Advanced Functional Materials

Cover image for Vol. 13 Issue 1

January, 2003

Volume 13, Issue 1

Pages 3–90

    1. Contents: Adv. Funct. Mater. 1/2003 (pages 3–5)

      Article first published online: 30 JAN 2003 | DOI: 10.1002/adfm.200390003

    2. Novel Nanostructures of Functional Oxides Synthesized by Thermal Evaporation (pages 9–24)

      Z.R. Dai, Z.W. Pan and Z.L. Wang

      Article first published online: 30 JAN 2003 | DOI: 10.1002/adfm.200390013

      The fundamental building blocks of smart devices, functional oxides, are reviewed. The review highlights the synthesis of a variety of single crystalline novel nanostructures, including nanobelts, nanowires, nanosheets, nanodiskettes (see Figure), and nanodendrites. Taking SnO2 and SnO as the examples, a wide range of novel nanostructures are illustrated, and their growth, phase transformation, and stability are discussed.

    3. Stabilization of Semiconducting Polymers with Silsesquioxane (pages 25–29)

      S. Xiao, M. Nguyen, X. Gong, Y. Cao, H. Wu, D. Moses and A.J. Heeger

      Article first published online: 30 JAN 2003 | DOI: 10.1002/adfm.200390000

      Brighter electroluminescence and higher external quantum efficiencies can be obtained from semiconducting polymers by anchoring them to polyhedral oligomeric silsesquioxanes (POSS). Additionally, the end-capped derivatives of the widely-used electroluminescent polymers MEH-PPV and PFO show improved thermal stability compared to the original materials, and the PFO hybrid electroluminesces with an improved blue-color when incorporated in the same device configuration as the un-capped analog.

    4. Solventless Acid-Free Synthesis of Mesostructured Titania: Nanovessels for Metal Complexes and Metal Nanoclusters (pages 30–36)

      Ö. Dag, I. Soten, Ö. Çelik, S. Polarz, N. Coombs and G.A. Ozin

      Article first published online: 30 JAN 2003 | DOI: 10.1002/adfm.200390001

      Ordered mesostructured titania materials with embedded metal nanoparticles are synthesized using a novel solvent-free pathway. Atmospheric water induces self-organization of a non-ionic surfactant solution in pure titanium(IV) ethoxide. Various metal salts can be immobilized during the synthesis, which, after reduction, leads to the formation of mesostructured titania–metal hybrid materials (see Figure).

    5. Nanocrystalline Transition-Metal Oxide Spheres with Controlled Multi-Scale Porosity (pages 37–42)

      D. Grosso, G.J. de A.A. Soler-Illia, E.L. Crepaldi, B. Charleux and C. Sanchez

      Article first published online: 30 JAN 2003 | DOI: 10.1002/adfm.200390002

      Industrial production of innovative multiscale porosity materials could be facilitated by the new and easily scaled-up process reported here. Nanocrystalline transition-metal oxide spheres of hierarchically and periodically organized porosity (see Figure) have been prepared through a one-step method that combines sol–gel chemistry, multiscale templating approaches, aerosol processing, and specific treatments.

    6. Electron Transport in a Methanofullerene (pages 43–46)

      V.D. Mihailetchi, J.K.J. van Duren, P.W.M. Blom, J.C. Hummelen, R.A.J. Janssen, J.M. Kroon, M.T. Rispens, W.J.H. Verhees and M.M. Wienk

      Article first published online: 30 JAN 2003 | DOI: 10.1002/adfm.200390004

      The transport properties of electrons in C60 based molecules (see Figure), as used in conjugated polymer based solar cells have been investigated. At room temperature, the electrons in the C60 based molecules are a factor of four thousand more mobile than the holes in the conjugated polymer. These results are of fundamental importance to further the understanding of polymer/C60 solar cells.

    7. Self-Assembly and Characterization of Mesostructured Silica Films with a 3D Arrangement of Isolated Spherical Mesopores (pages 47–52)

      K. Yu, B. Smarsly and C.J. Brinker

      Article first published online: 30 JAN 2003 | DOI: 10.1002/adfm.200390005

      Mesoporous silica thin films with a 3D ordered arrangement of isolated spherical pores are created by self-assembly and characterized (see Figure). The preparation method was based on solvent-evaporation-induced self-assembly with a silica precursor and a diblock copolymer as the structure-directing agent. The calcined films exhibited no measurable microporosity, thereby indicating that the 3D-ordered spherical mesopores are not interconnected.

