Transparent Conductive Substrates Research Articles

Direct Assembly of Large Area Nanoparticle Arrays

A major goal of nanotechnology is the assembly of nanoscale building blocks into functional optical, electrical, or chemical devices. Many of these applications depend on an ability to optically or electrically address single nanoparticles. However, positioning large numbers of single nanocrystals with nanometer precision on a substrate for integration into solid-state devices remains a fundamental roadblock. Here, we report fast, scalable assembly of thousands of single nanoparticles using electrophoretic deposition. We demonstrate that gold nanospheres down to 30 nm in size and gold nanorods <100 nm in length can be assembled into predefined patterns on transparent conductive substrates within a few seconds. We find that rod orientation can be preserved during deposition. As proof of high fidelity scale-up, we have created centimeter scale patterns comprising more than 1 million gold nanorods.

Controlling Nerve Growth with an Electric Field Induced Indirectly in Transparent Conductive Substrate Materials.

Innovative neurostimulation therapies require improved electrode materials, such as poly(3,4-ethylenedioxythiophene) (PEDOT) polymers or IrOx mixed ionic-electronic conductors and better understanding of how their electrochemistry influences nerve growth. Amphibian neurons growing on transparent films of electronic (metal) conductors and electronic-ionic conductors (polymers and semiconducting oxides) are monitored. Materials are not connected directly to the power supply, but a dipole is created wirelessly within them by electrodes connected to the culture medium in which they are immersed. Without electrical stimulation neurons grow on gold, platinum, PEDOT-polystyrene sulfonate (PEDOT-PSS), IrOx , and mixed oxide (Ir-Ti)Ox , but growth is not related to surface texture or hydrophilicity. Stimulation induces a dipole in all conductive materials, but neurons grow differently on electronic conductors and mixed-valence mixed-ionic conductors. Stimulation slows, but steers neurite extension on gold but not on platinum. The rate and direction of neurite growth on PEDOT-PSS resemble that on glass, but on IrOx and (Ir-Ti)Ox neurites grow faster and in random directions. This suggests electrochemical changes induced in these materials control growth speed and direction selectively. Evidence that the electric dipole induced in conductive material controls nerve growth will impact electrotherapies exploiting wireless stimulation of implanted material arrays, even where transparency is required.

Reversible Electrochemical Mirror Devices Using Room Temperature Ionic Liquid Electrolyte

