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Schuchert T.,Fraunhofer Institute for Optronics, System Technologies and Image Exploitation | Voth S.,Fraunhofer Institute for Optronics, System Technologies and Image Exploitation | Baumgarten J.,Fraunhofer Institute for Organics, Materials and Electronic Devices
Proceedings of the 4th Workshop on Eye Gaze in Intelligent Human Machine Interaction, Gaze-In 2012 | Year: 2012

This paper presents a novel system for sensing of attentional behavior in Augmented Reality (AR) environments by analyzing eye movement. The system is based on light weight head mounted optical see-through glasses containing bidirectional microdisplays, which allow displaying images and eye tracking on a single chip. The sensing and interaction application has been developed in the European project ARtSENSE in order to (1) detect museum visitors attention/interest in artworks as well as in presented AR content, (2) present appropriate personalized information based on the detected attention as augmented overlays, and (3) allow museum visitors gaze-based interaction with the system or the AR content. In this paper we present a novel algorithm for pupil estimation in low resolution eye-tracking images and show first results on attention estimation by eye movement analysis and interaction with the system by gaze. © 2012 ACM.


Kim Y.H.,TU Dresden | Kim Y.H.,Fraunhofer Institute for Organics, Materials and Electronic Devices | Lee J.,TU Dresden | Lee J.,Electronics and Telecommunications Research Institute | And 6 more authors.
Advanced Functional Materials | Year: 2013

Efficient transparent organic light-emitting diodes (OLEDs) with improved stability based on conductive, transparent poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) electrodes are reported. Based on optical simulations, the device structures are carefully optimized by tuning the thickness of doped transport layers and electrodes. As a result, the performance of PEDOT:PSS-based OLEDs reaches that of indium tin oxide (ITO)-based reference devices. The efficiency and the long-term stability of PEDOT:PSS-based OLEDs are significantly improved. The structure engineering demonstrated in this study greatly enhances the overall performances of ITO-free transparent OLEDs in terms of efficiency, lifetime, and transmittance. These results indicate that PEDOT:PSS-based OLEDs have a promising future for practical applications in low-cost and flexible device manufacturing. Transparent organic light-emitting diodes (OLEDs) with conductive, transparent poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) electrodes are carefully optimized by tuning the device structure. The efficiency of PEDOT:PSS-based OLEDs is comparable to that of conventional indium tin oxide-based OLEDs. Long-term stability of OLEDs with PEDOT:PSS is significantly improved, showing a promising future for practical applications. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Kim Y.H.,Fraunhofer Institute for Organics, Materials and Electronic Devices | Kim Y.H.,University of Minnesota | Schubert S.,Fraunhofer Institute for Organics, Materials and Electronic Devices | Timmreck R.,Fraunhofer Institute for Organics, Materials and Electronic Devices | And 2 more authors.
Advanced Energy Materials | Year: 2013

n-Doped C60 is reported as a new electrode material for indium-tin-oxide-free organic solar cells. All layers from the bottom to top electrode are prepared in one step in a vacuum chamber. The organic solar cells based on the n-C60 electrodes assisted by a semitransparent metal grid exhibit efficiencies as high as 2.9%. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Kim Y.H.,TU Dresden | Kim Y.H.,Fraunhofer Institute for Organics, Materials and Electronic Devices | Kim J.S.,Korea Institute of Science and Technology | Kim J.S.,Korea University | And 8 more authors.
Advanced Functional Materials | Year: 2013

