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When studying electrochemical oxygen reduction reactions in homogeneous media, special attention must be given to the significant background activity present with conventional electrode materials. The intrinsic electrocatalytic activity of different materials can be investigated using complementary methods, such as the rotating ring-disc electrode (RRDE) technique and chronoamperometric electrolysis with product quantification. This report presents a detailed investigation of the electrocatalytic ability of hydroxy anthraquinone derivatives and riboflavin towards hydrogen peroxide (H2O2) production viaa novel RRDE subtraction method together with chronoamperometric electrolysis. Qualitative trends linking the two methods were obtained, such as a higher excess current correlating with both higher productivity and selectivity. As such, a valuable tool is provided to increase the understanding of the electrocatalytic ability of homogeneous solutions toward improving the oxygen reduction reaction.

Nowadays, hydrogen fuel is becoming more popular, and it is attracting significant attention as a sustainable and environmentally benign energy source owing to its zero emission of harmful substances and high energy density. Hydrogen generation through the electrocatalytic hydrogen evolution reaction (HER) employs economically inexpensive and self-supported electrocatalysts that hold immense potential to provide a sustainable and cost-effective fuel in the future energy scenario. A self-supported NiO@TiO2nanofiber composite on Ti-foil is synthesized via a hydrothermal approach, and it is used as an electrocatalyst in the HER under alkaline conditions. The surface morphology, crystalline structure, and chemical composition of the electrode are analyzed by using high-resolution scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy, which confirms that NiO nanoparticles are anchored to the surface of TiO2nanofibers. Investigation of the electrocatalytic properties of the NiO@TiO2nanofiber composite in a 1 M KOH electrolyte solution for the HER showed an overpotential of 144 mV at 10 mA cm–2with a Tafel slope of 152.34 mV dec–1. The NiO that is anchored to the TiO2nanofibers creates more catalytically active sites, which increases the surface area and enhances the HER performance. The charge transfer resistance of Rct= 41.6 Ω is determined from the electrode kinetics analyzed by using an electrochemical impedance spectroscopy Nyquist plot. The chronopotentiometric stability test confirms that the NiO@TiO2composite electrode shows a robust production of H2gas with only 7.6% potential deviation after 12 h of electrocatalytic activity. Furthermore, a Faradaic efficiency of 86% for hydrogen is achieved after 100 min of the HER. The results confirm that the NiO@TiO2nanofiber composite is a promising candidate material for the electrocatalysis of the HER.

Benzoporphyrins and their derivatives are of high interest in organic semiconductor technology due to their peculiar physical properties valuable for optoelectronic applications. Following our previous work successfully developing meso-thienyl- or meso-bithiophenyl-substituted zinc benzoporphyrins as efficient ternary components for bulk heterojunction solar cells, we describe herein detailed spectroscopic studies on doping of solid films of these benzoporphyrins under iodine atmosphere. Solid-state doping and oxidative polymerization are investigated by Raman and Fourier transform infrared spectroscopy. Structural and vibrational changes upon doping are explored with supporting data from density functional theory calculations. Furthermore, the optical and spectroscopic characteristics of the films of these materials are also monitored during the doping, and the polaron formation as evidenced by in situ attenuated total reflection Fourier transform infrared and UV–vis spectroscopy is observed. These results suggest that the target zinc benzoporphyrins, both in monomeric and in polymeric forms, should be good candidates in several other optoelectronic applications.

Nanostructure incorporation into devices plays a key role in improving performance, yet processes for preparing two-dimensional (2D) arrays of colloidal nanoparticles tend not to be universally applicable, particularly for soft and oxygen-sensitive substrates for organic and perovskite-based electronics. Here, we show a method of transferring reverse micelle-deposited (RMD) nanoparticles (perovskite and metal oxide) on top of an organic layer, using a functionalized graphene carrier layer for transfer printing. As the technique can be applied universally to RMD nanoparticles, we used magnetic (γ-Fe2O3) and luminescent (methylammonium lead bromide (MAPbBr3)) nanoparticles to validate the transfer-printing methodology. The strong photoluminescence from the MAPbBr3under UV illumination and high intrinsic field of the γ-Fe2O3as measured by magnetic force microscopy (MFM), coupled with Raman measurements of the graphene layer, confirm that all components survive the transfer-printing process with little loss of properties. Such an approach to introducing uniform 2D arrays of nanoparticles onto sensitive substrates opens up new avenues to tune the device interfacial properties.

