Vacuum Deposition Method Research Articles

Mobility Evaluation of [1]Benzothieno[3,2- b][1]benzothiophene Derivatives: Limitation and Impact on Charge Transport.

Among contemporary semiconductors, many of the best performing materials are based on [1]benzothieno[3,2- b][1]benzothiophene (BTBT). Alkylated derivatives of these small molecules not only provide high hole mobilities but also can be easily processed by thermal vacuum or solution deposition methods. Over the last decade, numerous publications have investigated molecular structures and charge transport properties to elucidate what makes these molecules so special. However, the race toward ever higher mobilities resulted in significantly deviating values, which exacerbates linking molecular structure to electronic properties. Moreover, a recently arisen debate on overestimation of organic field-effect transistor mobilities calls for a revaluation of these numbers. We synthesized and characterized four BTBT derivatives with either one or two alkyl chains (themselves consisting of either 8 or 10 carbon atoms) and investigated their spectroscopic, structural, and electrical properties. By employing two-probe, gated four-point probe and gated van der Pauw measurements, we compare field-effect mobility values at room and low temperatures and discuss their feasibility and viability. We attribute mobility changes to different angles between molecule planes and core-to-core double-layer stacking of asymmetric BTBT derivatives and show higher mobilities in the presence of more and longer alkyl chains. A so-called "zipper effect" brings BTBT cores in closer proximity promoting stronger intermolecular orbital coupling and hence higher charge transport.

Two N,N-chelated difluoroboron complexes containing phenanthroimidazole moiety: Synthesis and luminescence properties

Two new N,N-chelated difluoroboron complexes, PIBF2-Cz and PI-BODIPY, containing phenanthroimidazole moiety were synthesized and characterized by elemental analysis, NMR spectroscopy and MS. Their photophysical and electrochemical properties and thermal stabilities were investigated systematically. The results showed that these N,N-chelated difluoroboron complexes not only exhibit excellent thermal stabilities but also emit strong green emissions with photoluminescence quantum efficiency of 95.71% and 67.22% in chloroform solutions. Furthermore, based on these N,N-chelated difluoroboron complexes, the green organic light-emitting devices with a configuration of ITO/NPB (20 nm)/TBADN: difluoroboron complex (x wt%, 30 nm)/TPBi (30 nm)/Liq (2 nm)/Al (100 nm) have been successfully fabricated by vacuum-deposition method, in which the devices fabricated from PIBF2-Cz exhibited the best electroluminescence performance with a maximum brightness of 20290 cd/m2 and a maximum luminous efficiencies of 7.97 cd/A and a maximum external quantum efficiency (EQE) of 1.88%.

Solution‐Grown Serpentine Silver Nanofiber Meshes for Stretchable Transparent Conductors

AbstractMetal fiber nanomeshes, fabricated by depositing metals on the electrospun nanofiber templates, have come into the spotlight as promising stretchable transparent conductors. However, most currently stretchable metal fibers are produced via expensive vacuum deposition methods. This work reports a low‐cost approach to prepare transparent, conducting, and serpentine silver nanofiber mesh elastomers (SNME). The key of forming SNME is buckling the electrospun polymer nanofiber templates into wavy structure and subsequently electrolessly depositing silver on the templates. Optoelectronic performance of the SNME is elaborately optimized by tuning the number of Ag nanoseeds and the electroless deposition time. The resulting SNME exhibit a high visible light transmittance of 81%, a low sheet resistance of 9.2 Ω sq−1, and an excellent stretchability with 2.4‐times of resistance increases after repeated stretching to 70% for 1000 cycles. In situ observations indicate that the SNME are capable of straightening and rearranging to adapt to the tensile deformation. Its application potential as an ideal platform for fabricating intelligent interfaces is demonstrated by using the SNME as a wearable resistance sensor which can monitor finger joint motions.

Sumitomo invests in JOLED

Sumitomo has acquired a $45 million stake in JOLED, a Japanese firm that is about to build the world’s first plant to produce electronic displays via printing. Organic light-emitting diode (OLED) displays are currently produced using a vacuum deposition method that results in significant waste of expensive materials. By contrast, the printing method applies circuitry directly onto a glass or plastic substrate. Expected to come on-line in 2020 in Nomi, Japan, JOLED’s plant will be able to process 20,000 glass substrates per month.

