SYMPOSIUM Q

11:00 AM *Q2-S2.1 (invited)
Highly Ordered Nano Structure Hybrid Material for High Efficient Photovoltaic Device. (#662) Wei-Fang Su, Chun-Wei Chen, Chi-An Dai, Lee-Yi Wang; Department of Materials Science and Engineering, National Taiwan University, Taipei, Taiwan.

Hybrid materials made from conducting polymer-nanoparticle are attractive for photovoltaic devices because of the prospect of light weight, low cost, high throughput, high energy density using reel-to-reel or spray deposition on flexible substrate. The hybrid materials serve as the photo-electrical active layer in the photovoltaic device. Upon the absorption of solar energy by hybrid material, excitons are formed and diffused into the interfaces between polymer and nanoparticle. Then the excitons are separated into electrons and holes. The electrons are transported through the pathways built by nanoparticles and the holes are transported through the polymer. Thus the electricity is generated. In this research, we are able to greatly improve the efficiency of the hybrid solar cell by fabricating highly ordered nano structure hybrids, studying the interlayer characteristics of hybrid and device physics, and modifying the surface of nanoparticles. The device usually has the construction of ITO/PEDOT/hybrid/Al four layers. We have established time resolved photoluminescence (TRPL) and time of flight (TOF) to measure exciton life and charge carrier mobility respectively. The inclusion of CdSe nanoparticles into MEHPPV conducting polymer in the hybrid solar cell increases the ordering in polymer and its absorption spectrum was red shifted. The hybrid also exhibits an order increase in power efficiency (2006 Nanotechnology 17, 1260-1263). The exciton life time of hybrid can be decreased to less than half of the neat polymer by blending low cost and nontoxic TiO2 nanorod into MEHPPV (2006 Nanotechnology, 17, 5781-5785). The efficiency of MEHPPV-TiO2 solar cell can be increased by 2.5 times by inserting a TiO2 nanorod layer between the hybrid active layer and Al electrode due to the enlargement of the interconnecting network between the hybrid and electrode (2006 Nanotechnology 17, 5387-5392). The carrier mobility can be increased by 9 times using column structured ZnO electron transport layer infiltrated with the P3HT-TiO2 hybrid due to efficient charge transport (2007 J. Mater. Chem., 17, 4571-4576). We have used conducting molecules to modify the surface of CdSe nanoparticles such as thiophenol or p-hydroxy thiophenol to facilitate the charge transport, 10 times increase in output current is observed (2008, Journal of Materials Chemistry, 18, 675-682). The solar cell fabricated from surface modified TiO2 nanoparticles with carboxylate linker and P3HT hybrid has achieved the relatively high power conversion efficiency of 2.2% under simulated AM 1.5 illumination (100 mW/cm2) because of the reduced recombination of charge carriers.(2008, J. Mater. Chem. in press and 2008 Appl. Phys. Lett. 92, 053312). The efficiency of the device is expected to be further improved by using newly developed self assembled highly ordered nano structure copolymers of P3HT-P2VP (2007 J. Am. Chem. Soc., 129(36), 11036-11038) and low bandgap polyfluorene-co-polythiophene (2007 Macromolecules 40, 8189-8194). This project is supported by the National Science Council of Taiwan (95-3114-P-002-003-MY3) and the AOARD of US Air Force (AOARD-07-4014). Key words: block copolymer, self-assemble, CdSe, TiO2, hybrid, conducting polymer, solar cell

11:30 AM *Q2-S2.2 (invited)
Charge Transport in Self-Assembled Materials for Organic Photovoltaics. (#1136) Tobin J. Marks, Michael R Wasielewski; Department of Chemistry, Northwestern University, Evanston, Illinois, USA.

An important goal of our research is to explore the fundamental structural and electronic requirements for efficient energy and electron transfer in extended arrays of donor-acceptor molecules. In this presentation we will describe new molecules designed to provide building blocks for the self-assembly of photoactive materials for solar energy conversion using organic photovoltaics. We are currently exploring molecular building blocks in which photoinduced multi-step electron transfer leads to long-lived radical ion pairs. These structures are comprised of a donor-acceptor system in which two-step charge separation occurs following photoexcitation. This building block self-assembles into a stacked, helical supramolecular structure in which the electron donors and acceptors are segregated. The long lifetime of the photogenerated radical ion pairs within the covalent building blocks allows competitive charge hopping to occur between non-covalent donors and acceptors in the segregated charge pathways within the supramolecular structure. The structure of the supramolecular assembly was determined in solution using X-ray scattering techniques at the Advanced Photon Source synchrotron at Argonne National Laboratory. The structures are determined at concentrations comparable to those at which spectroscopic measurements of their energy and electron transfer dynamics are made; thus providing a direct measure of how structure controls photodriven charge separation within the assembly. Implementation of segregated pathways for electron and hole transport using self-assembly is important for developing new materials for organic photovoltaics.

12:00 PM Q2-S2.3
Origin of Open-Circuit Voltage of Hybrid Metal Oxide / Polymer Solar Cells. (#1147) Punniamoorthy Ravirajan¹, Thilini Ishwara², Donal Bradley², Jenny Nelson²; ¹Department of Physics, University of Jaffna, Sri Lanka ; ²Imperial College London, United Kingdom.

The origin of open-circuit voltage (VOC) in organic donor-acceptor heterojunction devices has been the subject of much interest in recent years. Whilst arguments based on the semiconductor metal-insulator-metal picture indicate that VOC should be limited by the difference in work functions between the two electrodes, experimental studies of polymer/fullerene devices showed a dependence of VOC on the fullerene acceptor strength and negligible dependence on the cathode work function. Experimental and modeling studies confirmed that in bilayer devices VOC can be controlled by the difference between the highest occupied molecular orbital (HOMO) of the donor and the lowest unoccupied molecular orbital (LUMO) of the acceptor, and is only partly dependent on the difference in work functions of the electrodes. In bulk heterojunctions where both donor and acceptor phases contact both electrodes, the electrode work functions are also expected to influence VOC. Nevertheless, the most detailed study of polymer/fullerene devices confirmed that VOC varies linearly with the energy difference between the LUMO of the acceptor and the HOMO level of the donor, using a total of different donor materials. In this work, we use polymers with different ionization potential (IP) as the donor and metal oxide with different quasi Fermi-level as acceptor in hybrid polymer/metal oxide solar cell devices. We show that in order to obtain the correct relationship between VOC and the ionization potential of the donor, variations in the photogenerated carrier density between different polymer materials must be taken into account. Once corrected for differences in optical absorption, the measured eVOC values vary linearly with energy separation between HOMO and quasi Fermi-level of metal oxide, with a slope of 0.8 +/- 0.1, in good agreement with a recent study of VOC in polymer:fullerene devices. This indicates that VOC is limited by the difference between the energy separation and the quasi Fermi level of the metal oxide. VOC can be tuned further by modifying the metal oxide Fermi level using an adsorbed monolayer of permanent dipole moment molecules. We demonstrate that treatment of metal oxide with such molecular monolayers results in changes in charge injection and VOC that are consistent with the sign of the dipole moment. The implications for optimization of hybrid polymer - metal oxide device efficiency will also be discussed.

12:15 PM Q2-S2.4
Nanoscaled Morphology and Performance of Molecular-Weight-Dependent poly(3-hexylthiophene)/TiO₂ Nanorod Hybrid Solar Cells. (#932) Ming-Chung Wu, Hsi-Hsing Lo, Hsueh-Chung Liao, Wei-Che Yen, Yun-Yue Lin, Chun-Wei Chen, Yang-Fang Chen, Wei-Fang Su; National Taiwan University, Taipei, Taiwan.

Polymer solar cells have attracted a great amount of interest recently due to their potential applications in developing low-cost, solution processable, large-area, mechanically flexible photovoltaic devices. The environmentally friendly and low-cost TiO2 nanocrystal is a promising material in hybrid organic/inorganic photovoltaic device applications. It has been known that the device performance of polymer-based solar cells strongly depends on the morphology, efficiency of charge separation and transport and interfacial contact. McGehee et al. have used atomic force microscopy to study the morphology of P3HT thin films made from different molecular weights (MWs). They have found that the field effect mobility of P3HT increases as the MW increases. Similar observation of the molecular-weight-dependent mobilities was also found in a diode geometry using the space charge limited current measurement. Heeger et al. have also demonstrated the dependence of MWs on the morphology and photovoltaic performance based on P3HT/PCBM. They concluded that the best performance can be achieved by using an optimum ratio between high MW and low MW components. Recently, scanning near-field optical microscopy (SNOM) becomes one of the high-resolution microscopic techniques that have been used to identify the relative distribution of polymers within a blend. The SNOM is a particularly valuable analytical tool for the study of conjugated polymer since many of the important processes pertinent to their applications involve the emission or absorption of photons. In this article, we would like to report the nanoscaled morphology dependence of P3HT/TiO2 nanorod bulk heterojunctions with different polymer MWs by employing the scanning near field microscopy (SNOM), atomic force microscopy (AFM), and confocal Raman microscopy. In addition, the correlation between the morphology and transport behavior for P3HT/TiO2 nanorod hybrids with different MWs are also explored by the time of flight (TOF) mobility measurement. Finally, the photovoltaic performances of the devices based on the hybrids with different MWs are also presented. In this study, we have investigated the effect of polymer molecular weight on the morphology and performance of poly (3-hexylthiophene)/TiO2 nanorod hybrid photovoltaic devices by using scanning near field optical microscopy (SNOM), atomic force microscopy (AFM) and confocal Raman microscopy. From the topography and absorption mapping images, it has been found that the rod-like structure of the low molecular weight polymer hybrid film generates a great amount of grain boundaries and forms a less continuous absorption mapping image. In contrast, the larger domain structure of the high molecular weight polymer hybrid film exhibits continuous absorption mapping, as a result of enhanced polymer stacking and electronic delocalization. The nanoscaled morphology of the hybrid samples with different molecular weights also reveals the nature of photovoltaic performance and carrier transport behavior investigated by the time-of-flight technique.

LUNCH 12:30 PM - 2:00 PM

2:00 PM *Q2-S3.1 (invited)
Iodine-Free Solid-State Dye-Sensitized Solar Cells: Effect of Ionic Liquid on Hole conducting PEDOT. (#259) Shozo Yanagida, Center for Advanced Science and Innovation, Osaka University, Japan.

