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Geochimica et Cosmochimica Acta, 73 (13 / Supplement), ISSN:0016-7037, ISSN:1872-9533

Geochimica et Cosmochimica Acta, 73 (13 / Supplement), ISSN:0016-7037, ISSN:1872-9533

Irradiation of unsupported samples of hydrogenated amorphous silicon below 100 K with 360-MeV Xe ions results in macroscopically visible changes in sample dimensions. These changes have two different causes. Formation and growth of cavities lead to an isotropic increase of the specimen dimensions and to a drastic decrease of the mass density. Simultaneously plastic flow occurs, which produces additional but anisotropic changes of the specimen dimensions. The dimensions perpendicular to the beam grow whereas the dimension parallel to the ion beam shrinks. Neither effect saturates in the investigated fluence range (Φt< 1014Xe/cm2) and both are absent in crystalline silicon. The effects are most likely provoked by electronic excitations and/or ionizations in the wake of the fast ions. With respect to plastic flow,a–Si:H behaves like metallic and oxide glasses. Formation of cavities and their growth, however, seem to occur only in tetrahedrally coordinated solids.

Contactless measurements of the transient photoconductivity in {ital a}-Si:H and in {ital a}-Si{sub 1{minus}{ital x}}Ge{sub {ital x}}:H alloys are reported. A decrease of the effective electron mobility with increasing Ge content is observed. Because of a difference of dependence of the excitation density, two different processes are distinguished that lead to this decrease of the mobility. One is attributed to trapping and the other one leads to a decrease of the drift mobility. No increase of the recombination rate upon alloying of {ital a}-Si:H with Ge is observed as, on the contrary, the long-time decay in alloys is slower than in pure {ital a}-Si:H.

Hydrogen profiles for layered a-Si:H structures are presented. Substantial accumulation of hydrogen at the p-i interface is found. Additional incorporation of hydrogen in p-layers is also observed for intermediate boron doping levels compared to intrinsic layers. Hydrogen profiles in single pin and in pinpin amorphous silicon structures enable determination of individual layer thickness.

The optoelectronic properties of a-Si:H films grown at different substrate temperatures between 30°C and 250°C were evaluated in-situ by contactless Time Resolved Microwave Conductivity (TRMC) measurements. The transient photoconductivity induced by 532nm laser pulses during the growth of multilayer systems composed of a-Si:H layers deposited at different temperatures made a direct comparison of these films possible. The maximum height of the TRMC signal was observed to decrease strongly with decreasing deposition temperature. Additionally, the annealing of layers deposited at low temperatures was studied by TRMC, stationary photoconductivity, IR and ESR measurements. Whereas a considerable increase of the photoconductivity and the TRMC signal and a decrease in the spin density was observed during annealing at 250°C, the IR transmission spectra remained unchanged.

Geochimica et Cosmochimica Acta, 72 (12 / Supplement), ISSN:0016-7037, ISSN:1872-9533

ISSN:0016-7037 ISSN:1872-9533

At the moment there are efforts to replace the classical transparent conducting coating, Indium Tin Oxide, (or other TCO's) by a new class of materials, which are easier to handle and cheaper in mass production. Possible choices are transparent conductive coatings, which consist of polymers. In this investigation PEDOT:PSS is used. Carbon nanotubes are added in order to render the film electrically conductive. A prerequisite for its use is long-term stability. Therefore the degradation of PEDOT: PSS/ carbon nanotubes as a function of time is determined.

The electrical properties of various lead-free electrically conductive adhesives are investigated. They are intended to replace the solder, which is normally used to connect the interconnector tapes to the busbar. Compared to solder joints conductive adhesives offer the advantage of lower contact formation temperature with reasonable low contact resistances.

23rd European Photovoltaic Solar Energy Conference and Exhibition, 1-5 September 2008, Valencia, Spain; 651-654, Polymer solar cells have evolved as a promising cost-effective alternative to silicon-based solar cells. However, low efficiency of these plastic solar cells limits their feasibility for commercial use. The efficiencies of polymer photovoltaic cells got a major boost with the introduction of the bulk heterojunction (BHJ) concept consisting of an interpenetrating network of electron donor and acceptor materials. In this work we describe the preparation of BHJ organic solar cells using blend films of poly[4,4’-bis(alkylsulfanyl)- 2,2’-bithiophene] (P3ST) and 1-(3-methoxycarbonyl)-propyl-1-phenyl-(6,6)C61 (PCBM). Photovoltaic cells were prepared with a layer sandwiched between electrodes with different work functions. The electrical performance of the devices were compared with the corresponding one prepared using a blend of commercial poly(3-hexylthiophene) (P3HT) and PCBM. The quantum efficiency of the device fabricated with P3ST/PCBM blend shows a better response in the visible region compared to the one with P3HT/PCBM.