    8. Tunneling Current in Polycrystalline Organic Thin-Film Transistors (pages 53–60)

      G. Horowitz

      Article first published online: 30 JAN 2003 | DOI: 10.1002/adfm.200390006

      A model is developed to describe the temperature-independent behavior of charge-carrier mobility at low temperatures in organic field-effect transistors made of vacuum-evaporated films. The model is based on the films’ polycrystalline nature, where charge transport is mostly limited by grain boundaries. A complete 2D model for charge tunneling through the barriers is developed, and a quantitative check of the model is made by fitting of the gate voltage dependent current measured on an octithiophene transistor at low temperature.

    9. Surfactant-Assisted Synthesis of Alumina with Hierarchical Nanopores (pages 61–65)

      W. Deng, M.W. Toepke and B.H. Shanks

      Article first published online: 30 JAN 2003 | DOI: 10.1002/adfm.200390007

      Aluminas with hierarchical nanopore structures (see Figure) were synthesized by a surfactant-assisted method. The factors affecting the appearance of the hierarchically structured alumina material are presented. A potential mechanism for the formation of the aluminas is proposed. The materials have excellent potential for use as catalysts, since the macropores facilitate mass transfer to the high surface area contained within the mesopores.

    10. Raman Anisotropy Measurements: An Effective Probe of Molecular Orientation in Conjugated Polymer Thin Films (pages 66–72)

      H.-M. Liem, P. Etchegoin, K.S. Whitehead and D.D.C. Bradley

      Article first published online: 30 JAN 2003 | DOI: 10.1002/adfm.200390008

      A direct structural probe of molecular orientation in aligned conjugated polymer films is shown to be provided by Raman anisotropy measurements. The data can be collected in situ for standard device structures and film thicknesses, with microscopic resolution and chemical specificity. Additionally, molecular orientation can be more directly and accurately characterized than is possible using optical dichroism measurements. Measuring the alignment of conjugated polymers within thin-film samples is essential for a complete picture of their optical and transport properties, and for the further development of optoelectronic devices.

    11. Controlling the Morphology of Nanocrystal–Polymer Composites for Solar Cells (pages 73–79)

      W.U. Huynh, J.J. Dittmer, W.C. Libby, G.L. Whiting and A.P. Alivisatos

      Article first published online: 30 JAN 2003 | DOI: 10.1002/adfm.200390009

      Highly efficient solar cells can be fabricated from a hybrid nanorod–polymer solution when precise control of the film morphology can be achieved. The morphology of thin films from blends of CdSe and poly(3-hexylthiophene), which is easily studied via atomic force microscopy (see Figure, 5 μm2 scan area), can be finely tuned through the use of a binary solvent mixture and thermal treatment for impressive increases in device efficiency.

    12. Selective Growth of Carbon Nanotubes for Nanoscale Transistors (pages 80–84)

      W.B. Choi, B.-H. Cheong, J.J. Kim, J. Chu and E. Bae

      Article first published online: 30 JAN 2003 | DOI: 10.1002/adfm.200390010

      Nanoscale transistors can be fabricated via the selective growth of vertically aligned carbon nanotubes (see Figure). These nanotube arrays are grown in nanoholes formed in an anodized aluminum oxide template. Each device element is formed on a vertical carbon nanotube attached to bottom (source) and upper (drain) electrodes and a gate electrode, which can then be integrated in large arrays with the potential for tera-level density.

    13. Effects of Postproduction Treatment on Plastic Solar Cells (pages 85–88)

      F. Padinger, R.S. Rittberger and N.S. Sariciftci

      Article first published online: 30 JAN 2003 | DOI: 10.1002/adfm.200390011

      An increase in both the external quantum efficiency and the short-circuit current of organic polymer-based solar cells can be achieved by using a simple postproduction process. Poly(3-hexylthiophene) [6,6]-phenyl C61-butyric acid methyl ester-based solar cells have been subjected to a tempering cycle at elevated temperatures whilst simultaneously applying an external electrical field. Using this treatment, an enhancement of the short-circuit current density to 8.5 mA cm–2 under illumination with white light of 800 W m–2 and an increase in external quantum efficiency to 70 % are demonstrated.

    14. Author Index and Subject Index Adv. Funct. Mater. 1/2003 (page 90)

      Article first published online: 30 JAN 2003 | DOI: 10.1002/adfm.200390012