High performance indium tin oxide (ITO)-free small molecule organic solar cells and organic light-emitting diodes (OLEDs) are demonstrated using optimized ZnO electrodes with alternative non-metallic co-dopants. The co-doping of hydrogen and fluorine reduces the metal content of ZnO thin films, resulting in a low absorption coefficient, a high transmittance, and a low refractive index as well as the high conductivity, which are needed for the application in organic solar cells and OLEDs. While the established metal-doped ZnO films have good electrical and optical properties, their application in organic devices is not as efficient as other alternative electrode approaches. The optimized ZnO electrodes presented here are employed in organic solar cells as well as OLEDs and allow not only the replacement of ITO, but also significantly improve the efficiency compared to lab-standard ITO. The enhanced performance is attributed to outstanding optical properties and spontaneously nanostructured surfaces of the ZnO films with non-metallic co-dopants and their straightforward integration with molecular doping technology, which avoids several common drawbacks of ZnO electrodes. The observations show that optimized ZnO films with non-metallic co-dopants are a promising and competitive electrode for low-cost and high performance organic solar cells and OLEDs. ZnO thin films are optimized by co-doping of non-metallic dopants for high optical and electrical performance. The ZnO-based organic photovoltaic (OPV) cells and organic light-emitting diodes (OLEDs) show highly improved efficiencies compared to indium tin oxide (ITO)-based devices. The optimized ZnO films are very promising electrodes for highly efficient and cost-effective OPV cells and OLEDs. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Schwab T.,TU Dresden | Fuchs C.,TU Dresden | Scholz R.,TU Dresden | Zakhidov A.,Fraunhofer Institute for Organics, Materials and Electronic Devices | And 3 more authors.
Optics Express | Year: 2014

Bragg scattering at one-dimensional corrugated substrates allows to improve the light outcoupling from top-emitting organic light-emitting diodes (OLEDs). The OLEDs rely on a highly efficient phosphorescent pin stack and contain metal electrodes that introduce pronounced microcavity effects. A corrugated photoresist layer underneath the bottom electrode introduces light scattering. Compared to optically optimized reference OLEDs without the corrugated substrate, the corrugation increases light outcoupling efficiency but does not adversely affect the electrical properties of the devices. The external quantum efficiency (EQE) is increased from 15 % for an optimized planar layer structure to 17.5 % for a corrugated OLED with a grating period of 1.0 μm and a modulation depth of about 70 nm. Detailed analysis and optical modeling of the angular resolved emission spectra of the OLEDs provide evidence for Bragg scattering of waveguided and surface plasmon modes that are normally confined within the OLED stack into the air-cone. We observe constructive and destructive interference between these scattered modes and the radiative cavity mode. This interference is quantitatively described by a complex summation of Lorentz-like resonances. © 2014 Optical Society of America.


Hein M.P.,TU Dresden | Zakhidov A.A.,Fraunhofer Institute for Organics, Materials and Electronic Devices | Lussem B.,TU Dresden | Jankowski J.,TU Dresden | And 5 more authors.
Applied Physics Letters | Year: 2014

The key active devices of future organic electronic circuits are organic thin film transistors (OTFTs). Reliability of OTFTs remains one of the most challenging obstacles to be overcome for broad commercial applications. In particular, bias stress was identified as the key instability under operation for numerous OTFT devices and interfaces. Despite a multitude of experimental observations, a comprehensive mechanism describing this behavior is still missing. Furthermore, controlled methods to overcome these instabilities are so far lacking. Here, we present the approach to control and significantly alleviate the bias stress effect by using molecular doping at low concentrations. For pentacene and silicon oxide as gate oxide, we are able to reduce the time constant of degradation by three orders of magnitude. The effect of molecular doping on the bias stress behavior is explained in terms of the shift of Fermi Level and, thus, exponentially reduced proton generation at the pentacene/oxide interface. © 2014 AIP Publishing LLC.


Sachse C.,TU Dresden | Muller-Meskamp L.,TU Dresden | Bormann L.,TU Dresden | Kim Y.H.,TU Dresden | And 5 more authors.
Organic Electronics: physics, materials, applications | Year: 2013

Percolation networks from silver nanowires can be used as a transparent electrode and promising alternative to the commonly used ITO. Here, the deposition of such a nanowire based network by dip coating, a versatile and scalable method, is described and characterized in detail. After identifying appropriate processing parameters, nanowire grids with conductivity and transmittance values rivaling ITO have been achieved. As a main issue, the roughness of the film was addressed and the influence on the device in terms of shunt paths was investigated. Using this network as anode, small molecule organic solar cells with varying stack structure were fabricated and yield efficiencies comparable to cells on ITO. © 2012 Elsevier B.V. All rights reserved.


