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Organic Electronics is an interdisciplinary and cutting-edge research field leading to innovative applications and products like ultra-thin and high-efficient organic LED displays, light-weight and transparent organic solar cells or printed organic field-effect transistors (to name only few). The core functional materials in such devices are organic (semi-)conductors like conjugated polymers, oligomers or small molecules. As a sequel to our former contribution in the World Journal of Chemical Education (Vol 6, No. 1), we present in this paper a hands-on, quick and easy experiment for the synthesis of the (semi-)conductive polymer PEDOT:PSS. This experiment can be integrated into laboratory trainings and enriches the portfolio for teachers and lab-instructors dealing with organic electronics.

We report on bulk structures of a family of quaterthiophene (4T) derivatives with linear and branched end groups such as α,α′-dihexylquaterthiophene (Hex-4T-Hex), α,α′-didecyl-quaterthiophene (Dec-4T-Dec) and α,α′-bis(2-ethylhexyl)quaterthiophene (EH-4T-EH), tetramethyldisiloxane-based dimers D2-Und-4T-EH and D2-Und-4T-Hex, and carbosilane-siloxane-based tetramers D4-Und-4T-EH and D4-Und-4T-Hex. The dimers and tetramers contain undecylenic (Und) spacers between the disiloxane and 4T- units of the molecule. The impact of the molecular architecture on the bulk structure at different temperatures is addressed with X-ray diffraction and differential scanning calorimetry. For all of the studied quaterthiophene-containing organosilicon multipods the formation of 4T-crystal sublattice is observed. The alkyl periphery plays an important role in the molecular packing and thermal stability of the ordered phase. They can stabilize or destabilize the crystal phase, depending on their length and architecture. The quat...

Niobium nitride thin films are deposited on 2″ silicon (100) wafers using a modified industrial metal-organic (MO) CVD reactor of the type AIX-200RF, starting from tert-butylamido-tris-(diethylamido)-niobium (TBTDEN) and ammonia. Films of thicknesses 50-200 nm are deposited at temperatures ranging from 400 °C to 800 °C under reactor pressures of 1 and 5 mbar using various ammonia flow rates, and are characterized by the use of complementary techniques, namely X-ray diffraction (XRD), scanning electron microscopy (SEM), secondary neutral mass spectrometry (SNMS), Rutherford backscattering spectrometry (RBS), X-ray photoelectron spectroscopy (XPS), and electrical measurements. Films deposited above 450 °C consist of the cubic δ-NbN phase, apart from the presence of Nb-O and Nb-O-N species predominantly in the outermost film regions. The lowest specific resistivities, determined by four point probe measurements, are in the range 500–600 µΩ cm. A NbN/SiO2/p-Si gate stack is fabricated using the grown niobium nitride films. From the capacitance-voltage (C-V)-curves, flat-band voltages are extracted which, when plotted against SiO2-insulator thickness, yield a work function of 4.72 eV for as-deposited films.

Niobium nitride films were deposited on Si(100) substrates using tert-butylamido-tris-(diethylamido)-niobium (TBTDEN) as the precursor in a commercial state-of-the-art MOCVD reactor. The depositions were carried out in the temperature range 400 - 800oC and the films were characterized for their crystallinity by X-ray diffraction (XRD) and surface morphology by scanning electron microscopy (SEM). Composition studies by secondary neutral mass spectrometry (SNMS) revealed that the films to be stoichiometric niobium nitride with very low concentrations of carbon or oxygen as impurities. Electrical characterization showed that the specific resistivity was strongly dependent on the substrate temperature during deposition. Furthermore, the work function of the as-deposited niobium nitride films and forming gas annealed films were determined.

Elektronische Bauelemente preisgunstig zu drucken statt aufwendig lithographisch zu strukturieren, ist ein Ziel der Polymerelektronik. Leitende, halbleitende und isolierende Kunststoffe stehen zur Verfugung, doch wartet auf dem Weg zu „Plastik-Chips” noch eine ganze Reihe von Aufgaben auf Synthese- und Polymerchemiker, Oberflachen- und Halbleiterphysiker sowie Prozessentwickler.