Mechanically interlocking redox-active anthraquinone onto single-walled carbon nanotubes (AQ-MINT) gives a new and advanced example of a noncovalent architecture for an electrochemical platform. Electrochemical studies of AQ-MINT as an electrode reveal enhanced electrochemical stability in both aqueous and organic solvents compared to physisorbed AQ-based electrodes. While maintaining the electrochemical properties of the parent anthraquinone molecules, we observe a stable oxygen reduction reaction to hydrogen peroxide (H2O2). Using such AQ-MINT electrodes, 7 and 2 μmol of H2O2are produced over 8 h under basic and neutral conditions, while the control system of SWCNTs produces 2.2 and 0.5 μmol, respectively. These results reveal the potential of this rotaxane-type immobilization approach for heterogenized electrocatalysis.

Using enzymes as bioelectrocatalysts is an important step toward the next level of biotechnology for energy production. In such biocatalysts, a sacrificial cofactor as an electron and proton source is needed. This is a great obstacle for upscaling, due to cofactor instability and product separation issues, which increase the costs. Here, we report a cofactor-free electroreduction of CO2to a high energy density chemical (methanol) catalyzed by enzyme–graphene hybrids. The biocatalyst consists of dehydrogenases covalently bound on a well-defined carboxyl graphene derivative, serving the role of a conductive nanoplatform. This nanobiocatalyst achieves reduction of CO2to methanol at high current densities, which remain unchanged for at least 20 h of operation, without production of other soluble byproducts. It is thus shown that critical improvements on the stability and rate of methanol production at a high Faradaic efficiency of 12% are possible, due to the effective electrochemical process from the electrode to the enzymes via the graphene platform.

The efficiency of organo-lead halide perovskite-based optoelectronic devices is dramatically lower for amorphous materials compared to highly crystalline ones. Therefore, it is challenging to optimize and scale up the production of large-sized single crystals of perovskite materials. Here, we describe a novel and original approach to preparing lead halide perovskite single crystals by applying microwave radiation during the crystallization. The microwave radiation primarily causes precise heating control in the whole volume and avoids temperature fluctuations. Moreover, this facile microwave-assisted method of preparation is highly reproducible and fully automated, it and can be applied for various different perovskite structures. In addition, this cost-effective method is expected to be easily scalable because of its versatility and low energy consumption. The crystallization process has low heat losses; therefore, only a low microwave reactor power of 8–15 W during the temperature changes and of less than 1 W during the temperature holding is needed.

In this contribution, we show CH3NH3PbI3–xClxperovskite solar cells (PSCs) processed in ambient air from a solution containing the diketone, acetylacetone (AA) solvent as an additive. PSCs with the AA additive show enhanced photovoltaic properties. The optimized PSC with 10 vol % AA additive shows an average open-circuit voltage (VOC) of about 1.02 V, short-circuit current density (Jsc) of around 18.7 mA/cm2, fill factor of about 76%, and power conversion efficiency of around 14.5%. Atomic force microscopy topographic imaging depicts that the addition of AA into the MAPbI3–xClxsolution enhances the crystal growth with comparable improvement in the surface smoothness. Electrochemical impedance spectroscopy and intensity modulated photovoltage spectroscopy investigations show that incorporation of AA resulted in the improvement of charge carrier dynamics in the bulk and across interfaces, and reduction of recombination pathways. Moreover, MAPbI3–xClxfilms with the AA additive exhibit stronger photoluminescence compared to the pristine MAPbI3–xClxfilms. This appears to confirm that the AA solvent additive plays a vital role to reduce the trap states and recombination conduits across the film, which boosts the enhancement of radiative recombination pathways. We believe that this additive is highly practical and a viable option to fabricate and optimize large-area, stable, thin film PSCs in ambient environment.

