Research

8 pages, 17034 KiB

Open AccessArticle

The Transmittance Modulation of ZnO/Cu/ZnO Transparent Conductive Electrodes Prepared on Glass Substrates

by Dooho Choi

Materials 2020, 13(18), 3916; https://doi.org/10.3390/ma13183916 - 04 Sep 2020

Cited by 5 | Viewed by 2013

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 (

φ_{H} = \frac{T_{a v e}^{10}}{R_{s}}

) 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)

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12 pages, 2486 KiB

Open AccessArticle

Room-Temperature-Processed Amorphous Sn-In-O Electron Transport Layer for Perovskite Solar Cells

by Seungtae Baek, Jeong Woo Han, Devthade Vidyasagar, Hanbyeol Cho, Hwi-Heon HA, Dong Hoe Kim, Young-Woo Heo and Sangwook Lee

Materials 2020, 13(1), 32; https://doi.org/10.3390/ma13010032 - 19 Dec 2019

Cited by 7 | Viewed by 3181

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)

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14 pages, 2089 KiB

Open AccessArticle

Transparent ZnO Thin-Film Deposition by Spray Pyrolysis for High-Performance Metal-Oxide Field-Effect Transistors

by Junhee Cho, Seongkwon Hwang, Doo-Hyun Ko and Seungjun Chung

Materials 2019, 12(20), 3423; https://doi.org/10.3390/ma12203423 - 19 Oct 2019

Cited by 33 | Viewed by 3399

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 (V_th) 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)

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9 pages, 2850 KiB

Open AccessArticle

Fabrication of Soft Sensor Using Laser Processing Techniques: For the Alternative 3D Printing Process

by Myeongjoo Seo, Suwon Hwang, Taeseung Hwang and Junyeob Yeo

Materials 2019, 12(18), 2955; https://doi.org/10.3390/ma12182955 - 12 Sep 2019

Cited by 9 | Viewed by 2547

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)

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Graphical abstract

11 pages, 1774 KiB

Open AccessArticle

FEP Encapsulated Crack-Based Sensor for Measurement in Moisture-Laden Environment

by Minho Kim, Hyesu Choi, Taewi Kim, Insic Hong, Yeonwook Roh, Jieun Park, SungChul Seo, Seungyong Han, Je-sung Koh and Daeshik Kang

Materials 2019, 12(9), 1516; https://doi.org/10.3390/ma12091516 - 09 May 2019

Cited by 15 | Viewed by 3585

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)

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11 pages, 4696 KiB

Open AccessArticle

Design of Polarization-Independent and Wide-Angle Broadband Absorbers for Highly Efficient Reflective Structural Color Filters

by Kyu-Tae Lee, Daeshik Kang, Hui Joon Park, Dong Hyuk Park and Seungyong Han

Materials 2019, 12(7), 1050; https://doi.org/10.3390/ma12071050 - 30 Mar 2019

Cited by 18 | Viewed by 3664

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)

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10 pages, 2916 KiB

Open AccessFeature PaperArticle

Shear-Assisted Laser Transfer of Metal Nanoparticle Ink to an Elastomer Substrate

by Wooseop Shin, Jaemook Lim, Younggeun Lee, Sewoong Park, Hyeonseok Kim, Hyunmin Cho, Jaeho Shin, Yeosang Yoon, Habeom Lee, Hyun-Jong Kim, Seungyong Han, Seung Hwan Ko and Sukjoon Hong

Materials 2018, 11(12), 2511; https://doi.org/10.3390/ma11122511 - 11 Dec 2018

Cited by 4 | Viewed by 3823

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)

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16 pages, 3228 KiB

Open AccessFeature PaperArticle

Design of Shape Memory Alloy Coil Spring Actuator for Improving Performance in Cyclic Actuation

by Je-sung Koh

Materials 2018, 11(11), 2324; https://doi.org/10.3390/ma11112324 - 19 Nov 2018

Cited by 42 | Viewed by 7771

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)

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