Devices that utilize reversible electrochemical mirrors (REM) have a number of applications including thermal and light management for terrestrial and space based systems. These systems use the concept of reversible electrodeposition to plate and strip highly reflective metallic films, i.e. mirrors, in the device to facilitate reflection and transmission or absorption of radiation. Figure 1 provides an illustration of a REM device whereby a transparent support, typically glass or plastic contains a transparent conducting layer that functions as the mirror electrode. An electrolyte containing the metal ions available for reduction and oxidation of the optically tailored metallic film is contained between the mirror electrode and the counter electrode, which may or may not be transmissive depending on the technology application. Electrodeposition of species such as silver, copper, tin, aluminum or gold generates a mirror like surface through the transparent electrode that facilitates reflection of radiation that aids in thermal management for satellite applications or light management for smart window applications. The mirror deposit can then be oxidized from the transparent electrode by applying a less negative or positive voltage with respect to the deposition voltage, permitting transmission of radiation. The cell may also be designed such as to cycle between reflective and absorptive states by changing the nature of the counter electrode. Conventional REM devices utilize electrolytes based on organic solvents such as gamma-butylrolactone and dimethyl sulfoxide. For space based applications, these electrolytes are unsuitable due to their vapor pressures and potential for evaporation if the cell seal is compromised. Room temperature ionic liquid electrolytes (RTIL) are an attractive alternative to these conventional systems due to their negligible vapor pressure in addition to their excellent chemical and thermal stability and their large electrochemical windows. RTIL base electrolytes may be tailored to deliver specific properties based on their cation and anion species, making the electrolytes tunable for specific applications. RTILs with anionic species such as chloride, bromide and iodide have been evaluated as potential alternatives to the conventional organic electrolytes for REM devices. These systems have shown promise in terms of mirror formation and long cycle life; however, they exhibit high sensitivity to water, including atmospheric moisture, which can limit their usefulness in REM devices. The present work focuses on deposition and stripping of silver thin films from RTIL with relative low moisture sensitivity. Simple, two electrode cells were built using transparent electrodes with electrically conductive films (i.e. indium tin oxide, platinum and silver) and air and moisture stable RTIL electrolytes for electrochemical characterization and plating/stripping cycling experiments. Highly reflective and reproducible silver mirror formation using air and moisture stable RTIL based electrolytes has been demonstrated. Limited cycle lifetime in terms of the number of plating and stripping cycles with acceptable mirror formation was initially encountered. The thin conductive films applied to the transparent electrodes are susceptible to redox reactions which can limit their lifetimes, and as such relatively low voltages are applied in attempts to maintain the integrity of the electrodes and thus the REM device. Furthermore, the primary challenge with extended cycling of REM devices is the incomplete removal of the reflective surface leading to degradation of the mirror’s reflectivity with cycling. It is speculated that residual surface oxide effectively blocks complete stripping of the silver deposit and/or deposition of an acceptable reflecting mirror, adversely affecting device cycling lifetime. Therefore, a major challenge in the development of REM devices, whereby a reflective surface such as silver is alternatively plated and dissolved on a transparent conductive substrate, is that a buildup of undissolved reflective material on the electrode surface over successive cycles causes a loss of reflectivity and transmission. To counter this, an electrode maintenance cycle was introduced periodically within mirror plating and stripping cycles to aid in complete oxide removal, preparing the electrode surface for the next plating cycle. This maintenance cycle is introduced as a multiple cyclic voltammetry scan (cyclic potential sweep cleaning) and was found to extend device cycling lifetime. Data is presented on the development of conditions for plating and stripping cycles as well as the electrode maintenance cycle and scale up considerations and activities are also discussed. Acknowledgement: Funding for this work is gratefully acknowledged from Air Force STTR Grant Number FA9453-17-C-0490. Platinum coated ITO electrodes were prepared by Dr. John Bryan Plumley. Figure 1

Effective shell wall thickness of vertically aligned ZnO-ZnS core-shell nanorod arrays on visible photocatalytic and photo sensing properties

Development of hierarchical core-shell semiconductor heterostructures ensue significant advancement in catalytic functional structures with improvised optical functionalities. Shell wall controlled vertically aligned ZnO-ZnS core-shell nanorod (NR) heterostructures were grown on transparent conductive substrates along the c-axis by sulfidation of aligned ZnO nanorod arrays for visible photocatalytic properties. The effects of the sulfidation time on the morphology, crystalline properties, optical property, photocurrent response, and photocatalytic activity of the catalyst arrays were studied under UV and visible light irradiation. The shell wall thickness of these heterostructures influenced in great extent the effective photo responsive charge separation and improved carrier mobility. ZnO-ZnS core-shell heterostructure having the shell wall thickness of 20 nm has exhibited more efficient visible photocatalytic behavior due to effective separation of carriers and improved visible absorption. On further increasing the wall thickness the catalytic efficiency was reduced due to the poor carrier (hole) mobility in the polycrystalline shell grains which induced the higher recombination rate. Stability and reusability of ZnO-ZnS core-shell nanostructures reveals that the ZnS acted as a protective layer over the ZnO NR arrays. In appraisal with ZnO NR arrays, the control over the shell wall thickness of ZnO-ZnS core-shell NR array attributed to the excellent visible photocatalytic activity and improvised absorption of light in visible region at ZnO-ZnS interface and effective separation of photogenerated electron-hole pairs at ZnO-ZnS heterojunctions.

Electrophoretically Deposited Y2O3:Bi3+,Eu3+ Nanosheet Films with High Transparency for Near-Ultraviolet to Red Light Conversion.

