IMDEA Madrid Institute for Advanced Studies

Madrid, Spain

IMDEA Madrid Institute for Advanced Studies

Madrid, Spain

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Urbani M.,Autonomous University of Madrid | Urbani M.,IMDEA Madrid Institute for Advanced Studies | Gratzel M.,Ecole Polytechnique Federale de Lausanne | Nazeeruddin M.K.,Ecole Polytechnique Federale de Lausanne | And 2 more authors.
Chemical Reviews | Year: 2014

Among the several approaches for harnessing solar energy and converting it into electricity, dye-sensitized solar cells (DSSC) represent one of the most promising methods for future large-scale power production from renewable energy sources. In these cells, the sensitizer is one of the key components harvesting solar radiation and converting it into electric current. The electrochemical, photophysical, and ground and excited state properties of the sensitizer play an important role for charge transfer dynamics at the semiconductor interface. Moreover, for long-term stability and practical applications, electrolytes based on the iodine/triiodine couple also suffer from two other disadvantages: the corrosive effect toward the metal electrodes, and the partial absorption of the visible light by triiodine anions. These issues hence constitute one of the reasons that have encouraged the development of alternative iodine-free redox couples in liquid electrolytes for DSSCs.

Martin N.,Complutense University of Madrid | Martin N.,IMDEA Madrid Institute for Advanced Studies
Chemical Communications | Year: 2013

Tetrathiafulvalene (TTF) is among the most versatile and well-known molecules which exhibits outstanding redox properties and a remarkable electron donor character. Its first synthesis was published in a short communication by Wudl in 1970. In this viewpoint, its synthesis and characterization are discussed and, most importantly, the significance of TTF in the development of electrically conducting materials (organic or synthetic metals) and its further application in molecular electronics are highlighted. © 2013 The Royal Society of Chemistry.

An B.-K.,Catholic University of Korea | Gierschner J.,IMDEA Madrid Institute for Advanced Studies | Park S.Y.,Seoul National University
Accounts of Chemical Research | Year: 2012

π-Conjugated organic molecules represent an attractive platform for the design and fabrication of a wide range of nano- and microstructures for use in organic optoelectronics. The desirable optical and electrical properties of π-conjugated molecules for these applications depend on their primary molecular structure and their intermolecular interactions such as molecular packing or ordering in the condensed states. Because of the difficulty in satisfying these rigorous structural requirements for photoluminescence and charge transport, the development of novel high-performance π-conjugated systems for nano-optoelectronics has remained a challenge.This Account describes our recent discovery of a novel class of self-assembling π-conjugated organic molecules with a built-in molecular elastic twist. These molecules consist of a cyano-substituted stilbenic π-conjugated backbone and various terminal functional groups, and they offer excellent optical, electrical, and self-assembly properties for use in various nano-optoelectronic devices. The characteristic "twist elasticity" behavior of these molecules occurs in response to molecular interactions. These large torsional or conformational changes in the cyanostilbene backbone play an important role in achieving favorable intermolecular interactions that lead to both high photoluminescence and good charge carrier mobility in self-assembled nanostructures.Conventional π-conjugated molecules in the solid state typically show concentration (aggregation) fluorescence quenching. Initially, we describe the unique photoluminescence properties, aggregation-induced enhanced emission (AIEE), of these new cyanostilbene derivatives that elegantly circumvent these problems. These elastic twist π-conjugated backbones serve as versatile scaffolds for the preparation of well-defined patterned nanosized architectures through facile self-assembly processes. We discuss in particular detail the preparation of 1D nanowire structures through programmed self-assembly.This Account describes the importance of utilizing AIEE effects to explore optical device applications, such as organic semiconducting lasers (OSLs), optical memory, and sensors. We demonstrate the rich electronic properties, including the electrical conductivity, field-effect carrier mobility, and electroluminescence of highly crystalline 1D nanowire and coaxial donor-acceptor nanocable structures composed of elastic twist π-conjugated molecules. The electronic properties were measured using various techniques, including current-voltage (I-V), conducting-probe atomic force microscopy (CP-AFM), and space-charge-limited- current (SCLC) measurements. We prepared and characterized several electronic device structures, including organic field-effect transistors (OFETs) and organic light-emitting field-effect transistors (OLETs). © 2011 American Chemical Society.

Gierschner J.,IMDEA Madrid Institute for Advanced Studies | Park S.Y.,Seoul National University
Journal of Materials Chemistry C | Year: 2013

The last few years have seen a steady increase in small molecule based conjugated materials, which promise innovative (opto)electronic applications. This requires however a systematic understanding of structure-property relationships, which can only be achieved via libraries of structurally well-defined single crystalline materials based on systematically designed molecular structures. In this feature article, we are presenting structure-property relationships of functionalized distyrylbenzene (DSB), which is one of the most extensively investigated π-conjugated molecular materials. This will provide a general insight into the specific implications of intermolecular arrangements on their solid state optoelectronic properties, discussing H- vs. J-aggregation, herringbone vs. π-stacks, the occurrence of excimers, size effects, and polycrystallinity. The systematic insight into DSB functionalization will then suggest pathways towards targeted molecular design strategies, with special focus on the cyano-vinylene motif (DCS materials) which allows for highly fluorescence solid state samples due to synergetic packing effects promoted by its twist elasticity and secondary bonding interaction. Finally, recent advances in the application of DSB-/DCS-based materials are shortly reviewed. © 2013 The Royal Society of Chemistry.

