polymer absorbs strongly in the visible region at ca. 480-550 nm and it can act as the electron transporter. Sulfonated polyaniline was used as the hole-transporting polyanion layer. The ITO/(polyanion/polycation) n/A1 devices were found to exhibit photovoltaic properties under the illumination of AM1 solar radiation. The short-circuit current I sc, open-circuit voltage V oc, and the fill factor FF were measured to be 14 μA/cm 2, 0.84 V and 0.16 respectively. It was found that the power conversion efficiencies of the devices were dependent on the device thickness. This simple layer-by-layer self-assembly method allowed us to control the devices thickness accurately.published_or_final_versio

Hydrogen peroxide treatment induced rectifying behavior of Aun-ZnO contact

Conversion of the Aun-ZnO contact from Ohmic to rectifying with H2 O2 pretreatment was studied systematically using I-V measurements, x-ray photoemission spectroscopy, positron annihilation spectroscopy, and deep level transient spectroscopy. H2 O2 treatment did not affect the carbon surface contamination or the EC -0.31 eV deep level, but it resulted in a significant decrease of the surface OH contamination and the formation of vacancy-type defects (Zn vacancy or vacancy cluster) close to the surface. The formation of a rectifying contact can be attributed to the reduced conductivity of the surface region due to the removal of OH and the formation of vacancy-type defects. © 2007 American Institute of Physics.published_or_final_versio

The Spectrum of Goldstini and Modulini

When supersymmetry is broken in multiple sectors via independent dynamics, the theory furnishes a corresponding multiplicity of "goldstini" degrees of freedom which may play a substantial role in collider phenomenology and cosmology. In this paper, we explore the tree-level mass spectrum of goldstini arising from a general admixture of F-term, D-term, and almost no-scale supersymmetry breaking, employing non-linear superfields and a novel gauge fixing for supergravity discussed in a companion paper. In theories of F-term and D-term breaking, goldstini acquire a mass which is precisely twice the gravitino mass, while the inclusion of no-scale breaking renders one of these modes, the modulino, massless. We argue that the vanishing modulino mass can be explained in terms of an accidental and spontaneously broken "global" supersymmetry.Comment: 10 pages, 2 figures; v2: typo corrected, references updated; v3: version to appear in JHE