Search

For electronic devices, a tradeoff exists between the structural stability and electrical conductivity of silver nanowires (Ag NWs). Self-assembled monolayers (SAMs) containing sulfur functional groups formed on the Ag nanowire surface through Ag–S covalent bonds can act as a passivation layer, thereby improving the corrosion resistance. This work explored the effect of 2-mercaptobenzimidazole (MBI) SAM on the thermal and oxidation resistance of Ag NW films. The conductivity, surface morphology, chemical properties, and thermal stability of MBI-modified Ag NW films were analyzed via four-point probe measurements, field-emission scanning electron microscopy, x-ray photoelectron spectroscopy (XPS), and thermal characterization. In particular, the results show that the MBI layer can significantly reduce the oxidation of Ag NW films at room temperature for 60 days. Moreover, the MBI layer improved the thermal stability of the Ag NW films up to 230°C by inhibiting Ag diffusion. The unmodified Ag NW film completely lost conductivity after heating and oxidation treatment. In contrast, the sheet resistance of the Ag NW film modified by 0.1 wt.% MBI only increased from 65 Ω/ $$\square$$ to 106 Ω/ $$\square$$ , and 156 Ω/ $$\square$$ after heating treatment and oxidation test, respectively.

Various physical structures have improved light-harvesting and power-conversion efficiency in organic photovoltaic devices, and optical simulations have supported the improvement of device characteristics. Herein, we experimentally investigated how microlens arrays manipulate light propagation in microlens films and material stacks for organic photovoltaics to understand the influence of the constituent materials and sizes of the microlens. As materials to fabricate a microlens array, poly(dimethylsiloxane) and Norland Optical Adhesive 63 were adopted. The poly(dimethylsiloxane) microlens array exhibited higher total transmittance and higher diffuse transmittance, further enhancing the effective optical path and light extinction in material stacks for organic photovoltaics. This resulted in more current generation in an organic photovoltaic device with a poly(dimethylsiloxane) microlens array than in a Norland Optical Adhesive 63 microlens array. The sizes of the microlenses were controlled from 0.5 to 10 μm. The optical characteristics of microlens array films and material stacks with microlenses generally increased with size of the microlens, leading to a 10.6% and 16.0% improvement in the light extinction and power-conversion efficiency, respectively. In addition, electron and current generation in material stacks for organic photovoltaics were calculated from light extinction. The theoretical current generation matched well with experimental values derived from organic photovoltaic devices. Thus, the optical characterization of physical structures helps to predict how much more current can be generated in organic photovoltaic cells with a certain physical structure; it can also be used for screening the physical structures of organic photovoltaic cells.

A major problem in the application of mesoporous TiO2 as an electron transport layer for flexible perovskite solar cells is that a high-temperature sintering process is required to remove organic a...

Infectious diseases and the deaths caused due to contact with germ-contaminated surfaces are severe problems worldwide. Antibacterial materials based on silver nanowires (AgNWs) have a structural advantage when addressing this issue; this is because agglomeration is minimized when nanowires are fabricated into a film. Therefore, employing AgNWs for antimicrobial applications has garnered continuous interest, and increased research for further improvements has been observed. In this study, a AgNW film was fabricated onto glass by spin-coating and then subjected to surface irradiation up to a dose of 1200 kGy, using a low-energy electron beam (e-beam). This "e-beam" irradiation changed the surface morphology and chemical composition; consequently, this improved the performance of the film. The generation of a silver oxide (Ag

Electrical properties of silver nanowire (AgNW)-based transparent electrodes have been improved without transmittance loss by forming a composite with zinc oxide (ZnO). Here, we identified the dominant effect responsible for the improvement of electrical conductivity of the transparent AgNW:ZnO composite electrodes by fabricating the AgNW:ZnO composite electrodes with different architectures and theoretically calculating the overall resistance of their equivalent circuits. Specifically, when we compared the overall resistances of the AgNW:ZnO electrodes with various architectures by experiment, the electrode with only the electrical bridge effect showed the lowest electrical resistance. In addition, while the theoretical overall resistances were comparable on changing the interconnect resistances between the silver nanowires in the equivalent circuits of all architectures, they decreased dramatically with the decreasing ZnO bridging resistance. Thus, it was concluded that the electrical bridge effect is more important than the capillary force effect which decreases the interconnect resistance between the silver nanowires for the enhancement of the electrical properties of AgNW:ZnO composite electrodes. It was also found that the AgNW:ZnO electrodes with only the electrical bridge effect showed better device performances when applied to optoelectronic devices such as organic photovoltaics.