Fluorescent films were fabricated by depositing Y2O3:Bi3+,Eu3+ nanosheets, which emit red light under near-UV irradiation. The Y2O3:Bi3+,Eu3+ nanosheets were obtained by calcining hydroxide precursor nanosheets synthesized through a hydrothermal method. An aqueous dispersion of positively charged Y2O3:Bi3+,Eu3+ nanosheets with polyethyleneimine adsorbed to the surface was prepared for their deposition. Fluorescent nanosheets were electrophoretically deposited on a transparent conductive substrate under a constant voltage. The obtained nanosheet films were dense and uniform and showed excellent photostability against the excitation light. Growth of the nanosheet film caused a decrease in transmittance and an increase in the photoluminescence intensity. The former effect was attributed to light scattering from inner voids and the rough surface of the film. A polyvinylpyrrolidone (PVP) coating on the film improved the transmittance to be greater than 70% over the visible region. These effects were attributed to antireflection effects at the film surface owing to the low refractive index of PVP. Furthermore, suppression of light scattering by coating the rough surface with a smooth PVP film and filling of voids in the nanosheet film with PVP also improved the transmittance.

Synthesis of Cu2ZnSn(SxSe1−x)4 thin films directly on transparent conductive glass substrates by solvothermal method

In this paper, the single-step solvothermal method was proposed to grow directly Cu2ZnSn (SxSe1−x)4 (CZTSSe) thin films on FTO substrates. The composition ‘x’ was varied by changing the molar ratios of thiourea to selenourea in the precursor solutions. The effects of the molar ratios of thiourea to selenourea on the structure, morphology and optical properties of CZTSSe thin films were investigated by X-ray diffraction, Raman spectroscopy, scanning electronic microscopy, energy dispersive spectrometry and UV–Vis spectrophotometry. The results indicated that CZTSSe thin films are composed of a large number of uniform sphere-like particles, and the diameter of particles varies from 600 to 280 nm when the molar ratios is changed from 1 to 0. The major XRD diffraction peaks shift towards lower diffraction angles, the Raman peak position of A1 mode of CZTSSe thin films moves consecutively towards the lower frequency due to the S replacement by Se. CZTS and CZTSe thin films are single kesterite structure, however, CZTSSe thin films are mixture structure of kesterite and wurtzite. By varying the molar ratios of thiourea to selenourea in the precursor solution, the atom ratios of S/Se in CZTSSe NCs thin films can be well controlled over the whole range, resulting in tunable optical band gap from 1.54 to 1.38 eV.

Structural, electrical, and optical properties of sol-gel-derived zirconium-doped barium titanate thin films on transparent conductive substrates

Barium zirconium titanate (Ba(Zr x Ti1−x)O3, BZT) super smooth thin films are synthesized through modified sol-gel dip coating route on fluorine-doped tin oxide substrates with a suitably low calcination temperature. The Fourier tranformed infrared spectroscopy proves that impurities and starting materials are completely removed in the calcination process. Crystallographic phases of the samples are identified by the X-ray diffractometry and confirms that all samples are crystallized into a single perovskite phase. Introducing zirconium into the structure causes a reduction in dielectric constant of barium titanate. The optical properties of the films are also investigated. The results indicate that all samples are highly transparent and zirconium reduces the absorption coefficient. Moreover, the band gap energy of barium titanate increases when doped with zirconium and the highest band gap energy of about 3.71 eV along with the lowest dielectric constant of 850 at frequency of 100 kHz are obtained in 15 at.% zirconium-doped sample.

Fabrication and photocatalysis of ZnO nanotubes on transparent conductive graphene-based flexible substrates

本论文以水热法在透明导电石墨烯柔性衬底(GPET)上生长氧化锌(ZnO)纳米管阵列, 发现其纳米管形成机理为选择性地沿(001)面生长, ZnO/GPET异质结具有较好的整流特性. 光催化测试表明, ZnO/GPET复合结构可提高光催化性能, 并具有良好的循环性. 此方法可在柔性衬底上稳定生长ZnO纳米管, 并可应用于相关光电器件及光催化领域中.

