Indium Tin Oxide Nanofibers Research Articles

Transparent and High-Performance Extended Gate Ion-Sensitive Field-Effect Transistors Using Electrospun Indium Tin Oxide Nanofibers

Herein, we propose a transparent high-performance extended-gate ion-sensitive field-effect transistor (EG-ISFET) using an electrospun indium-tin-oxide (ITO) nanofiber sensing membrane with a high specific surface area. Electrospinning is a simple and effective technique for forming nanofibers. Nevertheless, one-step calcination, such as conventional thermal annealing or microwave annealing, cannot sufficiently eliminate the inherent defects of nanofibers. In this study, we efficiently removed residual polymers and internal impurities from nanofibers via a two-step calcination process involving combustion and microwave annealing. Moreover, Ar plasma treatment was performed to improve the electrical characteristics of ITO nanofibers. Conformally coated thin-film sensing membranes were prepared as a comparative group and subjected to the same calcination conditions to verify the effect of the nanofiber sensing membrane. The characteristics of the ITO nanofiber and ITO thin-film sensing membranes were evaluated using scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), optical transmittance, and conductivity. Moreover, the sensor operation of the EG-ISFETs is evaluated in terms of sensitivity and non-ideal behaviors. The optimized process improves the sensor characteristics and sensing membrane quality. Therefore, the ITO nanofiber sensing membrane improves the sensitivity and stability of the EG-ISFET, suggesting its applicability as a high-performance biochemical sensor.

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.

Microwave calcination of electrospun ITO nanofibers and improvement of transparent electrode characteristics through vacuum rapid thermal annealing

In this study, we applied microwave annealing (MWA) to calcinate indium tin oxide (ITO) nanofibers synthesized by electrospinning and evaluated the potential of the process by comparison with conventional thermal annealing (CTA). The MWA calcination was carried out for 2 min at 1800 W (processing temperature of 530 °C) with microwave at the frequency of 2.45 GHz, and CTA calcination was carried out for 30 min at 600 °C. We found that ITO nanofiber electrodes calcined by MWA have nearly equivalent physical properties as those calcined by CTA despite a lower processing temperature and shorter processing time. Subsequently, we applied vacuum rapid thermal annealing (RTA) at 300 °C for 30 s to the calcined nanofibers, which increased the crystallite size and created vacancy-like oxygen defects, thereby increasing the electron concentration and further reducing the resistance of the ITO nanofiber electrodes. Therefore, low-thermal-budget MWA calcination and vacuum RTA can effectively improve the properties of ITO nanofibers and contribute to the development of transparent and flexible electrodes.

A Transparent Multidimensional Electrode with Indium Tin Oxide Nanofibers and Gold Nanoparticles for Bistable Electrochromic Devices.

Due to the high energy efficiency and a wide range of potential applications in daily life, bistable electrochromic devices (BECDs) have gained extensive attention in recent years. However, poor bistability and slow response rate are the main barriers, which restrict the development of BECDs. Herein, a transparent multidimensional electrode with indium tin oxide (ITO) nanofibers and gold nanoparticles was fabricated to improve both the bistability and responsiveness of devices. Its criss-crossed ITO nanofibers with high length-to-diameter ratios to reduce the distance of heterogeneous electron transfer and its gold nanoparticles to form a stable Au-S bond to avoid self-erasing of electrochromic materials have been demonstrated and discussed systematically. This device based on the transparent multidimensional working electrode had a shorter response time (1/5) and a longer bistability (12/1) compared with the prototype devices based on common fluorine-doped tin oxide electrodes. Besides, this device had a promising electrochromic performance with a high coloration efficiency of 448.27 cm2/C and a switching stability with no significant attenuation after 1200 cycles.

Role of ITO nanoparticles embedded into electrospun ITO nanofibers

Both crystallization and molecular density are significant to achieve high electrical conductivity of transparent electrodes. Herein, we investigated the embedding effects of indium tin oxide (ITO) nanoparticles (NPs) into ITO nanofibers (NFs) synthesized by utilizing an electrospinning technique from ITO precursor solutions. We found that the ITO NPs might act as nucleation seeds that initiate crystallization of ITO, evidenced by flake-like morphologies which cannot be observed without ITO NPs. XRD measurements reveal that the ITO is crystalline with a higher degree and the size of ITO crystallites increases in the presence of ITO NPs embedded into NFs. Embedding ITO NPs leads to the formation of short fibers, but there is still large space between fibers as they are vertically stacked in the films, resulting in low electrical conductivity. Interestingly, a high ratio of ITO NPs enhances the electrical conductivity, as compared to a low ratio, which we attribute to the high fiber density on substrates due to the formation of shorter ITO NFs. Our results highlight that the ITO NPs influence not only the ITO crystallization but also the lengths of NFs. High electrical conductivity of NF films can be obtained by a high degree of crystallization and the optimum NF length that reduces spaces between NFs in the films.

