TY  - JOUR
A1  - Brehmer, Ludwig
T1  - Supramolecular architectures for micro-sensorics and molecular electronics
Y1  - 1998
ER  - 
TY  - JOUR
A1  - Albrecht, Fred
A1  - Brehmer, Ludwig
A1  - Liemant, Alfred
T1  - Hopping transport in a disordered lattice simulation of dark discharge
N2  - On the basis of a stochastic model of hopping transport in disordered solids we present results of simulations of the dark discharge of surface charged thin films considering the energetic distribution of the localised states within the sheet. A non- linear differential equation with suitable boundary and initial conditions describes the time evolution of the space charge. We suppose a Gaussian distribution of energies for the carrier transporting states with a standard deviation s. The arrival time of carriers at the rear electrode of the sandwich sample is studied in dependence on film thickness, initial surface charge, and energetic disorder. Our calculations confirm that the transit time increases indirect proportional with initial surface charge and proportional with the square thickness. For standard deviations of energetic distribution of 0.05 eV up to 0.25 eV the normalised transit time grows as s1.44. We discuss this in terms of the stochastic transport model.
Y1  - 1998
ER  - 
TY  - JOUR
A1  - Janietz, Dietmar
A1  - Katholy, Stefan
A1  - Brehmer, Ludwig
T1  - Monolayer properties of Amphiphilic Tetrakis(phenylethynyl)benzene compounds
Y1  - 1998
ER  - 
TY  - JOUR
A1  - Geue, Thomas
A1  - Katholy, Stefan
A1  - Reiche, Jürgen
A1  - Brehmer, Ludwig
A1  - Caliebe, W.
T1  - Grazing incidence x-ray diffraction (GIXD) measurements of uranyl arachidate (UO2A2) LB films
Y1  - 1998
ER  - 
TY  - JOUR
A1  - Kaminorz, Yvette
A1  - Smela, E.
A1  - Inganäs, O.
A1  - Brehmer, Ludwig
T1  - Sensitivity of polythiophene planar light emitting diodes to oxygen
N2  - Surface light emitting diodes (SLEDs) with a polymer-on-top geometry were used to study the sensitivity of light emission to oxygen. In these devices, pre-fabricated electrodes were coated with a conjugated polymer, which was thus directly exposed to the environment. Oxygen caused an immediate ten-to hundred fold decrease in electroluminescence efficiency relative to that in nitrogen or argon. Above the voltage for light emission, there was a sharp increase in current. Removing the oxygen led to recovery of the light intensity over a period of minutes, but the current returned immediately to its lower, original level. The electroluminescence and photoluminescence spectra were identical and were unaltered in shape by oxygen exposure (only decreasing in size). However, photoluminescence was unaffected by oxygen alone. This result indicates that oxygen does not affect excitons directly, but rather influences an intermediate species on the path to exciton formation, one that is significant only in electroluminescence and not in photoluminescence. Under simultaneous exposure to oxygen and UV light, the photoluminescence irreversibly decreased, presumably due to photo-oxidation
Y1  - 1998
ER  - 
TY  - JOUR
A1  - Smela, E.
A1  - Kaminorz, Yvette
A1  - Inganäs, O.
A1  - Brehmer, Ludwig
T1  - Planar microfabricated polymer light-emitting diodes
N2  - Conjugated polymers are organic semiconducting materials that can emit light. These polymers have the advantages of being light, cheap, and easy to process, and in addition the band gap can be tailored. We report the microfabrication of surface light emitting diodes (SLEDs) on silicon substrates in which the electrodes are underneath the organic electroluminescent layer. Patterned electrodes are separated by a 2500Å-thick insulating layer of silicon oxide or are interdigitated with a separation of 10 or 20 µm; the luminescent polymer is spin-coated or solvent cast on top of the electrodes. This fabrication method is completely compatible with conventional silicon processing because the polymer is deposited last and the light is emitted from the upper surface of the diodes. Despite the large spacing between electrodes, and despite the absence of an evaporated top contact, the voltages required for light emission were not much greater than those used in conventional sandwich-type structures
Y1  - 1998
ER  -