Bulletin of the American Physical Society
APS March Meeting 2015
Volume 60, Number 1
Monday–Friday, March 2–6, 2015; San Antonio, Texas
Session S42: Electrically and Optically Active Polymers |
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Sponsoring Units: DPOLY Chair: Chelsea Chen, Lawrence Berkeley National Laboratory Room: 214B |
Thursday, March 5, 2015 8:00AM - 8:12AM |
S42.00001: ABSTRACT WITHDRAWN |
Thursday, March 5, 2015 8:12AM - 8:24AM |
S42.00002: Orthogonal Photolithography as transformative patterning technique for Organic Electronics and Photonics Alex Zakhidov Orthogonal photolithography (OP) takes advantage of the fact that the vast majority of organic semiconducting materials are either oleophilic or hydrophilic and are hence orthogonal to highly fluorinated chemicals. Therefore, appropriate fluorinated photoresists can be used to pattern organic layers without compromising performance of organic device. The availability of such orthogonal photoresists promises to enable the fabrication of complex device structures, expanding the range of possibilities for organic electronics. Particular, OP technique enables sub-pixel high-resolution patterning for OLED displays [1]. Once RGB sub-pixel structuring is realized it is expected to improve (up to 10 times) the efficiency of a display. Moreover, processing solvents used for OP can be used as encapsulation media to improve heat management of high brightness OLED devices [2]. Other applications of OP include ultra-small channel OTFTs [3], OTFT based circuits and high voltage failure/proof organic solar cells. \\[4pt] [1] S. Krotkus et al, Adv. Opt. Mat. DOI: 10.1002/adom.201400181 (2014).\\[0pt] [2] A.A. Zakhidov et al, Organic Electronics 13, 356 (2012).\\[0pt] [3] A.A. Zakhidov et al, Chem. Sci., 2, 1178 (2011). [Preview Abstract] |
Thursday, March 5, 2015 8:24AM - 8:36AM |
S42.00003: Self-assembled peptide nanostructure-based polymeric electronic materials Soma Khanra, Suchi Guha, Wendel Alves, Thiago Cipriano Peptide-based nanostructures derived from natural amino acids are superior building blocks for organic semiconductor-based and biocompatible devices as they can be used in a bottom-up process without the need for expensive lithography. Based on self-assembly and mimicking the strategies occurring in nature, peptide materials play a unique role in a new generation of hybrid materials for the electronics of the 21$^{\mathrm{st}}$ century. In this work we functionalize diphenylalanine (FF)-containing polypeptides with conducting polymers, such as Poly (3-hexylthiophene) (P3HT) and polyfluorene (PF). The FF:polymer composites were synthesized by two methods: liquid-vapor and solid vapor phase. Electron microscopy images show micrometer size tubes with approximately 200 nm in diameter with homogeneous morphology. Photodiodes and light-emitting diode structures have been fabricated from FF:P3HT and FF:PF, respectively. We compare the electrical and optical properties of the FF:polymer composite devices with pristine polymer devices. Our results show that FF nanostructures with organic semiconductors could open up a new generation of bio-compatible materials in organic electronics. [Preview Abstract] |
Thursday, March 5, 2015 8:36AM - 8:48AM |
S42.00004: Investigation of Different Organic Solar Cell Active Region Structures Deposited by Resonant Infrared Matrix-Assisted Pulsed Laser Evaporation (RIR-MAPLE) Adrienne Stiff-Roberts, Ryan McCormick, Ayomide Atewologun In this work, we use RIR-MAPLE to investigate organic solar cells (OSCs) featuring different P3HT:PC$_{\mathrm{61}}$BM active region structures: bulk heterojunction (BHJ), bilayer, and gradient composition. Two deposition capabilities of RIR-MAPLE, nanoscale domains in blended polymeric films and multi-layer polymeric films regardless of constituent solubility, enable the deposition of these structures. While the BHJ yields better exciton dissociation due to large donor/acceptor interfacial area, the bilayer provides better charge transport due to reduced interfacial recombination. In contrast, the gradient structure could optimize both exciton dissociation and charge transport. P3HT materials characterization includes UV-Vis absorbance for Spano analysis and grazing-incidence, wide angle X-ray scattering (GIWAXS) for structural information. The OSC device characterization includes external quantum efficiency (EQE) and current-density voltage measurements. In addition, a Dynamic Monte Carlo model is used to simulate the different structures in order to generate EQE spectra for comparison to the measured device performance. This work was supported, in part, by the Office of Naval Research under Grant N00014-10-1-0481 and the National Science Foundation Triangle MRSEC on Soft Matter. [Preview Abstract] |
Thursday, March 5, 2015 8:48AM - 9:00AM |
