The photoluminesence (PL) quantum efficiency of poly(p-phenylene vinylene) (PPV) varies with preparation and processing. We report the achievement of nearly 100% PL quantum efficiency through design and synthesis of alternating rigid conjugated segments of dimethoxy -PV (three dimethoxy -phenyl and two vinyl units) and flexible nonconjugated segments along the polymer backbone. There is enhanced solubility in desired solvents and increased interchain separation through the incorporation of the methoxy sidegroups, forming poly [1,6-hexanedioxy -2,6-dimethoxy-1,4-phenylene]-1,2-ethenylene-[3,6-dimethoxy-1,4-phenylene]-1,2-ethenylene-[3,5-dimethoxy-1,4-phenylene], or GDBBC. The nearly temperature-independence of the PL decay at different emission wavelengths of the alternating block co-polymer (ABC) shows that the excitons are highly localized due to the blocking by non-conjugated segments as well as due to increased interchain separation due to the methoxy sidegroups. The contrasting temperature- and time- dependent results for the corresponding PV oligomer and PPV, supports the role of reduced exciton migration in achieving high quantum efficiency. The results are compared to the exciton confinement at the interface of light emitting electron and hole transporting polymers, forming an exciplex, for which the luminescence decay is also temperature independent. Electroluminescent devices using GDBBC as the lightemitting layer and incorporating poly[1-phenyl-2-(p-n-carbazolylphenyl) acetylene], (PDPA-Cz), as hole transporting layer, in the structure ITO/PDPACz/GDBBC/Alq/MgAg have ~1% external quantum efficiency with green emission from the GDBBC. EL devices based on exciplex emission are also discussed.

Conjugated inorganic/organic hybrid polymers, poly(phenylene vinylene ferrocenyl vinylene), was prepared by condensation polymerization of bisphosphonate reagent and ferrocenedialdehyde. Conjugated polymers having long alkyl side chains is very soluble in various organic solvents and thin polymer films can be easily produced by spin-coating technique. UV-Vis., NMR, cyclicvoltammetry, and GPC analysis were used to characterize the properties of conjugated polymers, and the averaged molecular weight was in the range of 7,000~25,000 (vs. PS standard). Electrical conductivity measurement of this processible conjugated polymer either in powder or in thin solid film showed very low conductivity probably due to the slow chain-to-chain hopping process. Third order nonlinear optical property of the conjugated polymers was measured as high as ϰ(3) = 1.24×10−8 esu in spin-coated thin film.

We have previously shown that diphenylpolyenes incorporating diphenylamino donor substituents form exceptionally stable bipolaronic dications in solution, even at the bis-(diphenylamino)-E-stilbene level, whereas most previously known polyenylic bipolarons were unstable at lengths shorter than the tetraene1. Most recently we have also demonstrated that replacement of one of the diphenylamino substituents in the stilbene substrate with a N-(hydroxyethyl), N-ethylaminophenyl group yields a functionalized polyene that can easily be attached to PMMA as a pendant group, or to 3,5-dihydroxy-benzyl alcohol to form reactive dendrons2. These functionalized materials also form extremely stable bipolarons and are intensely fluorescent. In this presentation we will discuss the formation of G-0 dendrimers incorporating a series of polyenes related to the stilbene structure, and possible photonic applications.

1,1'-Binaphthyl-based chiral polymers and dendrimers have been synthesized and their potential applications have been explored. These materials have shown a variety of interesting properties such as electroluminescence, optical nonlinearity, enantioselective catalysis and chiral sensing.