The electronics era is flourishing and morphing itself into Internet of Everything, IoE. At the same time, questions arise on the issue of electronic materials employed: especially their natural availability and low-cost fabrication, their functional stability in devices, and finally their desired biodegradation at the end of their life cycle. Hydrogen bonded pigments and natural dyes like indigo, anthraquinone and acridone are not only biodegradable and of bio-origin but also have functionality robustness and offer versatility in designing electronics and sensors components. With this Perspective, we intend to coalesce all the scattered reports on the above-mentioned classes of hydrogen bonded semiconductors, spanning across several disciplines and many active research groups. The article will comprise both published and unpublished results, on stability during aging, upon electrical, chemical and thermal stress, and will finish with an outlook section related to biological degradation and biological stability of selected hydrogen bonded molecules employed as semiconductors in organic electronic devices. We demonstrate that when the purity, the long-range order and the strength of chemical bonds, are considered, then the Hydrogen bonded organic semiconductors are the privileged class of materials having the potential to compete with inorganic semiconductors. As an experimental historical study of stability, we fabricated and characterized organic transistors from a material batch synthesized in 1932 and compared the results to a fresh material batch.

In this work we introduce in situ UV–Vis–NIR transmission spectroscopic ellipsometry as an alternative spectroelectrochemical method to examine the π-electron orbital structure as well as intra- and interchain order in regioregular poly(3-hexylthiophene) (rr-P3HT) during electrochemical doping. With the suggested technique, we measure the dielectric tensor of the P3HT film through a typical electrochemical cell consisting of a glass cuvette. The method provides a stable controlled electrochemical environment with full control on the applied potential during the ellipsometric measurement. P3HT, which is a model semitransparent conducting polymer, undergoes a sequence of oxidation steps with increasing electrochemical potential. In the presented work, the doping is monitored up to a level where finally almost every second thiophene ring is positively charged. The reference free determination of the real and imaginary parts of the dielectric tensor components allows a quantitative analysis of resonance energies as well as the orientation dependent oscillator strength of interchain exciton and polaron resonances. This parameters are directly linked with (i) the intrachain structure, (ii) the degree of electron localization, (iii) the π–π stacking order, (iv) the average polymer orientation, and (v) the doping level. Additionally we could observe aggregation dependent doping efficiency. The film optical properties appear fully reversible upon the cyclic electrochemical doping which proves the stability of inter- as well as intramolecular structure while going through very high doping levels.

Abstract

We investigate the photostability of a set of organic semiconductor blends comprising a conjugated polymer as the donor and a fullerene as the acceptor using electron spin resonance (ESR). In the absence of oxygen, all blends show excellent stability. Even after several hundred hours of exposure to solar or UV radiation, the ESR spectra and the recombination of photoinduced charges recorded at low temperature are found to be unchanged. By contrast, the presence of oxygen leads to a fast light-induced degradation rendering the ability of the donor/acceptor system to form photoinduced charge carriers. Our findings suggest that conjugated polymer–fullerene blends exhibit very good photostability and that oxygen needs to be excluded in optoelectronic applications. Our findings also suggest that at low temperature, a universal recombination process of long-lived photoinduced charges is active, which does not depend on the electronic structure or the morphology of the investigated materials.

Herein, the magnetic field effect on the source–drain current of organic field‐effect transistors with semiconductor layers made of H‐bonded pigments is studied. In all devices, an external magnetic field reduces the source–drain current in the transistor. The magnetic field effect is independent of the direction of the applied magnetic field. The observed increase of the magnetoresistance seems to originate from the used semiconductor or the semiconductor–dielectric interface and is not influenced by the nature of the gate electrodes or the semiconductors’ deposition procedure (e.g., grain size, layer thicknesses, etc.). As all prepared devices do have single charge carrier nature, the formation of bipolarons is suggested to be responsible for the observed magnetic field effect. The presented experiments demonstrate that hydrogen‐bonded semiconductors behave no different than their classical van der Waals‐bonded fully conjugated semiconductors’ counterparts. The magnetic field effect in hydrogen‐bonded semiconductor‐based organic field‐effect transistors is investigated.