Investigation of the substrate effect for Zr doped ZnO thin film deposition by thermionic vacuum arc technique

ZnO is a fundamental wide band gap semiconductor. Especially, doped elements change the optical properties of the ZnO thin film, drastically. Doped ZnO semiconductor is a promising materials for the transparent conductive oxide layer. Especially, Zr doped ZnO is a potential material for the high performance TCO. In this paper, ZnO semiconductors were doped with Zr element and microstructural, surface and optical properties of the Zr doped ZnO thin films were investigated. Zr doped ZnO thin films were deposited thermionic vacuum arc (TVA) technique. TVA is a rapid and high vacuum deposition method. A glass, polyethylene terephthalate and Si wafer (111) were used as a substrate material. Zr doped ZnO thin films deposited by TVA technique and their substrate effect investigated. As a results, deposited thin films has a high transparency. The crystal orientation of the films are in polycrystal formation. Especially, substrate crystal orientation strongly change the crystal formation of the films. Substrate crystal structure can change the optical band gap, microstructural properties and deposited layer formation. According to the atomic force microscopy and field emission scanning electron microscopy measurements, all deposited layer shows homogeneous, compact and low roughness. The band values of the deposited thin film were approximately found as to be 3.1–3.4 eV. According to the results, Zr elements created more optical defect and shifted to the band gap value towards to blue region.

Devising the Specification of a Solar Cell Utilizing TiO2 Photoanode and Copper Oxides Photocathode

We have been studied the performance of Marine Microbial Fuel Cell (MMFC) composed of Titanium dioxide anode and marine microbial film cathode. In order to improve the power density of MMFC, we have studied to improve the photocatalytic effects of TiO2 anode such as the effect of impurities on TiO2, double layer coating of TiO2, the effect of heat treatment on TiO2, and the effect of dye sensitizing on TiO2. On the other hand, the photocathodic effect of Copper oxides cathode has been studied such as the effect of heat treatment on Copper oxides. Based on the photocatalytic semiconductor effects of TiO2 and Copper oxides, we tried to develop a solar cell coupled with TiO2 photoanode and Copper oxides photocathode. The base metal used for both electrodes was Type 329J4L stainless steel substrate. The surface cleaning and passivation treatment were performed to the substrate before coating of photoactive layers. To produce TiO2 electrode, the passivated substrate was coated with TiO2 first layer by screen printing method followed by 150 °C heat treatment for 60 minutes. The second layer of TiO2 was coated by screen printing and heat treatment was performed at 550 °C for 30 minutes. Besides, vacuum deposition method was used to the base substrate to produce Copper oxides cathode. A set of copper wires was evaporated and deposited on the substrate in vacuum evaporator. The copper-deposited substrate was then heat treated at 350 °C for 30 minutes to form Copper oxides film on the substrate. To compare the characteristics of electrodes, the passivated stainless steel was used as a cathode in couple with TiO2 electrode in the measurements. The electrolyte used for the measurement was artificial sea water (Aquamarine). The cell voltage measurement and power density measurement was performed by a potentiostat (Syrinx, SDPS- 501C, 511C). Two types of cell was prepared; TiO2 anode vs Copper oxides cathode cell and TiO2 anode vs passivated stainless steel cathode cell. Firstly, the measurement of cell voltage for these cells were performed under light irradiation. The light used for these experiments was a xenon lamp with 150 W and calibrated wavelength range of 250 nm to 800 nm which produced a light intensity of 10.5 mW/cm2 (equivalent to approximately 1/10th of 1 sun) onto the test electrode. From the results of cell voltage measurement, power density measurement of the cell was performed in dark condition and under irradiated condition from open circuit cell voltage to short circuit cell voltage. The current densities at which the maximum power density from these cells was obtained and at at which the linear portion of the graph (Tafel gradient) was obtained were recorded for AC impedance measurement as the EIS analysis. The AC impedance measurement of these cells were performed at the current density points obtained from above under irradiated and dark conditions. As the EIS analysis, the Cole-Cole plot and the Bode plot was obtained, and the equivalent circuit was constructed. The results from these experiments were compared and analysed. The results showed the open circuit cell voltage and maximum current density and hence maximum power density of the cell using TiO2 anode and Copper oxides cathode under light irradiation was increased compared to the cell without irradiation. This showed the photocatalytic effect of Copper oxides and Titanium dioxide. The performance of the cell with TiO2 anode vs Copper oxides cathode was increased compared to that of the cell with TiO2 anode and Stainless steel cathode. This is due to increased photocatalytic effect of copper oxide by vacuum deposition. By comparing AC impedance measurement results, the capacitive component of the impedance was reduced largely in the cell with TiO2-Copper oxides than TiO2-stainless steel cell. This leaded to a decrease of cell internal resistance by introducing Copper oxides cathode.

