G. Grüner

Printable Thin Film Supercapacitors Using Single-Walled Carbon Nanotubes

Thin film supercapacitors were fabricated using printable materials to make flexible devices on plastic. The active electrodes were made from sprayed networks of single-walled carbon nanotubes (SWCNTs) serving as both electrodes and charge collectors. Using a printable aqueous gel electrolyte as well as an organic liquid electrolyte, the performances of the devices show very high energy and power densities (6 W h/kg for both electrolytes and 23 and 70 kW/kg for aqueous gel electrolyte and organic electrolyte, respectively) which is comparable to performance in other SWCNT-based supercapacitor devices fabricated using different methods. The results underline the potential of printable thin film supercapacitors. The simplified architecture and the sole use of printable materials may lead to a new class of entirely printable charge storage devices allowing for full integration with the emerging field of printed electronics.

Organic molecular soft ferromagnetism in a fullerene C60

The properties of an organic molecular ferromagnet [C60TDAE0.86; TDAE is tetrakis(dimethylamino)ethylene] with a Curie temperature ;Tc = 16.1 kelvin are described. The ferromagnetic state shows no remanence, and the temperature dependence of the magnetization below ;Tc does not follow the behavior expected of a conventional ferromagnet. These results are interpreted as a reflection of a three-dimensional system leading to a soft ferromagnet.

Organic solar cells with carbon nanotube network electrodes

We fabricated flexible transparent conducting electrodes by printing films of single-walled carbon nanotube (SWNT) networks on plastic and have demonstrated their use as transparent electrodes for efficient, flexible polymer-fullerene bulk-heterojunction solar cells. The printing method produces relatively smooth, homogeneous films with a transmittance of 85% at 550nm and a sheet resistance (Rs) of 200Ω∕◻. Cells were fabricated on the SWNT/plastic anodes identically to a process optimized for ITO/glass. Efficiencies, 2.5% (AM1.5G), are close to ITO/glass and are affected primarily by Rs. Bending test comparisons with ITO/plastic show the SWNT/plastic electrodes to be far more flexible.

Carbon nanotube films for transparent and plastic electronics

A two-dimensional network – often referred to as a thin film – of carbon nanotubes can be regarded as a novel transparent electronic “material” with excellent – and tunable – electrical, optical and mechanical properties. The films display high conductivity, high carrier mobility and optical transparency, in addition to flexibility, robustness and environmental resistance. These attributes, coupled with room temperature printing or spraying technology, ensure that the material will have a significant impact on a variety of emerging technologies and markets, ranging from macroelectronics to solid state lighting, organic solar cells and smart fabrics. The performance parameters of the first devices fabricated – smart windows, OLEDs and organic solar cells – indicate that the material is ready for product development

A method of printing carbon nanotube thin films

This paper describes a fabrication method for carbon nanotube thin films on various substrates including PET (polyethylene terephthalate), glass, polymethyl-methacrylate (PMMA), and silicon. The method combines a polydimethysiloxane (PDMS) based transfer-printing technique with vacuum filtration, and allows controlled deposition—and patterning if needed—of large area highly conducting carbon nanotube films with high homogeneity. In the visible and infrared range, the performance characteristics of fabricated films are comparable to that of indium tin oxide (ITO) on flexible substrates.

Electrodynamics of Solids: Optical Properties of Electrons in Matter

The authors of this book present a thorough discussion of the optical properties of solids, with a focus on electron states and their response to electrodynamic fields. A review of the fundamental aspects of the propagation of electromagnetic fields, and their interaction with condensed matter, is given. This is followed by a discussion of the optical properties of metals, semiconductors, and collective states of solids such as superconductors. Theoretical concepts, measurement techniques and experimental results are covered in three interrelated sections. Well-established, mature fields are discussed (for example, classical metals and semiconductors) together with modern topics at the focus of current interest. The substantial reference list included will also prove to be a valuable resource for those interested in the electronic properties of solids. The book is intended for use by advanced undergraduate and graduate students, and researchers active in the fields of condensed matter physics, materials science and optical engineering.

Conductivity scaling with bundle length and diameter in single walled carbon nanotube networks

Transparent single walled carbon nanotube (SWNT) networks were printed on plastic substrates. Nanotubes in the network form small bundles, and the authors evaluated the dc conductivity (σdc) as a function of the average bundle length (Lav) in the network. They find σdc to vary as σdc∼Lav1.46 for bundles of the same diameter and give a qualitative argument for why this agrees with a model where the resistance between SWNT bundles dominates the overall network resistance.

Interaction of Aromatic Compounds with Carbon Nanotubes: Correlation to the Hammett Parameter of the Substituent and Measured Carbon Nanotube FET Response

We have used field-effect transistor (FET) devices with semiconducting single-walled carbon nanotubes (SWNTs) as the conducting channels to study interactions of aromatic compounds with SWNTs. Electronic detection occurs through charge-transfer effects, monitored as the change of the gate voltage (Vg) dependence of the source-drain current Isd. For monosubstituted benzene compounds, we find that the shift of the Isd − Vg characteristic is proportional to the Hammett sigma values (σp) of their substituents.

Weakly coupled grain model of high‐frequency losses in high Tc superconducting thin films

We propose a model of Josephson coupling between grains to explain the millimeter‐wave surface impedance of oriented, polycrystalline thin films of high Tc superconductors. An effective junction IcR product and effective grain size are calculated based on recent measurements of the surface impedance. We suggest a criterion on film quality for the observation of losses intrinsic in the superconductor. The effects of crystalline orientation on surface impedance are considered.

Magnetic impurities in non-magnetic metals

The properties of 3d transition metal impurities in simple metal hosts are summarized. There is a short discussion of the basic microscopic models, then the Anderson model is treated in some detail. The next section considers the s-d model and the Kondo effect. The main experimental features are reviewed and finally the question of dilute alloys is considered.