The design, synthesis, and properties of a novel, solution-processible organic semiconductor based on star-shaped oligothiophenes linked through flexible aliphatic branches to a carbosilane core are described. This four-arm dendrimer-like molecule not only forms smooth thin films on large surfaces but also shows improved monolayer formation compared to its linear prototype, α,α‘-dihexylquaterthiophene (Hex-4T-Hex). For the new material, three different types of structural organization (nanowires and mono- and multilayers) were found, all of which are favorable for charge transport through the material in organic field-effect transistors. These processability and structural properties, in combination with high field-effect mobility, high current modulation, and a threshold voltage of ∼0 V, suggest that star-shaped oligothiophenes with carbosilane cores are a promising new class of semiconducting materials for use in flexible organic electronics.

The efficient synthesis of decyl-end-capped thiophene−phenylene oligomers with different numbers and positions of 1,4-phenyl rings within a 2,5-oligothiophene conjugated chain, leading to electronic-grade pure semiconducting organic materials with improved oxidation stability, was elaborated. These are p-type organic semiconductors, showing high charge-carrier mobilities up to 0.4 cm2/Vs and on/off current ratios as large as 105 in organic thin-film transistors, as well as stage delays as low as 300 μs in the integrated circuits (ring oscillators). Long decyl end chains in these oligomers having 5−7 conjugated aromatic rings lead to limited solubility but improve the oligomers' crystallinity, making them promising semiconducting materials for organic electronic devices prepared by vapor evaporation. Investigation of the optical properties of the oligomers showed that they have a HOMO−LUMO energy gap approximately 0.2 eV higher than that of the corresponding oligothiophenes. Electrochemical measurements re...

The efficient synthesis of 1,4-bis(5-decyl-2,2′-bithien-5-yl)benzene, leading to “electronic-grade” pure semiconducting organic material, was elaborated. Cyclovoltamperometry measurements showed high oxidation stability of the thiophene-phenylene oligomer as compared to corresponding oligothiophenes. OTFT and integrated circuits, based on the synthesized oligomer, showed the mobilities as large as 0.3 cm2/Vs, on/off current ratios as large as 105, and signal delays as low as 300 μs (measured with ring oscillators). AFM measurements confirmed improved morphology of the oligomer films obtained by vacuum evaporation on room temperature substrates.

A voltabsorptometry study of the redox behavior of poly(3,4-ethylenedioxythiophene) films in tetrabutylammonium tetrafluoroborate solutions in acetonitrile shows the polymer to exhibit heterogeneous properties when both reduced and oxidized. The measurements are taken at characteristic wavelengths λ selected on the basis of stationary absorption spectra. The reduced polymer's heterogeneity is explained under the assumption that the polymer contains simultaneously linear (λ = 530 nm) and spiral (λ = 660 nm) structures. The formation of two oxidized polymer states is proved experimentally. Both states presumably result from strong (λ = 880 nm) and weak (λ = 1050 nm) interactions between the anion and the positively charged polymer chain. The oxidized 880-nm state is shown to arise from the 660-nm state, whereas the 1050-nm state forms of the 530-nm state.

Films of poly(3,4-ethylenedioxythiophene) (PEDT) are synthesized during anodic polarization from a water-acetonitrile mixture containing sulfo-cationite MF-4SK and without it. A comparison of electrochemical and spectroelectrochemical characteristics of the films and an elemental analysis evidence the formation of composite PEDT–MF-4SK. The immobilization of the polymer anion in the PEDT matrix is shown to alter its oxidation mechanism. For a neutral composite film, this mechanism includes the exit of sulfo-cationite cations and the entering of supporting anions.

We have designed and successfully synthesized star-shaped oligothiophenes, which could be used as semiconducting materials for solution-processible organic field-effect transistors (FETs). By systematically changing the chemical structure of the star-shaped oligothiophenes we obtained the structural requirements needed for making working FETs from them. UV-vis fluorescence measurements showed that a molecule of the star-shaped compounds under consideration is not a fully conjugated molecule, but it has three independently conjugated oligothienyl-phenylene blocks. A possible scheme of molecular packing of the star-shaped oligothiophenes in a lamellar structure was proposed and confirmed by atomic force microscopy (AFM) and X-ray diffraction (XRD) measurements. Although the star-shaped semiconductors show a somewhat lower mobility than their linear analogs, they possess better solubility and film-forming properties, leading to improved spin-coating processing. The best FETs were made by spin-coating 1,3,5-tris(5″-decyl-2,2′:5′,2″-terthien-5-yl)benzene from a chloroform solution, which resulted in a mobility of 2 × 10–4 cm2 V –1s–1, a 102 on/off ratio at gate voltages of 0 V and –20 V, and a threshold voltage close to 0 V.

