Mr. Michael Kröger Profile

Michael Kröger

at Technische Univ Braunschweig

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Author

Publications (9)

Proceedings Article | 22 September 2015 Paper

Long-lived and highly efficient green and blue phosphorescent emitters and device architectures for OLED displays

Christian Eickhoff, Peter Murer, Thomas Geßner, Jan Birnstock, Michael Kröger, Zungsun Choi, Soichi Watanabe, Falk May, Christian Lennartz, Ilona Stengel, Ingo Münster, Klaus Kahle, Gerhard Wagenblast, Hannah Mangold

Proceedings Volume 9566, 95662N (2015) https://doi.org/10.1117/12.2199079

KEYWORDS: Organic light emitting diodes, Electron transport, Excitons, External quantum efficiency, Polymethylmethacrylate, Luminescence, Fluorescence resonance energy transfer, Diodes, Energy efficiency, Energy transfer

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Proceedings Article | 16 October 2007 Paper

Concepts for high efficient white OLEDs for lighting applications

A. Hunze, R. Krause, S. Seidel, O. Weiss, F. Kozlowski, G. Schmid, J. Meyer, M. Kröger, H. H. Johannes, W. Kowalsky, T. Dobbertin

Proceedings Volume 6655, 665511 (2007) https://doi.org/10.1117/12.731599

KEYWORDS: Organic light emitting diodes, Excitons, External quantum efficiency, Quantum efficiency, Excimers, Molecules, Electron transport, Light sources and illumination, Solid state lighting, Flat panel displays

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Proceedings Article | 16 October 2007 Paper

Highly efficient fully transparent inverted OLEDs

J. Meyer, T. Winkler, S. Hamwi, S. Schmale, M. Kröger, P. Görrn, H.-H. Johannes, T. Riedl, E. Lang, D. Becker, T. Dobbertin, W. Kowalsky

Proceedings Volume 6655, 66550L (2007) https://doi.org/10.1117/12.734051

KEYWORDS: Organic light emitting diodes, Sputter deposition, Glasses, Electrodes, Visible radiation, Light sources and illumination, OLED lighting, Absorption, Transmittance, Transparency

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Proceedings Article | 13 February 2007 Paper

See-through OLED displays

W. Kowalsky, P. Görrn, J. Meyer, M. Kröger, H.- H. Johannes, T. Riedl

Proceedings Volume 6486, 64860F (2007) https://doi.org/10.1117/12.696402

KEYWORDS: Organic light emitting diodes, Visible radiation, Oxides, Transparency, Aluminum, Transistors, Zinc oxide, Oxygen, LCDs, Transparent conductors

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Proceedings Article | 23 September 2005 Paper

Monolithic integration of OFETs driving organic light emitting diodes

Michael Kröger, Eike Becker, Christian Schildknecht, Sören Hartmann, Hans-Hermann Johannes, Wolfgang Kowalsky

Proceedings Volume 5940, 59401I (2005) https://doi.org/10.1117/12.618157

KEYWORDS: Organic light emitting diodes, Field effect transistors, Transistors, Optical lithography, Dielectrics, Organic materials, LCDs, Polymers, Organic semiconductors, Gold

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Organic field effect transistors are expected to be applicable for low-cost, large-area electronic applications, e.g. the incorporation as active-matrix into displays based on organic light emitting diodes (OLED). There are two major challenges which have to be tackled. As the low charge carrier mobility allows only for comparatively low saturation currents, the ratio of channel width and length has to increase by several orders of magnitude, compared to poly-Si-technology. Furthermore, as organic semiconductor devices usually degrade upon exposure to solvents, standard photolithography cannot be applied once the organic materials have been deposited. Therefore, the definition of single pixels has to occur before the deposition of organic materials. We prepared OFETs employing a bottom-Al-gate, an 50 nm thick anodized Al-oxide gate dielectric and a inter-digital drain-source-structure (Au), topped with 30 nm of pentacene as active layer. By applying an inter-digital structure we increased the W/L-ratio to 4340. For the given configuration, a saturation current of 4 mA could be observed at -20 V drain-source- and -20 V gate-source-voltage. The drain-source-contacts enclosed a predefined ITO-anode shorted to drain and acting as OLED-anode. For preventing shortcuts between the OLED-cathode and the OFET, poly-vinyl-alcohol (PVOH) was spin-coated from an aqueous solution and structurized by photolithography. When the OFET characteristics were measured afterwards the field-effect- mobility dropped by two orders of magnitude but recovered due to desorption of residual water. Afterwards, the organic layers and a Al/LiF-cathode were deposited. The area covered by the OLED was 1.33mm². Applying an operating bias of 11 V between cathode and source, allows for switching of the OLED by changing the gate-source-voltage from +2.5 V to -5 V. The on-state-brightness is 850 cd/m² and the on-off-ratio 950. Considering a realistic filling factor of 40% the values observed may be sufficient for active-matrix display-applications.

Proceedings Article | 7 July 2005 Paper

A laser induced local transfer for patterning of RGB-OLED-displays

Michael Kroeger, Marc Hueske, Thomas Dobbertin, Jens Meyer, Henning Krautwald, Thomas Riedl, Hans-Hermann Johannes, Wolfgang Kowalsky

Proceedings Volume 5840, (2005) https://doi.org/10.1117/12.608702

KEYWORDS: Organic light emitting diodes, Optical lithography, Organic materials, Low-intensity laser therapy, Continuous wave operation, LCDs, Glasses, Infrared radiation, Laser scanners, 3D scanning

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Proceedings Article | 10 November 2004 Paper

Highly efficient phosphorescent guest-host-systems for hybrid inverted organic light-emitting diodes with sputtered indium-tin-oxide anodes

Michael Kroeger, Thomas Dobbertin, Daniel Schneider, Torsten Rabe, Eike Becker, Hans-Hermann Johannes, Wolfgang Kowalsky

Proceedings Volume 5519, (2004) https://doi.org/10.1117/12.558913

KEYWORDS: Organic light emitting diodes, Luminous efficiency, Electrodes, Sputter deposition, Flat panel displays, Laser induced fluorescence, Organic materials, Silicon, Doping, Thin films

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Proceedings Article | 8 September 2004 Paper

Inverted topside-emitting organic light-emitting diodes for active-matrix OLED displays

Thomas Dobbertin, Michael Kroger, Daniel Schneider, Eike Becker, Hans-Hermann Johannes, Wolfgang Kowalsky

Proceedings Volume 5464, (2004) https://doi.org/10.1117/12.545709

KEYWORDS: Organic light emitting diodes, Lithium, Electrodes, Thin films, Doping, Aluminum, Polymers, Absorption, Resistance, Metals

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Proceedings Article | 16 February 2004 Paper

Inverted topside-emitting organic light-emitting diodes

Thomas Dobbertin, Daniel Schneider, Anis Kammoun, Jens Meyer, Oliver Werner, Michael Kroeger, Thomas Riedl, Eike Becker, Christian Schildknecht, Hans-Hermann Johannes, Wolfgang Kowalsky

Proceedings Volume 5214, (2004) https://doi.org/10.1117/12.505811

KEYWORDS: Organic light emitting diodes, Electrodes, Metals, Aluminum, Luminous efficiency, Magnesium, Sputter deposition, Electroluminescence, Thin films, Polymers

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Showing 5 of 9 publications

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