Vezetési kihívások a magyarországi magyar–német vállalatoknál Az IMAGINE-projekt (Investigation of Management performance in INternational Enterprises) legfontosabb eredményei

A Pannon Egyetem Szervezési és Vezetési Tanszéke a Darmstadti Műszaki Egyetem Vállalatvezetési Tanszékével közösen több mint egy évtizede folytat a stratégiai menedzsment területén, ezen belül a vállalati és nemzeti kultúrákkal és a vállalati sikerrel kapcsolatos kutatásokat. A napjainkra befejezett IMAGINEprojekt (Investigation of Management performance in International Enterprises) a magyarországi tevékenységet folytató magyar–német transznacionális vállalatok vezetőire fókuszál. A projekt a vezetési stílust és a vezetés sikerét meghatározó tényezők elemzésével foglalkozik. Ezek az összefüggések a gyakorlat számára is hasznosítható eredményeket jelenthetnek. A szerzők összesen 86, Magyarországon működő magyar- német vállalat felső vezetője által kitöltött kérdőívet elemeztek

Carbon nanotubes as electronic interconnects in solid acid fuel cell electrodes

Carbon nanotubes have been explored as interconnects in solid acid fuel cells to improve the link between nanoscale Pt catalyst particles and macroscale current collectors. The nanotubes were grown by chemical vapor deposition on carbon paper substrates, using nickel nanoparticles as the catalyst, and were characterized using scanning electron microscopy and Raman spectroscopy. The composite electrode material, consisting of CsH_2PO_4, platinum nanoparticles, and platinum on carbon-black nanoparticles, was deposited onto the nanotube-overgrown carbon paper by electrospraying, forming a highly porous, fractal structure. AC impedance spectroscopy in a symmetric cell configuration revealed a significant reduction of the electrode impedance as compared to similarly prepared electrodes without carbon nanotubes

Polymer-Free Carbon Nanotube Based Solar Cells

Since their discovery in 1991 and 1994 by Iijima, multi walled (MWCNTs) and single walled carbon nanotubes (SWCNTs) have gained a lot of interest in the research community due to their unique mechanical (higher tensile strength than stainless steel), optical (multiple excitonic transitions) and electrical (intrinsic mobility of 105 cm2 V−1 s−1) properties. Being produced as black powder that contains roughly 1/3 metallic and 2/3 semiconducting nanotubes along with residual catalytic particles, carbon residues or defected nanotubes, it is important to further purify the raw nanotube powder to obtain pristine nanotubes only that can be used to exploit these remarkable properties. In order to incorporate SWCNTs as semiconducting channel material or as electrodes in transistors, it is of great importance to separate SWCNTs based on their electronic properties. Whereas, for optoelectronic applications, like photon emitters or solar cells it is necessary to sort semiconducting SWCNTs into chirality pure fractions with unique absorption features, i.e. the sorted nanotubes absorb at precise wavelengths (in the infrared, visible and UV). It is this ability to select SWCNTs with desired optical gaps that make SWCNTs an interesting material that also offers potential avenues to tailor or extend the light absorption within established solar cells. Through careful combination of the appropriate chiralities, a close match to the solar spectrum either in the visible or the infrared is possible. To realize this vision of tailored light absorption, large amounts of purified, electronic type sorted and chirality enriched SWCNTs are needed. In this thesis, an automated aqueous based gel permeation chromatography (GPC) is used to sort milligrams of polymer-free single chirality enriched nanotube material, where the exciton diffusion length is not limited by a wrapping polymer. Depending on the temperature, surfactant concentration and eluent differently coloured solutions are obtained that can be electronic type pure, chirality pure or a mixture of chiralities and/or electronic types. In order to prevent internal shorts, SWCNTs employed in solar cells need to obtain as little metallic nanotubes as possible. It is therefore crucial to easily and reliably characterize the sorted nanotube solutions with respect to the contained chiralities and semiconducting or metallic purity. One way of realizing such a characterization is optical absorption spectroscopy. A MATLAB® based program was developed throughout this thesis that is capable of addressing several issues involved in optical absorption spectroscopy of solutions: different approaches for background subtraction, the choice of different line profiles, the individual fit of the first or second transition (in the infrared and visible, respectively) or both at the same time and the inclusion of metallic nanotubes that allows for the evaluation of the metallic/semiconducting purity. Based on the spectral weight of each nanotube species identified in solution, absorbance spectra of carbon iv nanotube films can be fitted, where overlapping peaks are decongested into individual nanotube contributions. Following the sorting and characterization of single chirality SWCNTs, large-area films of (6,5) SWCNTs with uniform morphology are prepared using evaporation-driven self-assembly. The obtained SWCNT films are incorporated in an organic solar via a transfer process developed throughout this thesis that prevents the decomposition of hygroscopic layers in the solar cell. In conjunction with C60 a bi-layer organic solar cell with an all carbon donor and acceptor pair is formed. Transfer matrix calculations (TMCs) are employed to optimize the layer thicknesses of the solar cell in order to match the light intensity at the nanotubes first optical transition (in the infrared), their second transition (in the visible) or a combination thereof. The validity of this approach is verified by a detailed parameter study resulting in cutting edge internal quantum efficiency (IQE) of 86% through the nanotubes first transition. Having established a reliable solar cell architecture resulting in large IQE values for small diameter SWCNTs (large bandgap), the feasibility of preparing transparent organic solar cells from large diameter SWCNTs (small bandgap) in combination with C60 is tested by preparing organic solar cells from single chirality large diameter SWCNTs as well as mixtures of nanotubes with varying diameters. By carefully decongesting film absorption spectra and associated external quantum efficiency measurements, the nanotube diameter resulting in 0 % IQE is determined. Underlying mechanisms of this limit are discussed and possible strategies to circumvent this cut-off are presented in order to extend the absorption range beyond the (8,6) SWCNT with a diameter of 0.95 nm