Homopolymers based on 3,4-ethylenedioxythiophene (EDT) and bi(3,4-ethylenedioxythiophene) (BEDT) and polylayer compositions polymerized anodically from these precursors and bithiophene (BT) were studied electrochemically and spectroelectrochemically. The homopolymers obtained from EDT and BEDT were shown to have practically the identical properties although their polymerization potentials differ significantly. At close potentials, a true copolymer based on EDT and BT was formed. At different polymerization potentials (BEDT–BT system), a composition including numerical thin (up to 10 nm) polymeric layers was obtained potentiodynamically. In the electro- and spectroelectrochemical properties, this composition was like the true EDT–BT copolymer that was explained by the precursor copolymerization and the incorporation of one polymer into another. Independently of the polymerization potentials (EDT–BT, BEDT–BT systems), a composition from two- or four-thick (tens and hundreds nanometers) layers can be obtained galvanostatically. The first layer in such heterostructure always keeps the properties of its homopolymer. The properties of the second layer depend on the conductivity of the first layer in an oxidation region of the second layer. The first conducting layer facilitates the redox transformation of the second layer as compared to its homopolymer while the first isolating layer hinders this process.

We have fabricated organic thin-film transistors and integrated circuits based on the small-molecule organic semiconductors α,α′-didecylquaterthiophene, α,α′-didecylquinquethiophene, and α,α′-didecylsexithiophene. The organic semiconductors were deposited by thermal evaporation, with solution-processed and cross linked poly-4-vinylphenol serving as the gate dielectric layer. We have found that bottom-contact devices based on these materials have better electrical performance than top-contact devices, presumably due to more efficient carrier injection from bottom contacts due to the presence of the relatively long alkyl chains substituted at the α- and ω-positions of the oligothiophene molecules. Bottom-contact transistors have carrier mobility as large as 0.5 cm2/V s and on/off current ratio as large as 105, and ring oscillators fabricated using bottom-contact transistors and α,α′-didecylsexithiophene as the organic active layer have signal propagation delay as low as 30 μs per stage.

We discuss some recent findings relating to the structure of interfaces in semiconducting polymer devices. The structure of three different types of interface is characterized via neutron reflectivity and scanning force microscopy. In the first example we find that enrichment of dopant occurs at the surface of a doped polymeric conductor, and that this enriched layer penetrates several nanometres into the material. Secondly, we find that the interface between a semiconducting polymer and an insulating polymer is not molecularly sharp, but is rather broad with a width typically of the order of 1 nm. Finally we present some initial neutron reflectivity measurements on the interface between two different semiconducting polymers (one of which is deuterated). Again we find that this interface is diffuse, with a typical width of the order of a few nanometres.

α,α′-Didecylquater-, -quinque- and -sexi-thiophenes were synthesized by Kumada cross-coupling and oxidative coupling reactions. For the former reaction Pd(dppf)Cl2 was found to be a more efficient catalyst than the usually applied Ni(dppp)Cl2. Thermal behaviour of all new oligothiophenes was investigated by differential scanning calorimetry and polarizing optical microscopy. It was shown that all these compounds possess not only crystal phases but also high temperature ordered smectic mesophases and that the clearing point increases linearly with the number of conjugated thiophene rings. A degree of order in the crystal phase was estimated on the basis of thermodynamic data. The highest degree of order was proposed for α,α′-didecylquaterthiophene, which explains why the mobility of end-α,α′-capped quaterthiophenes in FET (field effect transistor) devices is comparable or sometimes better than those of corresponding quinque- and sexi-thiophene derivatives.