Developing efficient methods for capture and controlled release of carbon dioxide is crucial to any carbon capture and utilization technology. Herein we present an approach using an organic semiconductor electrode to electrochemically capture dissolved CO2in aqueous electrolytes. The process relies on electrochemical reduction of a thin film of a naphthalene bisimide derivative, 2,7-bis(4-(2-(2-ethylhexyl)thiazol-4-yl)phenyl)benzo[lmn][3,8]phenanthroline-1,3,6,8(2H,7H)-tetraone (NBIT). This molecule is specifically tailored to afford one-electron reversible and one-electron quasi-reversible reduction in aqueous conditions while not dissolving or degrading. The reduced NBIT reacts with CO2to form a stable semicarbonate salt, which can be subsequently oxidized electrochemically to release CO2. The semicarbonate structure is confirmed by in situ IR spectroelectrochemistry. This process of capturing and releasing carbon dioxide can be realized in an oxygen-free environment under ambient pressure and temperature, with uptake efficiency for CO2capture of ∼2.3 mmol g–1. This is on par with the best solution-phase amine chemical capture technologies available today.

The current study reports the application of chalcopyrite semiconductor CuInS2(CIS) nanofibers for the reduction of CO2to CO with a remarkable Faradaic efficiency of 77 ± 4%. Initially the synthesis of CuInS2nanofibers was carried out by adaptable electrospinning technique. To reduce the imperfection in the crystalline fiber, polyacrylonitrile (PAN) was selected as template polymer. Afterward, the desired chemical structure of nanofibers was achieved through sulfurization process. Making continuous CuInS2nanofibers on the cathode surface by the electrospinning method brings the advantages of being economical, environmentally safe, and versatile. The obtained nanofibers of well investigated size and diameter according to the SEM (scanning electron microscope) were used in electrochemical studies. An improvement of Faradaic efficiency was achieved with the catalytic active CuInS2in nanofibrous structure as compared to the solution processed CuInS2. This underlines the important effect of the electrode fabrication on the catalytic performance. Being less contaminated as compared to solution processing, and having a well-defined composition and increased catalytically active area, the CuInS2nanofiber electrodes prepared by the electrospinning technique show a 4 times higher Faradaic efficiency. Furthermore, in this study, attention was paid to the stability of the CuInS2nanofiber electrodes. The electrochemical reduction of CO2to CO by using CIS nanofibers coated onto FTO electrodes was carried out for 10 h in total. The observed current density of 0.22 mA cm–2and the stability of CIS nanofiber electrodes are found to be competitive with other heterogeneous electrocatalysts. Hence, we believe that the fabrication and application of nanofibrous materials through the electrospinning technique might be of interest for electrocatalytic studies in CO2reduction.

Organic microboxes composed of charge-transfer molecule (HB194) were prepared by the reprecipitation method. HB194 dissolved in an organic solvent was rapidly injected into water to produce nanoparticles. Nanoparticles prepared from organic solvents containing the carbonyl group were recrystallized in a dispersion to form microboxes. TiO2nanoparticles were loaded inside the microboxes to produce TiO2@HB194 hybrid microboxes.Organic microbox composed of charge-transfer molecule (HB194) was prepared by reprecipitation method. HB194 dissolved in organic solvent was rapidly injected to a water to produce nanoparticles. Nanoparticles prepared from organic solvents containing carbonyl group were recrystallized in a dispersion to form a microbox. TiO2nanoparticles were loaded inside the microbox to produce TiO2@HB194 hybrid microbox.

Lightweight, biodegradable, and inexpensive materials are desirable to enable low-cost photovoltaics. Paper fulfills these requirements and is compatible with standard roll-to-roll printing processes. Here we report 4% efficient organic solar cells fabricated on paper substrates with a zinc-coating acting as the back contact and evaporated MoO3/Ag/MoO3semitransparent top electrodes. We demonstrate that the rough surface of paper does not preclude its use in high-efficiency organic photovoltaics.