The photo-induced charge transfer between tetracyano-anthraquino-dimethane (TCAQ) derivatives and poly(2-methoxy-5-(3,7-dimethyloctyloxy)-1,4-phenylene vinylene) MDMO-PPV was studied by means of photoinduced absorption (PIA) spectroscopy in the VIS and IR spectral region and lightinduced electron spin resonance (LESR) spectroscopy. Three different TCAQ derivatives with alkyl-side chains for increased solubility compared to TCAQ and one of them attached to a C60 molecule serve as strong electron acceptors. The photoinduced absorption in the VIS near-IR range shows a broad plateau around 1.8 eV followed by two peaks at 1.35 and 1.24eV for all three acceptors. All PIA features have a power law excitation intensity dependence with an exponent close to 0.5 as expected for bimolecular kinetics. The modulation frequency dependent excited state absorption decreases with a power law. LESR studies of all donor-acceptor combinations show one radical line at a g = 2.0028 with.H = 3.5 Gauss, originating from TCAQ anion and the polymer cation.

Poly(dithieno[3,4-b:3',4'-d]thiophene) (pDTT1), poly(dithieno[3,4-b:3',2'-d]thiophene (pDTT2) and poly(dithieno[3,4-b:2',3'-d]thiophene) (pDTT3) are low band-gap polymers that undergo both p- (oxidation) and n- (reduction) type electrochemical reversible doping in organic electrolytes. In this work we report on the in-situ IR spectroscopic characterization of both doping types using attenuated total reflection (ATR) FTIR spectroelectrochemistry. Thin polymer films were prepared on Ge reflection elements by electrosynthesis. During electrochemical potential cycling experiments in a spectroelectrochemical cell, the evolution of infrared active vibrational (IRAV) modes, correlated with the generation of charge within the polymer chain, was studied. In addition to electrochemical doping, the polymers exhibit also charged excitations by photodoping. FTIR spectra recorded by illumination/dark cycles show photoinduced IRAV bands which are similar to those found for the electrochemically p-doped materials. The infrared spectroscopic results are compared with Raman spectra of the neutral polymers. The relationship between vibrational properties and structure of the polymers is discussed in terms of different contribution of the φ-electrons within the repeating units to the electronic structure of the conjugated backbone.

Alternating polyelectrolyte deposition (APD) is a room temperature process that can be used to produce noncentrosymmetric ordered films of nonlinear optical polymers (NLOP). In this study, second-order NLOP APD films of a stilbazolium-substituted polyepichlorohydrin, poly (diallyldimethylammonium chloride), and polyacrylic acid were prepared by alternately dipping a substrate into aqueous solutions of each polymer. Evidence for uniform layer to layer deposition includes a linear increase of UV-Visible absorbance, thickness measurements, and quadratic increase of second harmonic generated light intensity as a function of film thickness. Films have been uniformly deposited up to 0.1 micrometer thick. The surface morphology, roughness, and film thickness have been characterized by Tapping Mode Atomic Force Microscopy (TM AFM ). Work is in progress to deposit thicker films of the same quality and to improve NLO figures of merit.

Devices consisting of hexa-alkoxythriphenylene derivatives as hole transport materials and 8-hydroxyquinoline aluminium (Alq3) as emitting layer with ITO as anode and magnesium as cathode are presented. Moreover X-ray diffraction studies of evaporated triphenylene films were performed leading to a better understanding of crystal structure, morphology and the alignment of the triphenylene molecules on the surface of the substrate.

The photodegradation of light-emitting polymers was studied by measuring the decay of the photoluminescence with exposure time to He-Cd laser beam at room temperature. It was found that the photoluminescence intensity decreases very fast initially, and then tends to saturate on the order of several tens of minutes. More interestingly, it was found that the degradation induced by laser beam can be self-healed. By stopping the exposure of the sample to the laser beam, the photoluminescence intensity recovers gradually without any treatment.

Optical properties of organic multilayer structures with type-I and type-II energy lineups with respect to the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energy levels were investigated and compared. The fast energy transfer followed by carrier confinement in the material with lower HOMO-LUMO energy difference was proved for the structures with type-I energy lineup, while the tendency of separation of excited states, i.e., electrons and holes generated in the excited molecules, was demonstrated for those with type-II. These results indicate that the luminescence dynamics of organic multilayer structures are well discussed in terms of HOMO and LUMO energy lineups similarly to valence and conduction band energies in inorganic semiconductors.