Castellanos-Gomez A.,IMDEA Madrid Institute for Advanced Studies
Journal of Physical Chemistry Letters | Year: 2015

The recent isolation of atomically thin black phosphorus by mechanical exfoliation of bulk layered crystals has triggered an unprecedented interest, even higher than that raised by the first works on graphene and other two-dimensionals, in the nanoscience and nanotechnology community. In this Perspective, we critically analyze the reasons behind the surge of experimental and theoretical works on this novel two-dimensional material. We believe that the fact that black phosphorus band gap value spans over a wide range of the electromagnetic spectrum (interesting for thermal imaging, thermoelectrics, fiber optics communication, photovoltaics, etc.) that was not covered by any other two-dimensional material isolated to date, its high carrier mobility, its ambipolar field-effect, and its rather unusual in-plane anisotropy drew the attention of the scientific community toward this two-dimensional material. Here, we also review the current advances, the future directions and the challenges in this young research field. © 2015 American Chemical Society.

Vilatela J.J.,IMDEA Madrid Institute for Advanced Studies | Eder D.,University of Munster
ChemSusChem | Year: 2012

There is an ever-growing need to protect our environment by increasing energy efficiency and developing "clean" energy sources. These are global challenges, and their resolution is vital to our energy security. Although many conventional materials, such as metals, ceramics, and plastics, cannot fulfil all requirements for these new technologies, many material combinations can offer synergistic effects that create improved and even new properties. The implementation of nanocarbons, such as graphene and carbon nanotubes, into nanocomposites and, more recently, into the new class of hybrids, are very promising examples. In contrast to classical nanocomposites, where a low volume fraction of the carbon component is mixed into a polymer or ceramic matrix, hybrids are materials in which nanocarbon is coated with a thin layer of the functional compound, which introduces the interface as a powerful new parameter. Based on interfacial charge and energy transfer processes, nanocarbon hybrids have shown increased sensitivities in gas sensors, improved efficiencies in photovoltaics, superior activities in photocatalysts, and enhanced capacities in supercapacitors. This review compares the characteristics and potentials of both nanocarbon composites and hybrids, highlights recent developments in their synthesis and discusses key challenges for their use in various energy applications. Composites and hybrids go energy: The combination of graphene and carbon nanotubes into composites and, more recently, into the new class of hybrids creates new functional energy materials, whose synergistic effects are based on interfacial charge and heat transfer processes. In this Minireview, we provide a critical distinction between nanocomposites and nanocarbon hybrids with specific relation to sustainability as well as an overview of synthesis strategies. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Martin-Bragado I.,IMDEA Madrid Institute for Advanced Studies
Scripta Materialia | Year: 2012

A lattice kinetic Monte Carlo model is used to show the importance of twin defect formation created during solid-phase epitaxial growth (SPEG) to properly account for SPEG rates at different silicon substrate orientations. In particular, SPEG defect creation is fundamental to understanding the growth velocities in substrate angles close to Si(3 1 1) and Si(1 1 1). The model is compared with experimental observations and shows the feedback of twin defects on SPEG rates, shape evolution and interface roughness for different Si substrates. © 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Perez E.M.,IMDEA Madrid Institute for Advanced Studies
Angewandte Chemie - International Edition | Year: 2011

Standing on their own two feet! Inspired by naturally occurring molecular motors such as kinesins, dyneins, and myosins, a series of small-molecule walker systems have been synthesized (see picture). These artificial molecular motors are capable of moving directionally along their associated tracks, and show most of the features of their natural counterparts. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

O'Mahony T.,IMDEA Madrid Institute for Advanced Studies
Energy Policy | Year: 2013

In recent decades, Ireland has been an important example of a development pathway where rapid economic growth was accompanied by rising energy demand and increasing carbon emissions. Understanding the driving forces of carbon emissions is necessary for policy formulation and decomposition analysis is widely used for this purpose. This study uses an extended Kaya identity as the scheme and applies the log mean Divisia index (LMDI I) as the decomposition technique. Change in carbon emissions is decomposed from 1990 to 2010 and includes a measure of the effect of renewable energy penetration. Results illustrate that scale effects of affluence and population growth act to increase emissions and are countered primarily by energy intensity and fossil fuel substitution. Renewable energy penetration has a minor effect but has been increasing in recent years. Policy will need to significantly reduce intensity and increase renewables if applicable targets are to be reached. This requires not only a comprehensive suite of policies and measures but emphasis on the development path and 'non-technical' change for optimal outcomes. © 2013 Elsevier Ltd.

Mortensen A.,Ecole Polytechnique Federale de Lausanne | Llorca J.,IMDEA Madrid Institute for Advanced Studies
Annual Review of Materials Research | Year: 2010

In metal matrix composites, a metal is combined with another, often nonmetallic, phase to produce a novel material having attractive engineering attributes of its own. A subject of much research in the 1980s and 1990s, this class of materials has, in the past decade, increased significantly in variety. Copper matrix composites, layered composites, high-conductivity composites, nanoscale composites, microcellular metals, and bio-derived composites have been added to a palette that, ten years ago, mostly comprised ceramic fiber- or particle-reinforced light metals together with some well-established engineering materials, such as WC-Co cermets. At the same time, research on composites such as particle-reinforced aluminum, aided by novel techniques such as large-cell 3-D finite element simulation or computed X-ray microtomography, has served as a potent vehicle for the elucidation of the mechanics of high-contrast two-phase elastoplastic materials, with implications that range well beyond metal matrix composites. © 2010 by Annual Reviews. All rights reserved.

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