Micrometer- and Nanometer-Sized Polymeric Light-Emitting Diodes

A DNA and Self-Doped Conjugated Polyelectrolyte Assembled for Organic Optoelectronics and Bioelectronics

Deoxyribonucleic acid (DNA) and a self-doped conjugated polyelectrolyte, poly(4-(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl-methoxy)-1-butanesulfonic acid (PEDOT-S), are assembled for organic optoelectronics and bioelectronics. The DNA's helix-coil phase transition in water is studied as a function of composition by thermo-optical analysis. DNA and PEDOT-S are functionalized by using a surfactant, cetyltrimethylammonium chloride (CTMA), and DNA:CTMA, PEDOT-S:CTMA, and DNA:CTMA:PEDOT-S:CTMA complexes were characterized regarding thermal, optical, morphological, and structural properties. Finally, DNA and DNA:PEDOT-S mixtures are processed in water for fabricating organized films through brushing. The electrical properties of these films are characterized using an interdigitated electrode. The films show an electronic conductivity of ∼10^-6-10^-5 S/cm in a range of semiconductors.

Characterization of Solvent-Treated PEDOT:PSS Thin Films with Enhanced Conductivities

The conducting polymer of poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) is one of the most important and intensively investigated organic conducting materials. The PEDOT:PSS water dispersions with various concentrations of poly (4-styrenesulfonic acid) solution (PSSAS) were synthesized by 3,4-ethylenedioxythiophene (EDOT) in the presence of water. The fabrication of the solvent-treated PEDOT:PSS films through spin coating and solvent treatment processes was achieved with a solvent of pure water mixed with acetone (or MeOH, EtOH) in a ratio of 50:50. Moreover, both the organic solvent and water have synergetic effects while the PSS and PEDOT-attached PSS segments will form a coil-like and a linear (or extended-coil) structure, respectively. That may induce a stacking of the linear and planar PEDOT-attached PSS segments, which favors the formation of a crystalline phase. Finally, the maximum electrical conductivity of the PEDOT:PSS thin films with solvent treatment was investigated by means of X-ray diffraction (XRD) patterns and scanning electron microscope (SEM) images. Furthermore, we aimed to explain the synergetic effects of phase separation of the PEDOT:PSS thin films by both the organic solvent and water.

Organic Photovoltaics over Three Decades

The development of organic semiconductors for photovoltaic devices, over the last three decades, has led to unexpected performance for an alternative choice of materials to convert sunlight to electricity. New materials and developed concepts have improved the photovoltage in organic photovoltaic devices, where records are now found above 13% power conversion efficiency in sunlight. The author has stayed with the topic of organic materials for energy conversion and energy storage during these three decades, and makes use of the Hall of Fame now built by Advanced Materials, to present his view of the path travelled over this time, including motivations, personalities, and ambitions.

A step towards the processability of insoluble or partially soluble functional and structural variants of polymers based on 3,4-alkylenedioxythiophene

This work describes the processability of insoluble or partially soluble polymers based on 3,4-alkylenedioxythiophene.

Bis(diphenylamino)naphthalene host materials: careful selection of the substitution pattern for the design of fully solution-processed triple-layered electroluminescent devices

Two new triarylamine-based wide bandgap small molecules differing by the position of their substituents were investigated as hosts for solution-processed organic light-emitting diodes (OLEDs).

A Review of Patterned Organic Bioelectronic Materials and their Biomedical Applications

Organic electronic materials are rapidly emerging as superior replacements for a number of conventional electronic materials, such as metals and semiconductors. Conducting polymers, carbon nanotubes, graphenes, organic light-emitting diodes, and diamond films fabricated via chemical vapor deposition are the most popular organic bioelectronic materials that are currently under active research and development. Besides the capability to translate biological signals to electrical signals or vice versa, organic bioelectronic materials entail greater biocompatibility and biodegradability compared to conventional electronic materials, which makes them more suitable for biomedical applications. When patterned, these materials bring about numerous capabilities to perform various tasks in a more-sophisticated and high-throughput manner. Here, we provide an overview of the unique properties of organic bioelectronic materials, different strategies applied to pattern these materials, and finally their applications in the field of biomedical engineering, particularly biosensing, cell and tissue engineering, actuators, and drug delivery.

Conducting polymer nanofibers with controlled diameters synthesized in hexagonal mesophases

Conducting poly(diphenylbutadiyne) (PDPB) nanofibers with controlled diameters (5 to 25 nm) and relatively high conductivity were synthesized in soft templates using UV and gamma irradiation.

