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, such as polycrystalline silicon, hydrogenated amorphous silicon and 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 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.

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
  • steepest subthreshold slope: 59 mV/decade
  • smallest signal-propagation delay in a ring oscillator: 79 ns (VDD = 4.4 V)
  • largest sampling rate in a data converter: 100 kS/s (6 bit digital-to-analog converter, VDD = 3.3 V)
  • smallest power-delay product in a data converter: 1.8 nWs (6 bit digital-to-analog converter)

For organic TFTs with a channel length of less than 1 µm [1]:

  • largest on/off current ratio: 109
  • steepest subthreshold slope: 66 mV/decade
  • largest effective carrier mobility: 2.7 cm2/Vs

For organic TFTs fabricated on paper [3], [4]:

  • steepest subthreshold slope: 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)
[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]     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
[3]     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
[4]     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




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