The lithographic process for flexible transparent electrodes is essential for constructing wearable optoelectronic devices with a well-defined active area. Although photolithography is a well-established patterning process, and can generate small features, it involves toxic materials and high processing cost. Herein, we introduce a novel lithographic process for both silver nanowire (AgNW)-embedded and AgNW-exposed flexible transparent electrodes. We selectively control the adhesion between AgNWs and the substrate via a local surface treatment with ultraviolet/ozone (UV/ozone), oxygen plasma, and atmosphere plasma. Since strong adhesion leads to retention of AgNWs on the substrate during embedding of AgNWs in a UV-curable polymer, selective control of adhesion induces selective embedding of AgNWs, generating AgNW-embedded and AgNW-exposed transparent electrodes with desirable patterns. Additionally, this process is versatile enough to be applicable to various substrates including poly(methyl methacrylate) (PMMA)-coated surfaces, poly(ethylene terephthalate) (PET) films, and acrylic substrates, and various AgNWs with different surface energies. The critical work of adhesion to successfully pattern AgNW-based transparent electrodes is experimentally obtained. Conclusively, we demonstrate that patterning of AgNW-based electrodes by controlling the work of adhesion is economical and eco-friendly, and can be successfully applied for designing various optoelectronic devices such as organic photovoltaic cells and liquid crystal cells.

Electron beam (EB) curing is a foldable hard coating process and has attracted significant research attention in the field of flexible electronic devices. In this study, we report a method for enhancing material surface hardness with low-energy EB curing in a short time. The low-energy EB improved the coating hardness of films by inducing cross-linking polymerization of the silicon-containing monomer. The hardness of the cured coating layer was measured as 3 H using a pencil hardness tester, and the transparency of the coating was higher than 90%. Owing to a series of cross-linking reactions between Si-O-C and Si-OH groups under EB curing and the formation of Si-Si bonds, the cured layer exhibited remarkable durability in the 100000-flexible cycle test. Additionally, the natural oxidation of the C-O groups on the surface of the coating formed carboxyl groups that improved the hydrophilic properties of the coating layer. To the best of our knowledge, this is the first study to propose that the hardness of polyethylene terephthalate films can be improved using low-energy EBs to rapidly cure silicon-containing coatings. Our results provide a novel and commercially viable approach for improving the hardness of touch screens and foldable displays.

Silver nanomaterials (AgNMs) have been applied as antibacterial agents to combat bacterial infections that can cause disease and death. The antibacterial activity of AgNMs can be improved by increasing the specific surface area, so significant efforts have been devoted to developing various bottom-up synthesis methods to control the size and shape of the particles. Herein, we report on a facile heat-treatment method that can improve the antibacterial activity of transparent silver nanowire (AgNW) films in a size-controllable, top-down manner. AgNW films were fabricated via spin-coating and were then heated at different temperatures (230 and 280 &deg, C) for 30 min. The morphology and the degree of oxidation of the as-fabricated AgNW film were remarkably sensitive to the heat-treatment temperature, while the transparency was insensitive. As the heat-treatment temperature increased, the AgNWs spontaneously broke into more discrete wires and droplets, and oxidation proceeded faster. The increase in the heat-treatment temperature further increased the antibacterial activity of the AgNW film, and the heat treatment at 280 &deg, C improved the antibacterial activity from 31.7% to 94.7% for Staphylococcus aureus, and from 57.0% to 98.7% for Escherichia coli. Following commonly accepted antibacterial mechanisms of AgNMs, we present a correlation between the antibacterial activity and surface observations of the AgNW film.

A promising release technique for SU-8 using a water-soluble sacrificial layer based on germanium oxide is developed. The relatively high etching rate of germanium oxide in water and its high etching selectivity make it suitable as a sacrificial layer for the release of SU-8 structures. Moreover, a water-soluble sacrificial layer causes no damage to either the structural materials or SU-8 because it can be etched under much milder conditions. To demonstrate the effectiveness of a water-soluble sacrificial layer for releasing SU-8 structures, a large-area SU-8 structure is released using this approach. In addition, various microfabrication processes are demonstrated using releasable SU-8 structures: a metal lift-off process using SU-8 as a lift-off mask, fabrication of thick metal microstructures using SU-8 as a mold, and fabrication of a free-standing SU-8 micromixer. Display Omitted Releasing SU-8 structures using germanium oxide as a water-soluble sacrificial layerA metal lift-off process using SU-8 as a lift-off maskFabrication of thick metal microstructures using SU-8 as a moldFabrication of a free-standing SU-8 micromixer

The mesoporous TiO2 nanoparticle-based scaffold structure is the best electron transport layer (ETL) for perovskite solar cells (PSCs) and is still used in most PSCs with optimal photovoltaic characteristics. However, the high sintering temperature of TiO2 nanoparticles required to remove binders from the TiO2 paste limits PSC application to flexible electronics. In this study, a simple interface modification process involving ethanol rinsing is developed to enhance the photovoltaic characteristics of low-temperature processed PSCs. This easy and fast technique could enable remarkable performance by PSCs by significantly increasing the fill factor and current density, leading to a power conversion efficiency more than four times that of untreated solar cells.