Toward High Conductivity of Electrospun Indium Tin Oxide Nanofibers with Fiber Morphology Dependent Surface Coverage: Postannealing and Polymer Ratio Effects.

High electrical conductivity of metal oxide thin films needs uniform surface coverage, which has been the issue for the thin films based on electrospun nanofibers (NFs) that have advantage over the sputtered/spin-coated films with respect to large surface area and mechanical flexibility. Herein, we investigated a reduction in the sheet resistance of electrospun indium tin oxide (ITO) NF films with improved surface coverage. We found that the surface coverage depends significantly on the electrospinnable polymer concentration in the precursor solutions, especially after post-hot-plate annealing following the infrared radiation furnace treatment. The postannealing process increases crystallinity and oxygen vacancies. However, with a higher PVP content, it makes the surface of ITO NFs more prominently rough as a result of the formation of larger sphere-shaped ITO particles on the NF surface, which gives rise to poor surface coverage. A less poly(vinylpyrrolidone) (PVP) content in ITO NF films by electrospinning for short deposition times was found to improve surface coverage even after postannealing. The sheet resistance notably decreases, down to as low as 350 Ω/sq, with a high transmittance of over 90%. Our study provides an understanding on how to achieve high electrical conductivity of ITO NF films with high surface coverage, which can be utilized for the optoelectronic and sensing applications.

Highly Flexible Indium Tin Oxide Nanofiber Transparent Electrodes by Blow Spinning.

Transparent conductive film (TCF) has found wide applications. Indium tin oxide (ITO) is currently the most widely used transparent electrode. However, major problem of ITO is the lacking of flexibility, which totally limits its applications. Here, we report a highly flexible transparent electrode consisting of freestanding ITO nanofiber network fabricated by blow spinning, the advantage of which is its high-efficiency, low cost and safety. When the bending radius decreased to 0.5 mm, the resistance of the transparent electrodes only increased by 18.4%. Furthermore, the resistance was almost unchanged after thousands of bending cycles at 3.5 mm bending radius.

Electrochemistry and Spectroelectrochemistry with Electrospun Indium Tin Oxide Nanofibers

In this work, Indium tin oxide (ITO) nanofiber materials have been prepared and subsequently used for electrochemical and spectroelectrochemical analysis. Nanofibers have been electrospun from a suspension of polyvinylpyrrolidone (PVP) and indium and tin precursors with a ratio Sn/In=0.16. Their diameter could be adjusted between 110 and 235nm and the layer thickness was controlled between 12 and 120 μm. A calcination at 500°C in air followed by a thermal treatment at 1000°C under nitrogen atmosphere allowed to obtain conductive ITO nanofibers. XRD characterizations confirmed the successful transition of the starting material into indium tin oxide, showed the influence of the thermal treatment on grain size and provided some insight on their orientation. The electrochemical properties of the nanofibers have been characterized and optimized using dimethanolferrocene as a model probe. This porous ITO electrode have been applied to the electroanalysis of ascorbic acid with a sensitivity of 1.04mAmM−1cm−2 and to spectroelectrochemistry using Prussian blue as model system.

Preparation and photoelectric properties of indium tin oxide depositional optical fiber by centrifugal spinning

The purpose of this paper is to prepare an integrating light propagative, transparent and conductive optical fiber. This optical fiber is made by the coating of a thin layer of indium tin oxide (ITO) nanofibers. ITO nanofibers are fabricated via centrifugal spinning process and wrap around the quartz optical fiber. Field emission scanning electron microscopy, X-ray diffraction analysis, UV–Vis spectrophotometer, Avometer and Luminance colorimeter are used to characterize the morphology, crystal structure and photoelectric properties of ITO-coated optical fiber. Results show that the resistivity of ITO-coated optical fiber is around 0.87 (Ω cm); the average optical transmittance is more than 85 % in the visible range, and the ITO-coated optical fiber has a certain light propagation. This work laid the groundwork for future application in fiber sensors.

