Special Issue "Advanced/Alternative Transparent Conducting Oxides"

A special issue of Materials (ISSN 1996-1944).

Deadline for manuscript submissions: closed (31 July 2020).

Special Issue Editor

Prof. Dr. Junyeob Yeo
Website
Guest Editor
Department of Physics, Kyungpook National University, 80 Daehak-ro, Bukgu, Daegu 41566, South Korea
Interests: optics; laser processing; nano-processing; flexible/wearable electronics; transparent display; energy devices
Special Issues and Collections in MDPI journals

Special Issue Information

Dear Colleagues,

Transparent conducting oxides (TCO) are indispensable materials for opto-electronics, and high tranparency together with high electrical conductivity are the key parameters for transparent conductors. Since TCO materials are usually deposited on the glass substrate as a conductive thin film through a CVD or evaporator process, transparent conductive glass is the usual form for transparent conductors in conventional opto-eletronics. Among the various TCO materials, induim-doped tin oxide (ITO) and fluorine-doped tin oxide (FTO) are the most widely used material in both industry and research. These materials have been successfully applied to various large-area opto-electronics such as touch screen panels, LCD/OLED displays, smart windows, and solar cells to date.

Nowadays, TCO materials are more important for industry due to the increasing demands of flexible and wearable electronics. However, ITO and FTO are not suitable for flexible and wearable eletronics due to the several intrinsic drawbacks, such as its brittleness, which causes cracks upon bending. In addition, indium is a rare earth material, resulting in a relatively high material cost for ITO production. Therefore, advanced or alternative materials (eg. metal nanowire or CNT) for TCO are required to develop and investigate next generation smart electronics such as flexible and wearable electronics.

This Special Issue is mainly focused on alternative or advanced transparent conducting oxides, as well as materials synthesis, the fabrication process, and applications of TCO. Topics include, but are not limited to:

  • Searching and investigating various types of advanced/alternative transparent conducting oxides:

    - Doped oxide (indium, fluorine, zinc, etc.)-based transparent conductive oxides;

    - Advanced TCO of 1D materials: Carbon nanotubes (CNT), metal (Au, Ag, Cu, Ni) nanowire, other 1D materials;

    - Advanced TCO of 2D materials: graphene, graphene/metal nanowire hybrids, other 2D materials;

  • Research into the synthesis, process, and applications of advanced/alternative transparent conducting oxides;
  • New synthesis methods for advanced/alternative transparent conducting oxides;
  • New process and fabrication methods for advanced/alternative transparent conducting oxides;
  • New applications using advanced/alternative transparent conducting oxides.

Prof. Dr. Junyeob Yeo 
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Materials is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2000 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • transparent conducting oxides
  • ITO
  • FTO
  • metal nanowire
  • CNT
  • graphene
  • flexible electronics
  • wearable electronics

Published Papers (8 papers)

Order results
Result details
Select all
Export citation of selected articles as:

Research

Open AccessArticle
The Transmittance Modulation of ZnO/Cu/ZnO Transparent Conductive Electrodes Prepared on Glass Substrates
Materials 2020, 13(18), 3916; https://doi.org/10.3390/ma13183916 - 04 Sep 2020
Abstract
With the explosive development of optoelectronic devices, the need for high-performance transparent conductive (TCE) electrodes for optoelectronic devices has been increasing accordingly. The two major TCE requirements are (1) visible light average transmittance higher than 80% and (2) sheet resistance lower than 10 [...] Read more.
With the explosive development of optoelectronic devices, the need for high-performance transparent conductive (TCE) electrodes for optoelectronic devices has been increasing accordingly. The two major TCE requirements are (1) visible light average transmittance higher than 80% and (2) sheet resistance lower than 10 Ω/sq. In this study, we investigated the critical role of the top and bottom ZnO thicknesses for the ZnO/Cu/ZnO electrodes prepared on glass substrates. It was shown that the required Cu thickness to meet the conductivity requirement is 8 nm, which was fixed and then the thicknesses of the top and ZnO layers were independently varied to experimentally determine the optimized conditions for optical transparency. The thicknesses of the top and bottom ZnO layers were both found to significantly affect the peak transmittance as well as the average visible light transmittance. The ZnO/Cu/ZnO electrode exhibits peak and average transmittance of 95.4% and 87.4%, excluding the transmittance of glass substrates, along with a sheet resistance of 9.7 Ω/sq, with a corresponding Haacke’s figure of merit (φH=Tave10Rs) of 0.064, which exceeds the reported value for the ZnO/Cu/ZnO electrodes, manifesting the need of experimental optimization in this study. Full article
(This article belongs to the Special Issue Advanced/Alternative Transparent Conducting Oxides)
Show Figures