S42.00005: Intrinsic series resistance of organic photovoltaic devices Non Thongprong, Phillip Duxbury Bilayer organic photovoltaics (OPV) are theoretically and computationally studied in order to find intrinsic physical origins of series and parallel resistances; $R_s$ and $R_p$. New current density-voltage (J-V) characteristic equations were derived in a similar manner to the work by Giebink et al., using reasoning based on electron and hole quasi-Fermi energies. We also developed a computational model combining previous developments by Koster et al. and Barker et al. with the interface model of Giebink et al. The computational model reveals that there are space charge regions around the donor-acceptor interface. These regions are the cause of an intrinsic $R_s$ due to their low carrier density which induces a shift of the quasi-Fermi levels from the electrode work functions. Recombination of charge transfer excitons (polaron pairs) across the interface can be viewed as a leakage path. An intrinsic origin of $R_p$ in this model is then polaron pair recombination. Both resistances are dependent on the applied voltage and these dependences are calculated using our computational model. The analysis is extended to include the presence of traps, yielding expressions for $R_s$, $R_p$ and for the ideality factors as a function of applied voltage. [Preview Abstract] |
Thursday, March 5, 2015 9:00AM - 9:12AM |
S42.00006: Photovoltaic Cells Involving Nonconjugated Conductive Polymer, Iodine-doped Styrene-Butadiene-Rubber (SBR) Justin Van Cleave, Mrinal Thakur Photovoltaic cells have been fabricated using titanium dioxide/ iodine-doped Styrene-Butadiene-Rubber/ carbon on indium-tin-oxide coated PET substrates. Photo-currents and photo-voltages were measured for varying intensities of light from a white light bulb, with emission from 300 to 700 nm. Iodine-doped SBR has absorption in the range of $\sim$ 250 to 750 nm. The cells as fabricated were characterized and were found to show significantly higher conversion efficiencies than previously reported. For an incident light intensity of about 5 mW/cm$^{2}$ a maximum photo-current density of about 0.2 mA/cm$^{2}$ and photo-voltage of about 0.8 V were recorded. The low cost of nonconjugated conductive polymers including SBR may provide a cheaper alternative to other materials for photovoltaic applications. [Preview Abstract] |
Thursday, March 5, 2015 9:12AM - 9:24AM |
S42.00007: Polymer/solvent bicontinuous microemulsions for use as organic solar cell active layers Dylan Kipp, Olga Wodo, Baskar Ganapathysubramanian, Venkat Ganesan The paradigm for the optimal morphology of an organic solar cell is characterized by cocontinuous, interpenetrating donor and acceptor domains with nanoscale dimensions and high interfacial areas. One well known equilibrium morphology that fits these characteristics is the bicontinuous microemulsion noted in the context of flexible polymeric blends. Currently, design rules are not available for producing bicontinuous microemulsion morphologies from the kinds of conjugated polymer/fullerene mixtures typically used to form the active layer of organic solar cells. Motivated by the above considerations, we use single chain in mean field simulations to study the ternary composition space of semiflexible polymer $+$ flexible-semiflexible block copolymer $+$ solvent and locate the channels of morphologies with characteristics like that of the bicontinuous microemulsion. Our theoretical analysis results in empirical design rules for producing bicontinuous microemulsion morphologies from blends of conjugated polymer $+$ block copolymer $+$ fullerene. [Preview Abstract] |
Thursday, March 5, 2015 9:24AM - 9:36AM |
S42.00008: Block Copolymer nanocomposite thin films for high energy-density capacitors Saumil Samant, Shimelis Hailu, Christopher Grabowski, Michael Durstock, Dharmaraj Raghavan, Alamgir Karim The energy storage capacity of solid-state capacitors is governed by product of relative permittivity ($\varepsilon )$ and square of breakdown strength (Vbd) of dielectric medium. Polymer films are widely used as the dielectric medium in capacitors due to their high Vbd and low loss but they suffer from poor permittivities. Composite dielectrics combine the high $\varepsilon $ ceramic fillers with high Vbd polymer matrix but usually result in loss of Vbd due to aggregation induced field enhancements. For optimum enhancement of dielectric properties, it is essential to improve matrix-filler interaction and control the dispersion of fillers. To that effect we graft a BCP onto the nanofiller and disperse it within a host BCP with similar composition. Using Directed Self-assembly we fabricate BCP nanostructured films with highly dispersed functionalized nano-fillers that are not only expected to enhance the overall $\varepsilon $, but the well-ordered BCP nanostructures also improve Vbd by providing sharp interfacial barriers acting as charge traps. The impact of filler functionalization, BCP morphology and nanofiller loading on dispersion and capacitor performance will be reported. [Preview Abstract] |