Research and development on dye-sensitized nano-crystalline (nc) TiO2 solar cells (DSC) has been successively progressed, and they are now being recognized as an energy solution photovoltaic in the light of silicone crisis situation. DSC photovoltaics must achieve high stability and reliability under outdoor use at high (<85?C) and low (>-40?C) temperature, in other words, DSC manufacturing must pass standardized packaging durability tests of solar cells under such severe temperature conditions. The conventional DSC contains corrosive and volatile iodine in the hole- conducting phase. One of the solutions for stability issues is the introduction of organic hole-conductors as a substitute of the iodine/iodide electrolyte phase of DSC. Our research has clarified that poly-3,4-ethylenedioxythiophene (PEDOT) works not only as an excellent hole-conductor as a substitute of the iodide/iodine electrolytes [1] but also as excellent electron transfer catalysts on the cathode of fluorine-doped SnO2 (FTO) as well as gold works effectively so far [2]. In addition, the molecular-level integration at the interfaces plays a decisive role in optimization of the dyed-nc-TiO2/PEDOT-DSC, The in-situ photo-electrochemical polymerization of bis(ethylenedioxythiophene) (bis-EDOT) is one effective way to fill the nano-size pore spaces of the nano-crystalline TiO2 electrodes with hole conducting PEDOT. Further, the newly designed sensitizing dye molecules, cis-Ru[4,4'-di(hexythinelvinyl)-2,2'-bipyridyl](4,4'-dicarboxylic acid-2 ,2'-bipyridyl)(NCS)2 (HRS-1), which is quite comparable with N719 in efficiency, was introduced to the PEDOT-DSC devices, clarifying the important role of the molecular-level integration of PEDOT with 2-thiophen-2-yl-vinyl-conjugated pyridine ligand on the dyed-TiO2/PEDOT interfaces [3]. Taking into account the importance of the interface molecular integration and molecular self-organization of DSC, we will discuss about optimization of photo-electrochemical polymerization of bis-EDOT using commercially available Z907 ruthenium complex as sensitizing dye molecules and PEDOT/FTO electrodes as counter cathodes of DSC [4]. References 1) N. Fukuri, N. Masaki, T. Kitamura, Y. Wada, and S.Yanagida, J. Phys. Chem. B 110, 25251-25258, 2006. 2) Y. Saito, T. Kitamura, Y. Wada and S. Yanagida, Chem. Lett., 1060-1061 (2002). 3) A. J. Mozera, Y. Wada, K.-J. Jiang, N. Masaki, S. Yanagida, and S. N. Mori, Appl Phys. Lett. 89, 043509, 2006. 4) Y. Kim, Y. Sung, J. Xia, M. Lira-Cantu, N. Masaki, S. Yanagida, J. Photo. Photobiol. A: Chemistry, 193 77 (2008)

2:30 PM Q2-S3.2
Three Dimensional TiO₂ Electrodes for Dye Sensitized Solar Cells Covering Wide Range of Wavelength and All-Metal-TCO-Less Dye Sensitized Solar Cells. (#267) Shuzi Hayase, Yuhei Kashiwa, Yoshitaka Hara, Shinichi Kojima, Tatsuya Yokoyama, Yoshitaka Beppu, Yuhei Ogomi, Mitsuru Kono, Yoshihiro Yamaguchi; Kyushu Institute of Technology, Fukuoka Prefecture, Japan.

In order to increase solar cell efficiency, acquisition of lights up to near IR region is needed. However, it is difficult for single dye to cover the wide range of the wavelength. We propose TiO2 electrodes consisting of two-layer-hybrid TiO2 layer stained by two dyes selectively (two-layer-cell) and all-metal-TCO-less dye sensitized solar cells (TCO-less cell). 1. Two-layer-cell: The two-layer-cell consists of an upper layer stained with a dye absorbing longer wavelength and a bottom layer stained with a dye absorbing shorter wavelength. It was difficult to stain the TiO2 layer selectively with two dyes respectively by using a mere dipping process. We found that two-layer-cell can be prepared by dye-staining under pressurized CO2 atmosphere. It was proved that the two-layer-cell has advantage over cells consisting of randomly-stained-TiO2 layer (Cocktail type cell) in terms of high efficiency. We concluded that the advantage of the two-layer-cell was brought about by inhibiting inconvenient aggregations between the two dyes. The reason why the pressurized CO2 atmosphere makes the selective staining possible was explained by the low concentration of dye molecules in the pressurized CO2 atmosphere and high reactivity between the dye molecule and TiO2 surface. 2. All-metal-TCO-less cells: Since TCO glasses are expensive, TCO-less DSC has been desired. The TCO-less cell structure consisting of all methal electrodes is reported. In order to realize the cell structure, both of high conductivity of Ti electrode and high diffusion of ions through the Ti electrode, which are conflicting items, are needed. When the Ti electrode thickness became thicker than 150nm, the electrolyte diffusion through the Ti electrode was disturbed at the sacrifice of the increase in the conductivity of the Ti layer. We solved the problem by preparing thick Ti thick electrodes with straight nano-pores. All-metal-TCO-less dye sensitized solar cells with 7.4% efficiency is reported.

2:45 PM Q2-S3.3
Dye-sensitized Solar Cells with Organic/Inorganic Composite Electrolytes. (#896) Qingbo Meng, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Zhongguancun, Beijing, China.

Dye-sensitized Solar Cells with Organic/Inorganic Composite Electrolytes Qingbo Meng Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100080, China qbmeng@aphy.iphy.ac.cn Dye-sensitized solar cells (DSCs) have attracted great attention over the past decade owing to high-energy conversion efficiency and low production cost. Above 11% light to electricity conversion efficiency has been achieved in a DSC with an organic liquid based electrolyte containing I3-/I- as the redox couple.(Refs.1,2) However, several practical issues related to the presence of a liquid electrolyte, such as leakage and evaporation of the electrolyte, dye desorption and the corrosive action of the iodide/iodine redox couple, have limited the large-scale technological development of such devices. Approaches towards various electrolytes have facilitated the development of quasi-solid-state DSCs, such as polymeric ionic gels, room temperature molten salts. (Refs.3-5) Recently, several kinds of quasi-solid and solid state electrolytes, composed of organic-inorganic nanocomposites, have been investigated in our group. These solid electrolytes were based on lithium iodide (LiI) and organic ligand. LiI and organic ligand can form addition compound, which has the feature of monoionic transport of I- along three-dimensional (3D) diffusion paths in the crystal. To restrain the formation of large crystallites and improve the contact of TiO2 electrode with electrolyte, inorganic nanoparticles are dispersed into these systems. These electrolytes were successfully used to fabricate DSCs. The energy conversion efficiencies of these DSCs reached to 5.48% with electrolyte of LiI/hydroxypropionitrile/SiO2 and 6.1% with electrolyte of LiI/ethanol/SiO2. (Refs. 6-11) More recently, we also synthesized a new kind organic composite electrolyte by the in-situ reaction of acetylacetone, pyridine and iodine in 3-methoxypropionitrile. The efficiency of DSCs using this electrolyte reaches 6.72%.(Ref.12 ) Acknowledgement: We gratefully acknowledge the support of the National Natural Science Foundation of China under Grant No 20725311, 20673141, 20703063 and 20721140647, the National Basic Research Program of China ("973") under Grant No 2006CB202606, the National High Technology Research and Development Program ("863") under Grant No 2006AA03Z341. References 1 O'Regan B. and Gr?tzel M., Nature, 1991, 353, 737. 2 Gr?tzel, M. Inorg. Chem. 2005, 44, 6841. 3 Tennakone, K., Fernando, C. A. N., Dewasurendra, M. J., J. Photochem. 1987, 38, 75. 4 Meng Q.B.,Takahashi K., Zhang, X.T., Sutanto I., Rao T. N., Sato O., Fujishima A. Langmuir 2003, 19, 3572. 5 Wang, P., Zakeeruddin, S. M., Moser, J.-E., Gr?tzel, M. J. Phys. Chem. B 2003, 107, 13280. 6 Xue B.F., Wang H.X., Hu Y.S., Li H., Wang Z.X., Meng Q.B.,et al Photochem. Photobio. Sci. 2004, 3, 918. 7 Wang H.X., Wang Z.X., Xue B.F., Meng Q.B., et al, Chem. Comm. 2004, 2186 8 Wang H.X., Li H., Xue B.F., Wang Z.X., Meng Q.B., Chen L.Q., J. Am. Chem. Soc. 2005, 127, 6394. 9 Wang H.X., Liu X.Z., Wang Z.X., Li H., Li D.M., Meng Q.B., Chen L.Q., J. Phys. Chem. B 2006, 110, 5970. 10 An H.L., Xue B.F., Li DM, Li H., Meng Q.B., Guo L., Chen L.Q., Electrochem. Comm. 2006, 8, 170. 11 Xue B.F., Wang H.X., Hu Y.S., Li H., Wang Z.X., Meng Q.B., et al, Comp. Rendus Chim., 2006, 9, 627. 12 Liu X. Z., Qin D., Fan Y. Z., Li K. X., Li D. M., Meng Q. B. Electrochem. Comm. 2007, 9, 1735.

3:00 PM Q2-S3.4
ZnO Nanorods via Hydrothermal Processes. (#455) Serene Ng, John Wang; Department of Materials Science and Engineering, Faculty of Engineering, National University of Singapore, Singapore.

With a wide direct band gap of 3.37eV and large exciton binding energy of 60meV, ZnO exhibits the desired electronic and photonic properties, making it the material-of-choice for applications such as dye-sensitised solar cells. For this purpose, we have successfully synthesized ZnO nanorods assembled on ITO-glass substrates via a hydrothermal process, where the crystallisation and growth of ZnO nanorods are delicately controlled at low temperatures. To optimize the growth, alignment, packing density and uniformity of the ZnO nanorods, ITO-glass substrates were either spin-coated or RF-sputtered with a layer of ZnO thin film. It was observed that RF-sputtering gave an improved size distribution and surface roughness. The nanorods also had a wurtzite structure and were up to 3um in length and 0.1-0.2um in diameter. Their packing density is approximately 6 x 10^7 rods/cm^2, with a strong (002) preferential orientation, confirming the vertical alignment of nanorods. Several synthesis parameters are shown to strongly affect the growth, morphology and orientation of the nanorods, including the hydrothermal duration, temperature and pH of the solution. The nanorods have been investigated for their electrical transport and photoluminescence behaviour, which are discussed in relation to their structural parameters. In addition, the behaviour of these nanorods in dye-sensitised solar cells will be presented and addressed.

3:15 PM Q2-S3.5
Influence of Molecular Volumes of Ruthenium Sensitizers on the Conversion Efficiency of Dye-Sensitized Solar Cells (DSSCs). (#1283) Byeong-Kwan An, Rhiannon Mulherin, Benjamin Langley, Paul Meredith, Paul Burn; Centre for Organic Photonics and Electronics, The University of Queensland, Brisbane, Australia.

Nanostructured TiO2 dye-sensitized solar cells (DSSCs) have been intensively investigated in the past decade as a promising renewable energy source. In such DSSCs, the dye sensitizer is one of the key components for high solar-to-electrical energy conversion efficiency. Thus, considerable effort has been expended in developing new photovoltaic sensitizers with high power conversion efficiencies. So far, heteroleptic ruthenium(II) complexes with anchoring groups have been considered as one of the best candidates for DSSC sensitizers and they have achieved power conversion efficiencies over 11% in standard AM 1.5 sunlight. In this presentation, we report a study on the development of structural guidelines for heteroleptic Ru sensitizers aimed at improving the solar-to-electrical energy conversion efficiency. In particular, we will illustrate how the sensitizer molecular volume effects dye adsorption onto the TiO2 substrates and relate these to the photovoltaic properties of the cells.

AFTERNOON BREAK 3:30 PM - 4:00 PM

4:00 PM *Q2-S4.1 (invited)
Developments Towards Efficient, Low-Cost Dye Solar Modules. (#1435) Andreas Hinsch, Fraunhofer-Institut für Solare Energiesysteme ISE, Germany.

