Showing papers on "Indium tin oxide published in 2018"

Femtomolar Detection by Nanocoated Fiber Label-Free Biosensors.

Abstract: The advent of optical fiber-based biosensors combined with that of nanotechnologies has provided an opportunity for developing in situ, portable, lightweight, versatile, and high-performance optical sensing platforms. We report on the generation of lossy mode resonances by the deposition of nanometer-thick metal oxide films on optical fibers, which makes it possible to measure precisely and accurately the changes in optical properties of the fiber-surrounding medium with very high sensitivity compared to other technology platforms, such as long period gratings or surface plasmon resonances, the gold standard in label-free and real-time biomolecular interaction analysis. This property, combined with the application of specialty structures such as D-shaped fibers, permits enhancing the light–matter interaction. SEM and TEM imaging together with X-EDS tool have been utilized to characterize the two films used, i.e., indium tin oxide and tin dioxide. Moreover, the experimental transmission spectra obtained af...

Barrier Design to Prevent Metal-Induced Degradation and Improve Thermal Stability in Perovskite Solar Cells

Abstract: Metal-contact-induced degradation and escape of volatile species from perovskite solar cells necessitate excellent diffusion barrier layers. We show that metal-induced degradation limits thermal stability in several perovskite chemistries with Au, Cu, and Ag gridlines even when the metal is separated from the perovskite by a layer of indium tin oxide (ITO). Channels in a sputtered ITO layer that align with perovskite grain boundaries are pathways for metal and halide diffusion into or out of the perovskite. Planarizing the perovskite morphology with a spin-cast organic charge-transport layer results in a subsequently deposited ITO layer that is uniform and impermeable. We show that it is critical to seal the edges of the active layers to prevent escape of volatile species. We demonstrate 1000 h thermal stability at 85 °C in CH3NH3PbI3 solar cells with complete-coverage silver contacts. Our barrier layer design enables long-term thermal stability of perovskite solar cells, a critical step to commercialization.

PEDOT:PSS monolayers to enhance the hole extraction and stability of perovskite solar cells

Abstract: A hole transport layer (HTL) plays a key role in efficient hole extraction and transfer in inverted planar perovskite solar cells. A 10–20 nm thick poly (3,4-ethylenedioxythiphene):poly(styrenesulfonate) (PEDOT:PSS) layer is the most popular HTL in such a device structure. But is it essential to construct such a thick PEDOT:PSS layer? To address this question, herein self-assembled PEDOT:PSS monolayers are obtained on the indium tin oxide (ITO) surface through a facile water rinsing process. Perovskite solar cells with water rinsed PEDOT:PSS as a HTL yield improved power conversion efficiency (PCE) from 13.4% to 18.0%, compared with the control cells with as-cast PEDOT:PSS. The main contribution is from the open-circuit voltage (Voc) and fill factor (FF). Characterization indicates that the majority of PEDOT:PSS is washed away, but an ultra-thin layer of PEDOT:PSS can attach strongly onto ITO via In–O–S chemical bonds between the PSS chain and ITO. Subsequently, PEDOT and PSS form a bilayered structure due to Coulomb interaction. Such an arrangement induces an oriented electric field from positively charged PEDOT to negatively charged PSS, which can accelerate the process of hole extraction. Moreover, the oriented arrangement of PEDOT:PSS monolayers provides higher work function and stronger hydrophobicity, leading to the enhancement in Voc and stability in the ambient environment. This work suggests that there is still room for the efficiency improvement of perovskite solar cells by optimizing the traditional functional layers.

Chitosan-Based Polysaccharide-Gated Flexible Indium Tin Oxide Synaptic Transistor with Learning Abilities

Abstract: Recently, environment-friendly electronic devices are attracting increasing interest. “Green” artificial synapses with learning abilities are also interesting for neuromorphic platforms. Here, solu...

Highly Efficient and Stable Flexible Perovskite Solar Cells with Metal Oxides Nanoparticle Charge Extraction Layers.

