Transparent Carbon Nanotube Films Research Articles

Enhanced Joule heating performance of flexible transparent conductive double-walled carbon nanotube films on sparked Ag nanoparticles

A hybrid flexible and transparent heater based on double-walled carbon nanotubes (DWCNTs) and silver nanoparticles (AgNPs) is fabricated on a polyethylene terephthalate substrate via facile spray-coating and spark-depositing techniques, respectively. The AgNPs are simply prepared by electrically sparking pure Ag wires in ambient environment with no vacuum system required. The optical, electrical and electrothermal properties of the hybrid AgNP/DWCNT and simple DWCNT film devices are investigated. The results show that the hybrid film heaters exhibit superior electrothermal performances to the DWCNT film heaters, as having higher maximum temperatures at the same applied voltages, as well as faster thermal heating and cooling responses. The simple DWCNT heater with optical transmittance of 72.7% at a wavelength of 550 nm reaches the maximum temperature of 95.0 °C, whereas the hybrid AgNP/DWCNT heater with optical transmittance of 64.0% reaches higher maximum temperature of 118.6 °C, as electrically supplied at 8 V. Furthermore, the mechanical flexibility of the hybrid and DWCNT film heaters is studied with different folding directions, and a little deviation in their electronic conduction is observed, while still performing good heating temperature after a bending test. This simple hybrid film heater demonstrates the efficient electrothermal performances, which can be utilized as a flexible and transparent heating device in various practical applications.

Grid-type transparent conductive thin films of carbon nanotubes as capacitive touch sensors

Transparent conductive films are used in a wide variety of devices. While solar cell top electrodes as well as tablet and mobile phone screens require high optical transparency and low sheet resistance (>80% and <10 Ω/□) to maximize power efficiency; other, less demanding applications, such as those in capacitive touch panels and antistatic coatings, in which only small currents are involved, can be managed with coatings of moderate conductivity. In this paper, we show that area-selective argon plasma treated polyethylene terephthalate surfaces are suitable for localized deposition of carbon nanotubes from their aqueous dispersions by a simple dip coating and subsequent drying processes. The as-deposited carbon nanotubes form entangled networks in microscopic patterns over the plasma-treated surface areas with sheet resistance of <1 kΩ/□ and optical transparency of ~75%. Based on this process, we demonstrate grid-type transparent conductive thin films of carbon nanotubes as capacitive touch sensors. Since each process step is robust, easy to up and downscale, and may be implemented even in roll-to-roll and sheet-to-sheet fabrication, the demonstrated technology is promising to produce grid-type structures even at an industrial scale in the future.

Direct Patterning of Carbon Nanotube via Stamp Contact Printing Process for Stretchable and Sensitive Sensing Devices

HighlightsA dry transfer method for the mass production of transparent conductive carbon nanotube (CNT) films inspired by typography has been proposed.The strain sensors based on the CNT films have high stretchability and repeatability (gauge factor up to 9960 at 85% strain).These ultrathin strain sensors can detect human motion, sound, and pulse, suggesting promising application prospects in wearable devices.

Stable iodide doping induced by photonic curing for carbon nanotube transparent conductive films

Doping has become crucial for achieving stable and high-performance conductive transparent carbon nanotube (CNT) films. In this study, we systematically investigate the doping effects of a few materials including alkali metal iodides, nonmetal iodide, and metals. We demonstrate that photonic curing can enhance the doping effects, and correspondingly improve the conductivity of CNT films, and that such iodides have better doping effects than metals. In particular, doping with a nonmetal compound (NH4I) shows the largest potential to improve the conductivity of CNT films. Typically, doping with metal iodides reduces the sheet resistance (RS) of CNT films with 70–80% optical transmittances at λ = 550 nm from 600–2400 to 250–440 Ω/square, whereas doping with NH4I reduces RS to 57 and 84 Ω/square at 74 and 84% optical transmittances, respectively. Interestingly, such a doped CNT film exhibits only a slight increase in sheet resistance under an extreme environment of high temperature (85 °C) and high relative humidity (85%) for 350 h. The results suggest that photonic-curing-induced iodide doping is a promising approach to producing high-performance conductive transparent CNT films.