Dye solar cells (DSC) are under intensive investigation as a new type of solar cell technology since 15 years. Although still not commercially available, prototyping of DSC modules for certain applications like flexible solar cells and integration into decorative glass facades^I is underway. Recently, progress has been reported on the efficiency^I and on the long-term stability^II of so-called monolithic dye solar cells^III, a concept which in particular is attractive in terms of low material costs. Last year, we reported on results gained in a German network project on material development for monolithic dye solar cells^V. In this paper, the potential of the monolithic dye solar cell concept in terms of efficiency is evaluated. It turned out, that the monolithic concept is well suited for the further efficiency enhancement of dye solar cells beyond 10 %. In particular, the optimisation of the diffusion limited charge transport in the electrolyte and the implementation of new efficient dyes and photoelectrode materials are addressed. I. A. Hinsch, H. Brandt, W. Veurman, S. Hemminga, M. Nittel, U. Würfel, P.Putyra, C. Lang-Koetz, M. Stabe, S. Beucker, K. Fichter, ,,Dye solar modules for facade applications:recent results from project Colorsol″, Proc. 17th International Photovoltaic Science and Engineering Conference, 3 - 7 December 2007, Fukuoka, Japan II. H. Pettersson, T. Gruszecki, R. Bernhard, L. Haggman, M. Gorlov, G. Boschloo, T. Edvinsson, L. Kloo and A. Hagfeldt, ″ The Monolithic Multicell: A Tool for Testing Material Components in Dye-Sensitized Solar Cells″, Prog. Photovolt: Res. Appl. 2007; 15: 113-121. III. N. Kato, K. Higuchi, Y. Takeda, A. Takeichi, T. Motohiro, T. Sano, and T. Toyoda, ″Long-term stability of the DSC module under outdoor working conditions″, Proc. Renewable Energy 2006, October 9-13, 2006, Makuhari, Japan IV. A. Hinsch, R. Kinderman, M. Späth, E. Rijnberg, J.A.M. van Roosmalen, ″The perfomance of dye-sensitised solar cells with a one-facial, monolithic layer built-up prepared by screen printing″, Proc. 2^nd World Conference and Exhibition on Photovoltaic Solar Energy Conversion, Vienna (1998) V. A. Hinsch, P. Putyra, U. Würfel, H. Brandt, K. Skupien, A. Drewitz, F. Einsele, D. Gerhard, H. Gores, S. Hemming, S. Himmler, G. Khelashvili, G. Nasmudinova, U. Opara-Krasovec, U. Rau, S. Sensfuß , J. Walter, P. Wasserscheid, ″Developments towards low-cost dye solar modules″, Proc. 22nd European Photovoltaic Solar Energy Conference and Exhibition, 3 - 7 September 2007, Milan, Italy

4:30 PM *Q2-S4.2 (invited)
Catalyst-Free Growth of Vertically Aligned Zinc Oxide Nanowires for Photovoltaic Application. (#965) Shu-Te Ho, Heh-Nan Lin; Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu, Taiwan.

Zinc oxide nanostructures have been the focus of extensive research activities in recent years due to their widespread applications in electrical, optical, and sensing devices. We report large-scale and selective-area growths of vertically aligned zinc oxide nanowires by thermal evaporation via a catalyst-free surface-roughness-assisted mechanism on various substrates including sapphire, glass, indium-tin-oxide (ITO) coated glass, and fluorine-doped tin oxide (FTO) coated glass. The nanowires are single-crystalline and have diameters ranging between 20 and 100 nm and lengths ranging from a few hundred nanometers to a few microns depending on the growth periods. Dye-sensitized solar cells (DSSC) are constructed on ITO and FTO coated glass substrates. The relationships between the solar cell efficiencies and the nanowire spatial properties such as diameter, length, spacing, etc. are explored. Additionally, single nanowires are placed between gold electrodes by a dielectrophoresis process and the electrical transport properties are studied. The correlation between the electrical properties of the nanowires and the solar cell efficiencies will be discussed.

5:00 PM Q2-S4.3
Enhancing the Efficiencies of Bulk Heterojunction Solar Cells. (#1281) Karsten Krueger, Paul Schwenn, Paul Burn, Paul Meredith; Department of Physics, The University of Queensland, Brisbane, Australia.

With serious concerns regarding climate change as a result of burning fossil fuels for energy it is important that efficient, cost effective and environmentally friendly forms of energy are developed. Organic thin film bulk heterojunction solar cells are one promising candidate for energy harvesting because of their low cost, mechanical flexibility and simple, scalable large surface area production. So far, verified efficiencies of more than 5.4% have been reported for these types of devices. The optimal choice of the donor and acceptor materials is critical for the development of highly efficient devices. In addition, the precise control of the morphology of the donor-acceptor blend is of the utmost importance to achieve high performance. In this presentation, the effects of several performance enhancing methods, like slow solvent evaporation ("solvent annealing") and thermal annealing are investigated to optimize the morphology of the active layer. Furthermore, other device modifications such as the inclusion of cathode interfacial layers are investigated to improve the charge injection/extraction properties of the device. We have obtained conversion efficiencies of more than 4% with devices based on poly(3-hexylthiophene) as donor and phenyl-C61-butyric acid methyl ester as the acceptor material. During this process, we identified several pit falls regarding processing that can limit the performance of bulk heterojunction solar cells.

5:15 PM Q2-S4.4
Organic Photovoltaics at CSIRO. (#758) Lynn Rozanski, Scott Watkins, Chris Fell; Australian Commonwealth Scientific and Research Organization (CSIRO) Energy Technology, Australia.

Organic photovoltaics (OPVs) are emerging as an inexpensive alternative to traditional silicon-based photovoltaics. The active materials used in OPVs can be solution processed under ambient conditions, allowing them to be applied to flexible substrates and potentially utilise existing roll-to-roll printing technology. At present, OPV technology is limited in terms of both performance and durability. The world's best devices have efficiencies around 5%, and even with encapsulation, lifetimes are currently insufficient for large-scale commercialisation. However, with careful design of new molecular materials, great potential exists to overcome these performance barriers. Device efficiency has suffered as a result of limited absorption across the solar spectrum as well as due to poor charge separation and mobility, when compared to inorganic alternatives. CSIRO Energy Technology has partnered with CSIRO Molecular and Health Technologies to design, synthesise and test novel materials for OPV devices. Novel block co-polymers containing pendant electron and hole transport groups have the potential to be a single-component active material, improving both charge separation and transport. In addition, the solar spectrum absorption can be enhanced through the use of polymer-functionalised nanoparticles. At our National Solar Energy Centre in Newcastle we are also examining numerous other challenges associated with scaling OPV devices to commercial volumes, including module design, printing and encapsulation.

Q2-S5.1
Self-Assembly and Properties of Low Dimensional Nanomaterials Based on ?-Conjugated Organic Molecules. (#126) Yuliang Li, Huibiao Liu, Daoben Zhu; Institute of Chemistry, Chinese Academy of Sciences, Zhongguancun, Beijing, China.

Self-assembly and Properties of Low Dimensional Nanomaterials Based on ?-Conjugated Organic Molecules Yuliang Li*, Huibiao Liu, Daoben Zhu Beijing National Laboratory for Molecular Science, CAS Key Laboratory of organic solid, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080, P. R. China e-mail: ylli@iccas.ac.cn One-dimensional nanostructures, such as nanowires and nanotubes, represent the smallest dimension for efficient transport of electrons and excitons and thus are ideal building blocks for hierarchical assembly of functional nanoscale electronic and photonic structures. In the present studies, we have described the design and molecular aggregates behaviors of conjugated organic molecules with photo-electro activity and the fabrication of low-dimensional organic conjugated nanomaterials by self-assembly techniques. The fabrication and properties of large oriented arrays nanostructures of organic charge transfer salts based on conjugated molecular are also studied. Interestingly we have demonstrated the ability to tune the morphologies of organic conjugated nanomaterials by controlling reaction conditions of the organic vapor solid phase reaction.

Q2-S5.2
Photo-Assisted C₆₀ Polymerization in Solid and Solution Process. (#488) Ryo Nokariya, Yasunari Iio, Shingo Ando, Nobuyuki Iwata, Hiroshi Yamamoto, Kazunobu Arii, Hiroki Takahashi; College of Science and Technology, Nihon University, Funabashi-shi, Chiba, Japan.

A three-dimensional (3D) C₆₀ polymer has been expected as promising ultra-hard materials, may be superior to a diamond. Our purposes of this work are to study a novel photo-assisted C₆₀ polymer synthesis process and/or to develop a quantitative evaluation technique of polymerization reactions using a Raman spectroscopy. As a laser source we adopted a free electron laser (FEL), high-power Excimer or YAG laser which was irradiated to various states of C₆₀: commercial C₆₀ powder, evaporated C₆₀ thin films, C₆₀ precipitated from a liquid phase. The computer simulation of the molecular vibration modes was examined to evaluate a Raman spectrum of polymerized C₆₀ molecules. The simulation revealed that a pentagonal pinch mode, Ag(2) peak shows a red-shift and/or broadens when a C₆₀ monomer changed into a dimmer or higher order of polymers. The Ag(2) peak energy shifts to the lower energy side because a carbon double bond in a hexagon of a C₆₀ cage is broken and transforms into an inter-molecular four-fold ring with a neighboring molecule. So it was understood that the value of the Ag(2) peak shift is a useful barometer to evaluate the degree of polymerization reactions. The FEL pulse was a few tens microsecond macro-pulse, which included few hundreds picoseond micro-pulses, and was repeated in 2 Hz. The power of the fundamental macro-pulse was ca. 2 mJ/pulse. The irradiation time was typically 30 min - 240 min. The C₆₀ powder was compressed at 600 MPa - 15 GPa. The pressed powder was annealed in vacuum and FEL 3rd harmonics with wavelength of 400nm - 600nm was irradiated. After FEL irradiation the maximum Ag(2) peak shift attained to ca. 15 cm^-1 in highly compressed powder samples. The result demonstrates that the laser irradiation for highly compressed C₆₀ is quite effective to promote polymerization. Under 500nm FEL irradiation C₆₀ films were deposited on 473 K mica substrates by thermal evaporation from a K-cell source. The Ag(2) peak shift was, however, not definite in the FEL irradiated thin film. On the other hand, YAG 2nd harmonics (532 nm) was irradiated with comparatively high energy, ca. 16 W/cm² was able to promote polymerization even for thin films. FEL was also irradiated to C₆₀ precipitation which was obtained from toluene or m-xylene saturated solution or by a liquid-liquid interfacial precipitation (LLIP) method. The polymerization took place only in the LLIP case. The Ag(2) peak shift was not so large, ca. 10 cm^-1 of which the value was in the order of already reported photopolymers. We concluded that the photo-assisted C₆₀ polymerization was promoted by high energy laser irradiation and/or by reduction of C₆₀ - C₆₀ molecular distance using high pressure or LLIP process.

Q2-S5.3
Magneto Resistance of Iodine Doped Single Wall Carbon Nanotubes. (#617) Ho Nam Yoo, Sejung Ahn, Young Woo Nam, Yu Kyung Kim, Ji Hyun Park, Zhaoxia Jin, Yung Woo Park; Nano Transport Laboratory, Department of Physics and Astronomy & Nano Systems Institute-National Core Research Center, Seoul National University, Republic of Korea.

We measured temperature dependence of four-probe dc conductivity and magnetoresistance (MR) of the iodine-doped single-wall carbon nanotube (SWNT) mats. Pressure contact with four platinum electrodes was made. The temperature dependent conductivities of undoped and iodine doped SWNTs met are similar to those of previous reports [1]. The MR is measured up to 14 tesla as a function of temperature. Negative MR is observed at T<20K. At T=4.2K, there is a negative minimum near H=8 tesla. As the temperature becomes higher, the negative minimum is flattened at high magnetic field. For 10K30K, there exist small positive MR peak at low field becoming negative at high field. Above T=70K, the MR remained positive up to 14 tesla. Another sample shows similar temperature dependent MR but the turning point temperatures are higher than the previous sample. The results are analyzed as weak localization with spin dependent scattering effect at high magnetic field. Reference [1] L. Gregorian, K.A. Williams, S. Fang, G.U. Sumanasekera, A.L .Loper, E.C. Dickey, S.J. Pennycook, and P.C. Eklund, Phys. Rev. Lett. 80, 5560 (1998)

Q2-S5.4
Ion Beam Effects on Glassy Polymeric Carbon Composites. (#1165) Bopha Chhay, Bangke Zheng, Claudiu Muntele, Daryush Ila; Alabama A&M University, USA.

Glassy Polymeric Carbon (GPC) is a material widely used because of its high temperature resistance, inertness and biocompatibility. GPC is obtained by molding in various shapes from a phenolic resin precursor. The heat treatment of the precursor is achieved in two stages up to 1000 ?C. In this work, we have introduced Carbon NanoTubes (CNT), Alumina (Al2O3) and Silicon Carbide (SiC) nanopowders in the precursor of GPC in order to obtain material composites with higher mechanical properties when compared to pure GPC. After pyrolysis, the GPC samples and GPC nanocomposites samples were bombarded with 3 MeV Si at a fluence of 1x1014 ions/cm2 in order to study the ion damage effects in the Young's modulus.