Abstract: In this study, the fabrication of highly efficient and durable flexible inverted perovskite solar cells (PSCs) is reported. Presynthesized, solution-derived NiOx and ZnO nanoparticles films are employed at room temperature as a hole transport layer (HTL) and electron transport layer (ETL), respectively. The triple cation perovskite films are produced in a single step and for the sake of comparison, ultrasmooth and pinhole-free absorbing layers are also fabricated using MAPbI3 perovskite. The triple cation perovskite cells exhibit champion power conversion efficiencies (PCEs) of 18.6% with high stabilized power conversion efficiency of 17.7% on rigid glass/indium tin oxide (ITO) substrates (comparing with 16.6% PCE with 16.1% stabilized output efficiency for the flexible polyethylene naphthalate (PEN)/thin film barrier/ITO substrates). More interestingly, the durability of flexible PSC under simulation of operative condition is proved. Over 85% of the maximum stabilized output efficiency is retained after 1000 h aging employing a thin MAPbI3 perovskite (over 90% after 500 h with a thick triple cation perovskite). This result is comparable to a similar state of the art rigid PSC and represents a breakthrough in the stability of flexible PSC using ETLs and HTLs compatible with roll to roll production speed, thanks to their room temperature processing.

Materials for Transparent Electrodes: From Metal Oxides to Organic Alternatives

Abstract: Nowadays, opto-electronic devices, such as displays, are omnipresent in our daily life. A crucial component of these devices is a transparent electrode, which allows the in- and out-coupling of light. With the goal of optimizing the electrode characteristics and improving device efficiencies, many approaches for the fabrication of thin, transparent conducting films have been studied. This review gives an overview of the different material classes which have been used as transparent electrodes, ranging from metal oxides, such as Indium Tin Oxide, metal and carbonaceous nanostructures, to conducting polymers and composites. For every material class a brief description of the fundamental principles, processing routes and the latest achievements is given. Furthermore, the different electrodes are compared regarding their opto-electronic performance, flexibility and surface roughness. Ultimately, advantages and drawbacks of the respective electrodes are discussed. This critical comparison of fundamentally different transparent conducting materials allows, on one hand, to make a sensible choice of electrode for specific applications, and, on the other hand, to point out scientific challenges that must still be addressed.

Phototunable Biomemory Based on Light-Mediated Charge Trap.

Abstract: Phototunable biomaterial-based resistive memory devices and understanding of their underlying switching mechanisms may pave a way toward new paradigm of smart and green electronics. Here, resistive switching behavior of photonic biomemory based on a novel structure of metal anode/carbon dots (CDs)-silk protein/indium tin oxide is systematically investigated, with Al, Au, and Ag anodes as case studies. The charge trapping/detrapping and metal filaments formation/rupture are observed by in situ Kelvin probe force microscopy investigations and scanning electron microscopy and energy-dispersive spectroscopy microanalysis, which demonstrates that the resistive switching behavior of Al, Au anode-based device are related to the space-charge-limited-conduction, while electrochemical metallization is the main mechanism for resistive transitions of Ag anode-based devices. Incorporation of CDs with light-adjustable charge trapping capacity is found to be responsible for phototunable resistive switching properties of CDs-based resistive random access memory by performing the ultraviolet light illumination studies on as-fabricated devices. The synergistic effect of photovoltaics and photogating can effectively enhance the internal electrical field to reduce the switching voltage. This demonstration provides a practical route for next-generation biocompatible electronics.

Transparent transmission-selective radar-infrared bi-stealth structure.

Abstract: We report a multifunctional metamaterial composite structure that not only provides the broadband radar and thermal infrared bi-stealth function but also possesses an in-band microwave transmission window and high optical transparency. It is composed of four metasurface layers made of indium tin oxide (ITO) films with different surface resistances, which are specifically designed to sequentially control the infrared emission, microwave absorption and transmission. The fabricated sample exhibits a low reflectivity less than 10% in 1.5-9 GHz and a transmission peak of 50% around 3.8 GHz up to the incident angle of 30 degrees. In the infrared atmosphere window, a low thermal emissivity of about 0.52 is achieved. Meanwhile, it keeps good optical transparency by the use of the ITO films. The optically transparent, low-infrared-emissivity, radar-reflectionless and frequency-selective-transmission properties will enable the promising application of communication-compatible multispectral stealth technology.

