Advanced Functional Materials

Cover image for Vol. 11 Issue 4

August, 2001

Volume 11, Issue 4

Pages 243–314

    1. Molecular Inorganic, Organic Crystalline, and Glassy Materials for Raman Laser Converters (pages 243–250)

      J. Hulliger, A. A. Kaminskii and H. J. Eichler

      Version of Record online: 6 AUG 2001 | DOI: 10.1002/1616-3028(200108)11:4<243::AID-ADFM243>3.0.CO;2-U

      Renewed interest in the field of stimulated Raman scattering (SRS) has emerged because of the discovery of SRS in crystals and glasses that contain molecular units exhibiting Raman active modes (e.g., see Figure). SRS laser systems are of interest in various fields, especially those that are difficult to reach by conventional solid-state lasers.

    2. Outsmarting Waveguide Losses in Thin-Film Light-Emitting Diodes (pages 251–253)

      K. Meerholz and D. C. Müller

      Version of Record online: 6 AUG 2001 | DOI: 10.1002/1616-3028(200108)11:4<251::AID-ADFM251>3.0.CO;2-Y

      Several attempts to overcome the problem of waveguide losses in light-emitting diodes (LEDs) have been made over past few years. This article summarizes the most important developments in this area and specifically highlights one attempt (see Figure), achieved by Tsutsui et al. and published in the latest issue of Advanced Materials.

    3. Synthesis and Characterization of a Low Bandgap Conjugated Polymer for Bulk Heterojunction Photovoltaic Cells (pages 255–262)

      A. Dhanabalan, J. K. J. van Duren, P. A. van Hal, J. L. J. van Dongen and R. A. J. Janssen

      Version of Record online: 6 AUG 2001 | DOI: 10.1002/1616-3028(200108)11:4<255::AID-ADFM255>3.0.CO;2-I

      A novel conjugated oligomeric material (see Figure) that exhibits a low optical bandgap as a result of the alternation of electron-rich and electron-deficient units along the chain has been fabricated via a Stille-type polymerization. Direct spectral evidence (photoinduced absorption (PIA) and photoluminescence spectroscopy) is given, revealing the photoinduced electron-transfer reaction between blends of this polymer and a methanofullerene.

    4. Structural and Spectroscopic Characterization of Nominal Yb3+:Ca8La2(PO4)6O2 Oxyapatite Single Crystal Fibers Grown by the Micro-Pulling-Down Method (pages 263–270)

      G. Boulon, A. Collombet, A. Brenier, M.-T. Cohen-Adad, A. Yoshikawa, K. Lebbou, J. H. Lee and T. Fukuda

      Version of Record online: 6 AUG 2001 | DOI: 10.1002/1616-3028(200108)11:4<263::AID-ADFM263>3.0.CO;2-M

      The micro-pulling-down (μ-PD) method is a novel way of creating apatite-type structures. Ytterbium-doped varieties have thus been fabricated and their crystallinity investigated. Absorption, emission, and fluorescence decay studies are presented here. These structures have potential applications in diode-pumped lasers. The Figure shows a photograph of single crystal fibers.

    5. Preparation of a Photoacid Generating Monomer and Its Application in Lithography (pages 271–276)

      H. Wu and K. E. Gonsalves

      Version of Record online: 6 AUG 2001 | DOI: 10.1002/1616-3028(200108)11:4<271::AID-ADFM271>3.0.CO;2-Q

      Chemically amplified resists with photoacid generating monomers incorporated in the polymer chain are revealed in this paper. The resists exhibit excellent film formation behavior and the acid generation seems to be independent of the composition of the copolymers. Their lithographic properties are investigated and presented, together with their synthesis. The Figure shows an SEM image of a sample stored for half a year.

    6. Tuning the Size and Shape of Zeolite L-Based Inorganic–Organic Host–Guest Composites for Optical Antenna Systems (pages 277–286)

      S. Megelski and G. Calzaferri

      Version of Record online: 6 AUG 2001 | DOI: 10.1002/1616-3028(200108)11:4<277::AID-ADFM277>3.0.CO;2-2

      A convenient way to prepare different crystalline materials in the size range of 30 nm up to 3000 nm has been developed. Fine-tuning of the size of zeolite L crystals in a large range is possible by changing the composition of the starting gel under otherwise constant reaction conditions. The design of efficient optical antenna functionalities for light harvesting, transport, and capturing is illustrated in the Figure.