Q2-S5.5
An Analysis on Multi-Layered Organic Field-Effect Transistors and the Related Charge Injection Mechanisms. (#77) Harry Kwok, Department of Electrical and Computer Engineering, University of Victoria, British Columbia, Canada.

Recently there has been major interest in studying ambipolar charge transport in organic semiconductors [1]. One of the reasons has to do with the need to construct complementary devices for use in low-power circuits. In addition, the study of multi-layered/stacked field-effect transistors is also of interest as far as light emission is concerned. In [2] for instance, work was reported on a stacked organic field-effect transistor (FET) structure with an n-channel FET on top of a p-channel FET using substrate gate construction. The authors devised the use of two different types of metal electrodes to facilitate electron and hole injection. Various biasing schemes were tested and the results indicated a blend of "transistor-like" and "diode-like" characteristics depending on the biasing conditions. Such an experiment provided insight into charge injection and recombination of interest to the study of light-emitting transistors. This work examined measurements on a stacked organic transistor reported in the literature with both n-channel and p-channel conduction. By extracting the dominant characteristics, we are able to better understand the device operation. In general, the I-V characteristics are well behaved with limitations linked to electron and hole injection. From the data, it may be deduced that interleaved "diode-like" and "transistor-like" characteristics dominated the device properties under different biasing conditions. At low bias, the transport mechanism appears to be dominated by recombination at the pentacene- PDCDI-C13H27 interface and "transistor-like" characteristics start to merge under large bias. As far as light emission is concerned, the condition when the source (Au) is grounded and the drain (Mg) and gate voltage is connected to negative voltages appears to offer the best prospect. As observed, the device properties are largely limited by the series resistance effect and recombination current. Furthermore, there are well defined regimes operating the multi-layered device as either a "diode" or a "transistor". It is anticipated that further refinement of the device structure and properties can result in more precise control on the operation of the device as a light-emitting device or a transistor. [1] H.L. Kwok, Proc. of SPIE: Organic Field-effect Transistors VI, Vol. 6658, 66580E1-8 (2007). [2] C. Rost, D.J. Gunlach, S. Karg, and W Rieb, JAP, 95 5782-5787 (2004).

Q2-S5.7
Improved Yield in Molecular Junction Device Using Bi-Layer SAM.. (#678) ho jong Chang, Gyeong Sook Bang, Ja-Ryong Koo, Hyoyoung Lee; IT Convergence & Components Laboratory, Electronics and Telecommunications Research Institute (ETRI), Yuseong-gu, Daejeon, Republic of Korea.

The prospect of molecular electronics based on a crossbar system of the metal-molecule-metal (MMM) junction is driven by the achievement of integrated circuits above the terabit level, where the self-assembled monolayers (SAM) capable of highly integrated density are used as active switching components. In general, for practical application of molecular electronics such as MMM junction, SAM device yield is known as less than 5%. As the thickness of SAM is typically 1-2 nm, it is hard to avoid electrical shorts due to the penetration of top metal particles into the SAMs. Thus, to reduce the electrical shorting, we represent a simple and effective strategy for reliable molecular junction using the thickness controlled bilayer with bifunctional heterostructure. Organic SAMs with alkyl chains above ten units were already reported as very good insulators. We introduce the rose bengal (RB) monoalyer on the AUT bilayer (RB-TUA-AUT). The thickness of the RB-TUA-AUT film is 4.5nm and the RB-TUA-AUT film consists of a highly ordered structure and act as an effective blocking layer[1]. We will present the characterization and the device yield with the rose bengal (RB) monoalyer on the AUT bilayer (RB-TUA-AUT) in a micro-pore and nanopore using the AFM (Atomic Force Microscope), grazing angle fourier transform infrared (FT-IR) spectroscopy, ellipsometry, x-ray photoelectron spectroscopy (XPS), focused ion beam (FIB) and scanning electron microscope(SEM). Additionally, we will discuss the conduction mechanism of the rose bengal (RB) monoalyer on the AUT bilayer. In this presentation, the detailed fabrication method and the device performance of our molecular junction devices will be discussed. [1] G. S. Bang, J. Park, J. Lee, N.-J. Choi, H.-Y. Baek, H. Lee, Langmuir 2007, 23, 5195.

Q2-S5.8
New Photo Curable Organic/Inorganic Hybrid Material as an Insulating Material. (#929) Do-Hoon Hwang¹, Yong Suk Yang¹, Jeong-Ik Lee¹, Seong Hyun Kim¹, Victor Lee², Geraud Dubois², Robert D. Miller², Choong-Hwa Jung¹; ¹Department of Applied Chemistry, Kumoh National Institute of Technology, Republic of Korea ; ²IBM ARC, USA.

Organic semiconductors have been developed to improve the mobility and other performance characteristics of OTFTs. Pentacene, pentacene derivatives, oligothiophenes, poly(3-hexylthiophene) and other hetero-aromatic polymers have been studied extensively as active organic semiconductors for OTFT application. Recently the mobility of pentacene based OTFTs has reached the level of hydrogenated amorphous silicon transistors, stimulating further attention. However, these high performance OTFTs were fabricated mainly on high-quality inorganic gate insulators. More recently several polymeric gate dielectrics such as poly(vinylphenol) (PVP), poly(methylmethacrylate) (PMMA), polyvinylalcohol(PVA), polyimide and layer-by-layer self-assembled dielectrics have been used as insulator of OTFTs. The gate dielectric polymers are required to form good films, have a high dielectric constant, good thermal stability and compatibility with active organic semiconductors. In addition, the insulators need to be patternable to minimize leakage and crosstalk in OTFTs with an active layer, and to create access to the gate electrode. The processing temperature for patterning also should be low enough to employ flexible plastic substrates. Until now several directly patternable organic/polymeric materials for the formation of electrodes or active channel layers of OTFTs have been demonstrated, however, only many fewer directly patternable organic materials have been reported as a gate dielectric in organic thin film transistors. In this study, a polyhedral oligomeric silsesquioxane derivative (POSS-OXT) containing photo-curable 4-membered cyclic oxetane functional groups was used as a gate dielectric of organic field effect transistor. The POSS-OXT was cross-linked and completely solidified by UV irradiation in the presence of a selected photo acid generator, and pinhole free uniform thin film was obtained. We fabricated a metal/insulator/metal device and the measured leakage current and capacitance of the device to evaluate the insulating properties of the POSS-OXT thin film. We fabricated an organic thin film transistor with pentacene as the active semiconductor and the photo-cross-linked POSS-OXT as an insulator. Acknowledgement: This work was supported by "SystemIC2010" project of Korea Ministry of Commerce, Industry and Energy.

Q2-S5.10
Band-Gap Engineering to Improve Performance of Passive Matrix Displays. (#1004) Girija Sankar Samal¹, K. N. Narayanan Unni¹, Saswat Bharat¹, Deepak Gupta²; ¹Samtel Centre for Display Technology, Indian Institute of Technology Kanpur, India ; ²Department of Materials and Metallurgical Engineering, Indian Institute of Technology Kanpur, India.

Our standard blue OLED demonstrates a current efficiency of 2.3 cd/A. To improve its current efficiency, we have doped the electron transport layer by a hole blocking material, which shows no improvement in current efficiency. But, doping the hole transport layer with another hole blocking layer has led to current efficiency as high as 4.3 cd/A. Our standard blue device consists of Indium Tin Oxide (ITO)/a proprietary hole injection layer (HIL), 100 nm/ hole transport layer (HTL) of N,N'-diphenyl-N,N'-bis(1-naphthyl)(1,1'-biphenyl)-4,4' diamine (NPB), 20 nm/ a proprietary blue host and dopant emissive layer (EML), 30 nm/ electron transport layer (ETL) of tris(8-hydroxyquinoline) aluminum (Alq3), 25 nm/LiF, 1 nm/Al. Using this blue device (and additional green and red OLEDs), a passive matrix full colour display of 96(3) x64 resolution was made. In this display, the peak blue brightness is below10cd/m2. In our standard device, the ETL is 25 nm thick and undoped. In order to evaluate the impact of ETL doping in a blue device also, we doped the first 10nm of ETL adjacent to EML with Bphen. The remaining 15 nm of ETL is undoped. When the amount of doping increases, the current in the device slightly deteriorates and also, there is an accompanied reduction in the current efficiency. The CIE color coordinates in the practical luminance range (beyond 5V) are mostly independent of voltage. However, the color coordinate of blue emission improves when the ETL is doped with 40 % BPhen. Because the placement of a doped HBL, specifically BPhen, after EML in a blue device does not increase the current efficiency, we have also doped the HTL of a standard device with HBL. The HTL is divided into two parts. The first 10 nm of HTL, adjacent to HIL, is undoped. In the next 10 nm, the HTL and HBL are mixed in various ratios. Thus placement of mixed HTL and HBL in our blue device adjacent to EML is consistent with the results of Tsai et al. [1]. The J-V characteristics of the devices in which a device with 40% or 60% TPBI leads to smaller currents, but the luminance reduction is only marginal when compared with the undoped device. As a consequence, the current efficiency in a device with 40% TPBI is dramatically improved, nearly twice the value for an undoped device. Furthermore, addition of TPBI has no adverse effect on the threshold voltage and the CIE colour coordinates of the device in which 40% TBPI is added in HTL are also similar to that for an undoped device. This presentation will also discuss results of several other additions of dopants in HTL. The results will be further supported by simulations. Finally, characteristics of a full colour display with doped HTL will be presented. References 1. C-H Tsai, C-H Liao, M-T Lee and C. H. Chen, "Highly stable organic light-emitting devices with a uniformly mixed hole transport layer," Appl. Phys. Lett., 87, 2005, p. 243505

Q2-S5.11
Electronic Structures of OLED Cathode Interfaces - Ca/LiF/Alq3 and Ca/NaF/Alq3. (#1027) D. Y. Kim, J. W. Kim, J. Lee, Yongsup Park; Department of Physics and Applied Physics, College of Electronics and Information, Kyung Hee University, Republic of Korea.

We have studied the interface electronic structures of Ca/LiF/tris-(8-hydorxyquinoline)Al (Alq3) and Ca/NaF/Alq3 using X-ray and ultraviolet phtoelectron spectroscopy (XPS and UPS). The UPS revealed that the deposition of Ca on LiF/Alq3 or NaF/Alq3 created gap states between Fermi level and highest occupied molecular orbital (HOMO) peak of Alq3. The N 1s core level peak measured with XPS exhibited large satellite peak with Ca deposition. The satellite peak intensity increased with Ca thickness, eventually dominating the original N 1s peak at about 2.0 nm of Ca. Such a strong satellite peak was not generally observed for Ca/Alq3, suggesting that the presence of LiF mediates the transfer of charges from Ca. We could not find any definitive evidence that the Li atoms in LiF are liberated after the deposition of Ca and react directly with Alq3. The formation of Ca cluster is evidenced from the continuously decreasing Ca 2p binding energy with Ca thickness.

Q2-S5.12
Systematic Study on Optical and Morphological Properties of P3HT/PMMA Blends and Fabrication of the Luminescent Nanostructure. (#1009) Ming-Chung Wu, Hsueh-Chung Liao, Sharon Chen, Yi-Jen Wu, Yun-Yue Lin, Chun-Wei Chen, Yang-Fang Chen, Wei-Fang Su; National Taiwan University, Taipei, Taiwan.