Synthesis of Silver Nanowires with Reduced Diameters Using Benzoin-Derived Radicals to Make Transparent Conductors with High Transparency and Low Haze.

Abstract: Reducing the diameter of silver nanowires has been proven to be an effective way to improve their optoelectronic performance by lessening light attenuation. The state-of-the-art silver nanowires are typically around 20 nm in diameter. Herein we report a modified polyol synthesis of silver nanowires with average diameters as thin as 13 nm and aspect ratios up to 3000. The success of this synthesis is based on the employment of benzoin-derived radicals in the polyol approach and does not require high-pressure conditions. The strong reducing power of radicals allows the reduction of silver precursors to occur at relatively low temperatures, wherein the lateral growth of silver nanowires is restrained because of efficient surface passivation. The optoelectronic performance of as-prepared 13 nm silver nanowires presents a sheet resistance of 28 Ω sq–1 at a transmittance of 95% with a haze factor of ∼1.2%, comparable to that of commercial indium tin oxide (ITO).

Transparent broadband metamaterial absorber enhanced by water-substrate incorporation.

Abstract: In this paper, a transparent metamaterial absorber (MA) loaded with water substrate is presented, which can simultaneously achieve enhanced broadband microwave absorption and tunable infrared radiation. As a proof, the indium tin oxide (ITO) films are first introduced here as a frequency selective surface (FSS) on the top layer and reflective backplane on the ground layer. Next the distilled water combined with the polymethyl methacrylate (PMMA) substrate is employed as a hybrid substrate in the middle. Simulation and experimental measurements show that the transparent water-substrate MA can achieve broadband microwave absorption with efficiency over 90% in the frequency band of 6.4-23.7GHz, and the proposed hybrid substrate has almost no influence on its original transmittance. Moreover, owing to the available water circulation system, the infrared radiation of the proposed MA is also demonstrated to be controlled by the temperature of the injected water. Based on its multifunction and high performance, it is expected that the proposed design may find potential applications, such as glass window of stealth equipment, electromagnetic compatible buildings/facilities, etc.

Highly Bendable and Durable Transparent Electromagnetic Interference Shielding Film Prepared by Wet Sintering of Silver Nanowires

Abstract: Electromagnetic (EM) wave emissions from wearable or flexible smart display devices can cause product malfunction and have a detrimental effect on human health. Therefore, EM shielding strategies are becoming increasingly necessary. Consequently, herein, we prepared a transparent acrylic polymer-coated/reduced graphene oxide/silver nanowire (Ag NW) (A/RGO/SANW) EM interference (EMI) shielding film via liquid-to-vapor pressure-assisted wet sintering. The film exhibited enhanced Ag NW network formation and antireflection (AR) effects. The wet-sintered Ag NW shielding film had a threshold radius of curvature (ROC) of 0.31 mm at a film thickness of 100 μm, demonstrating its high flexibility, whereas the conventional indium tin oxide (ITO) shielding film had a threshold ROC of ∼5 mm. The EMI shielding effectiveness (SE) of the A/RGO/SANW multilayer film was approximately twice that of the ITO film at a similar relative transmittance (84–85%). The optical relative reflectance of the Ag NW layer was reduced due ...

Low-Temperature Atomic Layer Deposition of Metal Oxide Layers for Perovskite Solar Cells with High Efficiency and Stability under Harsh Environmental Conditions