Light-soaking tests of zinc oxide photoanodes sensitized with an indoline dye on different transparent conductive substrates

Dye-sensitized solar cells (DSCs) were prepared using porous zinc oxide (ZnO) films on aluminum-doped zinc oxide (AZO) and fluorine-doped tin oxide (FTO) transparent conductive glass substrates. X-ray diffraction measurements revealed that, the porous ZnO films were crystallographically oriented differently on the two transparent substrates. The two DSCs were prepared using metal-free indoline dye as the sensitizer and a liquid electrolyte as the hole conductor. Measurements of the power conversion efficiency of the two DSCs over a period of time showed deterioration in the conversion efficiency of the DSCs with the deterioration being faster in ZnO/FTO than ZnO/AZO. The deterioration is attributed mainly to the decrease in light-harvesting ability of the sensitizer and recombination of photo-excited electrons resulting in the decrease in the short-circuit photocurrent densities and the open-circuit voltages in both DSCs during the light-soaking process.

Graphene on {116} faceted monocrystalline anatase nanosheet array for ultraviolet detection.

A structure composed of a nanosheet array may trap photons, which could be used to enhance the optical response via resonances; this may be highly useful in ultraviolet (UV) detection, photocatalysis, solar cells, etc. Moreover, anatase nanosheets exposed with the active {001}, {111}, and {116} facets are promising in applications such as Li-ion battery, photocatalysis, and electrochemistry. Therefore, in this study, the {116} faceted single-crystalline anatase nanosheet array with the sheet spacing in the range of several hundred nanometers was directly grown on the transparent conductive substrates. A photo-detector was fabricated by transferring a graphene electrode to the top of the anatase nanosheet array. The resultant device is inactive to visible-light irradiation and instantly responds to the UV light, which is due to the unique UV absorption property of the anatase nanosheet array and the advantage of the Schottky junction between the interfaces of graphene and anatase. The energy barrier between the two materials is 0.122 eV. We have provided a thorough research on graphene/monocrystal anatase-NSs.

Recent status on MOF thin films on transparent conductive oxides substrates (ITO or FTO)

MOF thin films on a conductive support are reviewed with a particular focus on the growth control and the binding strength of the films.

Anisotropic flexible transparent films from remaining wood microstructures for screen protection and AgNW conductive substrate.

Flexible transparent conductive films or substrates prepared from plastics or cellulose are widely used in optoelectronic devices. However, all of these films or substrates are fabricated by complex and expensive methods, which consume much energy and time. In this work, we report for the first time a remarkably facile and effective approach for fabricating flexible transparent films directly from wood. The resulting films exhibit an array of exceptional optical and mechanical properties. The well-aligned cell structures in natural wood are maintained during delignification, leading to anisotropic films with high transparency (≈90% transmittance). These anisotropic films with well-aligned cell structures show mechanical tensile strengths higher than those of the original wood, and can be used as screen protection films for cellphones. Furthermore, ultrathin, highly transparent, and outstandingly conductive films have been prepared from such films and silver nanowires (AgNWs) using the Meyer technique. A conductive film with an optimal area density (341 mg m-2) of AgNWs showed outstanding synergistic properties, with a transmittance of 80% and a sheet resistance of 11 Ω sq-1, equal to the conductivity of ITO. Of importance here is that the low-cost anisotropic transparent wood film shows promising potential for electronics applications in solar cells, flexible displays, and other products.