Thursday, March 5, 2015 9:36AM - 9:48AM |
S42.00009: Theoretical Prediction of Room Temperature Thermal Superconductivity in Single Polythiophene Chains Wei Lv, Asegun Henry We used molecular dynamics simulations and a new formalism for calculating the modal contributions to thermal conductivity to study individual polythiophene chains. The simulations suggest that it is possible to achieve divergent/infinite thermal conductivity (e.g., thermal superconductivity) in individual polythiophene chains. The new modal analysis method allowed for exact pinpointing of the modes responsible for the anomalous behavior, which turned out to be transverse vibrations in the plane of the aromatic rings at low frequencies $\sim$ 0.05 THz. Within the 5 ns of integration time, one mode in particular exhibits a thermal conductivity contribution greater than 100 W m-1 K-1, which is larger than many 3D bulk materials that consist of a large multitude of modes. Further investigation showed that the divergence arises from persistent correlation between the three lowest frequency modes on chains that have exact multiples of 30 unit cells in length. Sonification of the superconducting mode heat fluxes indicated distinct patterned differences between the convergent and divergent simulations, which suggests the phenomena may differ from previous models and a new explanation of the anomalous behavior may be required for polymers. [Preview Abstract] |
Thursday, March 5, 2015 9:48AM - 10:00AM |
S42.00010: Nonvolatile 1D Photonic Films Composed of Lamellar Forming Block Copolymer/Ionic Liquid Atsushi Noro, Yusuke Tomita, Yushu Matsushita, Joseph Walish, Edwin Thomas Block copolymer photonic films were prepared by infiltrating an ionic liquid (IL) into lamellar-forming polystyrene-b-poly(2-vinylpyridine) (PS-P2VP) block copolymer thin films with approximately 50/50 composition. The nonvolatile nature of IL enabled direct nanostructural observation of the films under the vacuum at room temperature by transmission electron microscopy, which revealed selective swelling of P2VP layers by the IL. Ultra-small angle X-ray scattering also provided the quantitative nanostructure information of the photonic films, revealing the domain periodicity distance was over 100 nm. In addition to these nanostructural observations, reflectivity spectra of the photonic films were also investigated by a fiber optic spectrophotometer. The wavelength at the peak top of reflected light from the photonic films was found to increase with increasing the molecular weight of block copolymers used for film preparation. Furthermore, tunablity of the wavelength was attained by infiltrating the IL into blend thin films of lamellar-forming PS-P2VP block copolymer. [Preview Abstract] |
Thursday, March 5, 2015 10:00AM - 10:12AM |
S42.00011: DNA in Nanoscale Electronics Jason Slinker, Marc McWilliams, Chris Wohlgamuth, Alon Gorodetsky Functional nanoelectronics are sought for next generation integrated circuits, but several challenges limit the use of most nanoscale devices on large scales. DNA has great potential for use as a molecular wire due to high yield synthesis, near-unity purification, and nanoscale self-organization. Nonetheless, a thorough understanding of ground state DNA charge transport (CT) under biologically relevant conditions, where the double-helical structure is preserved, is lacking. We measured DNA CT through double-stranded DNA monolayers on gold by assessing 17 base pair bridges at discrete points with redox active probes. This was performed under temperature-controlled and biologically relevant conditions with cyclic and square wave voltammetry, with redox peaks analyzed to assess transfer rate and yield. We demonstrated that the yield of transport is strongly tied to the stability of the duplex, linearly correlating with the melting temperature. Transfer rate was found to be temperature-activated and to follow inverse distance dependence, consistent with a hopping mechanism of transport. These results establish the governing factors of CT speed and yield through DNA for device configurations, guiding subsequent application in nanoscale electronics. [Preview Abstract] |
Thursday, March 5, 2015 10:12AM - 10:24AM |
S42.00012: DNA guided nickel ion chain memristive system development and characterization Chia-Ching Chang, Hsueh-Liang Chu, Wen-Bin Jian, Yu-Chang Chen DNA is a nanowire in nature with multiple base-pairs. Ni ions were chelated and aligned in base-pairs of DNA and created a DNA guided Ni ion chain (Ni-DNA). Herein, we demonstrate that Ni-DNA exhibits a programmable multi-state memristive system with an added capacitive component. Each Ni ion in Ni-DNA has low and high oxidation state and can be programmed sequentially by applying different polarities and writing time of bias voltage. Therefore, multi-state information can be written, read, and erased on this DNA memristive system. Thus, this Ni-DNA conducting nanowire can be used in combination with other two-terminal devices for a variety of applications in memory as well as n-nary computing. This study also indicates the biomolecules-based self-organized nanostructure can be used as a template for nanodevices fabrication. [Preview Abstract] |