Abstract: Rapid progress achieved on perovskite solar cells raises the expectation for their further development toward practical applications. Moisture sensitivity of perovskite materials is one of the major obstacles which limits the long-term durability of the perovskite solar cells, especially in outdoor operation where rainfall and water accumulation on the solar panels often occur. Micro/nanopinholes within the functional layers of the devices usually lead to water vapor penetration, thus subsequent decomposition of perovskites, and finally poor device performance and shortened operational lifetime. In this work, low-temperature atomic layer deposition (ALD) technique was utilized to incorporate pinhole-free metal oxide layers (TiO2 and Al2O3) into an inverted perovskite solar cell consisting of indium tin oxide/NiO/perovskite/PC61BM/TiO2/Ag. The interface properties between the inserted TiO2 layer and the perovskite layer were investigated by X-ray photoelectron spectroscopy. The results showed that TiO2 ALD fabrication process had made negligible degradation to the perovskite layer. The TiO2 layer can significantly reduce interfacial charge recombination loss, improve interfacial contact, and enhance water resistance. A maximum power conversion efficiency (PCE) of 18.3% was achieved for devices with TiO2 interface layers. A stacked Al2O3 encapsulation layer was designed and deposited on top of the devices to further improve device stability under harsh environmental conditions. The encapsulated devices with the best performance retained 97% of the initial PCE after being stored in ambient condition for a thousand hours. They also showed great water resistance, and no significant degradation in terms of PCE and photocurrent of the devices was observed after they were immersed in deionized water for as long as 2 h. Our approach offers a promising way of developing highly efficient and stable perovskite solar cells under real-world operational conditions.

Simultaneous label-free and pretreatment-free detection of heavy metal ions in complex samples using electrodes decorated with vertically ordered silica nanochannels

Abstract: In this work, indium tin oxide coated glass (ITO) decorated with vertically-ordered mesoporous silica film (VMSF/ITO) is synthesized and applied as electrochemical sensor for simultaneous label-free and pretreatment-free detection of Pb2+, Cu2+, and Cd2+ in human serum and soil leaching solution. Using differential pulse voltammetry (DPV), the electrochemical detection consists of electro-deposition of metal species and subsequent anodic stripping in the silica nanochannels. Because of the electrostatic enrichment and nano-confinement effects, VMSF/ITO is able to simultaneously detect Pb2+, Cu2+, and Cd2+ in a mixture with low detection limits (2.6 nM, 32 nM and 230 nM, respectively). Moreover, VMSF confer the electrode with excellent anti-fouling and anti-interference property through steric exclusion and electrostatic repulsion. Direct analysis of complex biological (human serum) and environmental (soil leaching solution) samples could be finished within 10 min without the usual need of tedious pretreatment. Furthermore, the VMSF/ITO sensor can be reused for several times without performance degradation.

Emerging Novel Metal Electrodes for Photovoltaic Applications.

Abstract: Emerging novel metal electrodes not only serve as the collector of free charge carriers, but also function as light trapping designs in photovoltaics. As a potential alternative to commercial indium tin oxide, transparent electrodes composed of metal nanowire, metal mesh, and ultrathin metal film are intensively investigated and developed for achieving high optical transmittance and electrical conductivity. Moreover, light trapping designs via patterning of the back thick metal electrode into different nanostructures, which can deliver a considerable efficiency improvement of photovoltaic devices, contribute by the plasmon-enhanced light-mattering interactions. Therefore, here the recent works of metal-based transparent electrodes and patterned back electrodes in photovoltaics are reviewed, which may push the future development of this exciting field.

Highly flexible transparent electrodes based on mesh-patterned rigid indium tin oxide

Abstract: We developed highly bendable transparent indium tin oxide (ITO) electrodes with a mesh pattern for use in flexible electronic devices. The mesh patterns lowered tensile stress and hindered propagation of cracks. Simulations using the finite element method confirmed that the mesh patterns decreased tensile stress by over 10% because of the escaped strain to the flexible film when the electrodes were bent. The proposed patterned ITO electrodes were simply fabricated by photolithography and wet etching. The resistance increase ratio of a mesh-patterned ITO electrode after bending 1000 times was at least two orders of magnitude lower than that of a planar ITO electrode. In addition, crack propagation was stopped by the mesh pattern of the patterned ITO electrode. A mesh-patterned ITO electrode was used in a liquid-based organic light-emitting diode (OLED). The OLED displayed the same current density-voltage-luminance (J-V-L) curves before and after bending 100 times. These results indicate that the developed mesh-patterned ITO electrodes are attractive for use in flexible electronic devices.