Development of Spray Coating Methods for Large Area Sol-Gel ZnO/Ag Nanowire Composite Transparent Conducting Substrates

Development of Spray Coating Methods for Large Area Sol-Gel ZnO/Ag Nanowire Composite Transparent Conducting Substrates

Analysis of Optical Losses in a Photoelectrochemical Cell: A Tool for Precise Absorptance Estimation

AbstractOptical losses in a photoelectrochemical (PEC) cell account for a substantial part of solar‐to‐hydrogen conversion losses, but limited attention is paid to the detailed investigation of optical losses in PEC cells. In this work, an optical model of combined coherent and incoherent light propagation in all layers of the PEC cell based on spectroscopic measurements is presented. Specifically, photoelectrodes using transparent conductive substrates such as F:SnO2 coated with thin absorber films are focused. The optical model is verified for hematite photoanodes fabricated by atomic layer deposition and successfully used to determine wavelength‐dependent reflection, transmission, layer absorptances, and charge generation rates. Furthermore, the calculated absorptances enable 20–30% more accurate calculations of the absorbed photon‐to‐current efficiency of PEC cells. Our optical model is a powerful tool for the optimization of the optical performance of PEC cells focusing on single absorber or tandem configurations and represents a cornerstone of a complete (optical and electrical) model for PEC water splitting cells.

One-pot synthesis of MoS2/In2S3 ultrathin nanoflakes with mesh−shaped structure on indium tin oxide as photocathode for enhanced photo-and electrochemical hydrogen evolution reaction

A bifunctional MoS2/In2S3 hybrid composite that has both photo- and electrocatalytic activity toward hydrogen evolution reaction (HER) is prepared by a facile one pot hydrothermal method. The characterizations by scanning electron microscope (SEM), high resolution transmission electron microscope (HRTEM) and Photoluminescence (PL) shows that the MoS2/In2S3 hybrid exhibits ultrathin nanoflakes with mesh-shaped structure on transparent conductive substrates, and the as prepared catalyst composite obviously improves the separation of electro-hole pairs. The as prepared hybrid nanosheets with Mo:In of 1/2 integrate In-doped MoS2 to reduce the stacking and increase the active surface area. The novel mesh-shaped nanostructure with a moderate degree of disorder provides not only simultaneously intrinsic conductivity and defects but also higher electrochemically active surface area (ECSA). By electrochemical measurements, such as linear sweep voltammetry (LSV), electrochemical impedance spectroscope (EIS) and cyclic voltammetry (CV), we find that the MoS2/In2S3 hybrid possesses much better photo/electrochemical activity than pristine MoS2 or In2S3. MoS2/In2S3 ultrathin nanoflaks are anticipated to be a superior photoelectrocatalyst for PEC cells, and the rational use of the MoS2/In2S3 cathode offers a new avenue toward achieving effective photo-assistant electrocatalytic activity.

Self‐Organization Based Fabrication of Bimetallic PtPd Nanoparticles on Transparent Conductive Oxide Substrates

Bimetallic PtPd nanoparticles are of special interest for their tunable properties in a wide range of applications as plasmonics, energy storage, catalysis. So, in this work we present a simple and versatile method for the production of bimetallic PtPd nanoparticles on a transparent and conductive substrate, such as fluorine‐doped tin oxide/glass (FTO/glass) substrate. The method is based on the deposition of thin Pt/Pd bilayers on the FTO substrate. Then, we induced the melting, alloying, and dewetting process of the Pt and Pd layers by nanosecond laser irradiation with the consequent formation of the bimetallic PtPd nanoparticles. We characterized the nanoparticles by Scanning Electron Microscopy, Rutherford backscattering spectrometry, and X‐Ray Diffraction measurements. In particular, the microscopic analysis showed that the average diameter of the nanoparticles is independent on the thickness of the deposited bilayers and on the layers sequence. On the other hand, the X‐ray diffraction measurements confirmed that the structure of the nanoparticles consists in a PtPd alloy structure. The formation process of the nanoparticles is, finally, discussed on the basis of the general microscopic mechanisms involved in the laser‐induced melting, alloying, and dewetting of the metallic films.