Characterization of low-temperature solution-processed LiCoO2 thin-film cathode with molecular weight control of polyvinylpyrrolidone

Numerous LiCoO2 cathode thin-films have been prepared for all-solid-state thin-film battery applications. Preparation methods include sputtering, pulsed laser deposition, electron beam evaporation, screen printing, and spin coating. When compared to vacuum deposition methods, the solution-processed fabrication methods could result in significant cost savings and large-area production. Unfortunately, high-temperature annealing (Tanneal > 700 °C) of LiCoO2 cathode thin film is usually crucial for achieving a high performance layered phase. Here, we report on phase control of spin-coated LiCoO2 thin film by varying the molecular weight of polyvinylpyrrolidone (PVP) at low temperature. We could achieve thick and smooth film morphology by optimizing the PVP molecular weight. This method could be a promising cathode layer for low-cost thin-film batteries.

Effects of fixture rotation on coating uniformity for high-performance optical filter fabrication

Abstract Coating uniformity is critical in fabricating high-performance optical filters by various vacuum deposition methods. Simple and planetary rotation systems with shadow masks are used to achieve the required uniformity [J. B. Oliver and D. Talbot, Appl. Optics 45, 13, 3097 (2006); O. Lyngnes, K. Kraus, A. Ode and T. Erguder, in ‘Method for Designing Coating Thickness Uniformity Shadow Masks for Deposition Systems with a Planetary Fixture’, 2014 Technical Conference Proceedings, Optical Coatings, August 13, 2014, DOI: http://dx.doi.org/10.14332/svc14.proc.1817.]. In this work, we discuss the effect of rotation pattern and speed on thickness uniformity in an ion beam sputter deposition system. Numerical modeling is used to determine statistical distribution of random thickness errors in coating layers. The relationship between thickness tolerance and production yield are simulated theoretically and demonstrated experimentally. Production yields for different optical filters produced in an ion beam deposition system with planetary rotation are presented. Single-wavelength and broadband optical monitoring systems were used for endpoint monitoring during filter deposition. Limitations of thickness tolerances that can be achieved in systems with planetary rotation are shown. Paths for improving production yield in an ion beam deposition system are described.

Obtaining memristor elements based on non-noble materials

This study is aimed at creating memristor elements based on TiO2/TiOx layers with electrodes that do not contain noble and rare-earth metals, by vacuum deposition method. The characteristics of these elements analyzed by voltammetric methods show that the appearance of an N-type region of negative differential resistance on the current–voltage curve can be caused only by metal electrodes whose vacuum work function exceeds that of TiO2. The appearance of the N-type region on the current–voltage curve of a memristor element is possible only after electrically assisted vacuum forming. Mo–TiO2/TiOx–Ni/Cu structures, for which the ILR/IHR ratio reaches two orders of magnitude at a voltage of less than 4 V, have the most stable parameters.

Obtaining memristor elements based on non-noble materials

This study is aimed at creating memristor elements based on TiO2/TiOx layers with electrodes that do not contain noble and rare-earth metals, by vacuum deposition method. The characteristics of these elements analyzed by voltammetric methods show that the appearance of an N-type region of negative differential resistance on the current–voltage curve can be caused only by metal electrodes whose vacuum work function exceeds that of TiO2. The appearance of the N-type region on the current–voltage curve of a memristor element is possible only after electrically assisted vacuum forming. Mo–TiO2/TiOx–Ni/Cu structures, for which the ILR/IHR ratio reaches two orders of magnitude at a voltage of less than 4 V, have the most stable parameters.

Tuning polymorphism in 2,3-thienoimide capped oligothiophene based field-effect transistors by implementing vacuum and solution deposition methods

The impact of the processing method in controlling the polymorphism and field-effect charge mobility of 2,3-thienoimide-based oligothiophenes semiconductors was investigated.

Recent Development in ITO-free Flexible Polymer Solar Cells.