A short survey of technological aspects of electrochromism with various electroactive species is given. Different approaches with inorganic and organic materials have been pursued in the past. So far widespread usage of this technology for large area applications has not been achieved. Nevertheless one major technical product, self-darkening rear-view mirrors for cars, is already well established. This article reviews some research results on electroactive polythiophenes, especially poly(3,4-alkylenedioxythiophenes). Some promising results with the commercially available electrically conducting polymer Baytron P (PEDT/PSS) are presented. It is demonstrated that an all solid-state electrochromic multilayer assembly based on a polymeric electrochromic material might be close to technical realization. The coating of large area substrates with aqueous poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) dispersion can be a way to an economically viable product.

Organic light-emitting diodes fabricated by subsequently spin-coating two layers-a hole-transporting followed by a metal chelate emissive layer - onto poly(3,4-ethylene-dioxythiophene)/poly(styrenesulfonate) are presentedfor the first time. The electron-hole recombination occurs in a layer consisting of Ga complexes (see Figure), which exhibit high fluorescence quantum yields, and their emission spectra are blue-shifted relative to that of tris(8-hydroxyquinoline) aluminum. By doping this spin-coated emission layer with fluorescent emitters the emission band can be shifted within the visible spectral range.

Light-emitting diodes have been prepared by depositing three organic layers successively by spin-coat and evaporation techniques. The first layer of PEDT/PSS smoothens the ITO surface, reduces the probability of electrical shorts and is beneficial for a high overall yield of the operating devices. Above all, this layer promotes hole-injection as an important parameter for higher efficiencies and prolonged operation life. The second layer of spin-coated dendritic phenylamines (TDAPB) with high glass transition temperature modulates the injection of holes into the emitting layer, formed by evaporated Alq. By comparing characteristics and operation lifetime data of devices with and without PEDT/PSS it is shown that the combination of polymeric and monomeric organic layers leads to highly efficient devices, opening new ways to modify device architectures.

Starting from its early days about 10 years ago, the OE-A roadmap has constantly reported technical progress for organic and printed electronics. Based on data gathered from several expert groups, the OE-A biannually publishes an updated version. As a technology roadmap, it has been a strategic tool for OE-A members to synchronize efforts for research and development. This article highlights the 6th edition of the OE-A roadmap and links its content to global trends and dynamics of existing markets. The 'organic growth path' stated by the OE-A roadmap required a complex roadmapping process to consider technology movements in established markets and the development of new markets. Exemplified by selected applications, this article explains the complexity, challenges and benefits of the roadmapping process and links the real OE-A roadmap to roadmapping concepts.

Die Hartung von 4-Phenyl-4-(2,3-epoxypropoxy)benzoat (I) mit den isomeren Aminophenylaminobenzoaten II bis V fuhrt zu unterschiedlich geordneten Epoxidnetzwerken. Die Bildung verschiedener Intemediate wahrend der Hartungsreaktion wurde anhand von Modellverbindungen studiert. Aus der Reaktion der monoamino-substituierten Phenylbenzoate VI bis IX mit Epoxid wurden die Reaktionskostanten fur die Addition an das primare und das sekundare Wasserstoffatom der Aminogruppen bestimmt. Die kinetischen Daten lassen sich fur eine schrittweise Simulation des Hartungsverlaufs verwenden. Es wurden Argumente dafur gefunden, das sich bei Verwendung der Amine mit 4-Aminobenzoat-Strukturen gut geordnete, schnell vernetzende Intermediate bilden. 4-Phenyl-4-(2,3-expoxypropyl)benzoate (I) can be cured to thermoset networks with a different degree of order by using isomeric aminophenyl aminobenzoates II to V as curing agents. The formation of intermediates during the curing reaction was studied by means of model compounds. From the reaction of the monoamino-substituted phenylbenzoates VI to IX the reactivities for the primary and the secondary aminoprotons towards epoxide was determined. The kinetic data were used for a stepwise simulation of the curing reaction. Arguments were found that in case of diamines with 4-aminobenzoate structure well ordered intermediates are formed, which crosslink in an early stage of the reaction.

