Transparent Conductive Single-Walled Carbon Nanotube Networks with Precisely Tunable Ratios of Semiconducting and Metallic Nanaotubes (original) (raw)
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We report on a complete characterization of the optical dispersion properties of conducting thin films of single-wall carbon nanotubes ͑SWCNTs͒. The films studied exhibit sheet resistances between 50 and 1000 ⍀ / sq and optical transparencies between 65% and 95% on glass and quartz substrates. These films have the potential to replace transparent conducting oxides in applications such as photovoltaics and flat-panel displays; however, their optical properties are not sufficiently well understood. The SWCNT films are shown to be hole conductors, potentially enabling their use as hole-selective contacts and allowing alternative device designs. The fundamental optical, morphological, and electrical characteristics of the films are presented here, and a phenomenological optical model that accurately describes the optical behavior of the films is introduced. Particular attention is paid to ellipsometry measurements and thorough evaluation of the reflection and absorption spectra of the films.
Surface & Coatings Technology, 2008
This paper presents a simple and convenient process for the fabrication of carbon nanotube based optically transparent and electrically conductive thin films. Single-walled carbon nanotubes (SWNTs) are chemically treated to introduce negatively charged carboxylic groups on their surfaces, so that a stable SWNT aqueous dispersion can be obtained without any surfactant. The substrate surface is modified by a layer-by-layer nanoassembly technique, in which a positively charged hydrophilic polymer molecular layer is formed on the top of the substrate. This helps the SWNT dispersion to be cast onto the substrate using convenient wet coating techniques and increases the bonding force between the thin films and the substrates. Using the developed process, large sizes of conductive pure SWNT thin films that are uniform and highly transparent have been fabricated.
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Recent advancements in transparent carbon nanotube films: chemistry and imminent challenges
Journal of Nanostructure in Chemistry
Carbon nanotube (CNT)-doped transparent conductive films (TCFs) is an encouraging option toward generally utilized indium tin oxide-depended TCFs for prospective stretchable optoelectronic materials. Industrial specifications of TCFs involve not just with high electrical performance and transparency but also amidst environmental resistance and mechanical characteristic; those are usually excused within the research background. Though the optoelectronic properties of these sheets require to be developed to match the necessities of various strategies. While, the electrical stability of single-walled CNT TCFs is essentially circumscribed through the inherent resistivity of single SWCNTs and their coupling confrontation in systems. The main encouraging implementations, CNT-doped TCFs, is a substitute system during approaching electronics to succeed established TCFs, that utilize indium tin oxide. Here we review, a thorough summary of CNT-based TCFs including an overview, properties, his...
Transparent, Conductive Carbon Nanotube Films
Science, 2004
We describe a simple process for the fabrication of ultrathin, transparent, optically homogeneous, electrically conducting films of pure single-walled carbon nanotubes and the transfer of those films to various substrates. For equivalent sheet resistance, the films exhibit optical transmittance comparable to that of commercial indium tin oxide in the visible spectrum, but far superior transmittance in the technologically relevant 2-to 5-micrometer infrared spectral band. These characteristics indicate broad applicability of the films for electrical coupling in photonic devices. In an example application, the films are used to construct an electric field-activated optical modulator, which constitutes an optical analog to the nanotube-based field effect transistor.
Acs Nano, 2008
We study the optical and electrical properties of transparent conducting films made from lengthsorted single-wall carbon nanotubes (SWCNT). Thin films of length-sorted SWCNTs, formed through filtration from a dispersing solvent onto a filter substrate ("buckypaper"), exhibit sharp changes in their optical properties and conductivity () with increasing SWCNT surface concentration. At a given surface concentration, tubes longer than 200 nm are found to form networks that are more transparent and conducting. We show that changes of with SWCNT concentration can be quantitatively described by the generalized effective medium (GEM) theory. The scaling universal exponents describing the "percolation" transition from an insulating to a conducting state with increasing concentration are consistent with the two-dimensional (2D) percolation model. Shorter tubes and mixed length tubes form 3D networks. Furthermore, we demonstrate that the conductivity percolation threshold (x c ) varies with the aspect ratio L as, x c ϳ 1/L, a result that is also in accordance with the percolation theory. These findings provide a framework for engineering the optical and electrical properties of SWCNT networks for technological applications where flexibility, transparency, and conductivity are required.