Nanostructured hybrid thin films of CuSCN and rhodamine B (RB) are electrochemically self-assembled (ESA) by cathodic electrolysis in an ethanol/water mixture containing Cu2+, SCN–, and RB. By selecting the solvent, Cu2+/SCN–ratio, and the concentration of RB, we demonstrate several control parameters in the film formation. High loading of RB into the film has been achieved to reach a CuSCN:RB volume ratio of approximately 2:1. The RB solid could almost completely be extracted from the hybrid film by soaking the film in dimethylacetamide (DMA), leading to a large increase of the surface area. The crystallographic orientation of the nanostructure with respect to the substrate can be controlled. Efficient quenching of fluorescence of RB has been observed for the CuSCN/RB hybrid film, implying hole injection from RB excited state to CuSCN. Photoelectrochemical study on the porous crystalline CuSCN obtained after the DMA treatment and sensitized with RB revealed sensitized photocathodic action under visible light illumination, indicating the potential usefulness of the porous CuSCN electrodes for construction of tandem dye-sensitized solar cells.

New symmetrical arylene bisimide derivatives formed by using electron-donating–electron-accepting systems were synthesized. They consist of a phthalic diimide or naphthalenediimide core and imine linkages and are end-capped with thiophene, bithiophene, and (ethylenedioxy)thiophene units. Moreover, polymers were obtained from a new diamine, N,N′-bis(5-aminonaphthalenyl)naphthalene-1,4,5,8-dicarboximide and 2,5-thiophenedicarboxaldehyde or 2,2′-bithiophene-5,5′-dicarboxaldehyde. The prepared azomethine diimides exhibited glass-forming properties. The obtained compounds emitted blue light with the emission maximum at 470 nm. The value of the absorption coefficient was determined as a function of the photon energy using spectroscopic ellipsometry. All compounds are electrochemically active and undergo reversible electrochemical reduction and irreversible oxidation processes as was found in cyclic voltammetry and differential pulse voltammetry (DPV) studies. They exhibited a low electrochemically (DPV) calculated energy band gap (Eg) from 1.14 to 1.70 eV. The highest occupied molecular orbital and lowest unoccupied molecular orbital levels and Egwere additionally calculated theoretically by density functional theory at the B3LYP/6-31G(d,p) level. The photovoltaic properties of two model compounds as the active layer in organic solar cells in the configuration indium tin oxide/poly(3,4-(ethylenedioxy)thiophene):poly(styrenesulfonate)/active layer/Al under an illumination of 1.3 mW/cm2were studied. The device comprising poly(3-hexylthiophene) with the compound end-capped with bithiophene rings showed the highest value of Voc(above 1 V). The conversion efficiency of the fabricated solar cell was in the range of 0.69–0.90%.

Electrochemical capture of carbon dioxide (CO2) using organic quinones is a promising and intensively studied alternative to the industrially established scrubbing processes. While recent studies focused only on the influence of substituents having a simple mesomeric or nucleophilicity effect, we have systematically selected six anthraquinone (AQ) derivatives (X-AQ) with amino and hydroxy substituents in order to thoroughly study the influence thereof on the properties of electrochemical CO2capture. Experimental data from cyclic voltammetry (CV) and UV–Vis spectroelectrochemistry of solutions in acetonitrile were analyzed and compared with innovative density functional tight binding computational results. Our experimental and theoretical results provide a coherent explanation of the influence of CO2on the CV data in terms of weak and strong binding nomenclature of the dianions. In addition to this terminology, we have identified the dihydroxy substituted AQ as a new class of molecules forming rather unstable [X-AQ-(CO2)n]2–adducts. In contrast to the commonly used dianion consideration, the results presented herein reveal opposite trends in stability for the X-AQ-CO2•–radical species for the first time. To the best of our knowledge, this study presents theoretically calculated UV–Vis spectra for the various CO2-AQ reduction products for the first time, enabling a detailed decomposition of the spectroelectrochemical data. Thus, this work provides an extension of the existing classification with proof of the existence of X-AQ-CO2species, which will be the basis of future studies focusing on improved materials for electrochemical CO2capture.

