Vorschau

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Abstract

Semiconducting, single-walled carbon nanotubes (SWCNTs) have mechanical and electronic properties that render them a promising material for solution-processable, stretchable and flexible electronics. However, their strong tendency to form aggregates in dispersion constitutes a large obstacle to realize the film uniformity necessary for the transition of devices from laboratory to commercial scale. The resulting inhomogeneities in film morphology lead to an undesired spread in device performance. Based on the tailored formulation of colloidal inks via suitable solvents and additives the first part of this thesis presents a simple yet effective method to slow down aggregation of polymer-wrapped SWCNTs in organic solvents. This effect on aggregation by 1,10- phenanthroline as a stabilizing additive can be monitored with time-dependent absorption spectroscopy. The improved homogeneity of the SWCNT networks deposited from stabilized dispersions after several days of ink storage lead to higher charge carrier mobilities with strongly reduced device-to-device variations compared to inks without additive. The intrinsic ambipolarity of SWCNTs is a great disadvantage for their use in electronic circuits as it leads to large power dissipation. While pure hole conduction can be achieved relatively easily by doping with, for example, ambient oxygen, facilitating exclusive electron conduction represents a large challenge. A solution-processable n-dopant from the family of guanidino-functionalized aromatics (GFAs) is introduced to overcome this limitation. The resulting SWCNT network field-effect transistors (FETs) exhibit pure electron transport with high mobility while hole transport is fully suppressed, excellent switching behavior and good operational stability. Their application potential (combined with a doped p-type FET) is highlighted by complementary inverters with very low power dissipation. This modification of the charge transport behavior is applied to another promising solution-processable semiconductor, i.e., donor-acceptor-polymers. Doping of these polymers with two GFA compounds under various processing conditions improves electron injection and transport while hole transport is suppressed. Again, these transistors display good environmental stability under operating conditions. The extended applicability of the newly introduced GFA dopants to different semiconductors emphasizes their potential for transistors based on solution-processable semiconductor