Geochimica et Cosmochimica Acta, 72 (12 / Supplement), ISSN:0016-7037, ISSN:1872-9533

Economic Geology, 103 (5)

Geochimica et Cosmochimica Acta, 72 (12, Supplement), ISSN:0016-7037, ISSN:1872-9533

Geochimica et Cosmochimica Acta, 72 (12 / Supplement), ISSN:0016-7037, ISSN:1872-9533

Geochimica et Cosmochimica Acta, 71 (15 / Supplement), ISSN:0016-7037, ISSN:1872-9533

Geochimica et Cosmochimica Acta, 71 (15 / Supplement), ISSN:0016-7037, ISSN:1872-9533

Geochimica et Cosmochimica Acta, 71 (15 / Supplement), ISSN:0016-7037, ISSN:1872-9533

Geochimica et Cosmochimica Acta, 71 (15 / Supplement), ISSN:0016-7037, ISSN:1872-9533

The dispersion of conventional amorphous silicon (a-Si:H)/crystalline silicon (c-Si) heterojunction solar cells shows a single time constant behavior. However, when a multicrystalline substrate is used, an additional "hump" appears in the C-f and R-f curves. A possible explanation by the introduction of a second time constant fails. As an alternative, interface states are considered as the reason of the hump. Thus, an equivalent circuit is established which is used to extract the parallel conductance and capacitance caused by the interface states. A bell-shaped conductance (normalized to frequency) and a step-shaped capacitance appear as predicted by Shockley-Hall-Read theory. The evaluation can be further improved by application of the statistical model (assumption of a fluctuating surface potential). The final data are a surface state density Dit of 2.3 1012 V-1cm-2, a time constant tauit of 1.7 ms and a standard deviation a of 0.8

An experiment that is useful in investigating crystallinity evolution during fast cooling, comparable with cooling rates attained in industrial processes, is extremely attractive. In this paper, a setup able to quench thin polymer films while recording the sample thermal history and light intensity of a laser beam transmitted by the sample is described. A particular feature of the optical-measurement setup is the use of the light-emitting diode (LED) array as a receiver, enabling the monitoring of changes in the polarization properties as changes in light scattering of the polymer during crystallization. Furthermore, it could be demonstrated that the LED array can be used as a linear optical detector with photocurrent gain values exceeding ten when polarized slightly below reverse-bias breakdown.

Geochimica et Cosmochimica Acta, 70 (18 / Supplement), ISSN:0016-7037, ISSN:1872-9533

The Miocene epithermal Au-Ag deposits of Roşia Montană and Rodu-Frasin are located in the South Apuseni Mountains in Transilvania, western Romania, in the province of Alba Iulia. Both deposits lie in a northwesterly striking extensional structure. Miocene calc-alkaline magmatism is related to extensional tectonics due to block rotations during Carpathian orogenesis. Roşia Montană is among the biggest epithermal Au deposits in Europe with total reserves of 217.96 Mt of ore at 1.52 g/t Au and 7.5 g/t Ag (Wallier et al., submitted). This study represents the work of two completed Master thesis on the deposit of Roşia Montană and two ongoing master thesis on the deposit of Rodu-Frasin with main focus on fluid evolution studied by fluid inclusion analysis.

The synthesis of new molecules containing both electron and hole transporter units is reported. This class of compounds, named OC, may be used for assembling electroluminescent devices made by a single organic layer. The active moieties are the carbazole, as the hole transporter unit, and the oxadiazole, as the electron transporter unit. The chemical formulation and the complex geometry of the molecular frame allow good solubility in chlorinate solvents and the preparation of homogeneous films by spinning technique. Photoluminescence of molecules, both in solution and in film, occurs in the blue region of visible spectra, the exact peak position of emission depending on the pendants attached to the oxadiazole unit. The electroluminescence occurs in a higher wavelength region, with a blue-green emission. The electroluminescent devices consist in the simple sequence ITO–OC–Al and ITO–PEDOT–OC–Al. © 2005 Elsevier B.V. All rights reserved.

The effect of the electrical field on the conductivity of linear low-density polyethylene/carbon nanotubes/ (LLDPE/CNT) composites during temperature cycling has been investigated. Under applied voltage a positive resistivity temperature coefficient was observed during heating already at low (2–3 wt%) CNT content, followed by a large negative temperature coefficient during cooling whose value depends on the applied voltage. The resistivity values after thermal cycling were markedly lower, while they slightly increased in the absence of an electrical field. The effects of thermal cycling on structural and physical properties of the composites have been evaluated by X-ray diffraction and differential scanning calorimetry.