Polymer blending provides a simple, low-cost, and sometimes very effective way to obtain new materials for use in optoelectronic applications. For example, LEDs and PVs based on a blend of conjugated polymers are more efficient than those based on one single polymeric material because the phase separation that occurs in a thin film of a polymer blend creates a series of self-assembled heterojunctions where exciton dissociation (in a PV) or charge recombination (in an LED) can occur. Phase separation can take place at over a wide range of length scales and can happen both normal-to and within the plane of the film. Some studies have found spinodal phase separations and large PL spectrum changes in conjugated polymer and non-conjugated polymer blended films. When the blending ratio (conjugated polymer /non-conjugated polymer) is large, the morphology shows tens of micron-scale stripe patterns without photoluminescence spectrum changes. When the ratio is small, micro-isolated dots in non-conjugated matrix are formed. These dots emit light as conjugated polymer does, but the non-conjugated polymer matrix also emits light at within ~100 nm blue shift of the spectrum. This suggests that some MEH-PPV molecules are diluted into the PMMA matrix. The excitons of the conjugated polymer chains in the non-conjugated polymer rich region is well localized and emits light similar to conjugated polymer oligomers do. Extensive studies are now underway aiming at enhancing the intensity of photoluminescent and Raman scattering controlled noble metal surface plasmons. Excitation of the surface plasmons resonance (SPR) within metal nanoparticles or on roughened surfaces creates strong local optical fields. Surface enhanced Raman scattering and related optical phenomena observed in these nanoparticles have been considered as an enabling technology for highly compacted optoelectronic devices and sensors which take the advantage of both quantum confinement effects and nonlinear optical properties. In some cases, in order to fix the spatial relationship in the coupled active luminescent material system, quantum dots are dispersed in PMMA thin film to create planar Ag particle arrays as electron-beam lithography resist. However, semiconductor nanoparticles, as known as quantum dots, are difficult to disperse evenly in the polymer matrix system. By easy blending process, we can fabricate nanoscale periodic array using our luminescent resist, P3HT/PMMA resist. The PL spectra of P3HT/PMMA thin film exhibit blue-shift behaviors and long lifetime decay with decreasing P3HT concentration. To practically use the P3HT/PMMA blends in applications, we utilize P3HT/PMMA blending solution to fabricate luminescent nanopatterns by electron beam lithography. In this study, we tried to use various polymer solutions of P3HT with different molecular weights to blend with PMMA in different ratios as electron beam resist. We can see that no matter what the molecular weight is, the line width roughness increases with the increasing blending ratios due to the P3HT-domain size. The larger P3HT-rich domain size in higher blending ratios which can be easily observed in the AFM image, hinders e-beam lithography, hence, results in lower resolutions of P3HT/PMMA nanopatterns. When it comes to examining the effect of P3HT molecular weight in electron beam lithography, we have found that low molecular P3HT (M.W. ~ 13k) / PMMA resist exhibits the best performance among all resists with other molecular weights because lower molecular weight P3HT bears shorter polymer chains and leads to smaller domains. The P3HT/PMMA resist with the best performance, C4 resist, exhibits the lowest line width roughness about 4.23 nm, which is close to that of the pure PMMA, 4.05. The active luminescent P3HT/PMMA electron beam resist exhibits higher resolution than that QDs/PMMA composite resist, and the compatibility and stabilities of P3HT/PMMA is much better than that of QDs/PMMA. The resist can be used to fabricate a high-resolution planar 2D luminescent spatial structure for photoluminescence enhancing controlled by SPR principle, photonic crystals and optoelectronic applications.

Q2-S5.13
Polymer Light Emitting Diodes Based on DB-PPV/ZnO Nanocomposite Emissive Layer. (#1382) Mora Veera Madhava Rao, AOTC, Department of Microelectronics engineering, National Cheng Kung Universty, Taiwan.

Polymer Light Emitting Diodes Based on DB-PPV/ZnO Nanocomposite Emissive Layer Yan Kuin Su, M.V. Madhava Rao*, T.S. Huang and Chen-Han Yeh Institute of Microelectronics and Department of Electrical Engineering, National Cheng Kung University, Tainan 701, Taiwan, ROC. *Email: madhavmora@yahoo.com Even after 20 years of extensive research attention, organic/polymer light emitting diodes (OLEDs/PLEDs) continue to generate considerable interest as potential candidates for use in flat panel displays and solid state lighting(1-4). They have some advantages such as low fabrication cost, easy processing, lightweight, and can fabricated on large area display and flexible substrate etc.. However, the conjugated polymer is easy to affect by the moisture and oxygen in environment, and then influence the performance and life time to limit its applications in commercial, so there are many researchers discussing to improve the performance of PLED. We fabricated a polymer light emitting diode single layer structure had been made ITO/PEDOT:PSS/DB-PPV-ZnO/Ca/Al. We observed the roughness of emission layer increased when the ZnO nanoparticle composite with the proportion of ZnO nanoparticle increasing. The surface morphologies of the polymers were measured by AFM and SEM. The J-V and L-I characteristics indicate that addition of ZnO nanoparticles can facilitate electrical injection and charge transport. It demonstrated the ZnO nanoparticle have the ability to improve the current density, luminance and efficiency. After being annealed the nanocomposite device at 120oC, the highest luminance efficiency is 2.90 cd/A(5-6). References: 1). C.W. Tang, SA. Vanslyke, Appl. Phys. Lett. 1987, 51, 913. 2). J. Huang, G. Li, E. Wu, Q. Xu, Y. Yang, Adv. Mater. 2006, 18, 114. 3). X. Gong, S. Wang, D. Moses, G.C. Bazan, A. J. Heeger, Adv. Mater. 2005, 17, 2053. 4). Y. Xu, J. Peng, J. Jiang, W. Xu, W. Yang, Y. Cao, Appl. Phys. Lett. 2005, 87, 193502. 5). M.L. Tu, Y.K. Su, S.J. Chang, T.H. Fang, W.H. Chen and H. Yang, Japanese, J. Appl. Phys. 2005,44, 2787. 6). J.P. Liu, S.C. Qu, X.B. Zeng, Y. Xu, X.F. Gou, Z.J. Wang, H.Y. Zhou, Z.G. Wang, Appl. Sur. Sci. 2007, 253, 7506.

Q2-S5.14
A Novel Bicomponent Polypyrrole-Biopolymer Carbon Nanotubes Nano-Composite Fibre. (#835) Javad Foroughi, Intelligent Polymer Research Institute, The University of Wollongong, New South Wales, Australia.

Javad Foroughi, Geoffrey M. Spinks, Gordon G. Wallace ARC Centre of Excellence for Electromaterials Science Intelligent Polymer Research Institute, University of Wollongong, Australia Electrically conducting and robust nano-composite Polypyrrole alginate carbon nanotubes fibres have been produced successfully in first time by a wet spinning process. In situ polymerization of polypyrrole was achieved during spinning of alginate carbon nanotubes dispersion. The resultant a novel nano-composite fibre had been used as an actuator. The polypyrrole-biopolymer nano-composite fibres are shown to be electrochemically active. Their use in a range of electrochemical configurations including electronic-Textiles and artificial muscle nano-structures has been evaluated.

Q2-S5.15
Research Progress on PEDOT: A Review of Its Preparation, Modification, Properties and Applications. (#451) Yanmin Wang, Department of Polymer Science and Engineering, College of Materials Science and Engineering, Shandong University of Science and Technology, Qingdao Shandong Province, China.

In this paper the progress in study on conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) is reviewed. The preparation methods and its excellent advantages are presented. The modification ways such as its copolymer and composites are introduced in detail. And the applications of PEDOT are also summarized in this paper. The difficulty and the future of the its research are shown in this paper.

Q2-S5.16
Modified Polyimide Films Injected with High Energy Ion. (#547) Wang Xiao Qiang¹, Zhen Cong Mian²; ¹Northeastern University at Qinghuangdao, China ; ²Hebei Normal University, China.

The polymer films treated by ion beam, the physical properties and mechanical behavior optimized after being irradiated with high energy ion. The irradiation could caused the degradation and cross linkage of the macromolecule's fundamental chain. Its structure and solubility would also be changed. The electric resistance of polyimide (C22H10N2O5)n films would be lower obviously via ion implantation, this provides the foundation for the application of polymer films to device. In this research, the polyimide (PI) films were irradiated by 3Mev Si ions at room temperature. The composition and electrical properties were investigated. The Raman spectra indicated that the samples have a trend that is insulator->diamond-like->graphite gradually. The functional groups such as benzene ring and -CH3- were broken, diamond-like and graphite peaks appeared. The electrical resistances of samples irradiated with different ion dosis have a descend trend as the ion dosis increasing at the temperature range between room temperature and liquid nitrogen temperature. The results indicated that the carbonization is the important reason which has effect on the change of resistances.

Q2-S5.17
Synthesis and Characterization of Acrylic Acid Doped Soluble Conducting Poly (niline), Poly (o-toluidine) and Application as Sensor for Ammonia. (#1201) Vasant Vidyadhar Chabukswar, Department of Chemistry, Nowrosjee Wadia College, Pune, India.

Poly(aniline ), poly (o-toluidine ) have been synthesized in high yields by chemical oxidative polymerization method using ammonium persulfate (APS)as initiator and oxidizing agent in presence of acrylic acid. This is a new polymerization method for the direct synthesis of emeraldine salt of polyaniline and poly (o-toluidine) that is soluble in common organic solvent such as m-cresol, NMP, DMSO etc. The results are discussed with reference to HCl doped polymer. These polymers were characterized by FT-IR, UV-visible, X-ray diffraction (XRD) and electrical conductivity measurement. The as synthesised materials were used as a sensor for ammonia. Compared to conventional polyaniline, acrylic acid doped polymer exhibit higher sensitivity and reversibility. Further, the resistance is observed to decrease on exposing the acrylic acid doped polymer to ammonia vapours. A reverse trend is observed in the case of HCl doped polymer. The results are explained in term of the differences in the chemical interactions of the two polymer with respect to ammonia vapours. These results are supported by the X-ray diffraction and FT-IR studies. Final comparison of the material characterisation studies showed that the acrylic acid doped polymer served as a superior material for sensing ammonia compared to HCl doped polymer.

Q2-S5.18
Magneto Resistance of the Iodine Doped Poly(vinyl Alcohol)-Cu²⁺ Chelate. (#618) Ji Hyun Park, Yu Kyung Kim, Ho Nam Yoo, Young Woo Nam, Chong Su Cho, Yung Woo Park; Nano Transport Laboratory, Department of Physics and Astronomy & Nano Systems Institute-National Core Research Center, Seoul National University, Republic of Korea.

Organic semiconducting polymers can be classified into three types, such as ?-electron systems, charge-transfer complex systems, and metal chelates. Among various type of organic semiconducting polymers, poly(vinyl alcohol)-Cu2+ chelate doped with iodine (PVA/Cu2+/I2) is known to have good surface conductivity [1]. To investigate the intrinsic bulk conductivity, we have measured the temperature dependent conductivity of the (PVA/Cu2+/I2) down to T=4K under magnetic field up to H=7 tesla. Four-probe pressure contact using platinum electrodes is applied for the conductivity measurement. The room temperature conductivity is ?RT=10-2 ~10-3 S/cm and it shows a broad maximum peak at around T=60K {?(60K)/?RT=1.4}. The magneto resistance (MR, ??/?) is positive and increased linearly as magnetic field increases up to 7 tesla. The results indicate that the observed high conductivity of the (PVA/Cu2+/I2) is not simply from the surface conductivity. It can be a bulk property of the doped sample. References [1] F. Hihashi, C. S. Cho, H. Hinoki, O. Sumita, J. Polym. Sci., Polym. Chem. Ed. 17, 313 (1979)

Q2-S5.19
Operational Lifetime Studies of Dye Sensitised Solar Cells. (#1282) Benjamin Langley, Byeong-Kwan An, Rhiannon Mulherin, Paul Meredith, Paul Burn; Centre for Organic Photonics and Electronics, The University of Queensland, Brisbane, Australia.

