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Title: Solution processed polymer-sorted single walled carbon nanotubes for plastic electronics
Author: Bottacchi, Francesca
ISNI:       0000 0004 6061 6333
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2017
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Single walled carbon nanotubes (SWNTs) have been successfully employed in a wide range of large-area and low-cost optoelectronic devices, such as field-effect transistors (FETs), light emitting diodes, solar cells, and logic circuits. Most common synthesis methods produce a mixture of nanotube diameters that typically results in one-third of the as-synthesized nanotubes being metallic and the remaining two-thirds being semiconducting. These synthesis procedures have a big impact on many optoelectronic applications, where the presence of metallic SWNTs could dramatically degrade device performances. To overcome this problem and sort semiconducting nanotubes from metallic ones, a post-synthetics process called polymer sorting method has been recently developed. If, on the one hand, significant progress has been made to optimize sorting techniques, on the other hand the ability to accurately characterize the residual metallic content in highly pure semiconducting samples remains a major challenge. The primary aim of this thesis is the study of electronic transport processes occurring in polymer-sorted semiconducting SWNT networks. This is achieved with a detailed surface and material characterization, and with the design, fabrication and electrical characterization of field-effect transistors. In the first part of the thesis, the theoretical background of all materials and devices used is given, followed by the description of all procedures, methods, as well as of the fabrication and characterization techniques. In the second part of the thesis, experimental results on SWNT charge transport percolation, flexible field-effect transistors, flexible logic circuits, and alternative processing techniques are discussed. Best achievements include the quantification of residual metallic nanotubes through the application of the percolation model to FETs, the realization of flexible low-voltage SWNT FETs with a mobility of 8.1cm2V-1s-1, and the fabrication of flexible low-voltage SWNT complementary inverters with a gain higher than 85V/V. These results clearly demonstrate the potential of solution processed polymer-sorted semiconducting SWNTs for plastic electronics.
Supervisor: Anthopoulos, Thomas Sponsor: European Union
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral