Transparent Indium Tin Oxide Research Articles

Improvement of transparent conductive indium tin oxide based multilayer films on p-silicon through the inclusion of thin copper-aluminium metals interlayer

The distinguished transparent conductive indium tin oxide (ITO) based multilayer films with thin copper-aluminium (Cu-Al) metals interlayer (ITO/Cu-Al/ITO) were prepared on p-type silicon (Si) by radio frequency and direct current magnetron sputtering methods. The ITO/Cu-Al/ITO (ICAI) films structural, topological, optical and electrical properties coupled with electronic properties of ICAI/p-type Si interface were investigated at different post annealing temperature up to 600 °C. Despite the inclusion of Cu-Al metals interlayer, structural analysis results yielded an amorphous structure for the as-deposited films. The films become polycrystalline with a cubic bixbyite structure after post annealing treatment. Dominant In2O3 (222) and Cu (111) peaks intensities were observed at 500 °C and 600 °C indicating substantial enhancement in the films crystallinity at high moderate temperatures. The ICAI films reveal a smooth surface roughness with improved growth in grain size after post annealing treatment as examined by microscopic equipment.The films optical transmittance promptly increased from 73.2% (for as deposited film) to 88.7% (for annealed film at 600 °C) at 470 nm in the visible region with increasing post annealing temperature. The film annealed at 600 °C exhibits excellent electrical characteristics with a very low electrical resistivity of 2.44 × 10−5 Ω cm and sheet resistance of 3.26 Ω/sq. The ICAI films optoelectronic properties as calculated by figure of merit (FOM) show outstanding performance at 600 °C with a high FOM of 92.47 × 10−3 Ω−1 in spite of the reduced ITO films thickness. In addition, admirable ICAI/p-type Si interface quality was observed after post annealing treatment (at 600 °C) as indicated by current-voltage characteristics results. These improved ICAI multilayer films can be favourable for silicon heterojunction solar cells and other low resistance optoelectronic applications.

Toward the development of a label-free multiple immunosensor based on thin film transistor microelectrode arrays

A label-free immunosensor using thin film transistor microelectrode arrays (TFT-µEAs) derived from flat-panel technology has been developed for the first time. The TFT-µEAs used here incorporate a large sensing area of 15 mm × 15 mm with a 150 × 150 array of transparent indium tin oxide (ITO) electrodes placed at a 100 μm pixel pitch. Anti-human serum albumin (HSA) IgG was characterized to be immobilized on functionalized ITO electrodes. HSA, which is one of the indexes for liver functions, was successfully detected by recording the change of real-time current based on the change in the electric double layer capacitance before and after conjugation of HSA with anti-HSA IgG. Ionic strength and pH value of HSA solution were optimized. In 0.01 mM phosphate buffered saline with pH 6.0, linear range of HSA was determined as 0.3–300 pM. The present TFT-µEAs are applicable to a label-free multiple immunosensing by patterning antibodies on its surface.

Designing a solution-processable electron transport layer for transparent organic light-emitting diode

In this work, the extensively used opaque metal cathodes of the conventionally structured OLEDs were replaced with the widely used transparent electrode indium tin oxide (ITO) for solution-processed transparent organic light-emitting diode (T-OLED). A new solution-processable electron transport layer (ETL), aside from facilitating the efficient injection of electrons into the T-OLED, protected the organic emission layer (EML) of the T-OLED against the plasma damage during top ITO cathode sputter deposition. The newly designed solution-processed ETL was the composite of the zinc oxide nanoparticles (ZnO-NPs), and cesium carbonate-doped ethoxylated polyethyleneimine (d-PEIE) with the semi-hydrophilic poly (methyl methacrylate) (PMMA) interlayer coated on the EML insured the good wettability and contact of the hydrophilic ETL with the hydrophobic EML. The solution-processed T-OLED emitted the total maximum luminance of about 2417 cd/m 2 (bottom side emission at 1455 cd/m 2 and top emission at 962 cd/m 2 ), total maximum current efficiency at 3.12 cd/A (bottom and top emissions at about 1.78 and 1.34 cd/A, respectively), and total maximum power efficiency at 1.64 l m/W (bottom and top emissions at about 0.95 and 0.69 l m/W, respectively) while having a very high optical transmittance of around 85% at 550 nm light wavelength. • The solution-processed T-OLED with newly designed composite ETL was fabricated. • The electrion injection efficiency and plasma barrier effect of the composite ETL was studied. • The composite ETL had the uniform morphology with even distribution of ZnO in the PEIE matrix. • The T-OLED with composite ETL showed excellent blue light emission.

Label-free mechanoelectrical investigation of single cancer cells by dielectrophoretic-induced stretch assay

It is well-known that cancerous transformation induces many disruptions in the chemical, mechanical, and electrical functions of cells. However, limited data have been reported on their correlative behavior, such as mechanoelectrical responses. In this work, we have applied dielectrophoretic stimulation using transparent Indium Tin Oxide (ITO) microelectrodes to analyze the mechanical deformation of the cells. Our studies have shown high electrodeformation response in non-cancer cells (e.g., for the breast cell line (MCF-10A) ∼21 %). In contrast, the stretch response to the same applied dielectrophoretic stimulation was extremely weak in malignant cells (breast cell line (MDA-MB-231) ∼6 %). This observation points to a new cancer investigation technique based on the real-time correlation between dielectric properties and mechanical behaviors of single cells. Using the smaller electro-deformative ability of cancer cells compared to healthy ones, we have designed and proposed a label-free mechanoelectrical chip to detect metastatic cancer cells in unprocessed tumor samples. The methods of conventional pathology and immunofluorescence assays confirmed the results obtained from our "Dielectrophoretic Stretch Assay" (DSA). This method could help develop protocols for detecting micro invasions in small samples of suspicious masses or cytological samples diagnosis without requirement to pretreatment or labeling and in single-cell resolutions.

Improvement of the Optoelectrical Properties of a Transparent Conductive Polymer via the Introduction of ITO Nanoparticles and Its Application in Crystalline Silicon/Organic Heterojunction Solar Cells.

Compared with conventional transparent conductive indium tin oxide (ITO) films, poly(3,4-ethylenedioxythiophene):poly (styrenesulfonic acid) (PEDOT:PSS) as a conductive polymer material has been diffusely applied in organic optoelectronic devices. However, its optoelectrical properties need to be further improved. Therefore, a simple and universal approach with introducing ITO nanoparticles (NPs) was proposed to improve the optoelectrical properties of PEDOT:PSS thin films. The results show that the vertical conductivity (σDC⊥) and average transmittance (from 300 to 1200 nm) of PEDOT:PSS films were enhanced about 26.8 and 6.3%, respectively. Crystalline silicon (c-Si)/organic heterojunction solar cells (HSCs) with PEDOT:PSS/ITO NP hybrid films were fabricated and performances led to further improvement. The spatial distributions of relative electrical field intensity and the carrier generation rate of the HSCs under the standard AM 1.5 G condition were simulated, which were in good agreement with the experimental conclusions.

A Conformal Metamaterial-Based Optically Transparent Microwave Absorber With High Angular Stability

We put forward an optically transparent microwave absorber based on a conformal broadband metamaterial, which shows high angular stability. Our absorber is a double-layer sandwich structure mainly made of transparent polyvinyl chloride sheets and indium tin oxide films. To achieve wideband absorption and high angular stability, an impedance layer composed of square spiral elements is exploited to increase the absorption bandwidth. A compensation layer is then employed to address the mismatch between the impedance of the absorber and that of free space at high angular incidences. Experimental results show that a high light transmittance (69.4%), together with an adequate absorption bandwidth (85.7%) and angular stability (60°) may be achieved with planar and conformal configurations, including different curvatures.