Viologen-functionalized poly(ionic liquids): Spectroelectrochemical and QCM-D studies

Ionic Liquids (ILs) and poly(Ionic Liquids) (PoILs) have fully tunable properties due to their different ion combinations as well as cation or anion functionalization, which results in smart materials with endless possibilities. In this study, a solid electrochromic PoIL was synthesized using a novel functionalizable and polymerizable IL (1-propyl-3-vinylimidazolium chloride bromide) and a viologen (4,4′-bipyridine) that reacted to form a monomer. Its subsequent polymerization resulted in a mechanically stable, highly ionically and electronically conductive electrochromic polyelectrolyte with a thermal decomposition temperature higher than 309°C and a glass transition temperature of 13°C. Spectroelectrochemical studies of the polymer deposited as a thin film over a transparent conductive substrate demonstrated a reversible redox process with reduction and oxidation potentials of −0.45 and −0.3V, respectively, which was accompanied by a reversible color change from colorless (oxidized state) to purple (reduced state) with an optical contrast of 19% at 525nm, a switching time of nearly 20s and a coloration efficiency of 60cm2C−1. Additionally, the film was repetitively switched from colorless to purple and began to lose electroactivity after approximately 4h and 400cycles. However, electroactivity was still observed after 16h or 1600cycles. Moreover, quartz crystal microbalance with dissipation monitoring indicated that the polymer charge compensation process was accompanied by a huge viscoelastic change in the film, as demonstrated by the spread of the harmonics and important changes in dissipation.

Effects of {001} Facet of Anatase TiO2 Single-crystalline Nanosheets on Photoexcited Electron Transfer from Near-infrared Dye-sensitizer

Single-crystalline anatase TiO2 nanosheets predominantly exposing the {001} facet at a surface fraction of more than 75% were constructed on transparent conductive oxide glass substrates. Application of these nanoarchitectures of TiO2 demonstrated photoelectric conversion while using near-infrared absorbing dye-sensitizer. In contrast, regular mesoporous TiO2 films with a much larger effective surface area did not exhibit a photoelectric response with the same dye-sensitizer. The results obtained here emphasize the importance of the contacted crystalline facet of TiO2 in photoinduced charge separation for minimizing the potential drop for interfacial charge-carrier transfer in dye-sensitized solar cell systems. Especially, the observed improvement of electron injection by contacted facet could contribute to the efficient photoexcited electron injection from near-infrared dye-sensitizers possessing relatively small HOMO–LUMO gap.

Novel Reversible Humidity‐Responsive Light Transmission Hybrid Thin‐Film Material Based on a Dispersive Porous Structure with Embedded Hygroscopic and Deliquescent Substances

AbstractThe article describes a new concept of an optical hybrid thin‐film material that exhibits reversible humidity‐driven light transmittance (scattering) properties. The film consists of a dispersive porous structure, with embedded hygroscopic and deliquescent compounds, that is able to scavenge water molecules from humid air to fill up the pores and become transparent to the incident light. Upon exposure to dry air, water is released from the structure and the material recovers its original light scattering properties. The developed thin films can change their transparency when exposed to air with different relative humidity (RH), adjusting the light throughput. This material can, therefore, be used to design new optical switching systems, having the advantage that they do not require liquid crystal, transparent conductive glass substrates, or complex layer‐by‐layer architectures for operation. In this work, a thin film was prepared by the sol–gel technique using calcium chloride as deliquescent substance embedded in a hybrid silica–titania matrix. At dry air, the thin films show a highly dispersive state, with a light transmittance T = 0.06, while at 51% RH the film exhibits a transparent state with a transmittance T =0.67 (measured at 633 nm).

Preparation of Sn-doped semiconducting Fe2O3 (hematite) layers by aerosol pyrolysis

Fe2O3 films were deposited on transparent conductive substrates (fluorine doped tin oxide (FTO) on glass) by aerosol pyrolysis. The intrinsic nature of as-deposited films requires the addition of a suitable metal dopant. Sn proved to be well adapted to this task, as it increased photocurrents in junctions with an aqueous electrolyte by one order of magnitude as compared to undoped films. The maximum IPCE value (incident photon to current conversion efficiency) was 0.21 at 400nm for a 120nm thick film and a maximum photocurrent of 1630μA/cm2 at 0.65V vs. Ag/AgCl under simulated solar irradiation.