To combat infectious diseases, zinc oxide (ZnO) has been identified as an effective antibacterial agent, however, its performance can be adversely affected by harsh application environments. The ozone impact on ZnO antibacterial film needs to be evaluated prior to its application in an ozone disinfection system. In this study, ZnO films synthesized via sol-gel/spin-coating were subjected to ultraviolet&ndash, ozone (UVO) treatment for different periods. Surface investigations using scanning electron microscopy, ultraviolet&ndash, visible spectroscopy, and X-ray photoelectron spectroscopy revealed that the treatment-induced film changes. With longer UVO treatment, the surface porosity of the film gradually increased from 5% to 30%, causing the transmittance reduction and absorbance increase in visible-light range. Phase transformation of Zn(OH)2 to ZnO occurred during the first 10 min of UVO treatment, followed by oxygen uptake as a consequence of the reaction with reactive oxygen species generated during UVO treatment. However, despite these surface changes, the satisfactory antibacterial activity of the synthesized ZnO film against Staphylococcus aureus and Escherichia coli was sustained even after 120 min of UVO treatment. This indicates that the UVO-induced surface changes do not have a significant effect on the antibacterial performance and that the ZnO sol-gel film possesses good functional durability in ozone environments.

Wrinkles attract significant attention due to their ability to enhance the mechanical and optical characteristics of various optoelectronic devices. We report the effect of the plasma gas type, power, flow rate, and treatment time on the wrinkle features. When an optical adhesive was treated using a low-pressure plasma of oxygen, argon, and nitrogen, the oxygen and argon plasma generated wrinkles with the lowest and highest wavelengths, respectively. The increase in the power of the nitrogen and oxygen plasma increased the wavelengths and heights of the wrinkles; however, the increase in the power of the argon plasma increased the wavelengths and decreased the heights of the wrinkles. Argon molecules are heavier and smaller than nitrogen and oxygen molecules that have similar weights and sizes; moreover, the argon plasma comprises positive ions while the oxygen and nitrogen plasma comprise negative ions. This resulted in differences in the wrinkle features. It was concluded that a combination of different plasma gases could achieve exclusive control over either the wavelength or the height and allow a thorough analysis of the correlation between the wrinkle features and the characteristics of the electronic devices.

Sol-gel zinc oxide (ZnO) is very useful for constructing various optoelectronic devices including different types of sensors and solar cells at low cost and fast processing time. Here, we adopted a zinc acetate dehydrate, with low processing temperature and suitable for flexible electronics, as a precursor to produce ZnO thin film. Then, we explored the morphological and optical properties of various sol-gel ZnO layers depending on the humidity of the sol-gel process because the humidity affects the morphological and optical characteristics, dramatically changing the performance of optoelectronic devices. As a result, extremely high humidity produced a ZnO layer with rough surface, high dispersive transmittance, and high trap density because rapid hydrolysis does not give atoms enough time to move to thermodynamically-stable sites. On the other hand, extremely low humidity produced a ZnO layer with smooth surface, low dispersive transmittance and oxygen-deficient trap sites owing to insufficient hydrolysis. Therefore, a ZnO layer prepared at humidity of 25% had low surface roughness, low trap density, and desirable transmittance characteristics, achieving the best device performance when applied to organic solar cells. This study will be helpful in determining the optimum processing conditions to obtain optoelectronic devices with the best performance.

We herein report the effect of the viscosity of a prepolymer solution on the thickness uniformity of silver-nanowire-embedded flexible transparent electrodes. We adopted a model system with all the prepolymer solutions possessing identical physical properties except for the viscosity and then explored the most common prepolymer solutions for silver-nanowire-embedded flexible electrodes. In all experiments, single-step spin coating was conducted to coat the prepolymer solution on silver nanowires. We found that the electrodes were thinner for lower viscosity. However, the thickness ratio between the center and edge was comparable (50&ndash, 60%) and independent of the prepolymer solution viscosity. This indicates that the viscosity does not determine the thickness uniformity, and that the coating method itself is vital to obtain films with uniform thickness. The flexible electrodes were introduced into organic solar cells. Their device performance was comparable regardless of the position of the electrodes and their thickness. This is because the thickness difference of the flexible electrodes did not affect their transmittance significantly. Thus, we conclude that although different coating approaches are needed to obtain flexible electrodes with high uniformity, the performance of optoelectronic devices on silver-nanowire-embedded flexible electrodes is independent of them.