Highly conductive and transparent electrospun indium tin oxide nanofibers calcined by microwave plasma

In this work, indium tin oxide (ITO) nanofibers have been prepared by electrospinning of polymers and post-growth microwave plasma calcination (MPC). Interestingly, compared to traditional calcination in furnace, MPC can accelerate the degradation of high polar polymers and improve adhesion of ITO nanofibers to the sapphire substrate. Further characterizations reveal that the ITO nanofibers with diameters of 100–150 nm prepared by MPC at 600 °C can reach a low sheet resistance of 269 Ω/sq and a high transmittance of 90.7% at 550 nm simultaneously, which has not been previously reported by others. Our results show that the efficient MPC method has great potential in preparation of metal-oxide nanofibers for electrical and optical applications.

High-stability transparent flexible energy storage based on PbZrO3/muscovite heterostructure

Antiferroelectric materials for dielectric energy storage with fast charging-discharging rate is an important research direction. In this study, to build a platform for the potential application in flexible transparent devices, a combination of the muscovite substrate and the antiferroelectric PbZrO 3 (PZO) is studied as a model system. The growth of PZO is first optimized on rigid substrates and then transferred to muscovite with the form of epitaxial and polycrystalline films. The energy storage performance with robust electrical and mechanical stability is systematically demonstrated. High energy densities of 46~52 J/cm 3 were obtained; Compared with the epitaxial PZO, the polycrystalline PZO shows an increase of efficiency by 28% and possesses higher heat resistance. Moreover, fabricated on a transparent indium tin oxide electrode, the PZO heterostructure exhibits excellent energy performance and an optical transmittance of up to 70–80%. Through this study, a paradigm for reliable flexible transparent fast charging-discharging energy storage element is developed. • To build a platform for the potential application in flexible transparent devices, a combination of the muscovite substrate and the antiferroelectric PbZrO 3 (PZO) is studied as a model system. • The energy storage performance with robust electrical and mechanical stability is systematically demonstrated. High energy densities of 46~52 J/cm 3 were obtained. • Compared with the epitaxial PZO, the polycrystalline PZO shows an increase of efficiency by 28%. • Moreover, fabricated on a transparent indium tin oxide electrode, the PZO heterostructure exhibits excellent energy performance and an optical transmittance of up to 70–80%. • Through this study, a paradigm for reliable flexible transparent fast charging-discharging energy storage element is developed.

3D‐Printed Bioreactor with Integrated Impedance Spectroscopy for Cell Barrier Monitoring

AbstractCell culture experiments often suffer from limited commercial availability of laboratory‐scale bioreactors, which allow experiments to be conducted under flow conditions and additional online monitoring techniques. A novel 3D‐printed bioreactor with a homogeneously distributed flow field enabling epithelial cell culture experiments and online barrier monitoring by integrated electrodes through electrical impedance spectroscopy (EIS) is presented. Transparent and conductive indium tin oxide glass as current‐injecting electrodes allows direct visualization of the cells, while measuring EIS simultaneously. The bioreactor's design considers the importance of a homogeneous electric field by placing the voltage pick‐up electrodes in the electrical field. The device's functionality is demonstrated by the cultivation of the epithelial cell line Caco‐2 under continuous flow and monitoring of the cell layer by online EIS. The collected EIS data were fitted by an equivalent electric circuit, resulting in the cell layer's resistance and capacitance. This data is used to monitor the cell layer's reaction to ethylene glycol‐bis‐(2‐aminoethyl ether)‐N,N,N′,N′‐tetraacetic acid and forskolin. These two model substances show the power of impedance spectroscopy as a non‐invasive way to characterize cell barriers. In addition, the bioreactor design is available as a print‐ready file in the Appendix, enabling its use for other scientific institutions.

Upward flow boiling of HFE-7000 in high frequency AC electric fields

Abstract An experimental investigation of upward flow boiling of HFE-7000 has been conducted in a vertical tube under a high frequency alternating current (AC) electric field with the aid of high speed photography. Importantly, the test section was coated with 600 nm transparent Indium Tin Oxide (ITO) layer allowing visual access to the boiling dynamics within the tube while simultaneously functioning as an electrical heater element for the heat transfer and electrode for establishing the electric field. Experiments were performed for a constant mass flux of G=100 kg/m2s, inlet subcooling of 2K, applied heat flux ranging between 5 to 50 kW/m2, applied voltages from 0 to 10 kVp-p AC and frequencies of 100 Hz, 1000 Hz and 10,000 Hz. For the 100 Hz applied frequency, the evidence supports the hypothesis that there are strong electrophoretic forces augmenting the heat and mass transfer phenomenon, with better than two-fold enhancement in the heat transfer at low heat fluxes. This tends to diminish with applied heat flux. Interestingly, the EHD enhancement increases for all heat flux levels when the frequency is increased to 1000 Hz, with an observed change to polarization-force dominated EHD augmentation. Increasing further to 10,000 Hz results in diminished enhancement, resulting in a peak enhancement at 1000 Hz.

Dye and activated carbon from Canarium ovatum Engl. as photosensitizer and counter electrode for Titania-based dye sensitized solar cell

Natural dye from exocarp and activated carbon from charred shells of Canarium ovatum Engl nut was used in the fabrication of dye sensitized solar cell (DSSC). Anatase titania (titanium dioxide, TiO2) nanoparticles was used as semiconducting layer deposited on a transparent conductive indium tin oxide glass using doctor blade method. TiO2 film thickness and soaking time in dye were varied to show response in terms of fill factor (FF), short circuit current density (Jsc), open circuit photovoltage (Voc), and conversion efficiency (η). In a 2.0 cm2 active surface area tested under solar irradiance, assembled DSSC at optimum conditions garnered 0.768 desirability with FF, Jsc, Voc and n values of 0.601, 6.293 mA/cm2, 0.446 V, and 1.792, respectively.

Two-Dimensional Digital Beam Steering Based on Liquid Crystal Phase Gratings

Electrically tunable phase gratings are able to steer an incoming light beam without employing movable parts. Here, we present the design and implementation of a 2D beam steering device by cascading two orthogonal 1D liquid crystal (LC) based phase gratings, each having an array of 72 rectangular individually controlled pixels and driven by a custom 12-bit Pulse-Width Modulation (PWM) electrical driver. High-resolution structures in glass wafers coated with transparent Indium-Tin Oxide (ITO) have been prepared using Direct Laser Writing (DLW) techniques. With DLW, a high number of pixels can easily be drawn with an interpixel space of less than 3 μm, leading to devices with a high fill factor. The active area of the cascaded device is 1.1 × 1.1 mm2. We present a 72 × 72 point efficiency map corresponding to a maximum diagonal steering angle of 1.65°. Special attention has been paid to make the device compatible with space application by avoiding electronics in the active area.

Flexible electrochromic and thermochromic hybrid smart window based on a highly durable ITO/graphene transparent electrode

Abstract A flexible smart window with electrochromic (EC) and thermochromic (TC) properties is fabricated on a highly durable transparent indium-tin oxide (ITO)/graphene/polyethylene terephthalate (PET) electrode. An amorphous WO3 film and crystalline VO2 film are used as the EC and TC material, respectively, in the device. The ITO film deposited via atomic layer deposition acts as a protective layer and suppresses the plasma-induced damage of graphene, which typically occurs during the sputtering process. In this device, the amorphous WO3 film undergoes cathodic electrochromic reactions with high coloration efficiency, while the crystalline VO2 film shows characteristic thermochromic behavior. Thus, the flexible EC–TC hybrid smart window shows the controlled transmission of optical and solar energies according to the surrounding temperature and the applied voltage, allowing selective modulation of the visible and near-infrared light. The flexible EC–TC hybrid device is also very stable under mechanical bending, owing to the robust adhesion of the ITO film on the graphene support and the reduced plasma-induced damage of graphene. The fabricated high-performance, durable ITO/graphene/PET transparent electrode can pave the way for next-generation flexible optoelectronic devices as well as multifunctional flexible smart windows.