Ultrapure aluminium was thermally evaporated onto various plastics (polyethylene 2.6‐naphthalate, PEN; polyethylene terephthalate, PET; polyimide, PI and glass for comparison) and potentiostatically anodized in a citric buffer. The anodisation procedure was monitored coulometrically and each alumina film formed was characterized by impedance spectroscopy. The resulting anodic alumina films were amorphous (proven by X‐ray diffraction, XRD) and acted as dielectric material in a solid state capacitor with Au top electrode. The capacitors characteristics were evaluated using IV curves and frequency domain measurements. The performance of the capacitors demonstrated low leakage currents and low dielectric losses. The contrary properties capacity and breakdown voltage could be chosen by selecting the anodisation voltage. For each substrate apparent oxide formation factors and capacities were determined coulometrically. The ratio between apparent formation factor and projected area allowed determining the surface roughness. This surface roughness together with the high purity aluminium films and the anodisation compression was responsible for the unexpected high mechanical stability of this composite material.

Positively and negatively charged states in cPBEBT, which consists of EDOT/benzotriazole/EDOT as the building block, are studied using CV, in situ UV‐Vis, and FTIR‐ATR spectroscopy. The results show that cPBEBT is an ambipolar D‐A‐type polymer capable of conducting both holes and electrons. The injected positive and negative charges are distributed over the whole polymer backbone, which is proven by in situ FTIR‐ATR where spectral signatures associated with the benzotriazole unit are observed in both p‐ and n‐doped cPBEBT. HOMO and LUMO values obtained from CV and FTIR‐ATR experiments during oxidation and reduction are compared. cPBEBT is an example of the D‐A approach towards the improvement of the electronic properties of the resultant polymer.

Herein we report our recent efforts in employing natural materials and synthetic derivatives of natural molecules for organic field effect transistors (OFETs) and organic photovoltaics (OPVs). We evaluated dyes from the following chemical families: acridones, anthraquinones, carotenoids, and indigoids. These materials have proven effective in organic field effect transistors, with mobilities in the 4 × 10-4- 0.2 cm2/V-s range, with indigoids showing promising ambipolar behavior. We fabricated complementary-like voltage inverters with high gains using indigoids. The photovoltaic properties of these materials were characterized in metal-insulator-metal (MIM) diodes, as well as in donoracceptor bilayer devices. Additionally, we have found that indigoids and Quinacridone, show long-range crystalline order due to hydrogen binding, and have considerably higher relative permittivities () compared to typical organic semiconductors. Higher permittivities result in lower exciton binding energies and thus may lead to high photocurrents in photovoltaic devices.

D‐A‐D‐type polymers are of high interest in the field of photovoltaics and electrochromism. In this study we report the synthesis and electrochemical properties of PPyBT along with its photophysical properties and photovoltaic performance. PPyBT is soluble in common organic solvents and both n‐ and p‐type dopable, which is a desired property for conjugated polymers. During electrochemistry studies, the onset potentials of the polymer were determined as +0.2 V for oxidation and −1.4 V for reduction. Using these values, HOMO and LUMO energy levels were calculated. The photovoltaic properties of PPyBT were also studied. PL studies showed that there is a charge transfer between PPyBT (donor) and PCBM (acceptor).

Novel hole‐transporting dendrimeric molecules containing dioctylfluorene, spirobi(fluorene) and spiro(cylododecane‐fluorene) as the core unit and different numbers of carbazole and thiophene moieties as the peripheral groups are synthesized. All the dendrimers are characterized by 1H NMR, 13C NMR, FTIR, UV–vis, PL spectroscopy, and MALDI‐TOF. They are thermally stable with high glass transition and decomposition temperatures and exhibit chemically reversible redox processes. They are used as the hole‐transporting layer (HTL) material for multilayer organic light emitting diodes (OLEDs) with a low turn‐on voltage of around 2.5 V and a bright green emission with a maximum luminance of around 25400 cd m−2.