We investigated the effect of different spray-coating parameters on the electro-optical properties of Ag nanowires (NWs). Highly transparent and conductive Ag NW&ndash, graphene oxide (GO) hybrid electrodes were fabricated by using the spray-coating technique. The Ag NW percolation network was modified with GO and this led to a reduced sheet resistance of the Ag NW&ndash, GO electrode as the result of a decrease in the inter-nanowire contact resistance. Although electrical conductivity and optical transmittance of the Ag NW electrodes have a trade-off relationship, Ag NW&ndash, GO hybrid electrodes exhibited significantly improved sheet resistance and slightly decreased transmittance compared to Ag NW electrodes. Ag NW&ndash, GO hybrid electrodes were integrated into smart windows based on polymer-dispersed liquid crystals (PDLCs) for the first time. Experimental results showed that the electro-optical properties of the PDLCs based on Ag NW&ndash, GO electrodes were superior when compared to those of PDLCs based on only Ag NW electrodes. This study revealed that the hybrid Ag NW&ndash, GO electrode is a promising material for manufacturing the large-area flexible indium tin oxide (ITO)-free PDLCs.

Increasing interests in stretchable electronic devices have resulted in vigorous research activities, most of which are focused on structural configurations. Diverse structural configurations are available for stretchability, including stiff-island, serpentine, and buckled structures. With easily deformable shapes and simple fabrication processes, buckled structures have the potential to realize stretchability. However, conventional buckled structures exhibit stretchability only in a single-axis direction. In the present study, a new type of cross-buckled structure, which can overcome the limitations of conventional buckled structures is developed. The stretchable thin film solar cells with the cross-buckled structure showed stable mechanical and electrical characteristics under both stretching and compressing conditions. The cross-buckled structure for stretchable electronic devices is expected to broaden the fields of wearable electronics, stretchable displays, and biocompatible applications.

To improve the electrical properties of silver nanowire (Ag NW) transparent conductive electrodes (TCEs), the density of Ag NW networks should be increased, to increase the number of percolation paths. However, because of the inverse relationship between optical transmittance and electrical resistivity, the optical properties of Ag NW TCEs deteriorate with increasing density of the Ag NW network. In this study, a hybrid Ag NW electrode composed of randomly oriented and grid-patterned Ag NW networks is demonstrated. The hybrid Ag NW electrodes exhibit significantly improved sheet resistances and slightly decreased transmittances compared to randomly oriented Ag NW networks. Hybrid Ag NW TCEs show excellent mechanical flexibilities and durabilities in bending tests with a 5 mm radius of curvature. Moreover, flexible transparent film heaters (TFHs) based on the hybrid Ag NW electrodes show elevated maximum temperatures relative to TFHs based on randomly oriented Ag NW electrodes, when operated at the same input voltages.

This paper introduces a simple hydrazine treatment method to reduce the yellowing of silver nanowire transparent conductive electrodes. To investig ate the effects of hydrazine treatment on the yellowing of silver nanowire electrodes, the optical and electrical properties of silver nanowire electrodes were analyzed before and after hydrazine treatment. The optimal hydrazine treatment conditions were investigated by varying the concentrat ion and thickness of hydrazine; the effect of hydrazine treatment on the long-term stability of silver nanowires was also analyzed. (C) 2017 Author(s).

Despite their excellent electrical and optical properties, Ag nanowires (NWs) suffer from oxidation when exposed to air for several days. In this study, we synthesized a Cs carbonate-incorporated overcoating layer by spin-coating and ultraviolet curing to prevent the thermal oxidation of Ag NWs. Cs incorporation increased the decomposition temperature of the overcoating layer, thus enhancing its thermal resistance. The effects of the Cs carbonate-incorporated overcoating layer on the optoelectrical properties and stability of Ag NWs were investigated in detail. The Ag NW electrode reinforced with the Cs carbonate-incorporated overcoating layer exhibited excellent thermal oxidation stability after exposure to air for 55 days at 85 &deg, C and a relative humidity of 85%. The novel overcoating layer synthesized in this study is a promising passivation layer for Ag NWs against thermal oxidation under ambient conditions. This overcoating layer can be applied in large-area optoelectronic devices based on Ag NW electrodes.

We demonstrate a compact amorphous silicon (a-Si) solar module to be used as high-voltage power supply. In comparison with the organic solar module, the main advantages of the a-Si solar module are its compatibility with photolithography techniques and relatively high power conversion efficiency. The open circuit voltage of a-Si solar cells can be easily controlled by serially interconnecting a-Si solar cells. Moreover, the a-Si solar module can be easily patterned by photolithography in any desired shapes with high areal densities. Using the photolithographic technique, we fabricate a compact a-Si solar module with noticeable photovoltaic characteristics as compared with the reported values for high-voltage power supplies.