Dye Sensitised Solar Cells (DSSCs) based upon heteroleptic Ru(II) dyes have recently seen significant attention due to their high light-to-electricity conversion efficiency (∼11%, AM 1.5). However, these Ru(II) complexes are not wholly suitable for commercial outdoor applications as although high conversion efficiencies can be observed initially, devices utilising such complexes exhibit poor long term stability under light exposure and load. Lifetimes can be reduced by cell leakage, degradation of materials, dye desorption, and thermal stress. For practical device applications, it is essential that devices have excellent long-term stability under high light exposures and temperatures. In this presentation, we report the results of a study on Ru(II) complexes, which have focussed on the stability of the device to ambient conditions in an effort to understand the factors that effect long-term stability. We show that the standard long-term stability testing method does not compare favourably to the conditions that DSSCs would experience in practical applications.

Q2-S5.20
Synthesis and Characterization of Conjugated Perylene Bisimide Copolymers Tuned by Series of Oligo(phenyleneethynylene)s. (#127) Huibiao Liu, Yuliang Li, Daoben Zhu; Institute of Chemistry, Chinese Academy of Sciences, Zhongguancun, Beijing, China.

Synthesis and characterization of conjugated perylene bisimide copolymers tuned by series of oligo(phenyleneethynylene)s Huibiao Liu, Yuliang Li* , Daoben Zhu Beijing National Laboratory for Molecular Science, CAS Key Laboratory of organic solid, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080, P. R. China e-mail: ylli@iccas.ac.cn We designed and synthesized three conjugated copolymers based on perylene bisimide and oligo(phenyleneethynylene) (OPE) units. The electronic absorption, fluorescence and redox potentials of the copolymers were studied, which exhibited regular changes with the number of OPE chromophores increasing respectively. Photoelectrochemical measurements were also performed and quantum efficiencies were calculated. The result demonstrated that an increase in the number of OPEs in the polymers could improve the photocurrent generation efficiency.

Q2-S5.21
Dipyridophenazine Complexes for Potential Use in Solar Cells and OLEDs.. (#1416) Michael Fraser, Campbell Easton, Garth Irwin, Allan Blackman, Keith Gordon; University of Otago, Dunedin, New Zealand.

Metal complexes with ligands based on dipyrido[3,2a:2',3'-c]phenazine (dppz) are of interest as they can be used in solar energy systems and organic light emitting diodes (OLEDs). A synthetic and spectroscopic study of disubstituted dppz ligands and complexes is reported. The primary aim of which was to synthesize a series of sulfur containing disubstituted dppz ligands and there corresponding rhenium (I) tricarbonyl chloride and platinum (II) dichloride complexes. One reason for interest in these systems is that the dppz ligand has close lying unoccupied molecular orbitals that are partitioned on differing sections of the ligand. TD-DFT calculations using the B3LYP/6-31G(d) method resulted in vibrational spectra with good agreement to experimental FT-IR and FT-Raman spectra. The electronic effects of the substituents were established by 1H NMR spectroscopy and cyclic voltammetry. The electrochemical data showed the relative energies for the accepting molecular orbital upon reduction. Resonance Raman spectra was used for insight into the Frank-Condon state of the compounds. Emission spectra and excited state lifetimes are also reported.

Q2-S5.22
Thermoelectric Power of the Iodine Doped Poly(vinyl Alcohol)-Cu²⁺ Chelate. (#693) Yu Kyung Kim, Ji Hyun Park, Ho Nam Yoo, Young Woo Nam, Chong Su Cho, Yung Woo Park; Nano Transport Laboratory, Department of Physics and Astronomy & Nano Systems Institute-National Core Research Center, Seoul National University, Republic of Korea.

Thermoelectric power (TEP) of the iodine doped poly(vinyl alcohol)-Cu2+ chelate (PVA/Cu2+/I2) has been measured from room temperature down to 1.8K. The film type (PVA/Cu2+/I2) sample was mounted on top of two oxygen-free copper plates with pressure contact. At room temperature, the TEP is +110uV/K and it decreases linearly upon cooling to T=1.8K. The positive TEP and high room temperature value indicate that the (PVA/Cu2+/I2) is p-type semiconducting. And yet, the linear temperature dependence of TEP suggests metallic characteristics of the sample. In addition the magneto-TEP has been measured at H=7 tesla for T<28K. The magneto TEP shows a slight reduction compared to the zero-field results indicating little influence of the magnetic field on the TEP. The observed TEP results could be consistent with the model that the (PVA/Cu2+/I2) is a semiconducting organic polymer with good surface conductivity [1]. Reference [1] F. Hihashi, C. S. Cho, H. Hinoki, O. Sumita, J. Polym. Sci., Polym. Chem. Ed. 17, 313 (1979)

11:00 AM *Q3-S2.1 (invited)
Organic Semiconductor Lasers and Optical Amplifiers. (#1359) Ying Yang¹, Dimali Amarasinghe¹, Georgios Tsiminis¹, Arvydas Ruseckas¹, Homar S Barcena², Paul L Burn², Graham A Turnbull¹, Ifor David William Samuel¹; ¹Organic Semiconductor Centre, School of Physics and Astronomy, University of St Andrews, United Kingdom ; ²University of Queensland, Australia.

The attractive properties of organic semiconductors such as simple fabrication and scope for tuning properties make these materials attractive for a range of applications in electronics and optoelectronics. The great progress made in materials for organic light-emitting diodes has led to a newer field of organic semiconductor lasers. In addition to simple processing and tuneability, the strong absorption, high gain cross section, broad spectra and high solid state fluorescence quantum yields of organic semiconductors are attractive for applications as lasers. The development of practical polymer lasers requires progress in reducing the threshold for lasing so that convenient pump sources can be made. Pump lasers have been steadily reduced in size from large frame lasers to a microchip laser and more recently a gallium nitride laser diode. The need for another pump laser has limited the development of polymer lasers. We have overcome this problem by matching an InGaN LED as pump source to a fluorene copolymer laser. The LED is a convenient low cost electrical pump source and the polymer gives tuneable emission at wavelengths not readily accessible by inorganic semiconductors. Hence this hybrid optoelectronic device provides the key advantages of electrical pumping and simple fabrication expected from an electrically pumped polymer laser. In a different aspect of the development of lasers, we show that by using a first generation bis-fluorene cored dendrimer, two-photon pumped lasing can be achieved. This opens up the possibility of using convenient red pump sources to achieve visible lasing. The presence of gain in organic semiconductors can also be used to make optical amplifiers. These give broadband amplification of ultrafast optical pulses in the visible region of the spectrum. All-optical switching has for a long time been a major goal of research on organic materials. We now report achieving it in polymer optical amplifiers made from fluorene copolymers. A control light pulse can turn off the gain of the amplifier, which then recovers on a picosecond timescale.

11:30 AM Q3-S2.2
New Thin Film Materials for Organic Semiconductor Logic and Sensor Circuits. (#225) Howard E. Katz, Johns Hopkins University, Baltimore, Maryland, USA.

Among the challenges for application of organic semiconductor (OSC)-based devices are voltage reduction, enabling of complementary logic, and increased response speed. New materials that we are developing for these purposes include electron transporting semiconductors requiring minimal gate dielectric films, highly polarizable solution-deposited gate dielectrics, and chemically sensitive heterostructures just a few monolayers thick. We will specifically describe organic and polymer chemistry that has resulted in new naphthalenetetracarboxylic diimide and oxadiazole-containing n-OSCs for transistors, diodes, and solar cells, processes for layered ionic "conductors" that have very high capacitance as gate dielectrics in transistor circuits, and hydroxylated p-OSCs with selective responses to vapors of national security interest. N-channel transistors were made with semiconductor mobilities >0.2 cm2/Vs and turnon voltages <1 V. Detection of 100 ppb of a model phosphonate ester vapor with response times of tens of seconds were achieved. Diodes with >10 MHz response speeds and photovoltages approaching 1 V were demonstrated. Incorporation of these devices into energy harvesting and multifunctional circuit architectures will be discussed.

11:45 AM Q3-S2.3
Growth of Carbon Nanotube Architectures on Functional Surfaces. (#1471) Andrew I Minett, Jun Chen, Peter Sherrell, Yong Liu, Gordon Wallace; University of Wollongong, Australia.

Due to their high surface area, electro-chemical stability and versatility, carbon nanotube based electrodes have been attracting great interest for use in alternative energy applications such as supercapacitors, Li-ion batteries and fuel cells. In this presentation, we describe the production and modification of flexible pre-formed carbon nanotube architectures with various entities such as conducting polymers or metal nanoparticles for use as superior electrode materials. Growth on conducting surfaces has been observed, showing promise for a wide range of applications. Recently, we have reported on the direct use of some of these assemblies as electrodes for Li-ion batteries, supercapacitors or catalyst supports. To demonstrate the versatility of these carbon composite electrodes, the introduction of metal nanoparticles for catalysis or enhanced electrochemical properties allows the use of these electrodes as either the anode or cathode in fuel cell applications or as supercapacitors. Eight different metals have been deposited by a simple method with nanoparticle sizes as small as 4 nm. Energy densities of ∼ 70Wh/kg and power densities up to ∼ 10kW/kg for these composite electrodes highlight promise for alternative energy applications.

12:00 PM Q3-S2.4
Magneto Thermoelectric Power of the Iodine Doped Single Wall Carbon Nanotubes. (#818) Sejung Ahn, Young Woo Nam, Ji Hyun Park, Yu Kyung Kim, Ho Nam Yoo, Zhaoxia Jin, Yung Woo Park; Nano Transport Laboratory, Department of Physics and Astronomy & Nano Systems Institute-National Core Research Center, Seoul National University, Republic of Korea.

Magneto thermoelectric power (TEP) of the iodine doped single wall carbon nanotubes(SWCNT) has been measured from room temperature down to 2.5K. The film type SWNT sample was mounted on top of two oxygen-free copper plates with pressure contact. At zero magnetic field, the room temperature TEP is positive and +14uV/K. It decreases upon cooling to T=2.7K. The positive TEP indicates that the majority carrier in iodine doped SWCNT is hole. The magneto-TEP has been measured at H=7 tesla for T<100K. The magneto TEP becomes smaller than the zero field TEP value. At T=2.5K, the zero field TEP is +0.15uV/K and the 7 tesla magneto TEP is +0.13uV/K. For 20K100K. The reduction of TEP under magnetic field at low temperature could be due to the reduction of entropy per carrier since the magnetic field induces more ordered state of spins in the system. Detailed analysis of the magneto TEP including the slope change as function of temperature are on going.

12:15 PM Q3-S2.5
Kelvin Probe Microscopy Study of Donor- Acceptor Blends for Organic Solar Cells. (#723) Sunyoung Sohn, Jung-Ran Lim, Byungchul Son, Jouhahn Lee, Seung hun Eom, Soo-Hyoung Lee; Korea Basic Science Institute (KBSI), Republic of Korea.

The organic solar cells (OSCs) based on conjugated polymer-fullerene composites have been attracting interest due to the advantages such as cheap production cost, light weight, simple fabrication process, and flexible mechanical property against the Si based solar cells. The study of interface property between metal electrode and organic layer among the most important issues for the OSCs is an essential point for controlling the charge carrier injection into the organic active layer. Recently, the Kelvin Probe Microscopy (KPM) technique has been interesting because it was very useful analytical method to investigate the structural and electrical properties without damage and charging effect at the surface. In this work, the KPM analysis as a function of scan mode and applied voltage was applied for investigate the morphology, the composition crystals, and the electrical properties of Poly(3-hexylthiophene) (P3HT, donor):[6,6]-phenyl C61 butyric acid methyl ester (PCBM, acceptor) blend film as an active layer in the OSCs. For the formation of the active layer, 2 wt.% P3HT:PCBM solution in chlorobenzene was deposited with 90 nm thickness onto conventional ITO/PEDOT:PSS (40 nm) film by spin-coating. In order to find the cause of efficiency improvement in the OSCs, the P3HT crystallization at P3HT:PCBM composition, the dispersion of the amorphous P3HT:PCBM matrix, and the redistribution of PCBM cluster as a function of annealing condition were respectively measured using KPM. In conclusion, we believed that the efficient separation or collection of the photogenerated excitons at donor-acceptor interface from measuring the surface potential difference between the donor and acceptor materials in the KPM results can be ambiguous explained.