Highly conductive and transparent films of HAuCl4-doped single-walled carbon nanotubes for flexible applications

The rapid development of flexible and transparent electronics imposes growing demands on new highly conductive, optically transparent and mechanically robust materials. Single-walled carbon nanotubes (SWCNTs) are a unique material with diverse exceptional properties, which could be utilized in many fields of science and technology. We have synthesized high quality SWCNTs using an aerosol CVD method and examined doping technique to enhance their optoelectronic performance for transparent and conducting applications. We empirically selected the most effective dopant, HAuCl4, dissolved in various solvents (ethanol, acetonitrile, tetrahydrofuran, dimethylformamide, dimethyl sulfoxide, and n-methyl-2-pyrrolidone). We optimized the doping conditions and obtained the state-of-the-art sheet resistance value of as low as 40 Ω/□ at the transmittance of 90% at the wavelength of 550 nm.

Dense Carbon Nanotube Films as Transparent Electrodes in Low‐Voltage Polymer and All‐Carbon Transistors

AbstractDense but transparent films of long and clean carbon nanotubes grown by the floating catalyst method, transferred and patterned on glass substrates, are employed as source and drain electrodes in top‐gate field‐effect transistors with both low‐mobility semiconducting polymers and high‐mobility networks of polymer‐sorted semiconducting single‐walled carbon nanotubes. Significant enhancement of ambipolar charge injection into the polymer semiconductor compared to gold electrodes is observed, while the limitations of sheet resistance become apparent for the high‐mobility nanotube transistors. The injection of charges from gold compared to carbon nanotube electrodes into the semiconducting nanotube network is investigated by means of conductive atomic force microscopy indicating a less defined channel edge for the latter. Metal‐free, all‐carbon electrolyte‐gated transistors with a nanotube network semiconductor as well as nanotube source, drain, and gate electrodes show both hole and electron transport at very low operating voltages.

Flotation Assembly of Large-Area Ultrathin MWCNT Nanofilms for Construction of Bioelectrodes.

We report a simple, versatile, and rapid method for the fabrication of optically-transparent large-area carbon nanotube (CNT) films via flotation assembly. After solvent-induced assembly, floating films were transferred to a flat supporting substrate to form conductive and transparent CNT film electrodes. The resulting electrodes, with uniform 40 ± 20 nm multi-walled CNT (MWCNT) layers, were characterized by electrochemical and microscopy methods. The flotation method does not require specialized thin-film instrumentation and avoids the need for surfactants and pre-oxidized CNTs which can hamper electrochemical performance. A proof-of-concept nanostructured bioelectrode demonstrating high sensitivity for glucose was developed with an electropolymerized poly(pyrene-adamantane) layer for host–guest immobilization of active β-cyclodextrin tagged GOx enzymes. The polymer provides pyrene groups for cross-linking to CNTs and pendant adamantane groups for binding the β-cyclodextrin groups of the tagged enzyme. This demonstration offers a new approach for the preparation of stable and transparent CNT film electrodes with attractive electrochemical properties towards future photobio- and bio-electrochemical fuel cells, electrochemical sensors, and electroanalysis.

Carbon nanotubes length optimization for preparation of improved transparent and conducting thin film substrates

Abstract Transparent and conductive thin films of multiwalled carbon nanotubes (MWCNTs) with different lengths were prepared on glass substrates by the spin coating method. In order to reduce the MWCNTs length, they were functionalized. The initial length of MWCNTs (10–15 μm) was reduced to 1200, 205 and 168 nm after 30, 60 and 120 min refluxing time, respectively. After post annealing at 285 °C for 24 h, the electrical and optical properties were greatly improved for functionalized MWCNT thin films. They strongly depend on the length of CNTs. The optical transmittance of the film prepared using 30 min reflux CNTs was 2.6% and 6.6% higher than that of the 60 min and 120 min refluxed samples respectively. The sheet resistance of this film showed reductions of 45% and 80% as well. The film also exhibited the least roughness. The percolative figure of merit, which is proportional to the transparency and disproportional to the sheet resistance, was found to be higher for the sample with 30 min refluxed MWCNTs.

Dry-Deposited Transparent Carbon Nanotube Film as Front Electrode in Colloidal Quantum Dot Solar Cells.

Single-walled carbon nanotubes (SWCNTs) show great potential as an alternative material for front electrodes in photovoltaic applications, especially for flexible devices. In this work, a press-transferred transparent SWCNT film was utilized as front electrode for colloidal quantum dot solar cells (CQDSCs). The solar cells were fabricated on both glass and flexible substrates, and maximum power conversion efficiencies of 5.5 and 5.6 %, respectively, were achieved, which corresponds to 90 and 92 % of an indium-doped tin oxide (ITO)-based device (6.1 %). The SWCNTs are therefore a very good alternative to the ITO-based electrodes especially for flexible solar cells. The optical electric field distribution and optical losses within the devices were simulated theoretically and the results agree with the experimental results. With the optical simulations that were performed it may also be possible to enhance the photovoltaic performance of SWCNT-based solar cells even further by optimizing the device configuration or by using additional optical active layers, thus reducing light reflection of the device and increasing light absorption in the quantum dot layer.