Biocompatible‐ingestible electronic circuits and capsules for medical diagnosis and monitoring are currently based on traditional silicon technology. Organic electronics has huge potential for developing biodegradable, biocompatible, bioresorbable, or even metabolizable products. An ideal pathway for such electronic devices involves fabrication with materials from nature, or materials found in common commodity products. Transistors with an operational voltage as low as 4–5 V, a source drain current of up to 0.5 μA and an on‐off ratio of 3–5 orders of magnitude have been fabricated with such materials. This work comprises steps towards environmentally safe devices in low‐cost, large volume, disposable or throwaway electronic applications, such as in food packaging, plastic bags, and disposable dishware. In addition, there is significant potential to use such electronic items in biomedical implants.

A window to the world: Metal‐organic complexes such as zinc‐phthalocyanines and ‐naphthalocyanines show broad transmission windows in the visible spectral range and can be used together with fullerenes in semitransparent organic solar cells. By achieving a high transmission of visible light through silver electrodes, this property is exploited to construct organic solar cells that one can see through.

Conducting channel formation in organic field‐effect transistors (OFETs) is considered to happen in the organic semiconductor layer very close to the interface with the gate dielectric. In the gradual channel approximation, the local density of accumulated charge carriers varies as a result of applied gate bias, with the majority of the charge carriers being localized in the first few semiconductor monolayers close to the dielectric interface. In this report, a new concept is employed which enables the accumulation of charge carriers in the channel by photoinduced charge transfer. An OFET employing C60as a semiconductor and divinyltetramethyldisiloxane‐bis(benzocyclobutene) as the gate dielectric is modified by a very thin noncontinuous layer of zinc‐phthalocyanine (ZnPc) at the semiconductor/dielectric interface. With this device geometry, it is possible to excite the phthalocyanine selectively and photogenerate charges directly at the semiconductor/dielectric interface via photoinduced electron transfer from ZnPc onto C60. Thus the formation of a gate induced and a photoinduced channel in the same device can be correlated.

Novel fullerene‐containing Eu (III) complexes are obtained by mixing a fullerene derivative bearing chelating pyridinyl groups with an Eu (III) complex possessing three coordinated 4,4,4,‐trifluoro‐1‐(2‐naphtyl)‐1,3‐butanedione residues and two water molecules. One of the complexes designed is formed in water using a water‐soluble fullerene derivative as a precursor material. We investigate the photophysical properties of this new type of highly soluble self‐assembled fullerene‐derivative Eu3+coordination compounds. A strong emission line of the Eu3+4f–4f transition is recorded under excitation with UV irradiation. The behaviour of the complexes in organic matrices and water is studied as the first steps towards luminescence tagged fullerene derivatives for use in biomedicine and optoelectronics.

Die konjugierten Polymere als organische Halbleiter sind besondere Werkstoffe: Sie vereinen die Vorteile eines “Plastik”-Werkstoffes wie z.B. die Löslichkeit, Verarbeitungsfähigkeit, Dünnschichtherstellung, mechanische Flexibilität usw. und die elektrischen und optischen Eigenschaften eines Halbleiters und Metalls. Demnach werden diese Werkstoffe als aktive Substanzen in der gedruckten Optoelektronik interessant sein.

Organic field-effect transistors (OFETs) based on solution-processible polymeric as well as small molecular semiconductors have shown impressive improvements in their performance during recent years. These devices have been developed to realize low-cost, large-area electronic products. This review gives an overview of the materials' aspect, charge-transport, and device physics of OFETs, focusing mainly on the organic semiconductor and organic dielectric materials and their mutual interface. Recent developments in the understanding of the relationship between microstructure and charge transport, the influence of processing techniques, and gate dielectric are reviewed. Comparative data of charge-carrier mobility of most organic semiconductors have been compiled. Ambipolar charge transport in OFETs and its applications to integrated circuits as well as ambipolar light-emitting transistors are also reviewed. Many interesting questions regarding how the molecular and electronic structures at the interface of the organic semiconductor and organic insulator influence device performance and stability remain to be explored.

Conjugated polymers are widely used as electroactive materials because of their morphological changes induced by redox cycling. But this type of materials was recently shown to induce several other electromechanical actuations. While undoped conjugated polymer based diodes undergo common Maxwell stress and electro-thermal actuation under reverse and forward polarization, respectively, devices based on doped active material exhibit an unusual type of electromechanical strain. This strain, in between piezoelectricity and electrostriction, opens new routes for material investigation and potential applications in “smart” actuators.