We report a simple method for growing wafer-scale graphene films using PCBM (phenyl-C61-butyric acid methyl ester), a fullerene derivative, as a solid carbon source. PCBM films spin-coated on nickel catalyst were easily converted to graphene films having a thickness of a few layers by thermal annealing without any reactive gas. This method of converting PCBM to graphene is safe, unlike the chemical vapor deposition (CVD) method that uses explosive precursor gases. PCBM-derived graphene films were also transferred through a simple process to plastic substrates with a supporting layer for use in organic solar cells. The power conversion efficiency (PCE) of bulk heterojunction organic solar cells prepared on the PCBM-derived graphene electrode was 0.98%. This study indicates that PCBM-derived graphene films can serve as an inexpensive, flexible alternative to indium tin oxide (ITO) films, and

A new class of thin, releasable single-crystal silicon semiconductor device is presented that enables integration of high-performance electronics on nearly any type of substrate. Fully formed metal oxide–semiconductor fi eld– effect transistors with thermally grown gate oxides and integrated circuits constructed with them demonstrate the ideas in devices mounted on substrates ranging from fl exible sheets of plastic, to plates of glass and pieces of aluminum foil. Systematic study of the electrical properties indicates fi eld-effect mobilities of ≈ 710 cm 2 V − 1 s − 1 , subthreshold slopes of less than 0.2 V decade − 1 and minimal hysteresis, all with little to no dependence on the properties of the substrate due to bottom silicon surfaces that are passivated with thermal oxide. The schemes reported here require only interconnect metallization to be performed on the fi nal device substrate, which thereby minimizes the need for any specialized processing technology, with important consequences in large-area electronics for display systems, fl exible/stretchable electronics, or other non-wafer-based devices.

Although compound semiconductors like gallium arsenide have a substantial performance advantage over silicon in photovoltaic and optoelectronic applications, these do not outweigh the costly process of growing large, high-quality layers of these materials and transferring them to flexible or transparent substrates for use in devices such as solar cells, night vision cameras and wireless communication systems. But now John Rogers and his team demonstrate a new fabrication approach that may remove this disadvantage. They grow films of GaAs and AlGaAs in thick, multilayered assemblies in a single deposition sequence, then release the individual layers and distribute them over foreign substrates by printing. The technological potential of this strategy to large-area applications is illustrated with the fabrication of GaAs devices such as field-effect transistors on glass and photovoltaic modules on sheets of plastic. Although compound semiconductors like gallium arsenide (GaAs) offer advantages over silicon for photovoltaic and optoelectronic applications, these do not outweigh the costly process of growing large layers of these materials and transferring them to appropriate substrates. However, a new fabrication approach is now demonstrated: films of GaAs and AlGaAs are grown in thick, multilayered assemblies in a single sequence; the individual layers are then released and distributed over foreign substrates by printing. Compound semiconductors like gallium arsenide (GaAs) provide advantages over silicon for many applications, owing to their direct bandgaps and high electron mobilities. Examples range from efficient photovoltaic devices1,2 to radio-frequency electronics3,4 and most forms of optoelectronics5,6. However, growing large, high quality wafers of these materials, and intimately integrating them on silicon or amorphous substrates (such as glass or plastic) is expensive, which restricts their use. Here we describe materials and fabrication concepts that address many of these challenges, through the use of films of GaAs or AlGaAs grown in thick, multilayer epitaxial assemblies, then separated from each other and distributed on foreign substrates by printing. This method yields large quantities of high quality semiconductor material capable of device integration in large area formats, in a manner that also allows the wafer to be reused for additional growths. We demonstrate some capabilities of this approach with three different applications: GaAs-based metal semiconductor field effect transistors and logic gates on plates of glass, near-infrared imaging devices on wafers of silicon, and photovoltaic modules on sheets of plastic. These results illustrate the implementation of compound semiconductors such as GaAs in applications whose cost structures, formats, area coverages or modes of use are incompatible with conventional growth or integration strategies.

We report a new strategy, the directional peeling of a rigiflex mold with a nanostructure, to overcome several problems with general patterning techniques for liquid-crystal (LC) alignment. These include difficulty in generating the pretilt angle and in controlling the LC rising-up direction, formation of local domains, and weak optical properties. The directional peeling of the rigiflex mold results in pretilt-angle formation and controls the LC rising-up direction. In addition, a nanostructure with small spacing aligns the LC with a high order parameter because of a strong confinement effect and suppresses diffraction due to its small spacing. Eventually, the nanostructure achieves improvements in the optical properties. In summary, while recent patterning techniques for LC alignment only solve one problem, the directional peeling of the rigiflex mold with a nanostructure simultaneously overcomes several problems with LC alignment and optical properties.

We report on the fabrication of low operating voltage pentacene thin film transistors with PVP (poly-4-vinylphenol)/CeO2–SiO2/PVP triple dielectric layers on a flexible substrate. Our triple dielectric layers exhibited a markedly reduced leakage current characteristic and a relatively high capacitance. The field effect mobility, on/off current ratio and subthreshold slope obtained from pentacene thin film transistors were 0.67 cm2 V s−1, 105 and 0.36 V dec−1, respectively. It was demonstrated that the spin-coating polymer layer can be used to planarize the surface irregularities and to improve the dielectric and device properties.

