A series of conjugated polymers functionalized with different ruthenium polypyridine metal complexes were synthesized by the palladium catalyzed reaction. Two conjugated polymer systems have been studied: 1. poly(phenylenevinylene) with bis(2,2':6',2”-terpyridine) ruthenium (II) on the mainchain and 2. quinoxaline based polymers with tris(2,2'-bipyridine) ruthenium (II). The ruthenium polypyridine complexes exhibit a long-lived metal to ligand charge transfer excited state which can enhance the photosensitivity of the resulting polymers. Different physical properties such as the photoconductivity and charge mobility in these polymers are also studied.

A new technique for the deposition of amorphous organic thin films, low pressure organic vapor phase deposition (LP-OVPD), was used to fabricate organic light emitting devices (OLEDs) and optically pumped organic lasers. The OLED consisted of a film of aluminum tris- (8 hydroxyquinoline) (Alq3) grown on the surface of a film of N'-diphenyl-N,N'-bis(3- methylphenyl)1–l'biphenyl-4–4'diamine (TPD). Growth on both glass and polyester substrates was accomplished and the resulting heterojunction devices were found to have a performance similar to conventional, small molecular weight OLEDs grown using thermal evaporation in vacuum. The LP-OVPD grown OLED has an external quantum efficiency of 0.40 ± 0.05% and a turn-on voltage of approximately 6V. The optically pumped organic laser consisted of a film of Alq3 doped with the laser dye, benzoic acid, 2-[6-(ethylamino)-3-(ethylimino)-2,7-dimethyl-3Hxanthen- 9-yl]-ethyl ester, monohydrochloride (Rhodamine 6G). The laser output was centered at approximately 610nm and the lasing threshold was 30μJcm−2. The rapid throughput of LP-OVPD and its use of low vacuum in a horizontal reactor demonstrate its potential to facilitate low cost, roll-to-roll deposition of organic films for many photonic device applications.

A photolithographic technique to fabricate vacuum-deposited organic light emitting devices has been demonstrated. The photolithographically patterned, yet unpackaged devices show no sign of deterioration in room ambient when compared with devices fabricated using shadow masks. Furthermore, the environmental robustness of the encapsulated devices makes them particularly useful in fabricating high resolution, full color displays.

The moisture effect on the neutral and charged thiophene oligomers was investigated using ab initio methods. The influence of water molecules on the geometric relaxation of the neutral and charged tert-thiophenes is found to be important. The torsional distortion in neutral water/tert-thiophene complexes is larger than that of undoped or charged complexes. The relative orientation of the water molecule to thiophene changes dramatically upon the hole injection. The existence of water molecules in the polythiophene suppresses the hole mobility and, therefore, diminishes the efficiency of electroluminescence.

We provide a systematic and quantitative analysis of the design of flat panel displays (FPDs) based on organic light emitting devices (OLEDs). Key performance parameters are estimated for OLED-based displays; system issues, including addressing schemes and strategies required to achieve full color displays, are treated quantitatively. Furthermore, addressing schemes for recently demonstrated, full color, high resolution stacked OLEDs are discussed. Our analysis shows that OLED technology is suitable for many FPD applications, and can provide performance superior to that achieved using alternative display technologies.

Double-layer EL diodes composed of a spin-coated Polyvinylcarbazole (PVCz) layer and a vacuum-sublimed tris-(8-hydroxyquinoline)aluminum (Alq) layer were prepared. The diodes with the same device structure but with PVCz layer with added ionic impurities were also prepared. The diodes were driven at constant voltage and allowed to stand under short-circuit or reverse bias conditions. Observations of luminance-current density-voltage relations at constant voltage driving were repeated. The decrease of both luminance and current density during constant voltage driving were observed. Both spontaneous and reverse-bias assisted recovery of device performances were observed and these degradation and recovery phenomena were discussed in terms of the movement of ionic impurities in organic layers.

In the present contribution a new hole transporting molecule belonging to the triphenyldiamine family (N,N'-diphenyl-N,N'-bis(4-metylphenyl)- 1, 1'-biphenyl-4,4'- diamine) in a polycarbonate matrix is studied as the hole transport layer in a two layer device with Alq3 as emitting layer. The dependence of the electrical and emitting behaviour on the doping level is studied and compared with the vacuum deposited diamine layer also interfaced with Alq3

A soluble polyaniline (PANI) salt with moderate conductivity was synthesized by a novel emulsion polymerization process. The conductivity of the processed PANI films can be substantially increased by treating the polymer films with surfactants or with low molecular weight alcohols. Transmission electron microscopy (TEM) images of thin polymer films revealed the existence of small islands of conducting PANI embedded in a non-conducting, dopant matrix. The conductivity of the PANI films is affected by the spatial distribution and the connectivity of these small islands. The conductivity enhancement observed upon treatment with surfactants is due to self-assembly of conducting PANI molecules into an interconnected network morphology. In the case of alcohol treatment the film conductivity is enhanced due to extraction of excess dopant phase and the subsequent densification of PANI islands to form highly conducting pathways.