LUNCH 12:30 PM - 2:00 PM

2:00 PM *Q3-S3.1 (invited)
Searching for Deep Blue Phosphorescence for Organic Light-Emitting Diodes. (#1410) Paul L. Burn¹, S.-C. Lo¹, R. E. Harding¹, I.D.W. Samuel²; ¹Centre for Organic Photonics and Electronics, The University of Queensland, Brisbane, Australia ; ²University of St Andrews, United Kingdom.

Innovation in materials has played a crucial role in development of organic light-emitting diodes, and most research has concentrated either on small organic molecules or conjugated polymers. We have pursued an alternative approach to materials for LEDs based on conjugated dendrimers. These molecules consist of a core, conjugated dendrons (branches) and surface groups, and by suitable choice of these components, extremely efficient solution-processed LEDs can be made. In addition, dendrimers have proved convenient model systems in which to study important issues for all OLED materials such as the role of intermolecular interactions. One of the key challenges in materials development is the creation of compounds that emit saturated blue phosphorescence at room temperature. While small molecules based in iridium(III) complexes with carbene or phenyltriazolyl based ligands have been reported a question remains as to whether it is possible to design optimal hosts that are require to prevent the intermolecular interactions of the small molecule emissive chromophores within a film. In this presentation we will report recent advances in dendrimer design that enable the production of solution processed films that give deep blue phosphorescence with high photoluminescence quantum yields and will discuss how the dendron structure can effect the emissive properties of the films.

2:45 PM Q3-S3.3
Stable Green Light-Emission from poly[9,9-Bis(4'-N-octyloxyphenyl)fluorenyl-2,7-vinylene] Synthesized via the Gilch Polymerization Route. (#1123) Do-Hoon Hwang, Jong-Min Kang, Jae-Hoon Eom, Moo-Jin Park, Hoon-Je Cho, Jeong-Ik Lee, He-Yong Chu, Changhee Lee, Sung-Ho Jin, Hong-Ku Shim; Department of Applied Chemistry, Kumoh National Institute of Technology, Republic of Korea.

A new fluorene-containing poly(arylenevinylene) derivative, poly[9,9-bis(4-octyloxyphenyl)fluorenyl-2,7-vinylene] (PBOPFV), was synthesized via the Gilch polymerization route and its light-emission properties were characterized and compared with those of poly(9,9-di-n-octylfluorenyl-2,7-vinylene) (PFV). As is the case for poly(alkylfluorene)s, PFV exhibits a long wavelength emission that is additional to its emission in the blue-green region after thermal annealing or the passage of current. We have successfully suppressed this long wavelength emission by introducing an octyloxyphenyl group at the 9 position of the fluorene group. PBOPFV produces PL emission maxima at 478 and 510 nm and no significant changes were found in its PL emission spectrum even after thermal annealing at 150 oC for 2 h. Light-emitting devices were fabricated with ITO/PEDOT:PSS/polymer/LiF/Al configurations. The EL spectrum of the device constructed using PFV was found to undergo significant changes during device operation, whereas the EL spectrum of the device constructed using PBOPFV was found to be stable.

3:00 PM *Q3-S3.4 (invited)
Excited States of Coordination Complexes for OLED Materials. (#1293) Keith C Gordon, MacDiarmid Institute for Advanced Materials and Nanotechnology, Department of Chemistry, University of Otago, Dunedin, New Zealand.

Organic light emitting diode (OLED) materials are may be based on polymers or small molecules including metal complexes.1--3 There are a number of important parameters for successful OLED operation. These include ensuring that the charge transfer processes lead to excited state formation, the provision of a highly emissive unit such that excited states that are formed by the sequential electron and hole transfer processes result in light emission, and high emission quantum yields from the excited states formed. OLEDs may be designed form layers of suitable hole and electron transport materials with a emitting unit sandwiched in between or by making a blend of such species. Multifunctional molecules in which the emitting unit is covalently attached to a charge transport unit may offer better performance. An important design question if one if to use multifunctional materials is how the covalently bound species (emitter and charge-transfer centers) interact. We have used the Re(I) complexes to investigate the level of communication between an emission center, the Re(phen) chromophore and covalently attached hole-transport amine units. Using resonance Raman spectroscopy in concert with vibrational frequency DFT calculations it is possible to gauge the effect of the linker group on the perturbation of the MLCT chromophore. The DFT frequency calculations provide predicted bands that have a mean absolute deviation of < 9 cm-1 from those observed in FT-Raman spectra. The time-dependent DFT calculations also provide good correlation with the observed electronic absorption spectra. Thus the modelling appears to provide an accurate picture of the electronic structure of these compounds.

AFTERNOON BREAK 3:30 PM - 4:00 PM

4:00 PM *Q3-S4.1 (invited)
Fiber-Based Organic Light Emitting Devices. (#268) Brendan O'Connor, Kwang-Hyup An, Yiying Zhao, Kevin Pipe, Max Shtein; Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan, USA.

Organic semiconducting materials are amenable to deposition of device-quality thin films on a variety of low-cost substrates, including glass, plastic, and metal foils. Deposition of active devices on non-planar substrates is relatively unexplored, but can result in useful devices that utilize the substrate geometry to improve their optoelectronic performance and/or potentially reduce manufacturing cost. This talk will focus on thin-film organic light emitting devices (OLEDs) deposited conformally on fibers. Device performance is quantified, detailing the unique features and requirements of fiber-based OLEDs important for scale-up. In particular, the demonstrated fiber OLEDs do not employ indium tin oxide (ITO), instead using a metal/organic/metal layer structure. While the quantum efficiency values are similar for fiber-based and planar OLEDs with identical layer structures, the electroluminescence (EL) spectrum is shown to be invariant with observation angle for fiber-shaped OLEDs. A combination of optical microcavity effects and substrate symmetry explain the difference, and suggest new avenues for optimizing efficiency for white light devices. Implications and preliminary results for other devices, e.g. organic solar cells, will be discussed as well. Brendan O'Connor, Kwang H. An, Yiying Zhao, Kevin P. Pipe, and Max Shtein, "Fiber Shaped Organic Light Emitting Device." Advanced Materials (2007) Vol. 19: p.3897

4:30 PM Q3-S4.2
Molecular Design and D-A Distance Modulation for Efficient Conjugated Polymer-Based FRET DNA Detection. (#352) Han Young Woo, Rati Ranjan Nayak, Okhil Kumar Nag, Mijeong Kang; Pusan National University, Republic of Korea.

Homogeneous DNA hybridization assays based on fluorescence resonance energy transfer (FRET) are attractive and constitute one of the most popular DNA detection schemes. One successful DNA sensing method involves the use of cationic conjugated polyelectrolytes (CCPs) and the hybridization between fluorophore-labeled peptide nucleic acids (PNA) and complementary (or non-complementary) target DNA. Electrostatic interactions between CCPs and negatively charged DNA can be coordinated to give rise to efficient FRET and to design sequence-specific DNA assays. This scheme benefits from utilizing the light-harvesting (or antenna-like) properties of water-soluble CCPs to achieve sensory signal amplification in the presence of suitable energy or electron acceptors. The molecular structure of the CCP must play an important role in determining the overall aggregate size, the distance between the optically active backbone and the acceptor dye, and the degree to which FRET or energy-wasting photoinduced charge transfer (PCT) takes place. In this contribution, two cationic water-soluble conjugated polyelectrolytes ( P1i and P2i) were synthesized and examined as a FRET donor to fluorescein (Fl)-labeled single-stranded DNA (ssDNA-Fl) using steady-state and time-resolved photoluminescence (PL) spectroscopy. The two polymers have the same p-conjugation with the main structural difference being the presence of the spiro-anthracenyl substituents orthogonal to the polymer backbone of P2i. These spiro-substituents can function as a molecular spacer that increases the intermolecular separation in the electrostatic complex with ssDNA-Fl. We measured almost complete PL quenching of the excited Fl* after electrostatic complexation with P1i (PL lifetime 4 ns -> 78 ps) and relatively moderate quenching with P2i (PL lifetime 4 ns -> 552 ps). A quenching efficiency (?eT) of 98% and 86% was obtained for P1i/ssDNA-Fl and for P2i/ssDNA-Fl, respectively. However, both systems have same thermodynamic driving force for quenching as a result of them having the same electronic structures. This can be explained in terms of the reduced quenching (via PCT) by the increased D-A distance due to the existence of spiro-attached molecular spacers in P2i. It shows that thermodynamically favorable eT quenching can be controlled kinetically by modulating the D-A intermolecular distance using molecular spacers, which suggests an important molecular design guideline for efficient CPs-based FRET donors. In addition, several approaches to control D-A distance in molecular scale will be discussed for the optimized CPs-based FRET DNA detection.

4:45 PM Q3-S4.3
Evaluation of Cellular Adhesion for DLC Film Coating on an Artificial Heart Blood Pump. (#301) Kazuya Kanasugi, Tatsuya Fukui, Yasuharu Ohgoe, Kenji Hirakuri, Akio Funakubo, Yasuhiro Fukui; Tokyo Denki University, Japan.

Diamond-like carbon (DLC) films have been considerably interesting in a variety of applications, due to their attractive electrical, mechanical, chemical, and biological properties. Additionally, using radio frequency (r.f.) plasma chemical vapor deposition (CVD) technique, DLC films are deposited on most objects that are conductor and/or insulator at low temperatures. Therefore, it has been expected as a new biomaterial, and a large number of reports have suggested biomedical applications of DLC film coatings. However, it is very difficult to deposit DLC film on an irregular insulator objects such a surface of an artificial organ because major application of r.f. plasma CVD technique has been adapted only to flat substrates, such as silicon or glass wafers for integrated circuits fabrication. Therefore, DLC film coating also has been limited to the planar substrate. To deposit DLC film on an artificial heart blood pump, in our previous work, the special three-dimensional-type electrode using a large number of small metallic balls has also been developed, which is possible to adjust to be a shape of the artificial heart blood pump flexibly. The purpose of such deposition was improvement of biocompatibility of the blood pump. We succeeded in the DLC films deposition uniformly on an irregular object such as the blood pump using the special electrode. In this study, we focused on cytocompatibility of the DLC films, which were deposited on a blood pump surface by the special three-dimensional type electrode. In this experiment, DLC films were deposited on the pump's surface uniformly using the special electrode. Furthermore, in order to investigate the cellular adhesion of the DLC film deposited on the blood pump, we were evaluated for the three kinds of DLC films(DLC, Ar-modified DLC, O2-modified DLC)of the surface conditions. The DLC, Ar-modified DLC, and O2-modified DLC films were analyzed for the surface properties (structure, chemical composition, roughness and potential) using an Ar-laser Raman spectrophotometer (Raman), an X-ray photoelectron spectrometer with Mg K? radiation (XPS), an Atomic Force Microscopy (AFM) and the measurement of contact angle. The cell culture was carried out by the in-vitro, and mouse fibroblasts (NIH-3T3) have been grown on the DLC film coated for periods of up to 96 hours. The results of cell culture indicated the non-toxic nature on the surface of all the DLC films. Moreover, it was observed that the cellular adhesion of the DLC films on a blood pump were controlled by each surface condition. This result suggests that the surface modifications of the DLC films are possible to control an important factor for influencing the biological response. The surface modification using the argon and oxygen plasma treatment was effective in cellular adhesion.

5:00 PM Q3-S4.4
Thiophene-Based Ionic Liquid Mesogens and Polymers as Soft Electrodes for Bioelectronic Devices. (#427) Millicent Anne Firestone, Christopher T. Burns, Sungwon Lee; Argonne National Laboratory, Illinois, USA.