Thursday, March 5, 2015 10:24AM - 10:36AM |
S42.00013: Bio-inspired peptide nanostructures for organic field-effect transistors Grant Knotts, Thiago Cipriano, Amrit Laudari, Roberta Bianchi, Wendel Alves, Suchi Guha Peptide-based nanostructures derived from natural amino acids are superior building blocks for biocompatible devices as they can be used in a bottom-up process without the need for expensive lithography. A dense nanostructured network of \textsc{l},\textsc{l}$-$diphenylalanine (FF) was synthesized using the solid-vapor phase technique. The formation of the nanostructures and structure-phase relationship were investigated by electron microscopy and Raman scattering. Thin films of \textsc{l},\textsc{l}$-$diphenylalanine micro/nanostructures (FF-MNSs) were used as the dielectric layer in pentacene-based field-effect transistors (FETs) and metal-insulator-semiconductor diodes both in bottom-gate and top-gate structures. Bias-stress studies show that FF-MNS based pentacene FETs are more resistant to degradation than pentacene FETs using FF thin film (without any nanostructures) as the dielectric layer when both are subjected to sustained electric fields. Furthermore, it is demonstrated that the FF-MNSs can be functionalized for detection of enzyme-analyte interactions. This work opens up a novel and facile route towards scalable organic electronics using peptide nanostructures as scaffolding and as a platform for biosensing. [Preview Abstract] |
Thursday, March 5, 2015 10:36AM - 10:48AM |
S42.00014: Residual Stresses and Photoluminescence of Conjugated Polymer Thin Films Ya-Wei Yang, Yi Chien, Tsang-Lang Lin, Gunter Reiter, Arnold Chang-Mou Yang Molecular recoiling forces (residual stress) in ultrathin polymer films ($<$ 100 nm) were engendered by non-equilibrium chain conformations and intermolecular packing frozen from rapid solvent evaporation during film preparation. These forces when acting on conjugated macromolecules were found to contribute to large photoluminescence (PL) enhancements. The packing of the rigid-rod macromolecules into thin solid films, however, was somewhat different from that of flexible chains. As revealed by x-ray reflectivity, although the thicknesses of the solvent-trap layer ($\sim$2nm) next to substrate were almost identical, the local density was $\sim$10 times less in MEH-PPV films than that in polystyrene (PS) films (20 nm). It indicates that molecular strains induced by solvent evaporation were much smaller of conjugated polymers, hinting smaller residual stresses in the films. Concomitantly, local deformations of rubber substrate under a dewetting polymer film, a good measure of the molecular recoiling forces, were considerably smaller for MEH-PPV films than for PS. The PL dependence on residual stresses of pristine MEH-PPV films hence clearly elucidates the strong molecular stress effect on optoelectronic efficiencies. [Preview Abstract] |
Thursday, March 5, 2015 10:48AM - 11:00AM |
S42.00015: Polymeric Carbon Dioxide Capture Membranes for Artificial Photosynthesis Daniel Miller, Nathaniel Lynd Production of carbon-rich fuels via artificial photosynthetic processes depends on the continuous availability of a carbon source. In a proposed artificial photosynthetic system, hydrogen and oxygen from solar water splitting are combined with CO$_{\mathrm{2}}$ captured from the atmosphere to produce a liquid fuel such as methanol. Membrane-based processes provide advantages over other gas separation technologies, including mechanical simplicity, a relatively small footprint, and energy efficiency. We describe the synthesis and characterization of polymeric anion exchange materials for CO$_{\mathrm{2}}$ concentration from gas mixtures such as the atmosphere. Transport of CO$_{\mathrm{2}}$ through the membrane is promoted by an opposing flux of water, which reacts with CO$_{\mathrm{2}}$ through equilibrium reactions to form charged species (bicarbonate, carbonate, and hydroxide) within the membrane. CO$_{\mathrm{2}}$ transport will be discussed as a function of membrane material characteristics, including charge density, and process characteristics, including feed stream relative humidity and CO$_{\mathrm{2}}$ concentration on each side of the membrane. The development of several membrane materials will be discussed. Results of experimental gas transport studies will be presented. [Preview Abstract] |
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