Transparent carbon nanotube film as sensitive material for surface plasmon resonance based optical sensors

Semiconductive or metallic single wall carbon nanotubes have been deposited on gold nanoparticles monolayer and used as plasmonic based gas sensor.The coupling between carbon nanotubes and gold nanoparticles has the aim of combining the reactivity of the carbon nanotubes towards hazardous gases, such as H2, CO, NO2, with the localized surface plasmon resonance of gold nanoparticles, which it is known to be extremely sensitive to the changes in the dielectric properties of the surrounding medium, a working mechanism used for sensor devices.Two different techniques, ink-jet printer and dropcasting, were used for depositing the transparent carbon nanotubes film on the plasmonic layer. Ink-jet printed metallic single wall carbon nanotubes showed high sensitivity toward H2 at low operative temperature with the detection of low concentration of H2. On the contrary, the semiconductive single wall carbon nanotubes displayed very poor gas sensing properties.

Wire-shaped perovskite solar cell based on TiO2 nanotubes

In this work, a wire-shaped perovskite solar cell based on TiO2 nanotube (TNT) arrays is demonstrated for the first time by integrating a perovskite absorber on TNT-coated Ti wire. Anodization was adopted for the conformal growth of TNTs on Ti wire, together with the simultaneous formation of a compact TiO2 layer. A sequential step dipping process is employed to produce a uniform and compact perovskite layer on top of TNTs with conformal coverage as the efficient light absorber. Transparent carbon nanotube film is wrapped around Ti wire as the hole collector and counter electrode. The integrated perovskite solar cell wire by facile fabrication approaches shows a promising future in portable and wearable textile electronics.

Low-temperature solution process for preparing flexible transparent carbon nanotube film for use in flexible supercapacitors

Single-walled carbon nanotubes (SWNTs) possess high conductivity, mechanical strength, transparency, and flexibility, and are thus suitable for use in flexible electronics, transparent electrodes, and energy-storage and energy-harvesting applications. However, to exploit these properties, SWNTs must be de-bundled in a surfactant solution to permit processing and use. We report a new method to prepare a SWNT-based transparent conducting film (TCF) using the diazo dye 3,3′-([1,1′-biphenyl]-4,4′-diyl)bis(4-amino naphthalene-1-sulfonic acid), commonly known as Congo red (CR), as a dispersant. Uniform 20-nm-thick TCFs were prepared on rigid glass and flexible polyethylene terephthalate (PET) substrates. The CR-SWNT dispersion and the CR-SWNT TCFs were characterized via UV-Vis-NIR, Raman spectroscopy, FT-IR spectroscopy, transmission electron microscopy (TEM), field-emission scanning electron microscopy (FE-SEM) and dynamic light scattering (DLS) measurements. The sheet resistivity of the CRSWNT TCF was ~34 ± 6.6 Ω/□ with a transmittance of 81% at 550 nm, comparable to that of indium tin oxide-based films. Unlike SWNT dispersions prepared in common surfactants, such as sodium dodecyl sulfate (SDS), sodium cholate (SC), and Triton X-100, the CR-SWNT dispersion was amenable to forming TCF by drop coating. The CR-SWNT TCF was also very stable, maintaining a very low sheet resistivity even after 1,000 consecutive bending cycles of 8 mm bending radius. Further, manganese dioxide (MnO2) was electrochemically deposited on the CR-SWNT-PET film (MnO2-CR-SWNT-PET). The as-prepared MnO2-CR-SWNT-PET electrode exhibited high specific capacitance and bendability, demonstrating promise as a candidate electrode material for flexible supercapacitors.

Optically transparent carbon nanotube film electrode for thin layer spectroelectrochemistry.