Electrodeposition of zinc oxide on transparent conducting metal oxide nanofibers and its performance in dye sensitized solar cells

Transparent conducting nanofibers of indium tin oxide (ITO) and antimony tin oxide were prepared on fluorine doped tin oxide glass substrates by electrospinning. Onto the obtained nanofiber mats first a dense zinc oxide layer followed by a nanoporous ZnO layer were electrochemically deposited. Transmission electron microscopy shows that only ITO nanofibers were covered with dense ZnO layers. For application in dye-sensitized solar cells (DSSCs) the dense layer is needed in order to suppress the back reaction of photogenerated electrons from the ZnO to the electrolyte. Therefore only films with ITO nanofibers were tested as porous electron collection layers in DSSC in view of electron transport and electron collection efficiency, and compared to ZnO layers electrodeposited under identical conditions but without nanofibers. Contrary to the expectation the conductive nanofibers do not improve the electron transport in the photoelectrodes and the solar to electrical conversion efficiency is limited to about 2.4%. It is discussed why the presence of nanofibers mats, which was found to be advantageous for TiO2-based DSSCs before, is not favorable for ZnO-based DSSCs.

ITO Nanofibers Prepared from Electrospun ITH/PVA Precursors

Poly (Vinyl Alcohol)(PVA)/In-Sn hydroxide (ITH) nanofibers were prepared via electrospinning, then followed by calcining at 400 , 475 , and 550 to obtain indium tin oxide (ITO) nanofibers. The influencing factors of solution properties, viscosity and electrical conductivity on the formation and morphology of electrospun fibers was investigated. The microstructure of PVA/ITH and ITO nanocomposites were characterized by scanning electron microscopy (SEM). And the crystalline structure of ITO nanocomposites was analyzed by X-ray diffractometry (XRD). The results showed that the average diameter and variation coefficient of obtained PVA/ITH nanofibers decreased after the adding of ITH. The ITO nanofibers became thinner and more uneven with the increasing of calcined temperature. XRD patterns proved that ITO nanoparticles existed after calcined and showed the structure was strongly depended on the calcined temperature. The bixbyite and the corundum type could be fabricated according the calcined temperature.

Three-dimensional networks of ITO/CdS coaxial nanofibers for photovoltaic applications

When serving as the electrode of semiconductor sensitized solar cells (SSSCs), conductive transparent nanofibers can enlarge the surface area and accelerate the electron transport, and can thus be expected to enhance the final power conversion efficiency of the device. Here we report the fabrication of three dimensional networks of indium tin oxide (ITO) nanofibers on a conductive glass substrate with a low sheet resistance of 15 Ω sq−1 by using an electrospinning technique. A post-treatment involving polyethylene glycol impregnation and calcination is developed to realize the excellent electrical contact of ITO nanofibers with the substrate, and maintain the fibrous morphology of the nanofibers also. Light-harvesting CdS nanocrystals are electrodeposited onto ITO nanofibers, and then the obtained ITO/CdS coaxial nanofibers are constructed into SSSCs. We find that the performance of this novel SSSC is remarkably improved compared with CdS nanocrystals directly deposited on a flat conductive substrate, and an unprecedented photocurrent density of 9.27 mA cm−2 is achieved under the illumination of one sun (AM1.5, 100 mW cm−2). Our work indicates that the special designation of three-dimensional coaxial nanofibers can pave a new avenue to efficient photovoltaic devices.

Thickness dependence of structural and optical properties of indium tin oxide nanofiber thin films prepared by electron beam evaporation onto quartz substrates

► Indium tin oxide thin films grow as nanofibers by e-beam evaporation. ► The transparency of the films is strongly affected by film thickness. ► Dielectric constant of the films is independent on film thickness. ► Optical band gap and carrier concentration decrease with increasing film thickness. Indium tin oxide (ITO) thin films, produced by electron beam evaporation technique onto quartz substrates maintained at room temperature, are grown as nanofibers. The dependence of structural and optical properties of ITO thin films on the film thickness (99–662 nm) has been reported. The crystal structure and morphology of the films are investigated by X-ray diffraction and scanning electron microscope techniques, respectively. The particle size is found to increase with increasing film thickness without changing the preferred orientation along (2 2 2) direction. The optical properties of the films are investigated in terms of the measurements of the transmittance and reflectance determined at the normal incidence of the light in the wavelength range (250–2500 nm). The absorption coefficient and refractive index are calculated and the related optical parameters are evaluated. The optical band gap is found to decrease with the increase of the film thickness, whereas the refractive index is found to increase. The optical dielectric constant and the ratio of the free carrier concentration to its effective mass are estimated for the films.

Indium Tin Oxide Nanofibers and their Applications for Dye-Sensitized Solar Cells

Indium tin oxide (ITO) nanofibers were fabricated by the combination of sol-gel and electrospinning techniques, from a mixed solution of ITO precursors and an easily spinnable polymer, polyvinylpyrrolidone (PVP). The optimum conditions in electrospinning for the fabrication of smooth and uniform fibers were studied. Calcination of the composite fibers at 570åC resulted in degradation of PVP and highly crystalline nanofibers. The obtained ITO nanofibers showed one-dimensional structure with the diameters about 200 nm. These nanofibers were applied to construct the dye sensitized solar cells (DSSCs) as an upper layer of the transparent conducting oxide (TCO) substrate (between conventional TCO and the metal oxide photoelectrode). When the ITO nanofibers were applied, enhanced photovoltaic performance was attained as compared with the conventional devices.

Indium Tin Oxide Nanofibers and their Applications for Dye-Sensitized Solar Cells

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Indium Tin Oxide Nanofiber Film Electrode for High Performance Dye Sensitized Solar Cells

Dye-sensitized solar cells (DSC) were fabricated using transparent and conductive indium tin oxide (ITO) nanofiber film prepared by electrospinning. Scanning electron microscope (SEM) images confirmed that the prepared films were well attached, exceptionally long, and had an average diameter of around 200 nm. We found that the maximum efficiency of the device was as high as 3.97% with the structure of a double-layer nanofiber film. It was shown that an improvement as much as 16.76% was achieved. These achievements were obtained due to a reduction in grain boundaries, to an efficient high charge collection, and to rapid electron transport.

Low temperature high sensor response nano gas sensor using ITO nanofibers

Indium Tin Oxide (ITO) nanofibers were fabricated by the electrospinning process. Sensors based on these nanofibers were fabricated by applying silver paste as electrode. The morphology and crystal structure of ITO nanofibers were studied by Scanning Electron Microscopy (SEM) and X-ray diffraction (XRD), respectively. The optimal working temperature and sensor response of ITO nanofiber sensors were investigated. All results showed that ITO nanofiber sensors have good sensor response for NO 2 at temperatures as low as 50 °C.

Patterned indium tin oxide nanofiber films and their electrical and optical performance

We report on the preparation and characterization of indium tin oxide (ITO) nanofiberfilms with a patterned architecture that are transparent and conductive with a uniformfiber size. ITO nanofiber films with a crisscross pattern were prepared by theelectrospinning of a precursor solution containing ethanol, dimethyl formamide (DMF),indium chloride tetrahydrate, tin chloride pentahydrate and poly(vinyl pyrrolidone) (PVPK90) onto a metal mesh template, followed by calcinations after transfer to a glasssubstrate. The resulting ITO nanofibers had diameters of the order of 100 nmand were composed of single-crystalline nanoparticles that were pure in chemicalcomposition. The morphology, crystallinity and performance of the resulting nanofiberscould be controlled mainly by calcination. Optical and electrical investigationsdemonstrated that these nanofiber films are transparent conductors with an opticaltransmittance as high as 92%. The resulting patterned ITO nanofiber films would besuitable for applications such as solar cells, sensors and electromagnetic field filters.

Optical and electrical properties of indium tin oxide nanofibers prepared by electrospinning

Indium tin oxide (ITO) nanofibers were successfully prepared via an electrospinning method, followed byannealing at 400 °C. Mixed solutions of ITO nanoparticle sol and polyethylene oxide (PEO) were used asprecursors of the nanofibers. The PEO decomposed during annealing to yield ITO fibers.The fibers were characterized by scanning electron microscopy (SEM), x-ray diffraction(XRD), thermo-gravimetric/differential thermal analysis (TG/DTA), UV–visspectrophotometry and four-probe resistivity measurements. The diameter of the preparedfibers was controlled by adjusting the flow rate and the applied electric current.In2O3 crystallized in the ITO nanofibers with a crystallite size of 27 nm. The opticaltransmittance in the visible region approached 90% in films deposited for 5 min, confirmingthat the nanofiber film is still transparent in the optical region. The sheet resistance of thenanofiber film was linearly dependent on the inverse of the deposition time and on thePEO/ITO ratio.

Synthesis and Electrical Property of Indium Tin Oxide Nanofibers Using Electrospinning Method

In this study indium tin oxide (ITO) nanofibers were synthesized using an electrospinning method. The morphological properties of the ITO nanofibers were considered and their specific resistances were measured to determine their applicability as filler for a transparent conducting film. ITO/PVP composite nanofibers were successfully obtained by electrospinning using a precursor solution containing indium nitrate, tin chloride, and poly(vinlypyrrolidone). After the heat treatment of ITO/PVP composite nanofibers at 600 degrees C and 1000 degrees C, ITO nanofibers with an average diameter of about 168 nm and 165 nm were synthesized, respectively.