There has been recent interest in studying means by which to incorporate and adapt proteins as the basis of electronic devices. The use of conducting polymers as "soft" electrodes, that is, as replacements for bulk metal electrodes as a benign (to the protein) means of electronically addressing a protein represents a significant materials challenge. As a first step towards addressing this challenge we have synthesized and polymerized methylimidazolium-based ionic liquids that incorporate a thiophene moiety at the terminus of a C10 alkyl chain, characterized their structure and electronic properties. Both a bromide and nitrate salt of the amphiphilic thiophene IL was found to self-assemble in water (albeit the nitrate to a lesser extent), adopting columnar mesophases. Polarized optical microscopy and small-angle X-ray (SAXS) studies show that at low water content, the IL - water binary mixtures form liquid crystalline mesophase possessing significant short-range ordering due to strong pi interactions between adjacent thiophene moieties. At higher water content the short-range ordering is lost, but long-range ordering persists up to ca. 45 % (w/w) water. The chemical oxidative coupling of the nitrate monomer yields a highly water-soluble polymer. Electrochemical studies show that the polymer possesses a high oxidation potential (1.95 V) and thus, is resistant to chemical doping. In dilute aqueous solution, electronic absorption spectroscopy and X-ray scattering show the polymer adopts a random, coil-like conformational state. Slight improvement in the polymer conformation can be achieved by exchange of the counter anion. Initial studies examining the biocompatibility of these materials have also been conducted.

9:00 AM *Q4-S1.1 (invited)
Polypyrrole and Poly-3,4-Ethylenedioxythiophene Conducting Polymer Actuators. (#1412) Jadranka Travas-Sejdic, Paul A. Kilmartin, Rudolf Kiefer, Lijuan Zhang, Xerxes Mandviwalla, Rosalind Archer, Bruce MacDonald, Graham A. Bowmaker; Polymer Electronics Research Centre, University of Auckland, New Zealand.

Dimensional changes in conducting polymers such as polypyrrole (PPy), polyaniline (PANI) and poly(3,4-ethylenedioxythiophene) (PEDOT) during oxidation and reduction have been used for over 15 years to create movement, an actuating effect. This has opened up the possibility of the development of a new class of polymer based, large strain, artificial muscles, to stand alongside other prospective materials, such as dielectric elastomers, shape-memory allows and carbon nanotube fibres. In this talk recent results from our group on the development of PPy and PEDOT actuators in the form of either free-standing films or bending type trilayer actuators will be discussed. The actuating properties of these polymers, such as the extent and speed of actuation, will be related to polymer synthesis conditions, film morphology and actuator testing conditions. Examples will also be shown where trilayer actuators have been examined in fluidics channels to create movement of fluid in the channels and the use of the trilayers in the construction of a self-driven robotic device with on-board microchip controller and battery power source. Finally, the synthesis of novel conducting polymer nanostructures (e.g. nanotubes and nanofibres) will be presented and the possibility of their use as actuators will be discussed.

9:30 AM Q4-S1.2
Ion Implanted and Ion Beam Mixed Polyetheretherketone: Properties of a Novel Electrically Conductive Polymer. (#1216) Eric Loyd Tavenner¹, Rishi Patel², Barry Wood³, Kartik Ghosh⁴, Matt Curry², Ryan Giedd²; ¹Ian Wark Research Institute, The University of South Australia, Australia ; ²Center for Applied Science and Engineering, Missouri State University, USA ; ³Brisbane Surface Analysis Facility, The University of Queensland, Brisbane, Australia ; ⁴Department of Physics, Astronomy & Materials Science, Missouri State University, USA.

In 1982 it was discovered that ion beam modification of polymers can lead to large electrical conductivity changes [1]. Ion implantation is one of the few techniques that can change the characteristics of a material by non-equilibrium conditions, and this allows materials to be modified in such a way that would be near impossible by other techniques. However, due to the complexities of characterising and elucidating the processes that occur during ion implantation, the understanding of the modifications that occur with the ion implantation of polymers has not advanced to the same level as for chemically modified polymers. As a consequence of this, the ability to tailor the ion implantation procedure to a specific polymer to achieve desired characteristics is still only attainable through trial and error, thus the use of this technique to produce polymer based circuit elements, where a fine degree of control of material properties is required, is limited. Various schemes are being investigated to produce polymers that have properties such as high conductivity or tuneable semi-conductivity, however the majority of work has focused on development of these polymers by chemical processing either during production or by post production processing. Comparatively, there has been less study into the modification of polymers by ion implantation. In addition, the study of ion implanted polymers to date has covered a wide range of polymer types with varied implantation parameters, with very few common elements in the studies. The aim of this study is to understand the changes that occur to polymers during the implantation process, how these changes relate to the electrical conductivity, and to eventually develop functional electronic devices and components. In addition, ion implantation may be one of the few methods that can successfully marry organic components to inorganic devices and vice versa. The thermoplastic polyetheretherketone (PEEK) was implanted by three different, but complimentary, techniques: nitrogen ion implantation, tin ion implantation and finally nitrogen ion beam mixing of thin tin films into the polymer. Three sample groups were made from 0.1 mm thick PEEK films: one sample group was implanted with 50 kV nitrogen ions to a dose of 10¹⁶ ions/cm², another was implanted with either 10 kV or 45 kV tin ions to a dose of 10¹⁶ and 10¹⁷ ions/cm², and the last group was implanted in a similar manner as the first group but with a 100 Å thin tin or tin/antimony film thermally deposited before ion implantation. Through the course of this study it was discovered that the conductivity of PEEK can be incrementally changed from its inherent room temperature value of 1x10^-16 S/cm (resistivity of 1x10¹⁶ Ωcm) to a modified conductivity of 1500 S/cm (resistivity of 664 μΩcm). In addition, the ion beam mixed system displayed a metallic low temperature resistance trend as well as displaying superconducting properties with a T_c of ~ 2 K. [1] S. Forrest, M. Kaplan, P.Schmmidt, T. Venkatesan and A. Lovinger, Appl. Phys. Lett. 41(8), 708 (1982).

9:45 AM Q4-S1.3
Micrometer Scale Patterning of Organic Polymer Materials by an Electrostatic Printing Technique. (#917) Matthew Simon Alexander, Mark Daniel Paine, Katharine Lucy Smith, John Stark; Department of Engineering, School of Engineering and Materials Science, Queen Mary, University of London, United Kingdom.

Growing interest in plastic electronic devices is primarily being driven by their ease of processing and the ability to deposit organic materials onto low-cost substrates such as glass or plastic films. Ink-jet is an emerging technology in the direct printing (so called digital lithography) of conjugated polymer materials for application in smart cards, photocells, radio frequency tags and for the production of OLEDs for flat panel displays. The feature sizes that inkjet technology can produce are limited however by the fact that the droplet diameter is strongly coupled to the nozzle diameter. As a result drop volumes below 5pL are not currently possible. We have identified a new feature of electrospray atomization that allows the controlled ejection of fluid droplets at high frequency. Although similar to inkjet digital lithography in that materials are deposited in droplet form directly onto the substrate in the desired location, our modified electrospray process produces drop sizes ranging from picolitres down to femtoliter volumes. We have printed 1micron sized features of carbon pigment onto surfaces with a positional accuracy of a only few microns and the technique is also capable of printing liquids with a far wider range of viscosities and solid particle loading fractions than is possible with inkjet printers. This allows us to accurately deposit and pattern organic materials of interest to the world of electronic circuits and display technologies. We describe the operation of this novel patterning process and present our most recent advances in deposition and patterning of organic polymer materials.

10:00 AM Q4-S1.4
Development of Embedded Metal Line in a Plastic Substrate for Microfluidic Device by Blanket Mold Imprinting. (#608) Jung-Ho Seo, Hanyang University, Republic of Korea.

Lab-on-a-chip (LOC) is a term for devices that integrate laboratory functions on a single chip and that are capable of handling extremely small fluid volumes. Lab-on-a-chip devices are a subset of MEMS (microelectromechanical system) devices and often indicated by Micro Total Analysis Systems (uTAS) as well. One of the most active areas of LOC today aims the microfluidic device. Microfluidic is a broader term that describes also fluidic flow control devices like pumps and valves or sensors like flowmeters and viscometers. It is also applicated various medical diagnosis systems. Such a microfluidic device is very sensitive to substrate materials and fluidic flow control. As a substrate material, glass, Si and plastic have been used for microfluidic device fabrication. Si is hard to apply to microfluidic device as a substrate material because of its opaque and reaction with biochemical samples. Glass, which is transparent and no reaction with biochemical samples, has been used as a substrate material instead of Si. However, glass is relatively expensive and hard to process whereas the plastic has acceptable properties to fabricate microfluidic device such as low price, good optical property, no biochemical reaction, easy processing and no toxic material. As a method for metal line fabrication, conventional lift-off process by photolithography is a simple and easy method for pattering metal lines. However, fabricated metal lines are formed onto the substrate so that it reduces efficiency of small fluid volume flow of the microfluidic device. In this paper, we suggest blanket mold imprinting process as a new concept of metal line fabrication method on a plastic substrate. Metal film, Au, was deposited on the plastic substrate as an electrode of the microfluidic device. After metal deposition, the metal lines were formed by wet etching process after photolithography. The height of metal lines is 2000? onto the plastic substrate. It reduces efficiency of small fluid volume flow through the micro fluid channel. To solve this problem, the fabricated metal lines were embedded in the plastic substrate by using blanket mold imprinting method. Blanket mold is non-patterned silicon stamp with antistiction layer and it presses the metal lines into the plastic substrate with hot embossing equipment. After hot embossing process, all of the metal patterns which had various widths of line and space from 25umto 800um were successfully fabricated and remained less than 300? height in 4 inch PET plastic wafer.

10:15 AM Q4-S1.5
Electrochemically and Chemically Polymerized Polyaniline Nanofiber Based Gas Sensors. (#361) Kourosh Kalantar-Zadeh¹, Yongxiang Li², Michael Breedon¹, Abu Z. Sadek¹, Rashidah Arsat¹, Richard B Kaner³, Wojtek Wlodarski¹; ¹School of Electrical and Computer Engineering, RMIT University, Melbourne, Victoria, Australia ; ²Shanghai Institute of Ceramics, Shanghai, China ; ³University of California, Los Angeles, USA.

We report the synthesis and characterization of polyaniline nanofibers. These chemically and electrochemically synthesized polyaniline nanofibers were used for the development of gas sensors for hydrogen sensing applications. The electropolymerization of polyaniline was conducted in an acidic solution of aniline monomer. Upon application of a constant positive potential between the working and counter electrodes, the oxidation of polyaniline occurred forming an insoluble polymerization product which deposited onto the working electrode. Arrays of uniform and well oriented polyaniline nanofibers were obtained via this method. In the first step of this template free growth mechanism, a high voltage was applied to generate the necessary nucleation sites on the surface of the substrate. Once nucleation sites had completed, voltage was reduced to allow polymer to grow from the nucleation sites. The synthesis of polyaniline via chemical polymerization, required an oxidant which was slowly added to the aniline solution at low temperature with thorough stirring. This resulted in an irregular granular morphology of polyaniline at an aqueous/organic interface. Sensors were tested towards H2 gas. For the chemical polymerization method, two different acidic dopants, hydrochloric acid and camphor sulphonic acid were employed to investigate any potential effect on the dimensional parameters of polyaniline nanofibers, that may alter gas sensing properties. In these experiments, the transducers consist of surface acoustic wave devices based on 64 YX LiNbO3 substrates. Their structure consist of two-port resonators with 38 finger pairs in each input and output inter digital transducer (IDT), 160 reflectors, 700 um aperture width and a periodicity of 40 um. The centre-to-centre distance between the IDTs is 48 wavelengths. The IDTs were formed by patterning an 80 nm layer of gold and a 20 nm titanium (Ti) layer. The titanium layer was added to improve adhesion of the gold thin film. SAW gas sensors with polyaniline nanofiber sensing layers were tested towards hydrogen gas. The sensors showed remarkable sensitivity and short response time (less than a minute).