Tripodal ligand complexes of copper salts are described that display redoxdependent exciton coupled circular dichroism spectra. Significant spectral amplitude is observed at 400 nm in both solution and microcrystalline films. The synthesis and characterization of two new ligands and the preliminary characterization of the circular dichroism properties of their copper complexes is reported. The results constitute a significant step toward the development of molecules that can be used as on/off molecular switches.

Terrestrial digital photonic technology development will not satisfy all of the aerospace requirements since RF links are often required. Organic electro-optic devices are readily adaptable to RF functions into the 100 GHz and above frequency range. In addition to lossless links, they can be utilized for RF signal processing functions such as mixing, efficient harmonic generation and filtering. Devices can be densely packed with negligible cross talk.

In addition to the well known survivability requirements for space born applications (lifetime, reliability, thermal, shock, vibration and radiation hardness), issues of weight and power become dominant. Organic devices based on thin film technologies have an obvious potential advantage with respect to weight. However, integration with other optical and/or electronic components needs to be considered since connectors often dominated size and weight. Performance (when translated back into the electronic domain) scales as the optical power and device sensitivity squared. Thus, advances in device sensitivity can be nullified by increases in optical loss.

Films of end-substituted dihexyl-α-sexithiophene and –quinquethiophene were cast from solutions in aromatic solvents onto SiO2 and polyimide dielectrics at moderately elevated temperatures and reduced pressure. X-ray diffraction showed perpendicular orientation for most samples, while electron and optical microscopy revealed considerable variations in grain sizes, spacings, and uniformity depending on deposition conditions. For favorable morphologies, thin film transistor (TFT) mobilities were as high as those typically obtained from vacuum-deposited films, in the range of 0.01-0.2 cm2/Vs, with on/off ratios >1000 in accumulation mode.

We studied the low frequency noise in top-contact pentacene Thin Film Transistors (TFTs). The relative spectral noise density of the drain current fluctuations SI/I2 had a form of 1/f noise in the measured frequency range 1Hz - 3.5kHz.

Our studies of the noise dependencies on the gate-source VGS and drain-source VDS voltages showed that the dependencies differed from those observed for conducting polymers and resembled those reported for crystalline Si n-MOSFETs.

To compare the device noise level with those of other devices and materials, we extracted the Hooge parameter α. In order to calculate the total number of carriers we used a model simulating the device DC characteristics, similar to that for amorphous Si TFTs. The extracted Hooge parameter was 0.04. For an organic material this is an extremely small value, which is three orders of magnitude smaller that the Hooge parameter values reported for conducting polymers and only several times higher than the values for amorphous Si TFTs.

We report on a study of the complex dielectric permittivity in polyaniline (PAN), poly-o-toluidine (POT) and poly-o-ethylaniline (OPEA) in the undoped and weakly doped state in the frequency range 1 mHz upto 1 MHz. The doping concentration defined as y=[C1-]/[N] was chosen so that 0 ≤ y ≤ 0.07. OPEA with y=0.50 was also investigated. The objective of this work was to investigate the contribution of the mobile charge defects (polarons and bipolarons) on the conductivity and dielectric relaxation at such low doping levels. The three samples were chosen so as to compare the effects of introducing larger interchain disorder while maintaining a similar conduction mechanism. In all samples studied we observe the presence of a dielectric relaxation mechanism and the relaxation times depend on the doping level and disorder. The presence of a larger number of polarons as the doping level is increased leads to multiple paths for the system to relax leading to progressively non Debye like relaxation process. The results are interpreted in terms of creation and annihilation of polarons and bipolarons and their subsequent diffusion.

Fourier transform infrared (FTIR) spectroscopy is a powerful method to determine the doping induced structural changes and electronic band structure modifications of conjugated polymer films. Here, we report in situ attenuated total reflection (ATR) FTIR spectroelectrochemical results of reduction reactions (n-doping) of the conjugated ladder polymer polybenzimidazophenanthroline, BBL. The ATR-FTIR spectra are recorded in situ during continuous potential cycling of a BBL coated germanium reflection element in a three electrode spectroelectrochemical cell. The spectra and the structural changes during the reduction (n-doping) of the polymer film at different electrode potentials are presented. In contrast to most of the other conjugated polymers, this polymer shows four reversible redox reactions during n-doping, corresponding to various forms of BBL with different conductivities.