Summary:The electrochemical behaviour of four types of (phenylene ethynylene)‐alt‐(phenylene vinylene) hybrid polymers, 1, 2, 3, and 4have been investigated with respect to the influence of the grafted alkoxy side chains. In the case of the fully substituted polymers 2, 3, and 4, the strong insulating nature of longer linear octadecyl or bulky branched 2‐ethylhexyl side chains lowers the HOMO levels of the polymers thereby increasing the discrepancy, ΔEg, between the electrochemical, Egec, and the optical, Egopt, bandgap energies. Thus it is not possible to establish a direct correlation between the open circuit voltage, VOC, of bulk heterojunction solar cell devices of the configuration glass substrate/ITO/PEDOT:PSS/polymer 3:PCBM(1:3, w/w)/LiF/Al and the HOMO energy levels of polymer 3solely, as postulated in the literature. The photovoltaic (PV) parameters greatly depend on the grafted side chains.

Within the different organic photovoltaic devices the conjugated polymer/fullerene bulk heterojunction approach is one of the foci of today's research interest. These devices are highly dependent on the solid state nanoscale morphology of the two components (donor/acceptor) in the photoactive layer. The need for finely phase separated polymer–fullerene blends is expressed by the limited exciton diffusion length present in organic semiconductors. Typical distances that these photo-excitations can travel within a pristine material are around 10–20 nm. In an efficient bulk heterojunction the scale of phase separation is therefore closely related to the respective exciton diffusion lengths of the two materials involved. Once the excitons reach the donor/acceptor interface, the photoinduced charge transfer results in the charge separation. After the charges have been separated they require percolated pathways to the respective charge extracting electrodes in order to supply an external direct current. Thus also an effective charge transport relies on the development of a suitable nanomorphology i.e.bicontinuous interpenetrating phase structures within these blend films. The present feature article combines and summarizes the experimental findings on this nanomorphology–efficiency relationship.

Encouraging progress has been made over the last few years in the field of photovoltaic solar cells using organic materials. Among the different concepts which have been proposed, the bulk heterojunction approach formed by blending donor type conjugated polymers and acceptors like fullerenes is attractive and significant progress in improving the power conversion efficiency of these devices was obtained recently. One of the possible improvements of this type of solar cells is the implementation of new materials absorbing the red and near infrared part of the solar spectrum, where the maximal photon flux of the sun is located. In this article, we will describe this strategy of photon harvesting in organic solar cells and review recent advances in the search for new materials as candidates for polymeric absorbers.

Encouraging progress has been made over the last few years in the field of photovoltaic solar cells using organic materials. Among the different concepts which have been proposed, the bulk heterojunction approach (formed by blending donor type conjugated polymers and acceptors like fullerenes) is attractive and significant progress in improving the power conversion efficiency of these devices was obtained recently. One of the possible improvements of this type of solar cells is the implementation of new materials absorbing the red and near infrared part of the solar spectrum, where the maximal photon flux of the sun is located. In this article, we will describe this strategy of photon harvesting in organic solar cells and review recent advances in the search for new materials as candidates for polymeric absorbers.

Conjugated polymers are used increasingly for the fabrication of electronic and optoelectronic devices like light emitting diodes (LEDs) and photovoltaic (PV) elements. A breakthrough in realising a promisingly efficient conversion of solar energy into electrical energy has been achieved by using blends of soluble electron-donor type conjugated polymers with fullerenes as electron-acceptor, transporting component. This “bulk heterojunction” approach suggests the preparation of intrinsically bipolar materials as a way to control both electronic and morphological properties at once. On these bases, the covalent grafting of fullerene moieties to conjugated backbones seems promising for the preparation of intrinsically bipolar polymeric materials (double-cable polymers) alternative to conjugated polymer/fullerene composites. The recent developments on the design, the characterisation and the application of this novel class of fullerene functional materials are reviewed.