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Tsutsui T.,Kyushu University | Tsutsui T.,Chemical Materials Evaluation and Research Base CEREBA
Proceedings of the 20th International Workshop on Active-Matrix Flatpanel Displays and Devices: TFT Technologies and FPD Materials, AM-FPD 2013 | Year: 2013

Sixty years of research and development on organic semiconductors in Japan is reviewed. The concept of organic semiconductors was given as early as 1954, and early basic studies on organic semiconductors using single crystals of high-purity aromatic hydrocarbons started. Studies of device applications of organic semiconductors, organic electroluminescent devices, organic thin film transistors, and organic solar cells followed, and the first commercial products, small organic electroluminescent displays appeared in 1997. © 2013 JSAP. Source


Tsutsui T.,Chemical Materials Evaluation and Research Base CEREBA | Takada N.,Japan National Institute of Advanced Industrial Science and Technology
Japanese Journal of Applied Physics | Year: 2013

The technical history of when and how the basic understanding of the emission efficiency of organic light-emitting diodes (OLEDs) was established over the last 50 years is described. At first, our understanding of emission efficiency in single-crystal and thin-film electroluminescence (EL) devices in the early stages before the Eastman-Kodak breakthrough, that is, the introduction of the concept of multilayer structures, is examined. Then our contemplation travels from the Eastman-Kodak breakthrough towards the presently widely accepted concept of emission efficiency. The essential issues concerning the emission efficiency of OLEDs are summarized to help readers to obtain a common understanding of OLED efficiency problems, and detailed discussions on the primary factors that determine emission efficiency are given. Finally, some comments on remaining issues are presented. © 2013 The Japan Society of Applied Physics. Source


Suzuki A.,Chemical Materials Evaluation and Research Base CEREBA | Takahagi H.,Chemical Materials Evaluation and Research Base CEREBA | Uehigashi A.,Chemical Materials Evaluation and Research Base CEREBA | Hara S.,Chemical Materials Evaluation and Research Base CEREBA | Hara S.,Japan National Institute of Advanced Industrial Science and Technology
Digest of Technical Papers - SID International Symposium | Year: 2014

Comparisons among three water-vapor-transmission-rate (WVTR) measurement systems based on different principles have been performed in order to eliminate variability in measurement. A reliable WVTR measurement technique up to a level of 10-5g/m2/day has been successfully achieved. © 2014 Society for Information Display. Source


Okumoto H.,Japan National Institute of Advanced Industrial Science and Technology | Okumoto H.,Chemical Materials Evaluation and Research Base CEREBA | Tsutsui T.,Chemical Materials Evaluation and Research Base CEREBA
Applied Physics Express | Year: 2014

Self-heating effects in organic electronic devices are investigated by impedance spectroscopy (IS). A temperature modulation of the admittance couples the gigantic imaginary part of the capacitance to its small real part, which results in negative capacitance at low frequencies with high bias. We present a model to explain the effects and verify it experimentally for hole-only devices and organic light-emitting diodes. The negative capacitance widely observed in various electronic devices can be explained, at least in the organic electronic devices, by self-heating effects. The generic effects, which smear the device details, need to be eliminated to obtain IS signals that reflect the intrinsic device-specific properties. © 2014 The Japan Society of Applied Physics. Source


Suzuki A.,Chemical Materials Evaluation and Research Base CEREBA | Takahagi H.,Chemical Materials Evaluation and Research Base CEREBA | Uehigashi A.,Chemical Materials Evaluation and Research Base CEREBA | Hara S.,Chemical Materials Evaluation and Research Base CEREBA | Hara S.,Japan National Institute of Advanced Industrial Science and Technology
AIP Advances | Year: 2015

A reliable technique for evaluating a barrier film, which is a key component used to encapsulate flexible organic light-emitting diodes (OLEDs), is required to reliably appraise the lifetimes of such devices. The water vapor transmission rates (WVTR) is commonly used as an indication for a barrier film. In this paper, the variables affecting WVTR measurements were investigated because the results of such evaluations typically vary widely even at a level of 10-3 g m-2 day-1 at 40 °C and 90% relative humidity (RH). The reference films used for comparative measurements were prepared to eliminate the influence of the differences between individual barrier films. The measurement procedures were carefully investigated by using three WVTR measurement systems, which are based on different principles and different detectors. Consistency between the systems in terms of the WVTR was achieved at a level of 10-5 g m-2 day-1 at 40 °C and 90%RH. These results prove the reliability of not only our evaluation but also of these three systems, provided the measurements are performed correctly. The lag time was also analyzed to determine those factors that can affect the measurement time. It was found that the time required for a system to reach the adsorption-desorption equilibrium state can affect the measurement time. © 2015 Author(s). Source

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