In this study, pentacene thin-film transistors (TFTs) operating at low voltages with high mobilities and low leakage currents are successfully fabricated by the surface modification of the CeO2–SiO2 gate dielectrics. The surface of the gate dielectric plays a crucial role in determining the performance and electrical reliability of the pentacene TFTs. Nearly hysteresis-free transistors are obtained by passivating the devices with appropriate polymeric dielectrics. After coating with poly(4-vinylphenol) (PVP), the reduced roughness of the surface induces the formation of uniform and large pentacene grains; moreover, –OH groups on CeO2–SiO2 are terminated by C6H5, resulting in the formation of a more hydrophobic surface. Enhanced pentacene quality and reduced hysteresis is observed in current–voltage (I–V) measurements of the PVP-coated pentacene TFTs. Since grain boundaries and –OH groups are believed to act as electron traps, an OH-free and smooth gate dielectric leads to a low trap density at the interface between the pentacene and the gate dielectric. The realization of electrically stable devices that can be operated at low voltages makes the OTFTs excellent candidates for future flexible displays and electronics applications.

Here, we introduce a nanopatternable hydrophilic composite elastomer highly desirable for both nanostructure patterning via solvent-assisted micromolding (SAMIM) and microcontact printing of polar inks. This composite precursor is prepared by blending two UV-curable materials, Norland Optical Adhesives (NOA) 63 and poly(ethylene glycol) diacrylate (PEGDA), in an appropriate ratio; upon UV polymerization, a nanopatternable elastomer with preferential permeability both to aqueous and organic solvent is fabricated. Using this composite mold, nanoscale SAMIM of poly(4-vinylpyridine) (P4VP) and microcontact printing of a polar biomolecule, bovine serum albumin (BSA), was successfully demonstrated, paving the way for facile and efficient reproduction of various nanopatterns and a biomolecule-printed array platform.

In this paper, we have used organic/inorganic double gate dielectrics to enhance pentacene growth and dielectric properties for organic thin film transistors (OTFTs). The effects of poly-4-vinylphenol (PVP)/CeO2–SiO2 composite double gate dielectrics on the electrical properties of OTFTs have been investigated. The interface of the gate dielectric and organic semiconductor is one of the physical factors which govern the electrical performance of OTFTs and also the growth of pentacene is largely determined by the surface characteristics of the gate dielectric. Here, when a spin-coated organic smoothing dielectric on an inorganic metal oxide dielectric is used, the growth of pentacene and dielectric properties are significantly improved. We were able to manufacture high-quality pentacene TFTs with a mobility of 1.14 cm2 (V−1 s−1) and an on/off ratio of 104 at operating voltages of less than 5 V.

The long-term stability of pentacene thin-film transistors (TFTs) encapsulated with a transparent SnO 2 thin-film prepared by ion beam-assisted deposition (IBAD) was investigated. After encapsulation process, our organic thin-film transistors (OTFTs) showed somewhat degraded field-effect mobility of 0.5 cm 2 /(V s) that was initially 0.62 cm 2 /(V s), when a buffer layer of thermally evaporated 100 nm SnO 2 film had been deposited prior to IBAD process. However, the mobility was surprisingly sustained up to 1 month and then gradually degraded down to 0.35 cm 2 /(V s) which was still three times higher than that of the OTFT without any encapsulation layer after 100 days in air ambient. The encapsulated OTFTs also exhibited superior on/off current ratio of over 10 5 to that of the unprotected devices (∼10 4 ) which was reduced from ∼10 6 before aging. Therefore, the enhanced long-term stability of our encapsulated OTFTs should be attributed to well protection of permeation of H 2 O and O 2 into the devices by the IBAD SnO 2 thin-film which could be used as an effective inorganic gas barrier for transparent organic electronic devices.

The influence of CF4 plasma treatment of indium-tin-oxide (ITO) and polyimide (PI) on the patterning of ink-jet printed polymer is presented. Not much difference between the as-received ITO and PI surface energies was found, but a significant difference in surface energies between ITO and PI after CF4 plasma treatment was noted. It is expected that precise patterning can be achieved by using the difference in surface energies between the inside of the pixel and its surroundings. Also the effects of CF4 plasma treatment of ITO have been studied on the performance of polymer light-emitting diodes (PLEDs). X-ray photoelectron spectroscopy revealed that CF4 plasma treatment led to a decrease in the surface content of carbon contaminants and an increase in the surface content of fluorine, which in turn enhance the performance of PLEDs.

Diamond-like carbon (DLC) layer was deposited by the Cs+ ion sputtered negative ion deposition technique between hole transport layer and indium tin oxide (ITO) anode for polymeric electroluminescent device. An acidic poly(styrene sulfonate)-doped poly(3,4-ethylene dioxythiophene):poly-(styrenesulphonic acid) (PEDOT:PSS) solution acting as a hole transporting material etches the ITO surface and the PEDOT:PSS/ITO interface is not stable. X-ray photoelectron spectroscopy and Rutherford backscattering spectrometry have been used to measure the indium contamination in the organic layers such as PEDOT:PSS and poly[2-methoxy-5-( 2′-ethyl-hexyloxy)-1,4-phenylene vinylene]. From the result, it was found that the DLC buffer layer protects ITO surface from acidic PEDOT:PSS solution and restrains the indium diffusion into organic layer. The device with the DLC layer also has electroluminescent efficiency by almost 2 times in the polymeric electroluminescent device compared with the device without diamond-like carbon layer.