The irradiation of a variety of substituted cyclobutene-1,2-diones in the presence of cyclopentadiene leads to the formation of 1:1 adducts which contain the baric 5-spirocycyclopropyl Δ α,β -butenoliide unit. The structural similarity of these adducts to those produced originally upon irradiation with benzocyclobutene-1,2-dione in the presence of olefins suggested a possible common mechanism involving the formation of a ring-expanded oxacarbene intermediate

Unsymmetrical dimethylchlorosilyl-substituted α, α′- dialkylquater-, quinque-, and sexithiophenes were designed and successfully synthesized by a combination of Kumada and Suzuki cross-coupling reactions followed by hydrosilylation. Optimization possibilities of the hydrosilylation of low-soluble linear oligothiophenes by dimethylchlorosilane as well as the nonreactive byproducts formed are described. The molecular structures of the obtained dimethylchlorosilyl-functionalized oligothiophenes were proven by NMR and DCI MS techniques. These compounds were found to be stable and reactive enough, even in the presence of the nonreactive byproducts, to form semiconducting monolayers on dielectric hydroxylated SiO2 surfaces by self-assembly from solution. The semiconducting properties of these oligothiophene SAMs were as good as those of bulk oligothiophenes. This allowed the production of stable, even under ambient conditions, SAMFETs with a mobility of up to 0.04 cm2/(V s) and an on/off ratio up to 1 × 10 8. © 2010 American Chemical Society.

In this chapter different types of conjugated organosilicon materials possessing luminescent and/or semiconducting properties will be described. Such macromolecules have various topologies and molecular structures: linear, branched and hyperbranched oligomers, polymers, and dendrimers. Specific synthetic ap- proaches to access these structures will be discussed. Special attention is devoted to the role of silicon in these structures and its influence on their optical and electri- cal properties, leading to their potential application in the emerging areas of organic and hybrid electronics.

The introduction of mesogenic groups in main- and sidechains of epoxy thermosets results in an ordered multiphase network with cellular structure, if gelation occurs below the maximal cure temperature Tmax. Tmax is individual for a given combination of monomers. The multiphase network consists of relatively soft anisotropic cell nuclei and hard isotropic cell walls. If gelation occurs above Tmax single phase networks are obtained. The size of the cell nuclei strongly depends on the used monomers and varies up to two orders of magnitude. The multiphase structure was found to have no impact on the tensile elastic modulus.

Organic electronics open new fields of applications requiring large-area coverage, structural flexibility, low-temperature and low-cost processing. A key for this technology is access to suitable materials. Progress in conducting and semiconducting materials for organic electronics will be reported. Highly conductive PEDOT-grades have been developed for high resolution printing. Linear oligomeric and star shaped oligothiophenes will be discussed. These materials show outstanding carge carrier mobility and environmental stability when deposited from vacuum deposition. After fine tuning the deposition parameter by ink jet printing we also obtained transistors with excellent properties. The concept of "flexible core" star shaped oligothiophenes will be discussion which might be a way to combine both, high charge carrier and wet processing.

Self- assembly - the autonomous organization of components into patterns and structures(1) - is a promising technology for the mass production of organic electronics. Making integrated circuits using a bottom- up approach involving self- assembling molecules was proposed(2) in the 1970s. The basic building block of such an integrated circuit is the self- assembled- monolayer field- effect transistor ( SAMFET), where the semiconductor is a monolayer spontaneously formed on the gate dielectric. In the SAMFETs fabricated so far, current modulation has only been observed in submicrometre channels(3-5), the lack of efficient charge transport in longer channels being due to defects and the limited intermolecular pi-pi coupling between the molecules in the self-assembled monolayers. Low field- effect carrier mobility, low yield and poor reproducibility have prohibited the realization of bottom- up integrated circuits. Here we demonstrate SAMFETs with long- range intermolecular pi - pi coupling in the monolayer. We achieve dense packing by using liquid- crystalline molecules consisting of a pi- conjugated mesogenic core separated by a long aliphatic chain from a monofunctionalized anchor group. The resulting SAMFETs exhibit a bulk- like carrier mobility, large current modulation and high reproducibility. As a first step towards functional circuits, we combine the SAMFETs into logic gates as inverters; the small parameter spread then allows us to combine the inverters into ring oscillators. We demonstrate real logic functionality by constructing a 15- bit code generator in which hundreds of SAMFETs are addressed simultaneously. Bridging the gap between discrete monolayer transistors and functional self-assembled integrated circuits puts bottom- up electronics in a new perspective.

