Papers by Keyword: Fullerene

Abstract: We report here a series of polypyrrole/C60-H3PO4 two-layer photovoltaic cells fabricated by varying the C60 ratio with regard to polypyrrole. It is found that a slight amount of C60 can remarkably improve photovoltaic properties by four orders of magnitude; with C60 ratio the open-circuit voltage and short-circuit current increase, and at higher C60 ratio the photovoltaic working threshold is lowered too, the cell can even work efficiently in dark, more approaching the efficiency under strong illumination. The optimized device yields 1.2 V open-circuit voltage and 14 μA/cm2 short-circuit current, and a power conversion efficiency 0.01%. Our results show that polypyrrole is a potentially good material for photovoltaic cells. The effect of C60 in combination with polypyrrole is discussed.

Abstract: The short circuit current density (Jsc) of polymer solar cells is strictly related to the absorption of the blend film. Recently it has been shown that the use of [70]PCBM as electron acceptor can improve the current output of such devices because C70 derivatives have a stronger and broader absorption compared to C60 ones. The aim of this work is to study the influence of the fullerene on the optical behaviour of the photoactive blend film of a polymer solar cell. We have determined the optical constants of a P3HT:[70]PCBM blend film and studied their variation as a function of the annealing temperature. Afterward, we simulated the optical absorption of the active layer inside the device structure and calculated the maximum achievable Jsc with the aim to correlate the variation of the optical constants to the device output current. We compared this value with that one obtained using a P3HT:[60]PCBM blend.

Abstract: Organic photovoltaic(OPV) cells are rapidly gaining attention due to their potential to be fabricated at low cost in thin, flexible, and light-weight forms. For efficient generation of photo-induced charges,C60 has been indispensable electron acceptors in building heterojunctions with various suitable electron donors, such as CuPc, and Alq3 was always used as a new buffer layer to improve the degradation of heterojunction conductivity upon oxygen permeation In this work, the photoelectric properties of organic solar cells(ITO/CuPc/C60/ Al) were studied with a focus on the effect of substrate temperature. All the organic layers and the aluminum cathode were prepared onto ITO substrates by vacuum deposition at various substrate temperatures from room temperature to 363°CK. With increasing the substrate temperature , an improvement in crystallization of bilayer films(CuPc/C60) was observed by AFM. The results showed the photoconduction of the bilayer films increased because the bilayr films were well oriented, and the carrier mobility of the films were enhanced withby the increase of the substrate temperature.

Abstract: The purpose of this study is to fabricate a wheel using fullerenes with nano-scaled particles, and to investigate the polishing performance of fullerene wheel. A super smooth surface was formed on a silicon wafer by polishing the wafer with metal-bonded diamond wheels using a diamond abrasive grit of 0-0.125 μm and fullerenes with a diameter of 0.7 nm. We used two kinds of metal-bonded diamond wheels for pre-polishing and a metal-bonded fullerene wheel for the finishing process. Though the surface roughness after polishing with the fullerene wheel was almost equal to that obtained by polishing with the metal-bonded diamond wheel using diamond abrasive grit of 0-0.125 μm, the chemical-mechanical polishing process was clarified by AFM (atomic force microscope) observation when we used a metal-bonded fullerene wheel with 5wt% KOH (potassium hydroxide) solution. The greater number of smoothed portions on the surface of the silicon wafer indicated that the fullerenes provided the same polishing ability as that of the abrasive grit.

Abstract: A unified theoretical and/or computational odd-electrons approach is suggested for molecules, surfaces and magnetic solids making possible their consideration on the same conceptual basis as well as on the same computational footing. The current paper presents the approach application to the chemistry of fullerenes, carboneous nanotubes, surface science of silicon crystal, as well as to the molecular magnetism of both solid polymerized fullerenes and molecular crystals composed of transitional metal complexes.

Abstract: Carbon nanomaterials are among the best known and most promising products of the nanotechnology movement. Some early studies suggest that fullerenes and nanotubes may pose significant health risks, and this has given rise to an emerging literature on carbon nanotoxicology. This young field has now begun to yield insight into toxicity mechanisms and the specific material features involved in those mechanisms. This paper explores the potential to alter those material features through post-processing or reformulation with the goal of reducing or eliminating carbon nanomaterial health risks. The paper emphasizes the important roles of metal content and bioavailability, carbon surface chemistry, and nanomaterial aggregation state. The nanotechnology movement has been given a unique "window of opportunity" to systematically investigate the toxicity of nanotechnology products and to develop ways to manage health risks before large scale manufacturing becomes widespread.

Abstract: A continuous C70 nanowire arrays are prepared using a simple electrophoretic deposition method, composed of two steps: generation of the cluster; and deposition of cluster in the alumina membrane, which is proved to be a practicable technique to fabricate other fullerene low-dimensional nanostructures.

Abstract: One of the most amazing features of diamond is the p-type surface conductivity which occurs when intrinsic material is hydrogen terminated and brought into contact with appropriately chosen adsorbates. Experiments during the last decade have revealed the different roles of the surface acceptors and of the covalent carbon-hydrogen surface bonds: providing unoccupied electronic states, and lowering the energy barrier for electron transfer from the diamond, respectively. The simplest and historically first method to supply surface acceptors, i.e. exposing hydrogenated diamond to air, provides, unfortunately, the most complex electronic system acting as surface acceptors, namely solvated ions within atmospheric wetting layers. In that case electron transfer is accompanied by a red-ox reaction that finally induces the hole accumulation. A much simpler case of transfer doping has been demonstrated for C60F48 as molecular surface accpeptors. In this case, the doping yield as a function of surface coverage can be modelled quantitatively by the transfer doping mechanism. Also, pure C60 can be adopted for transfer doping, but the formation of the van-der-Waals solid is required in this case to circumvent the electron correlation energy for charge transfer to a single fullere cage. The C60 layers can be stabilized by oxygen-mediated polymerisation without loosing their doping efficiency.

Abstract: TriA-PI is a newly developed phenylethnyl terminated polyimide. It exhibits excellent mechanical properties and processability with high glass transition temperature (Tg>300°C). Nano-size particles of fullerene were dispersed throughout a thermosetting polyimide Triple API (TriA-PI) to elevate the glass transition temperature. The increase of the glass transition temperature of the composites with the fullerene was confirmed by dynamic mechanical analysis (DMA).

Abstract: In this paper, report on fullerene formation in a radio-frequency (RF) thermal plasma reactor has been presented. In order to determine the degree of evaporation of the graphite precursor used, analysis of SEM micrographs of deposited soot in different parts of RF reactor has been made. It was found that the degree of graphite evaporation and fullerene yield varied depending on the distance from the plasma torch nozzle. Carbon concentration and rotational temperature of C2 radicals in plasma flame have been calculated as well. The concentration of C2 radicals in plasma flame, which participated in fullerene formation, was in the range of (1.75-3.88)×1020 m-3.