Figure 1

Open AccessArticle
Room-Temperature-Processed Amorphous Sn-In-O Electron Transport Layer for Perovskite Solar Cells
Materials 2020, 13(1), 32; https://doi.org/10.3390/ma13010032 - 19 Dec 2019
Cited by 3
Abstract
We report amorphous tin-indium-oxide (TIO, Sn fraction: >50 atomic percentage (at%)) thin films as a new electron transport layer (ETL) of perovskite solar cells (PSCs). TIO thin films with Sn fraction of 52, 77, 83, 92, and 100 at% were grown on crystalline [...] Read more.
We report amorphous tin-indium-oxide (TIO, Sn fraction: >50 atomic percentage (at%)) thin films as a new electron transport layer (ETL) of perovskite solar cells (PSCs). TIO thin films with Sn fraction of 52, 77, 83, 92, and 100 at% were grown on crystalline indium-tin-oxide (ITO, Sn fraction: ~10 at%) thin films, a common transparent conducting oxide, by co-sputtering In2O3 and SnO2 at room temperature. The energy band structures of the amorphous TIO thin films were determined from the optical absorbance and the ultraviolet photoelectron spectra. All the examined compositions are characterized by a conduction band edge lying between that of ITO and that of perovskite (here, methylammonium lead triiodide), indicating that TIO is a potentially viable ETL of PSCs. The photovoltaic characteristics of the TIO-based PSCs were evaluated. Owing mainly to the highest fill factor and open circuit voltage, the optimal power conversion efficiency was obtained for the 77 at%-Sn TIO ETL with TiCl4 treatment. The fill factor and the open circuit voltage changes with varying the Sn fraction, despite similar conduction band edges. We attribute these differences to the considerable changes in the electrical resistivity of the TIO ETL. This would have a significant effect on the shunt and/or the series resistances. The TIO ETL can be continuously grown on an ITO TCO in a chamber, as ITO and TIO are composed of identical elements, which would help to reduce production time and costs. Full article
(This article belongs to the Special Issue Advanced/Alternative Transparent Conducting Oxides)
Show Figures

Figure 1

Open AccessArticle
Transparent ZnO Thin-Film Deposition by Spray Pyrolysis for High-Performance Metal-Oxide Field-Effect Transistors
Materials 2019, 12(20), 3423; https://doi.org/10.3390/ma12203423 - 19 Oct 2019
Cited by 5
Abstract
Solution-based metal oxide semiconductors (MOSs) have emerged, with their potential for low-cost and low-temperature processability preserving their intrinsic properties of high optical transparency and high carrier mobility. In particular, MOS field-effect transistors (FETs) using the spray pyrolysis technique have drawn huge attention with [...] Read more.
Solution-based metal oxide semiconductors (MOSs) have emerged, with their potential for low-cost and low-temperature processability preserving their intrinsic properties of high optical transparency and high carrier mobility. In particular, MOS field-effect transistors (FETs) using the spray pyrolysis technique have drawn huge attention with the electrical performances compatible with those of vacuum-based FETs. However, further intensive investigations are still desirable, associated with the processing optimization and operational instabilities when compared to other methodologies for depositing thin-film semiconductors. Here, we demonstrate high-performing transparent ZnO FETs using the spray pyrolysis technique, exhibiting a field-effect mobility of ~14.7 cm2 V−1 s−1, an on/off ratio of ~109, and an SS of ~0.49 V/decade. We examine the optical and electrical characteristics of the prepared ZnO films formed by spray pyrolysis via various analysis techniques. The influence of spray process conditions was also studied for realizing high quality ZnO films. Furthermore, we measure and analyze time dependence of the threshold voltage (Vth) shifts and their recovery behaviors under prolonged positive and negative gate bias, which were expected to be attributed to defect creation and charge trapping at or near the interface between channel and insulator, respectively. Full article
(This article belongs to the Special Issue Advanced/Alternative Transparent Conducting Oxides)
Show Figures