An experimental procedure which can provide a direct quantitative measure of contact injection efficiency into a trap free transport polymer is described. This technique combines coupled analyses of bias dependent injection current supplied by the contact under test with time-of-flight drift mobility measurements carried out on the same specimen film. This general procedure has been used in a broad range of experiments to evaluate the injection efficiencies from a series of hole injecting contacts of differing work functions into the molecularly doped polymer, TPD/Polycarbonate Two key results are emphasized: (1) Injection efficiency does scale on average with the interfacial barrier, the energy step estimated from substrate workfunction and MDP electrochemical data. In individual cases however, large variations about the norm are clearly identified and can be attributed to variations in the contact surface prior to coating, for example the relative degree of oxidation or, as TOFSIMS reveals, the interdiffusion of metal atoms from adhesive layers which secure the metal coating to a Si wafer substrate. (2) For the case of Au, the injection efficiency of a Au substrate was compared to the behavior of Au vacuum deposited onto the already formed coating under a variety of conditions. The injection efficiency from Au evaporated onto preformed coating initially varies with deposition conditions but relaxes with time under ambient conditions, eventually becoming ohmic. Significant details of this relaxation behavior are described and analyzed in an accompanying paper.

A trap-free Molecularly Doped hole-transport Polymer (MDP) provides a model system for the study of metal/polymer interfaces by enabling the use of a recently developed technique that supplies a quantitative measure of contact injection efficiency. The technique combines fielddependent injection current measurements from a contact under test with time-of-flighl (TOF) mobility measurements on the same sample. In the present case, MDP films were prepared with two top vapor-deposited contacts, one of Au (test contact) and one of AI (for TOF), and a bottom carbon-loaded polyimide electriode. An unusual phenomenon is investigated whereby injection from Au is initially blocking, evolving to ohmic over time. This contrasts with the behavior expected according to the relative work-functions of Au and of the polymer whereby Au should inject holes efficiently. The samples were aged at various temperatures below the glass transition of the polymer (85°C) and the evolution of current-field measurements and of capacitance is followed in detail over time and analyzed. All Au contacts eventually achieved ohmic injection. Rapid sequence data acquisition enabled the separation of two main processes in the injection evolution. Control measurements ensure that the evolution of the electrical properties is due to the Au/polymer interface behavior and not the bulk. The behavior of Au contacts evaporated under various deposition conditions was compared. Transmission electron microscopy results at the Au/MDP interface were obtained as both a function of time and of deposition conditions. Mechanisms operating at the interface of the evaporated Au films on the polymer are discussed.

In the course of the preparation of conductive molecular crystals using ‘percyano anions’, the molecular structure of HCDAH2- was revealed to be a planar geometry having a long diagonal line (≈ 10.4 Å). In (TTF)2(HCDAH)(CH3CN) [block-shaped TTF complex] (triclinic, P1, a = 8.258(5), b = 9.572(6), c= 10.070(4) Å, α = 89.89(5), β = 70.76(4), γ = 80.76(5)°, V = 740.7(7) Å3, Z = 2, final R-value = 0.074), the face-to-face type overlap between the side-byside arranged HCDAH dianions was observed. The donor packing pattern in (BEDOTTF) 6(HCDAH) (monoclinic, P21/a, a = 20.243(3), b = 4.086(1), c = 16.820(4) Å, b = 99.45(1)°, V = 1372.4(5) Å3, Z = 2/3, final R-value = 0.048) was determined to be HCP-type which is the second example in BEDO-TTF complexes.

Poly [2,5-thienylene vinylene] (PTV) has been studied extensively over the past decade for both its metallic conductivity behavior upon chemical doping, as well as its interesting third order nonlinear optical properties. PTV oligomers have been synthesized by our group 1, as well as others 2, and the formation of polaron-like radical-cations or bipolaron-like dications by oxidative doping has been demonstrated. In this paper we describe a general synthetic approach to PTV oligomers functionalized for copolymer formation by step-growth reaction.

The use of conducting polymers for corrosion prevention is an area which has gained increasing attention during the last decade [1]. This study explores the use of polyaniline based polymer coatings for corrosion prevention on mild steel. Data on coating degradation and passivation on electrochemically polarized painted metal specimens exposed to acid chloride solutions and artificial seawater at an ambient temperature are presented. A Systematic comparison between controls and designated coated sample sets has been made to demonstrate good corrosion protection efficiency with synergistic effects between conductive polymers and metals by classical DC monitoring techniques. Brief comparisons are made with data from simulated marine exposure. Meanwhile, in separate experiments, electrochemical data were obtained for conductive polymer primer coatings with epoxy top-coat under fully immersed conditions by using electrochemical noise (ECN) monitoring and scanning electrochemical microscopy (SECM) techniques to discover the initial localized corrosion phenomena in order to achieve further understanding of the protection mechanism. Additionally, electrochemical impedance (EIS) spectra were utilized for the assessment of anti-corrosion performance provided by conducting polymers to mild steel.