This article has been retracted at the request of the Editor-in-Chief and Author. Please see http://www.elsevier.com/locate/withdrawalpolicy . Reason: This article is part of an extreme case of duplicate publication in which the paper, or nearly identical copies of it, has appeared in at least nine other journals. The authors have acknowledged the abuse, which has also been brought to the attention of the responsible administrators at their institutions. Multiple publication represents a flagrant disregard of international copyright law and scientific ethics, it wastes reviewer's and journal staff time, and is also a very poor use of costly journal space which is explicitly reserved for publishing original work. Thin Solid Films takes a strong view on this matter.

We have fabricated highly stable organic electroluminescent devices based on spin-coated poly- p -phenylene-vynylene (PPV) thin films. The electrical properties of aluminum cathode, prepared by ion beam assisted deposition, on PPV have been investigated and compared to those by thermal evaporation. Although energetic particles of Al assisted by Ar + ion may damage the organic material, I – V – L characteristics are improved by applying thin Al buffer layer. In addition, a dense Al cathode inhibits the permeation of H 2 O and O 2 into PPV film through pinhole defects, and thus retards dark spot growth. It may be deduced from highly packed structure of Al cathode with smaller junction resistance between Al and PPV. In conclusion, the lifetime of organic light-emitting device (OLED) has been extended effectively by dense Al film through ion beam assisted deposition process.

Biaxially textured CeO2 films were deposited on Hastelloy C276 substrates at room temperature using ion-beam-assisted e-beam evaporation with the ion beam directed at 55° to the normal of the film plane. The crystalline structure and in-plane orientation of films were investigated by x-ray diffraction 2θ-scan and -scan. The orientation of the films was studied as a function of ion-to-atom ratio and film thickness. The ion-to-atom ratio was varied by independently adjusting the deposition rate and the ion current density. Under optimum condition, (200) textured CeO2 films have been successfully grown on Hastelloy C276.

Ion-beam-assisted deposition (IBAD) was used for cathode preparation in organic light-emitting diodes to fabricate dense electrode. Dark spot growth rate was decreased by employing the IBAD process due to a highly packed aluminum structure inhibiting the permeation of H2O and O2. However, undesirable leakage current was generated because energetic particles of Al assisted by Ar+ ion may damage the organic material resulting in reduction of contact resistance. The decrease of contact resistance in the IBAD device may be caused by large contact area, increase of density of states, and Li diffusion to phenyl-substituted poly-p-phenylene vinylene.

Highly stable organic electroluminescent devices based on spin-coated soluble phenyl-substituted poly- p -phenylene-vinylene (Ph-PPVs) thin films have been achieved. We investigated the electrical properties of ion beam assisted aluminum cathode contacting Ph-PPV and compared them to those of thermal evaporation. Although energetic particles of Al assisted by Ar + ion generate the damages in organic materials, I–V–L characteristics can be improved by using thin Al buffer layer to avoid damages. In addition, dense Al cathode inhibits the permeation of H 2 O and O 2 through pinhole defects, which results in retarding gas bubble formation. This may be explained by highly packed structure of Al cathode and decrease of the contact resistance between Al and Ph-PPV. It is believed that the larger contact area and increase of density of state in Ph-PPV minimize the contact resistance and that results in the longevity of organic light-emitting devices (OLEDs).

Stacked organic light-emitting diodes (SOLEDs) with 30-nm nanoparticle (NP) interfacial layers were investigated. Zinc oxide (ZnO) was used as an interfacial layer between two green polymer (GP) layers. SOLEDs with NP interfacial layers had higher device efficiency than did a single-unit device due to the high probability of exciton recombination that originated from the Auger electron-assisted energy up-conversion process. Although the current density and luminance of SOLEDs with ZnO NP interfacial layers were smaller than those of the reference device, the efficiency was doubled because of the big band alignment difference and the large band gap between GP and ZnO NP interfacial layers, which induced more radiative-exciton recombination.

We report on the photovoltaic properties of air-stable inverted organic solar cells in which zinc oxide (ZnO) of varying thicknesses is formed as the electron-transport layer by an atomic layer deposition (ALD) method. The device performance was found to be dependent on the ZnO thickness. Air-stable inverted solar cells with an optimized ZnO thickness reached a power conversion efficiency of 2.91%. This efficiency was found to be comparable to those of conventional organic solar cells. The use of the ZnO electron-transportlayerledtoimprovedairstability:thepowerconversionefficienciesofunencapsulatedorganicsolarcellsremained above 80% of their original values even after storage in air for thirty days.