Figure 1

Open AccessArticle
Fabrication of Soft Sensor Using Laser Processing Techniques: For the Alternative 3D Printing Process
Materials 2019, 12(18), 2955; https://doi.org/10.3390/ma12182955 - 12 Sep 2019
Cited by 1
Abstract
Recently, the rapid prototyping process was actively studied in industry and academia. The rapid prototyping process has various advantages such as a rapid processing speed, high processing freedom, high efficiency, and eco-friendly process compared to the conventional etching process. However, in general, it [...] Read more.
Recently, the rapid prototyping process was actively studied in industry and academia. The rapid prototyping process has various advantages such as a rapid processing speed, high processing freedom, high efficiency, and eco-friendly process compared to the conventional etching process. However, in general, it is difficult to directly apply to the fabrication of electric devices, as the molding made by the rapid prototyping process is usually a nonconductive polymer. Even when a conductive material is used for the rapid prototyping process, the molding is made by a single material; thus, its application is limited. In this study, we introduce a simple alternative process for the fabrication of a soft sensor using laser processing techniques. The UV laser curing of polymer resin and laser welding of nanowires are conducted and analyzed. Through the laser processing techniques, we can easily fabricate soft sensors, which is considered an alternative 3D printing process for the fabrication of soft sensors. Full article
(This article belongs to the Special Issue Advanced/Alternative Transparent Conducting Oxides)
Show Figures

Graphical abstract

Open AccessArticle
FEP Encapsulated Crack-Based Sensor for Measurement in Moisture-Laden Environment
Materials 2019, 12(9), 1516; https://doi.org/10.3390/ma12091516 - 09 May 2019
Cited by 4
Abstract
Among many flexible mechanosensors, a crack-based sensor inspired by a spider’s slit organ has received considerable attention due to its great sensitivity compared to previous strain sensors. The sensor’s limitation, however, lies on its vulnerability to stress concentration and the metal layers’ delamination. [...] Read more.
Among many flexible mechanosensors, a crack-based sensor inspired by a spider’s slit organ has received considerable attention due to its great sensitivity compared to previous strain sensors. The sensor’s limitation, however, lies on its vulnerability to stress concentration and the metal layers’ delamination. To address this issue of vulnerability, we used fluorinated ethylene propylene (FEP) as an encapsulation layer on both sides of the sensor. The excellent waterproof and chemical resistance capability of FEP may effectively protect the sensor from damage in water and chemicals while improving the durability against friction. Full article
(This article belongs to the Special Issue Advanced/Alternative Transparent Conducting Oxides)
Show Figures

