There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

We present the science and technology roadmap for graphene, related two-dimensional crystals, and hybrid systems, targeting an evolution in technology, that might lead to impacts and benefits reaching into most areas of society. This roadmap was developed within the framework of the European Graphene Flagship and outlines the main targets and research areas as best understood at the start of this ambitious project. We provide an overview of the key aspects of graphene and related materials (GRMs), ranging from fundamental research challenges to a variety of applications in a large number of sectors, highlighting the steps necessary to take GRMs from a state of raw potential to a point where they might revolutionize multiple industries. We also define an extensive list of acronyms in an effort to standardize the nomenclature in this emerging field.

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Science and technology roadmap for graphene, related two-dimensional crystals, and hybrid systems

The science and technology of ultracapacitors are reviewed for a number of electrode materials, including carbon, mixed metal oxides, and conducting polymers. More work has been done using microporous carbons than with the other materials and most of the commercially available devices use carbon electrodes and an organic electrolytes. The energy density of these devices is 3¯5 Wh/kg with a power density of 300¯500 W/kg for high efficiency (90¯95%) charge/discharges. Projections of future developments using carbon indicate that energy densities of 10 Wh/kg or higher are likely with power densities of 1¯2 kW/kg. A key problem in the fabrication of these advanced devices is the bonding of the thin electrodes to a current collector such the contact resistance is less than 0.1 cm2. Special attention is given in the paper to comparing the power density characteristics of ultracapacitors and batteries. The comparisons should be made at the same charge/discharge efficiency.

Ultracapacitors: Why, How, and Where is the Technology

Leu-M

In the last three decades, zero-dimensional, one-dimensional, and two-dimensional carbon nanomaterials (i.e., fullerenes, carbon nanotubes, and graphene, respectively) have attracted significant attention from the scientific community due to their unique electronic, optical, thermal, mechanical, and chemical properties. While early work showed that these properties could enable high performance in selected applications, issues surrounding structural inhomogeneity and imprecise assembly have impeded robust and reliable implementation of carbon nanomaterials in widespread technologies. However, with recent advances in synthesis, sorting, and assembly techniques, carbon nanomaterials are experiencing renewed interest as the basis of numerous scalable technologies. Here, we present an extensive review of carbon nanomaterials in electronic, optoelectronic, photovoltaic, and sensing devices with a particular focus on the latest examples based on the highest purity samples. Specific attention is devoted to each class of carbon nanomaterial, thereby allowing comparative analysis of the suitability of fullerenes, carbon nanotubes, and graphene for each application area. In this manner, this article will provide guidance to future application developers and also articulate the remaining research challenges confronting this field.

Carbon nanomaterials for electronics, optoelectronics, photovoltaics, and sensing

The optical limiting action of C60 in toluene solution is mainly due to reverse saturable absorption (RSA). It is shown that the formalism describing nonlinear optical response due to instantaneous two-photon absorption can be used in the case of sequential two-photon absorption, yielding effective values of the relevant parameters of optical nonlinearity due to RSA. The effective two-photon absorption parameter beta eff and the effective nonlinear refractive index parameter gamma eff', which are related respectively to the imaginary and real parts of the effective third-order susceptibility chi eff(3) were measured by the z-scan technique as a function of fullerene concentration and of incident laser intensity and wavelength over the 420-640 nm region. The concentration dependence of these parameters indicates that the solution is optically thin as far as the ground state of C60 is concerned, whereas the wavelength dependence confirms the applicability of the formalism used in the sequential two-photon absorption model. Comparisons are made with other z-scan results on C60.

http://iopscience.iop.org/article/10.1088/0953-4075/28/20/015/pdf

Concentration and wavelength dependence of the effective third-order susceptibility and optical limiting of C60 in toluene solution

An experimental investigation of the nonlinear refractive index (n2) of carbon disulfide and toluene by spectral shearing interferometry and z-scan techniques

We present a systematic study of the effects of post-fabrication annealing on the performance of photovoltaic devices that incorporate a photoactive donor–acceptor dispersed heterojunction system. Solar cells have been fabricated based on poly(3-octylthiophene) as donor (D) and single-wall carbon nanotubes as the electron acceptor (A) with a PEDOT:PSS hole transport layer. A post-fabrication annealing treatment was carried out at a temperature range of 40–200 °C. The best results were obtained at 120 °C; at this temperature the cell shows a short circuit current, Isc = 0.5 mA cm−2, an open circuit voltage, Voc = 0.75 V and a fill factor, FF = 0.6, resulting in a power conversion efficiency of η = 0.22% under AM 1.5 (100 mW cm−2) white light illumination. The annealing treatment led to a doubling of the power conversion efficiency. This was attributed to a better charge carrier transport in the polymer matrix and more effective charge separation and collection.

https://iopscience.iop.org/article/10.1088/0022-3727/39/6/010/pdf

Post-fabrication annealing effects in polymer-nanotube photovoltaic cells

Onion-like carbon and diamond nanoparticles for optical limiting

We have introduced functionalized single-walled carbon nanotubes (SWNTs) in bulk heterojunction polymer?fullerene photovoltaic devices. As compared with the pristine device with only fullerenes, the addition of SWNTs resulted in an improvement in both the short-circuit current density and the fill factor (FF). The best results were obtained with a P3HT/PCBM (1?:?1) mixture with 0.5?wt% of SWNTs under an open-circuit voltage (Voc) of 0.55?V, a short-circuit current density (Jsc) of 4.95?mA?cm?2 and a FF of 0.52 which led to a power conversion efficiency of 1.4% at illumination at 100?mW?cm?2 AM1.5. This device takes advantage of the electron accepting feature of fullerenes and the high electron transport capability of SWNTs. The results indicate that the addition of nanotubes enhances the performance of polymer photovoltaic cells.

https://iopscience.iop.org/article/10.1088/0022-3727/41/16/165110/pdf

Emmanuel Koudoumas

Papers

Concentration and wavelength dependence of the effective third-order susceptibility and optical limiting of C60 in toluene solution

An experimental investigation of the nonlinear refractive index (n2) of carbon disulfide and toluene by spectral shearing interferometry and z-scan techniques

Post-fabrication annealing effects in polymer-nanotube photovoltaic cells

Onion-like carbon and diamond nanoparticles for optical limiting

Carbon nanotube doping of P3HT:PCBM photovoltaic devices