The demands of exponentially growing Internet traffic, coupled with the advent of Dense Wavelength Division Multiplexing (DWDM) fiber optic systems to meet those demands, have triggered a revolution in the telecommunications industry. In the three short years of deployment, DWDM performance has accelerated dramatically. Channel counts have grown from 4 to 80, with 170 announced, and channel spacings have shrunk from 400 GHz to 50 GHz. Practical systems that put 1 TeraBit/sec. of information on a fiber are now on the horizon. This dramatic increase has been built upon, and has driven, improvements in fiber optic component technology, which has in turn driven improvements in photonic materials. The next generation of systems for the “all optical network” will require higher performance components coupled with dramatically lower costs. One approach to achieve significantly lower costs per function is to employ Planar Lightwave Circuits (PLC) to integrate multiple optical functions on a single substrate leading to a single package. In this way multiple components can be fabricated and interconnected at once, significantly reducing both the manufacturing and the packaging/assembly costs. The manufacture of PLCs, however, places demanding requirements on materials, design and fabrication processes. Parameters such as index of refraction, absorption and birefringence must be tightly controlled. PLCs have been made using inorganic crystals, such as Lithium Niobate, oxide glasses or polymers on silicon substrates and semi-conductor materials, such as Indium Phosphide (InP). All except InP are commercially available. In this paper we give an overview of the applications of PLCs in DWDM fiber optic transmission systems and discuss how material's requirements flow down from end-use requirements. The specific example of the use of polymer based thermo-optic switches for reconfigurable Optical Add/Drop Multiplexer (OADM) applications is discussed.

Calamitic liquid crystalline photoconductors such as 2-(4'-octylphenyl)-6-butyloxynaphthalene (8-PNP-O4) and 2-(4'-octylphenyl)-6-dodecyloxynaphthalene (8-PNP-O12) exhibit fast ambipolar carrier transport in all the smectic mesophases up to 1.0 × 10−2 cm2/Vs. The structural defects of liquid crystals, i.e. domain boundaries and disclinations in domains, are electrically inactive and cause neither shallow nor deep defect states due to their fluid nature. It is illustrated that the carrier transport does not suffer from these structural defects in polydomain, by examining transient photo-currents in very thick liquid crystalline layers over 100μm. With an insight that this allowance of the polydomain structure and the fluidity of liquid crystalline photoconductors provides us new aspects in terms of electric property and application, e.g. multi-gap processing, the position detect sensor is demonstrated in a wedge cell filled of 8-PNP-O12, referring the position sensitive transit time of photo-induced transient current.

The present result indicates that the photoconductive liquid crystalline material is available for multi-gap structured devices.

A route to kinetically stable interfaces between dissimilarly doped conjugated polymers is proposed. The route relies on the use of internally compensated conjugated polymers to kinetically control interfacial redox chemistry. As a demonstration of the feasibility of the proposed route, the enhanced stability of an interface between an oxidatively doped, internally compensated poly(acetylene) and an undoped poly(acetylene) is reported.

This work focuses on single - and bilayers of para - hexaphenyl (PHP) and C60 grown by Hot Wall Epitaxy. A detailed study of the growth process was performed on glass, ITO and (001)- oriented cleaved mica substrates. The ordering of the layers was investigated by X-ray diffraction, showing clear diffraction peaks for layers grown on mica. The PHP layers grown on mica show high optical anisotropy (dichroic ratios up to 14 in emission) according to the polarization dependent photoluminescence experiments. The highly ordered structure is also reflected in the surface morphology of the layer as observed by atomic force microscopy. The epitaxial growth on mica is mirrored by the main alignment of the surface structure to the orientation of the mica substrate.