Parametric Studies of a Mercury-Free DBD Lamp

Mercury discharge lamps are often used because of their high efficiency; however, the usage of mercury lamps will be restricted or forbidden for safety and environmental purposes. Finding alternative solutions to suppress mercury is of major interest. The aim of this work is to increase the luminous efficacy of a commercial-free mercury flat dielectric barrier discharge lamp (Planilum, St Gobain) in order to reach the necessary conditions for the lamp to be used as a daily lighting source. The lamp is made of two glass plates separated by a gap of 2 mm. The gap is filled by a neon xenon mixture. The external electrodes made of transparent ITO (indium tin oxide) are deposited on the lamp glass plates. The electrical signal applied to the electrodes generates a UV-emitting plasma inside the gap. Phosphors deposited on the glass allow the production of visible light. The original electrode geometry is plane-to-plane; this induces filamentary discharges. We show that changing the plane-to-plane geometry to a coplanar geometry allows the plasma to spread all over the electrode surface, and we can reach twice the efficacy of the lamp (32 lm/W) as compared to the original value. Using this new electrode geometrical configuration and changing the electrical signal from sinusoidal to a pulsed signal greatly improves the visual uniformity of the emitted light all over the lamp. Electrical and optical parametric measurements were performed to study the lamp characteristics. We show that it is possible to develop a free mercury lamp with an efficacy compatible with lighting purposes.

Highly transparent and conductive ITO substrates for near infrared applications

Indium tin oxide (ITO) is the most widely used transparent conductor in applications such as light emitting diodes, liquid crystal devices, touch screens, and photovoltaic cells. So far, its use has mainly been limited to the visible range (380 nm–750 nm), as it reflects at longer wavelengths and, consequently, its transmission is low. Here, we introduce a simple technique, based on high temperature annealing, which can reduce reflection in the near-infrared range (750 nm–2400 nm). With an optimized set of parameters, we were able to modulate the ITO properties and achieve a high transmission, greater than 80% including substrate contribution, at telecommunication wavelengths (C-band, 1530 nm–1565 nm) while still maintaining high electrical conductivity (resistivity <1.9 × 10−4 Ω cm). By using the newly developed infrared ITO transparent conductor, we demonstrate quantum dot solar cells with 27.7% enhancement in external quantum efficiency at the first exciton peak (1650 nm), and liquid crystal switching devices with 25% enhancement in transmission, with respect to device counterparts incorporating commercially available ITO.

Indium Tin Oxide Thin Film Deposition by Magnetron Sputtering at Room Temperature for the Manufacturing of Efficient Transparent Heaters

Indium tin oxide (ITO) thin films are widely used as transparent electrodes in electronic devices. Many of those electronic devices are heat sensitive, thus their manufacturing process steps should not exceed 100 °C. Manufacturing competitive high-quality ITO films at low temperature at industrial scale is still a challenge. Magnetron sputtering technology is the most suitable technology fulfilling those requirements. However, ITO layer properties and the reproducibility of the process are extremely sensitive to process parameters. Here, morphological, structural, electrical, and optical characterization of the ITO layers deposited at low temperature has been successfully correlated to magnetron sputtering process parameters. It has been demonstrated that the oxygen flow controls and influences layer properties. For oxygen flow between 3–4 sccm, high quality crystalline layers were obtained with excellent optoelectronic properties (resistivity <8 × 10−4 Ω·cm and visible transmittance >80%). The optimized conditions were applied to successfully manufacture transparent ITO heaters on large area glass and polymeric components. When a low supply voltage (8 V) was applied to transparent heaters (THs), de-icing of the surface was produced in less than 2 min, showing uniform thermal distribution. In addition, both THs (glass and polycarbonate) showed a great stability when exposed to saline solution.