Water-based metamaterial absorbers for optical transparency and broadband microwave absorption

Abstract: Naturally occurring water is a promising candidate for achieving broadband absorption. In this work, by virtue of the optically transparent character of the water, the water-based metamaterial absorbers (MAs) are proposed to achieve the broadband absorption at microwave frequencies and optical transparence simultaneously. For this purpose, the transparent indium tin oxide (ITO) and polymethyl methacrylate (PMMA) are chosen as the constitutive materials. The water is encapsulated between the ITO backed plate and PMMA, serving as the microwave loss as well as optically transparent material. Numerical simulations show that the broadband absorption with the efficiency over 90% in the frequency band of 6.4–30 GHz and highly optical transparency of about 85% in the visible region can be achieved and have been well demonstrated experimentally. Additionally, the proposed water-based MA displays a wide-angle absorption performance for both TE and TM waves and is also robust to the variations of the structure parameters, which is much desired in a practical application.

Indium Tin Oxide Broadband Metasurface Absorber

Abstract: Metamaterials have been designed to achieve a wide range of functionalities. Metamaterial absorbers are of particular interest for various applications such as infrared detectors, emissivity coatings, and photovoltaic cells. Various metamaterial platforms have been demonstrated to achieve perfect absorption and several attempts have been made to extend the absorption bandwidth of such devices. We demonstrate a broadband infrared absorber using an asymmetric Fabry–Perot cavity consisting of a monolithically fabricated two-layer metasurface. Superoctave optical absorption is achieved by tailoring the structure of the metasurface layers and the thickness of the cavity. The device yields absorptance of over 80% from λ = 4–16 μm, while maintaining the performance over a wide range of incident angles. In contrast to most metamaterial absorbers, our metasurface layers are made of customized indium tin oxide (ITO), conferring the advantage of CMOS compatibility compared to previous approaches using noble metals.

Alternative transparent conducting electrode materials for flexible optoelectronic devices

Abstract: Transparent Conductive Electrode (TCE) is an essential part of the optoelectronic and display devices such as Liquid Crystal Displays (LCDs), Solar Cells, Light Emitting Diodes (LEDs), Organic Light Emitting Diodes (OLEDs) and touch screens. Indium Tin Oxide (ITO) is a commonly used TCE in these devices because of its high transparency and low sheet resistance. However, scarcity of indium and brittle nature of ITO limit its use in future flexible electronics. In order to develop flexible optoelectronic devices with improved performance, there is a requirement of replacing the ITO with a better alternate TCE. In this work, several alternative TCEs including transparent conductive oxides, carbon nanotubes, conducting polymers, metal nanowires, graphene and composites of these materials are studied with their properties such as sheet resistance, transparency and flexibility. The advantage and current challenges of these materials are also presented in this work.

Coupling of Epsilon-Near-Zero Mode to Gap Plasmon Mode for Flat-Top Wideband Perfect Light Absorption

Abstract: Epsilon-near-zero (ENZ) materials, when probed at or near wavelengths corresponding to their zero permittivity crossing points, have unique and interesting properties that can be exploited for enhancing nanoscale light–matter interactions. Here, we experimentally show that over an order of magnitude increase in the absorption band of a periodically patterned metal–dielectric–metal structure can be obtained by integrating an indium tin oxide (ITO) subwavelength nanolayer into the insulating dielectric gap region. Through incorporation of a 12 nm thick ITO layer between the patterned gold nanodisks and the SiO2 dielectric layer, a 240 nm wide, flat-top perfect (>98%) absorption centered at 1550 nm wavelength is enabled. The demonstrated wideband, perfect absorption resonance is shown to be due to coupling between the gap plasmon mode of the metasurface and the ENZ mode in the nanoscale ITO film.

