The Max Planck Research Group Organic Electronics was established in 2005.
We develop materials and manufacturing approaches for the fabrication of low-voltage, high-frequency organic thin-film transistors (TFTs).
Unlike TFTs based on inorganic semiconductors (e.g., polycrystalline silicon, hydrogenated amorphous silicon, zinc oxide), organic TFTs can be fabricated at or near room temperature and thus on a wide range of unconventional substrates, including plastics, paper and fabrics.
This makes organic TFTs potentially useful for flexible, large-area electronics applications, such as bendable or rollable active-matrix displays and conformable sensor arrays.
As these will typically be mobile or wearable systems for which grid electricity will not be available, we focus on the development of organic TFTs capable of operating with voltages in the range of 0.5 to 3 V, which is the range of voltages provided by small batteries, photovoltaic cells or small energy harvesting devices.
Advanced TFT applications, such as high-resolution video-rate displays, will require TFTs with very high transit frequencies, so we explore approaches for the fabrication of low-voltage flexible organic TFTs with transit frequencies of 100 MHz and possibly 1 GHz.
To minimize not only the supply voltage, but also the power consumption of organic-TFT-based systems, we emphasize the development of complementary circuits based on low-voltage, air-stable p-channel and n-channel organic TFTs.
Flexible organic TFTs fabricated in our laboratory currently hold the following performance records [1], [2]:
- largest supply-voltage-normalized transit frequency: 7 MHz/V (21 MHz at VGS = VDS = -3.0 V)
- smallest channel-width-normalized contact resistance: 10 Ωcm
- largest on/off current ratio: 1010
- smallest subthreshold swing: 59 mV/decade
- smallest signal-propagation delay in a ring oscillator: 79 ns (VDD = 4.4 V)
- smallest signal-propagation delay in an inverter: 14 ns (VDD = 3.0 V)
For organic TFTs with a channel length of less than 1 µm [1], [3], [4]:
- largest on/off current ratio: 4x109
- smallest subthreshold swing: 59 mV/decade
- largest effective carrier mobility: 2.7 cm2/Vs
For organic TFTs fabricated on paper [5], [6]:
- smallest subthreshold swing: 90 mV/decade
- smallest signal-propagation delay in a unipolar ring oscillator: 2.5 µs (VDD = 4.0 V)
- smallest signal-propagation delay in a complementary ring oscillator: 10 µs (VDD = 4.0 V)
For organic complementary circuits fabricated on flexible substrates [7], [8]:
- largest supply-voltage-normalized small-signal gain: 180 V-1 (VDD = 1.0 V)
- largest noise margin: 89% of ½VDD
For organic-TFT-based data converters [9]:
- largest sampling rate: 100 kS/s (6 bit digital-to-analog converter, VDD = 3.3 V)
- smallest power-delay product: 1.8 nWs (6 bit digital-to-analog converter)
| [1] | Flexible low-voltage high-frequency organic thin-film transistors J. W. Borchert, U. Zschieschang, F. Letzkus, M. Giorgio, R. T. Weitz, M. Caironi, J. N. Burghartz, S. Ludwigs, H. Klauk Science Advances, vol. 6, no. 21, pp. eaaz5156/1-8, May 2020 | |
| [2] | High-gain, low-voltage unipolar logic circuits based on nanoscale flexible organic thin-film transistors with small signal delays T. Haldar, T. Wollandt, J. Weis, U. Zschieschang, H. Klauk, R. T. Weitz, J. N. Burghartz, M. Geiger Science Advances, vol. 9, no. 1, pp. eadd3669/1-9, January 2023 | |
| [3] | Nanoscale flexible organic thin-film transistors U. Zschieschang, U. Waizmann, J. Weis, J. W. Borchert, H. Klauk Science Advances, vol. 8, no. 13, pp. eabm9845/1-10, April 2022 | |
| [4] | Subthreshold Swing of 59 mV decade−1 in Nanoscale Flexible Ultralow-Voltage Organic Transistors M. Geiger, R. Lingstädt, T. Wollandt, J. Deuschle, U. Zschieschang, F. Letzkus, J. N. Burghartz, P. A. van Aken, R. T. Weitz, H. Klauk Advanced Electronic Materials, vol. 8, no. 5, pp. 2101215/1-12, May 2022 | |
| [5] | Low-voltage organic transistors with steep subthreshold slope fabricated on commercially available paper U. Zschieschang, H. Klauk Organic Electronics, vol. 25, pp. 340-344, October 2015 | |
| [6] | Low-Voltage, High-Frequency Organic Transistors and Unipolar and Complementary Ring Oscillators on Paper U. Kraft, T. Zaki, F. Letzkus, J. N. Burghartz, E. Weber, B. Murmann, H. Klauk Advanced Electronic Materials, vol. 5, no. 2, pp. 1800453/1-8, February 2019 | |
| [7] | Below-one-volt organic thin-film transistors with large on/off current ratios U. Zschieschang, V. P. Bader, H. Klauk Organic Electronics, vol. 49, pp. 179-186, October 2017 | |
| [8] | Optimizing the plasma oxidation of aluminum gate electrodes for ultrathin gate oxides in organic transistors M. Geiger, M. Hagel, T. Reindl, J. Weis, R. T. Weitz, H. Solodenko, G. Schmitz, U. Zschieschang, H. Klauk, R. Acharya Scientific Reports, vol. 11, pp. 6382/1-13, March 2021 | |
| [9] | A 3.3 V 6-Bit 100 kS/s Current-Steering Digital-to-Analog Converter Using Organic P-Type Thin-Film Transistors on Glass T. Zaki, F. Ante, U. Zschieschang, J. Butschke, F. Letzkus, H. Richter, H. Klauk, J. N. Burghartz IEEE Journal of Solid-State Circuits, vol. 47, no. 1, pp. 292-300, January 2012 |
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