Highly conductive low-temperature combustion-derived transparent indium tin oxide thin film

Highly conductive (conductivity 620 S cm−1) and transparent ITO thin films are achieved at low temperature (350 °C) through effective combustion solution processing via multistep coating. The properties show potential for next generation flexible and transparent electronics.

Evaluation of electrical resistivity, residual stress and surface roughness of sputtering indium tin oxide films with different thicknesses

This paper investigates the influence of film thickness on the electrical and mechanical properties of transparent indium tin oxide (ITO) thin films. Two groups of ITO thin films deposited on unheated substrates were prepared by the radio-frequency magnetron sputtering technique. The biaxial residual stress and surface roughness for two groups of ITO thin films were measured by a Twyman–Green interferometer and a Linnik microscopic interferometer, respectively. The electrical resistivity of the ITO films was measured by a four-point probe apparatus, the thickness was determined mechanically with a profilometer. The measurement results show that the average resistivity of ITO thin films decreases with increasing the deposited thickness. The compressive residual stress in the ITO thin films decreases with increasing the deposited thickness. We also find that an anisotropic stress in the two groups of ITO films is more compressive in a certain direction. The RMS surface roughness in the two groups of ITO films is less than 1 nm.

Preparation of optically transparent and conducting radio-frequency sputtered indium tin oxide ultrathin films

Highly conducting and optically transparent indium tin oxide (ITO) ultrathin films (thickness < 100 nm) are needed in order to improve the performance of optoelectronic devices, especially for plasmonic enhanced photovoltaic devices. ITO thin films (thickness ~ 60 nm) are deposited on glass substrates at room temperature by radio-frequency magnetron sputtering with a power of 200 W under argon atmosphere followed by rapid thermal annealing for 1 min at various temperatures in nitrogen environment. The effect of rapid thermal annealing on the physical and chemical changes of the ITO thin films is explored and co-related the changes with optoelectronic properties of the films as well. As-deposited thin films after rapid thermal annealing at 600°C display significant changes in the microstructure with occurrence of crystallites (average crystallite size ~ 11.9 nm), average optical transmittance (~ 88.2%) in the visible region, and electrical resistivity as low as 1.09 × 10−4 Ω-cm with high figure of merit of 2.27 × 10−2 Ω−1 — indicating their suitability as transparent conducting anode for the relevant electronics.

Solution-processed PEDOT:PSS:GO/Ag NWs composite electrode for flexible organic light-emitting diodes

Flexible organic light emitting diodes (OLEDs) have attracted considerable attention for the reason of light weight, high mechanical flexibility in display and lighting. The most widely used transparent anode indium tin oxide (ITO) is unsuitable for flexible OLEDs because of its easy cracking upon bending. In this paper, we proposed a simple two steps solution processing method to fabricate flexible PEDOT:PSS:GO/Ag NWs composite electrodes. The optimized PEDOT:PSS:GO/Ag NWs composite electrode exhibits an optical transmittance of 88.7% at a wavelength of 550 nm and a low sheet resistance of 17 Ω/sq, which arecomparable to that of ITO. With PEDOT:PSS:GO/Ag NWs composite electrodes, the turn on voltage, current density and maximum brightness of OLEDs based on composite electrode were 2.1 V, 6.2 cd/A and 22894 cd/m2, respectively, which were superior to that OLED based on ITO anode. The enhanced performance of OLEDs based on composite anode mainly attributed to the lower sheet resistance, smoother surface of the composite anode and the far surface plasma resonance (Far SPR) effect, a lower waveguide optical loss because of the introduction of Ag NWs in the electrode.