A rational design for the selective detection of dopamine using conducting polymers

A conducting polymer for the selective detection of dopamine has been designed by combining experimental measurements and theoretical calculations.

Highly efficient color-stable deep-blue multilayer PLEDs: preventing PEDOT:PSS-induced interface degradation

Highly efficient and stable blue light emission is observed in novel copolymers that are produced from specially designed building blocks. A PEDOT:PSS-induced chemical degradation of the polymer light-emitting diodes (PLEDs) is identified at the interface, and it is found to be accompanied by a shift in the emission color. A method to prevent this highly undesirable interaction is presented.

Kinetically driven self-assembly of a binary solute mixture with controlled phase separation via electro-hydrodynamic flow of corona discharge

This feature article describes a new and facile process to fabricate a variety of thin films of non-volatile binary solute mixtures suitable for high performance organic electronic devices via electro-hydrodynamic flow of conventional corona discharge. Both Corona Discharge Coating (CDC) and a modified version of CDC, Scanning Corona Discharge Coating (SCDC), are based on utilizing directional electric flow, known as corona wind, of the charged uni-polar particles generated by corona discharge between a metallic needle and a bottom plate under a high electric field (5-10 kV cm(-1)). The electric flow rapidly spreads out the binary mixture solution on the bottom plate and subsequently forms a smooth and flat thin film in a large area within a few seconds. In the case of SCDC, the static movement of the bottom electrode on which a binary mixture solution is placed provides further control of thin film formation, giving rise to a film highly uniform over a large area. Interesting phase separation behaviors were observed including nanometer scale phase separation of a polymer-polymer binary mixture and vertical phase separation of a polymer-organic semiconductor mixture. Core-shell type phase separation of either polymer-polymer or polymer-colloidal nanoparticle binary mixtures was also developed with a periodically patterned microstructure when the relative location of the corona wind was controlled to a binary solution droplet on a substrate. We also demonstrate potential applications of thin functional films with controlled microstructures by corona coating to various organic electronic devices such as electroluminescent diodes, field effect transistors and non-volatile polymer memories.

A new supramolecular hole injection/transport material on conducting polymer for application in light-emitting diodes

A new DNA-mimetic π-conjugated polymer poly(triphenylamine-carbazole) (PTC-U) has been prepared which exhibits high thermal stability, non-corrosion, excellent hole injection and electron-blocking abilities in the solid state owing to the uracil induced physical cross-linking. In addition, a trilayer device with PTC-U as a hole injection/transport layer is approximately 1.6 times higher than that of the commercial product PEDOT:PSS-based devices.

Zinc and Zinc Oxide Nanowires Grown on PEDOT:PSS/SiO2 Conductive Polymer Thin Films by Vapor Phase Transport Deposition

Easily available spin coating and vapor phase transport deposition techniques offer tremendous possibilities in fabricating inorganic/organic heterojunctions. We present here preliminary results from different thin film growth mechanisms including: i) PEDOT:PSS/Zn-nanowires/SiO2, ii) Zn-nanowires/PEDOT:PSS/SiO2, and iii) ZnO-nanowires/PEDOT:PSS/SiO2. The preliminary scanning electron microscopy and energy dispersive spectroscopy results show that Zn nanowires bond better to the non-annealed PEDOT:PSS thin films. It was also found that ZnO nanowires grow homogeneously on annealed PEDOT:PSS surfaces with colloidal Au nanoparticles as bonding reaction catalysts.

Coaxial nickel/poly(p-phenylene vinylene) nanowires as luminescent building blocks manipulated magnetically

A template-based strategy was developed which combines a wet-chemical technique and electrodeposition within nanoporous membranes. Morphological, structural and chemical characterization by means of electron microscopy and related techniques demonstrate unambiguously that coaxial nickel/poly(p-phenylene vinylene) (PPV) nanowires have been successfully synthesized. Moreover, modification of their optical and magnetic properties due to the nanoscale and the core-shell structure has been studied. The nickel-PPV nanowires exhibit a slightly blueshifted photoluminescence (PL), which is directly related to the tubular morphology of the PPV shell. The effect of the nickel core on the PL intensity of the PPV shell is discussed. The ferromagnetic behavior has been shown with the magnetization easy axis along the wire axis. These arrays of coaxial semiconducting polymer-metal nanowires embedded in a polymer membrane are interesting for flexible electronics and photovoltaic devices. Furthermore, their magnetic manipulation has been demonstrated, which opens the way to use them as multifunctional building blocks for bio-applications.