Figure 1

Open AccessArticle
Design of Polarization-Independent and Wide-Angle Broadband Absorbers for Highly Efficient Reflective Structural Color Filters
Materials 2019, 12(7), 1050; https://doi.org/10.3390/ma12071050 - 30 Mar 2019
Cited by 5
Abstract
We propose a design of angle-insensitive and polarization-independent reflective color filters with high efficiency (>80%) based on broad resonance in a Fabry–Pérot cavity where asymmetric metal-dielectric-metal planar structures are employed. Broadband absorption properties allow the resonance in the visible range to remain nearly [...] Read more.
We propose a design of angle-insensitive and polarization-independent reflective color filters with high efficiency (>80%) based on broad resonance in a Fabry–Pérot cavity where asymmetric metal-dielectric-metal planar structures are employed. Broadband absorption properties allow the resonance in the visible range to remain nearly constant over a broad range of incident angles of up to 40° for both s- and p-polarizations. Effects of the angles of incidence and polarization state of incident light on the purity of the resulting colors are examined on the CIE 1931 chromaticity diagram. In addition, higher-order resonances of the proposed color filters and their electric field distributions are investigated for improved color purity. Lastly, the spectral properties of the proposed structures with different metallic layers are studied. The simple strategy described in this work could be adopted in a variety of research areas, such as color decoration devices, microscopy, and colorimetric sensors. Full article
(This article belongs to the Special Issue Advanced/Alternative Transparent Conducting Oxides)
Show Figures

Figure 1

Open AccessFeature PaperArticle
Shear-Assisted Laser Transfer of Metal Nanoparticle Ink to an Elastomer Substrate
Materials 2018, 11(12), 2511; https://doi.org/10.3390/ma11122511 - 11 Dec 2018
Cited by 2
Abstract
Selective laser sintering of metal nanoparticle ink is an attractive technology for the creation of metal layers at the microscale without any vacuum deposition process, yet its application to elastomer substrates has remained a highly challenging task. To address this issue, we introduced [...] Read more.
Selective laser sintering of metal nanoparticle ink is an attractive technology for the creation of metal layers at the microscale without any vacuum deposition process, yet its application to elastomer substrates has remained a highly challenging task. To address this issue, we introduced the shear-assisted laser transfer of metal nanoparticle ink by utilizing the difference in thermal expansion coefficients between the elastomer and the target metal electrode. The laser was focused and scanned across the absorbing metal nanoparticle ink layer that was in conformal contact with the elastomer with a high thermal expansion coefficient. The resultant shear stress at the interface assists the selective transfer of the sintered metal nanoparticle layer. We expect that the proposed method can be a competent fabrication route for a transparent conductor on elastomer substrates. Full article
(This article belongs to the Special Issue Advanced/Alternative Transparent Conducting Oxides)
Show Figures

Figure 1

Open AccessFeature PaperArticle
Design of Shape Memory Alloy Coil Spring Actuator for Improving Performance in Cyclic Actuation
Materials 2018, 11(11), 2324; https://doi.org/10.3390/ma11112324 - 19 Nov 2018
Cited by 10
Abstract
Performance of the shape memory alloy (SMA) coil spring actuator in cyclic actuation as an artificial muscle is strongly related to the mechanical design of the coil geometry. This paper proposes a practical design method for improving the frequency and efficiency of the [...] Read more.
Performance of the shape memory alloy (SMA) coil spring actuator in cyclic actuation as an artificial muscle is strongly related to the mechanical design of the coil geometry. This paper proposes a practical design method for improving the frequency and efficiency of the SMA coil spring actuator; by designing the SMA coil spring to have large index (coil diameter/wire diameter) and pitch angle (LIP), cooling characteristics can be improved (increasing the actuation frequency) and large deformation can be obtained. The LIP design process is based on the two-state static model that describes the displacement-force relationship of the SMA coil spring in two states—a fully austenite phase and a fully martensite phase. The design process gives accurate design parameters of the SMA coil spring actuator that satisfy the required stroke and force. The model of the fully martensite phase of the SMA coil that includes the stress-induced detwinning enables the use of maximum shear strain of the SMA. The design method reduces the mass of an SMA without changing the stroke and increase the power density and efficiency. The cyclic actuation experiments demonstrate that the LIP design doubles the maximum frequency of SMA coil actuator with one-sixth the mass of the non-LIP design. Full article
(This article belongs to the Special Issue Advanced/Alternative Transparent Conducting Oxides)
Show Figures

Figure 1

Back to TopTop