Transparent electrodes have been widely used in electronic devices such as solar cells, displays and touch screens. Highly flexible transparent electrodes are especially desired for the development of next generation flexible electronic devices. Although indium tin oxide (ITO) is the most commonly used material for the fabrication of transparent electrodes, its brittleness and growing cost limit its utility for flexible electronic devices. Therefore, the need for new transparent conductive materials with superior mechanical properties is clear and urgent. Ag nanowire (AgNW) has been attracting increasing attention because of its effective combination of electrical and optical properties. However, it still suffers from several drawbacks, including large surface roughness, instability against oxidation and moisture and poor adhesion to substrates. These issues need to be addressed before wide spread use of metallic NW as transparent electrodes can be realized. In this study, we demonstrated the fabrication of a flexible transparent electrode with superior mechanical, electrical and optical properties by embedding a AgNW film into a transparent polymer matrix. This technique can produce electrodes with an ultrasmooth and extremely deformable transparent electrode that have sheet resistance and transmittance comparable to those of an ITO electrode.

Thin-film transistors (TFTs) were fabricated using an indium oxide (In2O3) thin film as the n-channel active layer by RF sputtering at room temperature. The TFTs showed a thickness-dependent performance in the range of 48-8 nm, which is ascribed to the total carrier number in the active layer. Optimum device performance at 8-nm-thick In2O3 TFTs had a field-effect mobility of 15.3 cm2 · V-1 · s-1, a threshold voltage of 3.1 V, an ON-OFF current ratio of 2.2 × 108, a subthreshold gate voltage swing of 0.25 V · decade-1, and, most importantly, a normally OFF characteristic. These results suggest that sputter-deposited In2O3 is a promising candidate for high-performance TFTs for transparent and flexible electronics.

We study the alignment properties of liquid crystals (LCs) with a negative dielectric anisotropy on a hydrogenated silicon carbide (SiC:H) film, which is an alternative alignment material. SiC:H layers align LC molecules with a negative dielectric anisotropy via ion beam (IB) irradiation and control the pretilt angle in a range from 90 to 75° depending on the change of IB irradiation angle. Also, when they are exposed to high temperatures for a long time, they show robust properties without degradation. We conclude that although the SiC:H alignment layers are not sensitive to IB irradiation compared with the SiC layers, they show a potential as alternative LC alignment layers for IB irradiation method.

The CF4 plasma treatment of indium–tin-oxide (ITO) greatly improves the performance of organic light-emitting diodes (OLEDs). The effects of plasma treatment on the chemical composition change and device performance were investigated by X-ray photoemission spectroscopy (XPS). The present results suggest that fluorine directly bonded to indium or tin on the ITO surface and markedly enhanced device performance.

In this study, we report on the fabrication of a low-voltage-driven bottom-gate amorphous indium–gallium–zinc-oxide (a-IGZO) thin-film transistor with a high-k oxide/polymer double-layer dielectric on a glass substrate. The hybrid double-layer dielectric was formed through a sequential process of e-beam evaporation of 300-nm-thick amorphous high-k oxide (SiO2–CeO2 mixture) and spin coating of poly(4-vinylphenol) (PVP). The channel layer was deposited by rf magnetron cosputtering with InGaZO4 and ZnO dual targets at room temperature in argon and oxygen mixed-gas atmosphere. The room-temperature-deposited a-IGZO channel with the hybrid double-layer dielectric exhibits the operating characteristics of a threshold voltage of 1.7 V, drain-source current on/off modulation ratio (Ion/Ioff) of ~2.9×104, and field effect mobility of 0.97 cm2 V-1 s-1 at 5 V.

We have fabricated highly stable organic electroluminescent devices based on spin-coated soluble phenyl-substituted poly-p-phenylene-vinylene (Ph-PPVs) thin films. The electrical properties of aluminum cathode, prepared by ion-beam-assisted deposition, on Ph-PPV have been investigated and compared to those prepared by thermal evaporation. Although energetic particles of Al assisted by Ar+ ion may damage the organic material, I–V–L characteristics are improved by evaporating a thin Al buffer layer prior to ion-beam-assisted deposition. In addition, a dense Al cathode inhibits the permeation of H2O and O2 into Ph-PPV film by suppressing pinhole defects, and thus retards dark spot growth. This may be deduced from highly packed structure of Al cathode with smaller contact resistance between Al and Ph-PPV. The lifetime of an organic light-emitting device has been extended by dense Al film through an ion-beam-assisted deposition process.

We demonstrate a LEGO-like assembly of free-standing film of individually operable components encapsulated in a polymer overcoat layer, leading to the integrated architecture without additional electrical connection. The free-standing components are produced by the peeling-off process. The sticky nature of polymer layer enables the construction of supercapacitor arrays and simple RLC circuits through interlocking the individual components.