Pentacyclo[6. 4. 02, 4. 03, 10. 07, 9]dodeca-5, 11-diene(4) is proposed as new potential precursor of the truncated tetrahedrane 1. The synthesis of several new pentacyclo[5. 4. 0. 02, 4. 03, 9. 06, 8] undec-10-ene (4, 5-homosnoutene) derivatives including homosnouten-5-one(10), 5-methylidenehomosnoutene(19a) as well as homosnoutene-5-carb-aldehyde(17b) and their reactions directed toward ring enlargement to the skeleton of 4 are reported. Although all the homosnoutenes resisted ring expansions, several unexpected new polycyclic systems were obtained. Any intermediate developing a cationic center at C(5) of the skeleton of 10 rearranged with release of strain and opening of one or both three-membered rings to give compounds such as 22 and 23. The aminomethyl derivatives 13a and 13b, upon diazotation, underwent a remarkable fragmentation to give 10 and homosnouten-5-o1(20), respectively. The 5-(dibromomethyl) homosnouten-5-o1(14), upon treatement with t-BuLi, rearranged to the pentacyclic ether 15, while the carbine 11b, generated by the thermal or photochemical decomposition of the tosylhydrazone salt of 17c, solely gave 19a by C, H insertion. The 1, 1-dicyclopropylethene unit in 19c was excited selectively upon irradiation, but the products 26 and 27 of this photochemical rearrangement were derived only from n-participation in diradical intermediates 25a-25c.

Polishing slurries for the copper chemical mechanical planarization (CMP) process consist of a complex composition of highly stable nanoparticle suspensions in the presence of chemical additives for etching and protecting the surface. The target of such dispersions is to achieve perfectly smooth surfaces of low topography. Key factors are the surface roughness, local geometry and total flatness of the whole wafer. Surface defects like scratches, dishing, etching and erosion e.g. due to strong particle adsorption, aggregates or chemical impact have to be avoided. Particle wafer interactions between silica particles of a silica CMP-dispersion and a copper wafer surface were analyzed by electron cpectroscopy for chemical analysis (ESCA), scanning electon microscopy (SEM) and zetapotential-measurements. The colloidal stability of the silica dispersion over a broad pH-range of 2.3 to 9.8 was analyzed in the presence of Na+-, Mg2+-, Cu2+-, and Al3+-ions in terms of the critical coagulation concentration (CCC), change in particle size and pH. Silica particles strongly and irreversibly adsorbed to the predominantly oxidic copper wafer surface at pH 2.3 but not at pH > 4. Over the whole pH-range a high colloidal stability was observed with a maximum at pH 2.3. CCC-values of 100–300 mmol/L versus Cu2+ were obtained. Even at high pH of 9.8, the behaviour could not be explained by the Derjaguin- Landauer-Verley-Overbeek (DLVO) theory. In the presence of Cu2+-ions a higher colloidal stability compared to divalent Mg2+-ions was observed at high initial slurry-pH of 9.8. Due to the acidic reaction of Cu2+ in the aqueous environment, the pH was reduced to 2–3, where colloidal silica showed the highest stability. Even at high removal rates in the polishing process of 1000 nm/min, the released Cu2+-concentration (40 mmol/L) was lower than the critical coagulation concentration (100 mmol/L).

We have studied the photocurrent decay under gate bias in organic thin-film transistor (OTFT) using inkjet printed α,ω-dihexylquarterthiophene layer. The OTFT shows high photocurrents under light illumination and very slow decay of photocurrents under positive gate voltage. This is due to the gate voltage-controlled trapping and detrapping of the electrons near the interface. With increasing exposure time, more electrons are trapped and thus make the photocurrent decay slower. It is found that there is a power-law dependence between light exposure time and decay time constant.

The conducting polymer poly(ethylene-dioxythiophene)/poly(styrenesulfonic acid) [PEDOT:PSS] has matured from an antistatic coating into many more elaborated applications within the past decade. Here we report on our ongoing work towards replacing transparent conducting oxides (TCO) layers by highly conducting PEDOT:PSS and improving hole-injection in small molecule and polymer light emitting diodes.