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Author: Fischer, Axel × Author: Liero, Matthias × End date: 2022 × Start date: 2021 ×

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Now showing 1 - 4 of 4
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    Drift–diffusion simulation of S-shaped current–voltage relations for organic semiconductor devices
    (Dordrecht : Springer Science + Business Media B.V., 2020) Doan, Duy Hai; Fischer, Axel; Fuhrmann, Jürgen; Glitzky, Annegret; Liero, Matthias
    We present an electrothermal drift–diffusion model for organic semiconductor devices with Gauss–Fermi statistics and positive temperature feedback for the charge carrier mobilities. We apply temperature-dependent Ohmic contact boundary conditions for the electrostatic potential and discretize the system by a finite volume based generalized Scharfetter–Gummel scheme. Using path-following techniques, we demonstrate that the model exhibits S-shaped current–voltage curves with regions of negative differential resistance, which were only recently observed experimentally. © 2020, The Author(s).
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    Introducing pinMOS Memory: A Novel, Nonvolatile Organic Memory Device
    (Weinheim : Wiley-VCH, 2020) Zheng, Yichu; Fischer, Axel; Sawatzki, Michael; Doan, Duy Hai; Liero, Matthias; Glitzky, Annegret; Reineke, Sebastian; Mannsfeld, Stefan C.B.
    In recent decades, organic memory devices have been researched intensely and they can, among other application scenarios, play an important role in the vision of an internet of things. Most studies concentrate on storing charges in electronic traps or nanoparticles while memory types where the information is stored in the local charge up of an integrated capacitance and presented by capacitance received far less attention. Here, a new type of programmable organic capacitive memory called p-i-n-metal-oxide-semiconductor (pinMOS) memory is demonstrated with the possibility to store multiple states. Another attractive property is that this simple, diode-based pinMOS memory can be written as well as read electrically and optically. The pinMOS memory device shows excellent repeatability, an endurance of more than 104 write-read-erase-read cycles, and currently already over 24 h retention time. The working mechanism of the pinMOS memory under dynamic and steady-state operations is investigated to identify further optimization steps. The results reveal that the pinMOS memory principle is promising as a reliable capacitive memory device for future applications in electronic and photonic circuits like in neuromorphic computing or visual memory systems. © 2019 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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    Electrothermal Tristability Causes Sudden Burn-In Phenomena in Organic LEDs
    (Weinheim : Wiley-VCH, 2021) Kirch, Anton; Fischer, Axel; Liero, Matthias; Fuhrmann, Jürgen; Glitzky, Annegret; Reineke, Sebastian
    Organic light-emitting diodes (OLEDs) have been established as a mature display pixel technology. While introducing the same technology in a large-area form factor to general lighting and signage applications, some key questions remain unanswered. Under high-brightness conditions, OLED panels were reported to exhibit nonlinear electrothermal behavior causing lateral brightness inhomogeneities and even regions of switched-back luminance. Also, the physical understanding of sudden device failure and burn-ins is still rudimentary. A safe and stable operation of lighting tiles, therefore, requires an in-depth understanding of these physical phenomena. Here, it is shown that the electrothermal treatment of thin-film devices allows grasping the underlying physics. Configurations of OLEDs with different lateral dimensions are studied as a role model and it is reported that devices exceeding a certain panel size develop three stable, self heating-induced operating branches. Switching between them causes the sudden formation of dark spots in devices without any preexisting inhomogeneities. A current-stabilized operation mode is commonly used in the lighting industry, as it ensures degradation-induced voltage adjustments. Here, it is demonstrated that a tristable operation always leads to destructive switching, independent of applying constant currents or voltages. With this new understanding of the effects at high operation brightness, it will be possible to adjust driving schemes accordingly, design more resilient system integrations, and develop additional failure mitigation strategies. © 2021 The Authors. Advanced Functional Materials published by Wiley-VCH GmbH
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    Drift-diffusion simulation of S-shaped current-voltage relations for organic semiconductor devices
    (Berlin : Weierstraß-Institut für Angewandte Analysis und Stochastik, 2019) Doan, Duy Hai; Fischer, Axel; Fuhrmann, Jürgen; Glitzky, Annegret; Liero, Matthias
    We present an electrothermal drift-diffusion model for organic semiconductor devices with Gauss-Fermi statistics and positive temperature feedback for the charge carrier mobilities. We apply temperature dependent Ohmic contact boundary conditions for the electrostatic potential and discretize the system by a finite volume based generalized Scharfetter-Gummel scheme. Using path-following techniques we demonstrate that the model exhibits S-shaped current-voltage curves with regions of negative differential resistance, which were only recently observed experimentally.