Polymer solar cells have shown good prospect for development due to their advantages of low-cost, light-weight, solution processable fabrication, and mechanical flexibility. Their compatibility with the industrial roll-to-roll manufacturing process makes it superior to other kind of solar cells. Normally, indium tin oxide (ITO) is adopted as the transparent electrode in polymer solar cells, which combines good conductivity and transparency. However, some intrinsic weaknesses of ITO restrict its large scale applications in the future, including a high fabrication price using high temperature vacuum deposition method, scarcity of indium, brittleness and scaling up of resistance with the increase of area. Some substitutes to ITO have emerged in recent years, which can be used in flexible polymer solar cells. This article provides the review on recent progress using other transparent electrodes, including carbon nanotubes, graphene, metal nanowires and nanogrids, conductive polymer, and some other electrodes. Device stability is also discussed briefly.

Impact of Zr content on multiphase zirconium–tungsten oxide (Zr–WOx) films and its MIS structure of Cu/Zr–WOx/p-Si Schottky barrier diodes

Metal–insulator–semiconductor (MIS) structure of Cu/Zr–WOx/p-Si Schottky diodes with different concentrations (0, 4 and 8 wt%) of Zr content were fabricated. The interfacial layer of zirconium–tungsten oxide (Zr–WOx) film was grown on p-type silicon (p-Si) wafer using jet nebulizer spray pyrolysis (JNSP) technique at the substrate temperature of 400 °C. After that, the Cu electrode was coated on the Zr–WOx film via vacuum deposition method. The multiphase (orthorhombic and cubic) crystal structures of Zr–WOx were revealed by X-ray diffraction (XRD) pattern. The surface morphological analysis using scanning electron microscope (SEM) showed the dissimilar structures of surface and energy dispersive X-ray diffraction (EDX) confirmed the presence of W, Zr and O atoms. Using UV–Visible (UV–Vis) and DC elecrical (I–V) analysis, the minimum band gap energy and average conductivity were obtained for higher concentration (8 wt%) of Zr content. The minimum barrier height (ΦB) and minimum ideality factor (n) values were attained for 4 wt% of Cu/Zr–WOx/p-Si Schottky barrier diode (SBD) under illumination condition.

Surface engineering of perovskite films for efficient solar cells

It is critical to prepare smooth and dense perovskite films for the fabrication of high efficiency perovskite solar cells. However, solution casting process often results in films with pinhole formation and incomplete surface coverage. Herein, we demonstrate a fast and efficient vacuum deposition method to optimize the surface morphology of solution-based perovskite films. The obtained planar devices exhibit an average power conversion efficiency (PCE) of 13.42% with a standard deviation of ±2.15% and best efficiency of 15.57%. Furthermore, the devices also show excellent stability of over 30 days with a slight degradation <9% when stored under ambient conditions. We also investigated the effect of vacuum deposition thickness on the electron transportation and overall performance of the devices. This work provides a versatile approach to prepare high-quality perovskite films and paves a way for high-performance and stable perovskite photovoltaic devices.

The concept of the phases ratio control during the formation of composite filamentary nanocrystals xInSe-(1–x)In2O3 on glass substrates

The method of vacuum deposition on substrates of glass marks the C-29 series PbSe deposited film and the film In the area 3x3 mm2 and a thickness of ∼1 μm. Films are oxidized in dry air at a temperature of 550 °C. Based on studies by X-ray microanalysis and scanning electron microscopy shows the principal possibility of formation of nanowires xInSe-(1–x)In2O3 on the PbSe/In structure. The results allowed to formulate the concept of the control of phases ratio in the forming nanowires xInSe-(1–x)In2O3 on glass substrates.

Study on Silver-plated Molybdenum Interconnected Materials for LEO Solar Cell Array

Atomic oxygen (AO) is one of the most important environmental factors that affected the performance of low earth orbit spacecraft in orbit. In which, silver was the most common materials as the interconnected materials. However, with the poor AO resistance of silver, the interconnectors could be failure easier, and the lifetime of the spacecraft was also reduced. In this paper, the silver-plated molybdenum interconnected materials made by Ag thin films deposited on the Mo foils by vacuum deposition methods was studied. And the effects of the preparation process on the micro-structure of the Ag thin films, the interfacial adhesive strength and the electrical conductivity of the composites were investigated. It was found that the Ag thin films deposited on the Mo substrates coated the Ag thin films by ion beam assisted deposition(IBAD) methods exhibited a perfectly (200) preferred orientation. The interfacial adhesive strength had been increased to 18.58MPa. And the composites also have excellent electrical performance.