Novel Plasma-Assisted Low-Temperature-Processed SnO2 Thin Films for Efficient Flexible Perovskite Photovoltaics

Abstract: The recent evolution of solution-processed hybrid organic–inorganic perovskite-based photovoltaic devices opens up the commercial avenue for high-throughput roll-to-roll manufacturing technology. To circumvent the thermal limitations that hinder the use of metal oxide charge transport layers on plastic flexible substrates in such technologies, we employed a relatively low-power nitrogen plasma treatment to achieve compact SnO2 thin-film electrodes at near room temperature. The perovskite photovoltaic devices thus fabricated using N2 plasma-treated SnO2 performed on par with thermally annealed SnO2 electrodes and resulted in a power conversion efficiency (PCE) of ca. 20.3% with stabilized power output (SPO) of ca. 19.1% on rigid substrates. Furthermore, the process is extended to realize flexible perovskite solar cells on indium tin oxide (ITO)-coated polyethylene terephthalate (PET) substrates with champion PCE of 18.1% (SPO ca. 17.1%), which retained ca. 90% of its initial performance after 1000 bending ...

Long-term stable silver nanowire transparent composite as bottom electrode for perovskite solar cells

Abstract: As the most promising alternative to traditional indium tin oxide (ITO), silver nanowire (AgNW) composite transparent electrodes with improved stabilities compared with that of the pristine AgNWs networks have been demonstrated in various devices. However, a stable AgNW/polymer composite as the bottom electrode for perovskite solar cells has not yet been reported. Here, a long-term stable, smooth AgNW composite with an antioxidant-modified chitosan polymer was developed. The modified polymer can effectively protect pristine AgNWs from side reactions with perovskite, whereas it does not block the carrier drift through the interface of the insulating polymer. The as-prepared AgNW/polymer composite electrode exhibited a root mean square roughness below 10 nm at a scan size of 50 μm × 50 μm, and its original sheet resistance did not change obviously after aging at 85 °C for 40 days in air. As a result, the perovskite solar cell employing the composite as the bottom electrode yielded a power conversion efficiency of 7.9%, which corresponds to nearly 75% of that of the reference device with an ITO electrode.

Gas sensing enhancing mechanism via doping-induced oxygen vacancies for gas sensors based on indium tin oxide nanotubes

Abstract: It’s demonstrated that the defects induced by doping can greatly influence the sensing properties of oxide-based gas sensors. In this work, the authors have designed indium tin oxide nanotubes (ITO NTs) with different Sn doping concentrations. Results showed that the walls of ITO NTs are comprised of the formed ITO and redundant In2O3 nanoparticles (NPs) at low doping concentration, and the doping-induced oxygen vacancies ( V o · · S ) can be tuned by Sn concentrations. Series of sensing tests to formaldehyde gas indicated that the ITO-7 NTs show the lowest working temperature (160 °C) and the highest specific response. Here, It is noted that to eliminate the influence of the coating amount of sensing performances, a concept of specific response was proposed i.e., Rair/(m–Rgas), where Rair and Rgas respectively stand for the resistances of gas sensors in the reference gas (in air this case) and in the test gas ambience, and m stands for the mass of the coated sensing materials. The decreased working temperature could be attributed to the formed In2O3 NPs/ITO tubular structure, and the enhanced specific response might be mainly associated with the V o · · S . Furthermore, a possible gas sensing enhancing mechanism via V o · · S for ITO-based gas sensors was proposed based on our results and analysis. This research would give some instructive advice to design high-performances oxide-based gas sensors via tuning the V o · · S .

Optical and electrical properties of ultra-thin indium tin oxide nanofilms on silicon for infrared photonics

Abstract: Optical and electrical properties of indium tin oxide (ITO) films on Si substrates in the thickness range from 10 nm to 100 nm were investigated. Spectroscopic ellipsometry was used to obtain the complex permittivity of the ultra-thin films in the spectral range from visible to long-wave infrared. It was found that as the thickness decreases, the Drude component of the electric permittivity becomes vanishingly small, eventually leaving only positive permittivity values. This coincides with an epsilon-near-zero wavelength red-shift from 1.5 to 2.1 um for the films that retain negative permittivities. Hall measurements were conducted to determine that the mobility of the films correspondingly decreased from 35 cm2/Vs to single digits. This decreasing mobility is the result of a non-electrical dead layer that was determined to be ~14 nm thick, which occurs at the ITO/Si interface and is due predominately to interfacial defects. The thickness of this dead layer depends on the deposition process and substrate. The optical and electrical properties of ultra-thin ITO films are useful for the precise design of infrared plasmonic modulators, perfect light absorbers and other photonic devices.