The organic donor tetrathiafulvalene (TTF, 1) and its derivatives are synthesized from tetrathianaphthalene (TTN, 2) in a one pot reaction. The reaction takes advantage of an isomerization of lithiated TTN into lithiated TTF and subsequent substitution with novel disulfide electrophiles yielding substituted T donors. The isomerization approach eliminates the need for a chemical coupling reaction of oxones or thiones (a yield limiting procedure), and simple byproducts eliminate the need for tedious purification. The novel methodology allows for a high yield preparation of bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF, 3a, 80%) and bis(propylenedithio)tetrathiafulvalene (BPDT-TTF, 3b), previously unavailable directly from TTF. A high yield of bis(phenylenedithio)tetrathiafulvalene (BPhDT-TTF, 3c, unavailable from dimercaptoisotrithione “DMIT”) is also achieved using the synthetic scheme. The method is general, and can be used to prepare a variety of novel organic donors based on TTF. Synthetic procedures along with all relevant characterization are presented.

A series of poly(N-alkylpyrrylene vinylenes)( alkyl = methyl(l), hexyl(2), dodecyl(3)) have been synthesized from the monomer, N-alkyl-2,5-bis(thiophenylmethylene)pyrrole, by base induced elimination and polymerization. The resulting deep purple conjugated polymers (2, 3) were soluble in a variety organic solvents. The electrical conductivities of the polymers lie in the range, 10−2 to 2.5 S/cm. The highest yield was obtained when the polymers were synthesized in refluxing THF with a monomer/ base mole ratio of 1/4. The optical band gap of the undoped polymers were 1.89 eV(1), 1.69 eV(2) and 1.65 eV(3). Characterization of the polymers includes IR, CV, 1H and 13C NMR, UV-vis spectroscopy, TGA and molecular weight studies.

We have synthesized a novel conjugated polymer containing terpyridine receptors. This conjugated, polymer-based fluorescent chemosensory system exhibits unusually high sensitivity toward transition metal ions (∼-10−9 M). The fluorescence quenching response of the terpyridine containing conjugated polymer to transition metal ions is related to a facile energy migration in which energy from absorption of a photon, can migrate through the conjugated polymer system and be quenched by trapping sites. Terpyridine receptors can readily bind to transition metal ions and create a low lying Metal to Ligand Charge Transfer (MLCT) state which can act as an excitation trap.

The alkoxycarbonylmethylurethanes of 9-(N-methyl-N-phenylamino)-5,7-nonadiyn-l-ol were synthesized and polymerized by 60Co gamma radiation. The resulting polydiacetylenes (PDA) are soluble, processable, and self-assemble into an acentric array. These PDAs are susceptible to postpolymerization functionalization via its dialkylaniline and ester groups, and hence comprise the most versatile PDA system for systematic chemical modification reported to date. Dialkylaniline functionalization via tetracyanoethylene and diazonium salt coupling led, respectively, to materials with interesting second order nonlinear optical properties and that exhibit directly photofabricated regular surface relief gratings. The latter materials provide the first example of a rigid rod polymer (lacking a detectable glass transition) to exhibit such phenomena. Moreover, these PDAs can form self-assembled multilayer structure in water by ester hydrolysis.

In the interest of obtaining crystalline polydiacetylene with absorption at longer wavelengths, new derivatives of 2,4-hexadiyne with planar, visible absorbing aromatic chromophores have been designed, synthesized, and thermally polymerized. The resulting polymers have a red shifted maximum with absorption extending to the infrared. Their Raman spectra show the usual polydiacetylene ene-yne structure, and X-ray powder diffraction reveals that the new polymers are crystalline.

Hole transporting properties and energy barriers at organic-organic interfaces relevant to electrophotographic and organic electroluminescent (EL) devices are described. Three wellknown hole transporting molecules, 1,1-bis(di-4-tolylaminophenyl)cyclohexane (TAPC), N,N′- diphenyl-N,N′-bis(1 -naphthyl)-(1,1 ′-biphenyl)-4,4′-diamine (NPB), and N,N,N′,N′-tetrakis(4- tolyl)-(1,1 ′-biphenyl)-4,4′-diamine (TTB) are used in this study. The ionization potentials (IP) and oxidation potentials (Eox) of these materials are determined by photoemission spectroscopy and electrochemical measurements, from which a conversion formula is obtained (IP ∼ 4.5 eV + eEox). Hole transport across organic-organic interfaces is investigated by time-of-flight transient photocurrent techniques. The efficiencies of hole injection are consistent with the energy barriers, when present, at these interfaces.

We have investigated the temperature dependence of the dynamics of radiative excited states in pristine thin films of tris(8-hydroxyquinoline) aluminum (Alq3). By measuring the transient photoluminescence (PL) response with subnanosecond resolution, our results revealed an increase in the radiative excited state lifetime and fluorescence quantum yield with decreasing temperature from 300K to 77K. At low temperature we observed a decrease in the bimolecular recombination rate constant, singlet exciton diffusion coefficient and diffusion length. A singlet exciton trapping model is used to explain these results.