    7. Control of Electrophosphorescence in Conjugated Dendrimer Light-Emitting Diodes (pages 287–294)

      J. M. Lupton, I. D. W. Samuel, M. J. Frampton, R. Beavington and P. L. Burn

      Version of Record online: 6 AUG 2001 | DOI: 10.1002/1616-3028(200108)11:4<287::AID-ADFM287>3.0.CO;2-Z

      How can you control the color of light emission by changing the driving conditions of a light-emitting device? The answer lies in new work on light-emitting dendrimers presented in this paper. Platinum porphyrin–based phosphorescent dendrimers (see Figure) are used as dopants in a variety of host materials. The electroluminescent and other spectral properties of these host–guest blends are thoroughly discussed.

    8. Growth of Single-Walled Carbon Nanotubes from Microcontact-Printed Catalyst Patterns on Thin Si3N4 Membranes (pages 295–298)

      G. Gu, G. Philipp, X. Wu, M. Burghard, A. M. Bittner and S. Roth

      Version of Record online: 6 AUG 2001 | DOI: 10.1002/1616-3028(200108)11:4<295::AID-ADFM295>3.0.CO;2-2

      The growth of single-walled carbon nanotubes (SWCNTs) by chemical vapor deposition (CVD) from methane and hydrogen on catalyst patterns prepared by microcontact printing on silicon nitride substrates is reported. Introducing hydrogen during deposition has been found to improve the yield enormously. The Figure shows an optical microscopy image after nanotube growth (see also cover).

    9. New Transparent Metal-like Bilayer Composite Films with Highly Conducting Layers of θ-(BET-TTF)2Br·3H2O Nanocrystals (pages 299–303)

      M. Mas-Torrent, E. Laukhina, C. Rovira, J. Veciana, V. Tkacheva, L. Zorina and S. Khasanov

      Version of Record online: 6 AUG 2001 | DOI: 10.1002/1616-3028(200108)11:4<299::AID-ADFM299>3.0.CO;2-N

      A novel conducting bilayer composite (BLC) film—a polycarbonate matrix with a conducting surface layer of a crystalline network of an organic conductor—is presented. A BLC film combines the high stability and physical properties of an organic conductor, in this case the molecular metal θ-(BET-TTF)2Br·3H2O, with the flexibility, transparency, and low density of a polymer matrix. The determination of the optimal conditions for the preparation of the new film, which is extremely transparent and has metal-like transport properties down to liquid helium temperature, is described (see also inside front cover).

    10. Synthesis and Electrochemical Properties of Novel 1,3,5-Tris(oligothienyl)benzenes: A New Generation of 3D Reticulating Agents (pages 305–309)

      F. Cherioux and L. Guyard

      Version of Record online: 6 AUG 2001 | DOI: 10.1002/1616-3028(200108)11:4<305::AID-ADFM305>3.0.CO;2-Y

      Very useful precursors for three-dimensional (3D) conducting polymers—novel 1,3,5-tris(5-oligothienyl)benzene derivatives (see Figure)—are reported to have been synthesized by an efficient and easy trimerization reaction. Their optimized 3D geometry is calculated semiempirically and their electrochemical behavior is described. New polymers synthesized by chemical or electrochemical oxidation of the precursors are presented.

    11. Enhanced Hole Injection into Amorphous Hole-Transport Layers of Organic Light-Emitting Diodes Using Controlled p-Type Doping (pages 310–314)

      X. Zhou, J. Blochwitz, M. Pfeiffer, A. Nollau, T. Fritz and K. Leo

      Version of Record online: 6 AUG 2001 | DOI: 10.1002/1616-3028(200108)11:4<310::AID-ADFM310>3.0.CO;2-D

      Increased thickness of transport layers in organic light-emitting diodes (OLEDs)—and thus extended device lifetime—can be achieved by controlled doping to influence the electrical properties of the transport layers, as demonstrated here. Coevaporation of the starburst amine TDATA (see Figure) with the very strong acceptor F4-TCNQ as dopant is shown to lead to an amorphous hole-transport material with properties well-suited for OLEDs.