Printed organic circuits have the potential to revolutionize the spread of electronic applications. This will be enabled by inexpensive and fast fabrication with printing techniques using soluble organic materials. Two main challenges have to be mastered on the way towards printed electronics. First, the development of stable transistors and an adapted chip design for organic materials, and second, the development of a reliable fabrication process. We present our results on high performance polymer transistors, mainly based on poly-3alkylthiophene (P3AT) as semiconducting material. Fast circuits up to 200 kHz and stable circuits with operation lifetimes of more than 1000 h under ambient conditions without any encapsulation are shown. We also report on a fully printed, all organic ring oscillator.

Using soluble polymers for the active layer and insulating layer, we report on a concept for the fabrication of fast integrated circuits based on p-type organic transistors only. Ring oscillators with frequencies above 100 kHz and propagation stage delays below 0.7 μs are presented. They show a very stable performance over time even without encapsulation, when stored and measured under ambient conditions. Regioregular poly(3-alkylthiophen) is used as the active semiconducting layer, a polymer blend as the insulator, a flexible polyester film as the substrate and metal electrodes. To enable vertical interconnects, the insulating layer is patterned.

Detailed investigations on shelf life and operation lifetime of polymer field-effect transistors (PFETs) and circuits are reported. All examined devices consisted entirely of polymer materials except the electrodes. Regioregular poly(3-alkylthiophene) was used as a semiconductor. Unencapsulated devices were produced, stored, and measured under ambient conditions. The performance of PFETs was maintained for more than 12 months after production. Even under extreme conditions of 85 °C and 85% relative humidity, a stable shelf life of more than 1400 h was measured. Transistors exceeded a continuous operation time of 1000 h. Operation lifetimes showed that the degradation did not follow the Arrhenius lifetime-temperature relationship. Similar results were found for ring oscillators.

The influence of intensive light exposure on high performance polymer field-effect transistors containing highly regioregular poly(3-alkylthiophene) as a semiconductor is reported. While the transistors show high stability under ambient air and light, a distinct degradation upon exposure to intensive light could be detected by its impact on the on currents. UV-Vis spectra were used to interpret the current decrease as being caused by a decrease of the conjugation length of the semiconductor, which is supported by IR spectrometry. The role of ambient air, in particular, oxygen, in the degradation process is shown.

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