Klumbies H.,TU Dresden | Muller-Meskamp L.,TU Dresden | Monch T.,TU Dresden | Schubert S.,TU Dresden | And 2 more authors.
Review of Scientific Instruments | Year: 2013

The reaction of calcium thin films with water - monitored optically or electrically - is widely used for evaluating ultrahigh barrier foils for the encapsulation of organic electronic devices. We studied the common optical and the electrical method and compared them with in situ atomic force microscope topography scans. All three methods were applied at the same sample in parallel in a typical test design containing a gas volume for water distribution next to the calcium layer of 60 and 1000 nm thickness, respectively. The common assumption for the interpretation of such measurement data is laterally homogeneous calcium consumption of the layer from top to bottom. In contrast, we observed a significant ratio of laterally inhomogeneous corrosion of the calcium on the micro-scale for both thicknesses. Some areas were strongly or completely corroded through the whole layer while others exhibited less or no corrosion. Furthermore, those corroded spots grew in lateral direction. As a consequence of lateral inhomogeneous calcium corrosion the electrical calcium measurement method underestimates the amount of calcium left; according to our results this does not affect the water vapor transmission rate (WVTR). Optical data evaluated by Lambert-Beer law underestimate the amount of calcium left as well and also underestimate the WVTR. If the data are evaluated, using a linear relationship between transmission and amount of calcium left, the both values are more precise. The scope of this study is to call attention to the existence of lateral inhomogeneity in calcium corrosion and its impact on the calcium permeation measurements. While more investigations would be needed to quantify the effect of this inhomogeneity on the electrical and optical method in general, the discussion sheds light on the way, calcium test data are influenced by lateral inhomogeneous calcium corrosion. Our observations highlight the need for careful interpretation of calcium test results, but also demonstrate its capabilities for precise ultrahigh barrier measurements. © 2013 American Institute of Physics.


Beyer B.,Fraunhofer Institute for Organics, Materials and Electronic Devices | Pfeifer R.,Fraunhofer Institute for Organics, Materials and Electronic Devices | Zettler J.K.,Fraunhofer Institute for Organics, Materials and Electronic Devices | Hild O.R.,Fraunhofer Institute for Organics, Materials and Electronic Devices | Leo K.,Fraunhofer Institute for Organics, Materials and Electronic Devices
Journal of Physical Chemistry C | Year: 2013

Bulk heterojunction organic solar cells with a vertical variation of the C60:ZnPc composition within the absorption layer have been fabricated. The resulting gradient layer has been characterized by UV/vis transmission and reflection spectroscopy. Depending on the mixing strategy, the formation of higher aggregated ZnPc species can be initialized earlier in a blended thin film. The gradient strength has been varied and its influence on the solar cell performance has been determined. A variation of the absorption layer thickness has been carried out to investigate a possible charge carrier transportation improvement. In order to explain the positive effect of a graded structure within the absorption layer, detailed voltage-dependent spectral response measurements have been performed. It is shown that not only the absorption behavior of the cell is improved, but also the charge carrier transportation properties. © 2013 American Chemical Society.


Schwab T.,TU Dresden | Schubert S.,TU Dresden | Hofmann S.,TU Dresden | Frobel M.,TU Dresden | And 5 more authors.
Advanced Optical Materials | Year: 2013

An ultra-thin MoO3-Au-Ag wetting layer metal electrode is investigated to eliminate present optical and electrical limitations of inverted top-emitting OLEDs. Its high transmittance suppresses microcavity effects and the MoO3 hole injection layer compensates limited charge injection from the top contact. Overall, an extensive approach is presented to solve the key problems of top-emitting OLEDs in general. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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