Annealing effects on CsPbI3-based planar heterojunction perovskite solar cells formed by vacuum deposition method

Cesium iodide (CsI) is attracting attention as a substitute for organic materials such as CH3NH3I. In this work, we fabricated sequential-vacuum-deposited planar heterojunction (PHJ) cesium lead iodide (CsPbI3) perovskite solar cells with enhanced efficiencies by varying the annealing time (0.5, 1, 5, and 10 min). The effect of performance enhancement was investigated as a function of varying annealing time at 350 °C employing a hot plate. The best-performing device was obtained with an annealing time of 1 min, delivered photocurrent density (JSC) of 12.06 mA/cm2, voltage (VOC) of 0.71 V, and fill factor (FF) of 0.67, leading to a power conversion efficiency (PCE) of 5.71% at standard AM 1.5G solar illumination.

Daytime Radiative Cooling Using Near-Black Infrared Emitters

Recent works have demonstrated that daytime radiative cooling under direct sunlight can be achieved using multilayer thin films designed to emit in the infrared atmospheric transparency window while reflecting visible light. Here, we demonstrate that a polymer-coated fused silica mirror, as a near-ideal blackbody in the mid-infrared and near-ideal reflector in the solar spectrum, achieves radiative cooling below ambient air temperature under direct sunlight (8.2 °C) and at night (8.4 °C). Its performance exceeds that of a multilayer thin film stack fabricated using vacuum deposition methods by nearly 3 °C. Furthermore, we estimate the cooler has an average net cooling power of about 127 W m–2 during daytime at ambient temperature even considering the significant influence of external conduction and convection, more than twice that reported previously. Our work demonstrates that abundant materials and straightforward fabrication can be used to achieve daytime radiative cooling, advancing applications such ...

Synthesis and Evaluation of the Semiconductor Behavior in Vanadium Indanone Derivatives Thin Films

In this work, we propose a method to synthesize vanadium (IV) 2-benzyli-dene-1-indanone derivatives, used to prepare film structures by thermal evaporation. The complexes possess high melting point allowing the using of vacuum deposition methods. All the samples were grown at room temperature (25℃) and low deposition rates (0.4 Å/s). The surface morphology and structure of the deposited films were studied by scanning electron microscopy (SEM) and spectroscopy dispersive energy (EDS). Optical absorption studies of the complex films were performed in the 200 - 1100 nm wavelength range. The Tauc band gap (Eg) of the thin films was determined from the (αhν)1/2 vs. hν plots for indirect transitions. The vanadium (IV) complex films show optical activation energies in the range of organic semiconductors. Multilayer nylon 11/vanadium indanone devices were fabricated using ITO and silver electrodes. The d.c. electrical properties of the device were also investigated. It was found that the temperature-dependent electric current in the structure showed a semiconductor behavior. At lower voltages below 7 V, the current density in the forward direction was found to obey an ohmic I-V relationship; for higher voltages above 7 V, the conduction was dominated by a space-charge-limited (SCLC) mechanism. The electrical activation energies (Ea) of the complexes were in the 2.17 - 2.31 eV range.

Investigating Polymer-Metal Interfaces by Grazing Incidence Small-Angle X-Ray Scattering from Gradients to Real-Time Studies.

Tailoring the polymer–metal interface is crucial for advanced material design. Vacuum deposition methods for metal layer coating are widely used in industry and research. They allow for installing a variety of nanostructures, often making use of the selective interaction of the metal atoms with the underlying polymer thin film. The polymer thin film may eventually be nanostructured, too, in order to create a hierarchy in length scales. Grazing incidence X-ray scattering is an advanced method to characterize and investigate polymer–metal interfaces. Being non-destructive and yielding statistically relevant results, it allows for deducing the detailed polymer–metal interaction. We review the use of grazing incidence X-ray scattering to elucidate the polymer–metal interface, making use of the modern synchrotron radiation facilities, allowing for very local studies via in situ (so-called “stop-sputter”) experiments as well as studies observing the nanostructured metal nanoparticle layer growth in real time.