Carbon nanotube (CNT) film was evaluated as an optically transparent electrode (OTE) for thin layer spectroelectrochemistry. Chemically inert CNT arrays were synthesized by chemical vapor deposition (CVD) using thin films of Fe and Co as catalysts. Vertically aligned CNT arrays were drawn onto a quartz slide to form CNT films that constituted the OTE. Adequate conductivity and transparency make this material a good OTE for spectroelectrochemistry. These properties could be varied by the number of layers of CNTs used to form the OTE. Detection in the UV/near UV region down to 200 nm can be achieved using these transparent CNT films on quartz. The OTE was characterized by transmission electron microscopy, scanning electron microscopy, Raman spectroscopy, UV-visible spectroscopy, cyclic voltammetry, electrochemical impedance spectroscopy, and thin layer spectroelectrochemistry. Ferricyanide, tris(2,2'-bipyridine) ruthenium(II) chloride, and cytochrome c were used as representative redox probes for thin layer spectroelectrochemistry using the CNT film OTE, and the results correlated well with their known properties. Direct electron transfer of cytochrome c was achieved on the CNT film electrode.

Direct and Dry Deposited Single-Walled Carbon Nanotube Films Doped with MoO(x) as Electron-Blocking Transparent Electrodes for Flexible Organic Solar Cells.

PSS. The single-walled carbon nanotube organic solar cell in this work shows a power conversion efficiency of 6.04%. This value is 83% of the leading ITO-based device performance (7.48%). Flexible application shows 3.91% efficiency and is capable of withstanding a severe cyclic flex test.

Preparation of Transparent and Conductive Double-Walled Carbon Nanotube Films

Preparation of Transparent and Conductive Double-Walled Carbon Nanotube Films

ウェットコーティングによるCNT透明導電フィルム

ウェットコーティングによるCNT透明導電フィルム

About the influence of temperature in single-walled carbon nanotubes: Details from a new Drude–Lorentz-like model

The most important quantities referred to transport phenomena in nanostructures are well described by the Drude–Lorentz model and generalizations. I have presented a new “time-domain” Drude–Lorentz-like model for nano-transport and its quantum generalization; the model is general and offers good fitting using experimental data obtained from scientific literature. It allows interesting applications in the field of nanostructured materials, also in the biological and medical fields. I consider in this paper the elaboration of experimental data of SWCN; implemented data offer interesting details regarding the influence of temperature for velocity and diffusivity in transparent carbon nanotube films.

High-Performance Carbon Nanotube Transparent Conductive Films by Scalable Dip Coating

Transparent conductive carbon nanotube (CNT) films were fabricated by dip-coating solutions of pristine CNTs dissolved in chlorosulfonic acid (CSA) and then removing the CSA. The film performance and morphology (including alignment) were controlled by the CNT length, solution concentration, coating speed, and level of doping. Using long CNTs (∼10 μm), uniform films were produced with excellent optoelectrical performance (∼100 Ω/sq sheet resistance at ∼90% transmittance in the visible), in the range of applied interest for touch screens and flexible electronics. This technique has potential for commercialization because it preserves the length and quality of the CNTs (leading to enhanced film performance) and operates at high CNT concentration and coating speed without using surfactants (decreasing production costs).

Transparent conductive thin films of single-wall carbon nanotubes encapsulating dopant molecules

Transparent conductive thin films of single-wall carbon nanotubes (SWCNTs) doped with organic dopant molecules encapsulated inside the SWCNTs are reported. Doping with tetrafluorotetracyano-p-quinodimethane encapsulated within the SWCNTs improved the ratio of direct current to optical conductivity in the SWCNT thin films by a factor of about 1.8. Thermal stability of the improvement in electrical conductivity by encapsulation doping is investigated as a function of annealing temperature. We found that encapsulation doping provides stable conductivity enhancement in transparent thin films of SWCNTs compared to doping by adsorbed dopant molecules outside the SWCNTs.

Thermal and structural dependence of the band gap of quantum dots measured by a transparent film heater

We report the temperature dependence of the optical absorption and emission spectra of quantum dots (QDs) for three different nanocrystal (NC) structures (CdSe core, CdSe/CdS core/shell, and CdSe/CdS/ZnS core/multishell) in the solid film state. For this, a transparent single-walled carbon nanotube (SWCNT) film attached to a QD thin layer was tested as a heater. The temperature dependence of spectral shifts in both absorption and emission of QDs was measured in the range 300–450 K, and the Stokes shift was calculated by measuring the energy difference between the absorption and emission peaks. We found that the Stokes shift decreased as QD shells were added and the temperature was increased, indicating a weaker electron–phonon coupling in the QDs with additional shells at higher temperature. Finally, the band gap of the QDs was measured as a function of temperature. The Debye temperature was obtained by empirically fitting the energy band gap.