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Title: Single-walled carbon nanotube electrodes for all-plastic, electronic device applications
Author: Kim, Sung Soo
ISNI:       0000 0004 2699 762X
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2011
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In this thesis, new mechanically robust, high performance transparent conducting films of commercially sourced arc-made Single-Walled Carbon Nanotubes (SWCNTs) on both glass and flexible substrates were produced using spin-coating or spray deposition, interlayer or stencil patterning methods and used for fabricating efficient, flexible polymer-fullerene bulk hetero-junction solar cells. After carefully optimizing the dispersion process of SWCNTs with H2O:SDS (up to 0.03 wt.%) and developing and efficient surfactant removal/p-doping procedure with nitric acid, highly conductive and smooth SWCNT thin films (ca. 30 nm) were obtained with more than 6,500 Scm-1 at > 69 % transmittance and 7 nm (r.m.s.) roughness. In particular, SWCNT films spray coated from H2O:SDS exhibited electrical conductivities of up to 7694 ± 800 Scm-1. To our knowledge, these values are the highest so far reported for SWCNT electrodes. Peak values for the ratio of the dc conductivity to the optical conductivity (σdc/σop) were obtained as up to 24, which is quite similar to state of the art SWCNT films so far reported. In addition, two patterning methods were developed to define electrode patterns of SWCNT thin films for electronic device applications. Interlayer lithography provided a fast and high resolution patterning procedure for SWCNT thin films at micron and sub-micron length scales, which is important for the fabrication of high-speed transistors requiring short channel lengths, and offers an attractive route to fabricating high-density integrated circuits. In addition, stencil patterning provides a simple and fast method, which is well suited for low resolution electronic device applications such as organic solar cells. The patterned highly conductive SWCNT electrodes were incorporated into P3HT:PCBM bulk heterojunction solar cell applications, obtaining the best device performance of 3.6 %, which is the best result so far reported in the literature. Finally, to break through the limited performance (σdc/σop < 25) of SWCNT thin films, layered hybrid thin films of SWCNTs on reduced Graphene-Oxide were fabricated by a simple spray coating method and the optimised hybrid films were incorporated into relatively efficient organic solar cells (2 % efficiency).
Supervisor: de Mello, John ; Wang, Xuhua Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral