MDPI - Publisher of Open Access Journals

14 pages, 2759 KB

Open AccessArticle

Conical Nanotubes Synthesized by Atomic Layer Deposition of Al₂O₃, TiO₂, and SiO₂ in Etched Ion-Track Nanochannels

by Nils Ulrich, Anne Spende, Loïc Burr, Nicolas Sobel, Ina Schubert, Christian Hess, Christina Trautmann and Maria Eugenia Toimil-Molares

Nanomaterials 2021, 11(8), 1874; https://doi.org/10.3390/nano11081874 - 21 Jul 2021

Cited by 12 | Viewed by 3759

Abstract

Etched ion-track polycarbonate membranes with conical nanochannels of aspect ratios of ~3000 are coated with Al₂O₃, TiO₂, and SiO₂ thin films of thicknesses between 10 and 20 nm by atomic layer deposition (ALD). By combining ion-track [...] Read more.

Etched ion-track polycarbonate membranes with conical nanochannels of aspect ratios of ~3000 are coated with Al₂O₃, TiO₂, and SiO₂ thin films of thicknesses between 10 and 20 nm by atomic layer deposition (ALD). By combining ion-track technology and ALD, the fabrication of two kinds of functional structures with customized surfaces is presented: (i) arrays of free-standing conical nanotubes with controlled geometry and wall thickness, interesting for, e.g., drug delivery and surface wettability regulation, and (ii) single nanochannel membranes with inorganic surfaces and adjustable isoelectric points for nanofluidic applications. Full article

(This article belongs to the Section Nanofabrication and Nanomanufacturing)

► Show Figures

Figure 1

12 pages, 3691 KB

Open AccessArticle

Effect of Au Nanoparticles and Scattering Layer in Dye-Sensitized Solar Cells Based on Freestanding TiO₂ Nanotube Arrays

by Kang-Hun Lee, Seung-Hee Han, Ana Chuquer, Hwa-Young Yang, Jaehi Kim, Xuan-Hung Pham, Won-Ju Yun, Bong-Hyun Jun and Won-Yeop Rho

Nanomaterials 2021, 11(2), 328; https://doi.org/10.3390/nano11020328 - 27 Jan 2021

Cited by 7 | Viewed by 3605

Abstract

The development of high efficiency dye-sensitized solar cells (DSSCs) has received tremendous attention. Many researchers have introduced new materials for use in DSSCs to achieve high efficiency. In this study, the change in power conversion efficiency (PCE) of DSSCs was investigated by introducing [...] Read more.

The development of high efficiency dye-sensitized solar cells (DSSCs) has received tremendous attention. Many researchers have introduced new materials for use in DSSCs to achieve high efficiency. In this study, the change in power conversion efficiency (PCE) of DSSCs was investigated by introducing two types of materials—Au nanoparticles (Au NPs) and a scattering layer. A DSSC fabricated without neither Au NPs nor a scattering layer achieved a PCE of 5.85%. The PCE of a DSSC based on freestanding TiO₂ nanotube arrays (f-TNTAs) with Au NPs was 6.50% due to better electron generation because the plasmonic absorption band of Au NPs is 530 nm, which matches the dye absorbance. Thus, more electrons were generated at 530 nm, which affected the PCE of the DSSC. The PCE of DSSCs based on f-TNTAs with a scattering layer was 6.61% due to better light harvesting by scattering. The scattering layer reflects all wavelengths of light that improve the light harvesting in the active layer in DSSCs. Finally, the PCE of DSSCs based on the f-TNTAs with Au NPs and a scattering layer was 7.12% due to the synergy of better electron generation and light harvesting by plasmonics and scattering. The application of Au NPs and a scattering layer is a promising research area for DSSCs as they can increase the electron generation and light harvesting ability. Full article

(This article belongs to the Special Issue Synthesis and Application of Optical Materials)

► Show Figures

Graphical abstract

12 pages, 9423 KB

Open AccessArticle

Highly Ordered TiO₂ Nanotube Arrays with Engineered Electrochemical Energy Storage Performances

by Wangzhu Cao, Kunfeng Chen and Dongfeng Xue

Materials 2021, 14(3), 510; https://doi.org/10.3390/ma14030510 - 21 Jan 2021

Cited by 22 | Viewed by 3980

Abstract

Nanoscale engineering of regular structured materials is immensely demanded in various scientific areas. In this work, vertically oriented TiO₂ nanotube arrays were grown by self-organizing electrochemical anodization. The effects of different fluoride ion concentrations (0.2 and 0.5 wt% NH₄F) and [...] Read more.

Nanoscale engineering of regular structured materials is immensely demanded in various scientific areas. In this work, vertically oriented TiO₂ nanotube arrays were grown by self-organizing electrochemical anodization. The effects of different fluoride ion concentrations (0.2 and 0.5 wt% NH₄F) and different anodization times (2, 5, 10 and 20 h) on the morphology of nanotubes were systematically studied in an organic electrolyte (glycol). The growth mechanisms of amorphous and anatase TiO₂ nanotubes were also studied. Under optimized conditions, we obtained TiO₂ nanotubes with tube diameters of 70–160 nm and tube lengths of 6.5–45 μm. Serving as free-standing and binder-free electrodes, the kinetic, capacity, and stability performances of TiO₂ nanotubes were tested as lithium-ion battery anodes. This work provides a facile strategy for constructing self-organized materials with optimized functionalities for applications. Full article

(This article belongs to the Section Advanced Nanomaterials and Nanotechnology)

► Show Figures

Figure 1

10 pages, 3270 KB

Open AccessArticle

Highly Ordered TiO₂ Nanotube Electrodes for Efficient Quasi-Solid-State Dye-Sensitized Solar Cells

by A Reum Lee and Jae-Yup Kim

Energies 2020, 13(22), 6100; https://doi.org/10.3390/en13226100 - 21 Nov 2020

Cited by 6 | Viewed by 2346

Abstract

Free-standing TiO₂ nanotube (NT) electrodes have attracted much attention for application in solid- or quasi-solid-state dye-sensitized solar cells (DSSCs) because of their suitable pore structure for the infiltration of solid electrolytes. However, few studies have been performed on the relationship between nanostructures [...] Read more.

Free-standing TiO₂ nanotube (NT) electrodes have attracted much attention for application in solid- or quasi-solid-state dye-sensitized solar cells (DSSCs) because of their suitable pore structure for the infiltration of solid electrolytes. However, few studies have been performed on the relationship between nanostructures of these NT electrodes and the photovoltaic properties of the solid- or quasi-solid-state DSSCs. Here, we prepare vertically aligned and highly ordered TiO₂ NT electrodes via a two-step anodization method for application in quasi-solid-state DSSCs that employs a polymer gel electrolyte. The length of NT arrays is controlled in the range of 10–42 μm by varying the anodization time, and the correlation between NT length and the photovoltaic properties of quasi-solid-state DSSCs is investigated. As the NT length increases, the roughness factor of the electrode is enlarged, leading to the higher dye-loading; however, photovoltage is gradually decreased, resulting in an optimized conversion efficiency at the NT length of 18.5 μm. Electrochemical impedance spectroscopy (EIS) analysis reveals that the decrease in photovoltage for longer NT arrays is mainly attributed to the increased electron recombination rate with redox couples in the polymer gel electrolyte. Full article

(This article belongs to the Special Issue Next-Generation Solar Cells)

► Show Figures

Figure 1

11 pages, 5575 KB

Open AccessArticle

Au-Embedded and Carbon-Doped Freestanding TiO₂ Nanotube Arrays in Dye-Sensitized Solar Cells for Better Energy Conversion Efficiency

by Won-Yeop Rho, Kang-Hun Lee, Seung-Hee Han, Hyo-Yeon Kim and Bong-Hyun Jun

Micromachines 2019, 10(12), 805; https://doi.org/10.3390/mi10120805 - 22 Nov 2019

Cited by 7 | Viewed by 3177

Abstract

Dye-sensitized solar cells (DSSCs) are fabricated with freestanding TiO₂ nanotube arrays (TNTAs) which are incorporated with Au nanoparticles (NPs) and carbon materials via electrodeposition and chemical vapor deposition (CVD) method to create a plasmonic effect and better electron transport that will enhance [...] Read more.

Dye-sensitized solar cells (DSSCs) are fabricated with freestanding TiO₂ nanotube arrays (TNTAs) which are incorporated with Au nanoparticles (NPs) and carbon materials via electrodeposition and chemical vapor deposition (CVD) method to create a plasmonic effect and better electron transport that will enhance their energy conversion efficiency (ECE). The ECE of DSSCs based on the freestanding TNTAs is 5.87%. The ECE of DSSCs, based on the freestanding TNTAs with Au NPs or carbon materials, is 6.57% or 6.59%, respectively, and the final results of DSSCs according to the freestanding TNTAs with Au NPs and carbon materials is increased from 5.87% to 7.24%, which is an enhancement of 23.34% owing to plasmonic effect and better electron transport. Au NPs are incorporated into the channel of freestanding TNTAs and are characterized by CS-corrected-field emission transmission electron microscope (Cs-FE-TEM) and elemental mapping. Carbon materials are also well-incorporated in the channel of freestanding TNTAs and are analyzed by Raman spectroscopy. Full article

(This article belongs to the Special Issue Nanostructured Photovoltaic Devices)

► Show Figures

Graphical abstract

11 pages, 1894 KB

Open AccessArticle

Enhanced Efficiency in Dye-Sensitized Solar Cells by Electron Transport and Light Scattering on Freestanding TiO₂ Nanotube Arrays

by Won-Yeop Rho, Da Hyun Song, Sang Hun Lee and Bong-Hyun Jun

Nanomaterials 2017, 7(10), 345; https://doi.org/10.3390/nano7100345 - 24 Oct 2017

Cited by 12 | Viewed by 4483

Abstract

Dye-sensitized solar cells (DSSCs) were fabricated with closed- or open-ended freestanding TiO₂ nanotube arrays as photoelectrodes that were decorated with carbon materials and large TiO₂ nanoparticles (NPs) to enhance energy conversion efficiency. The energy conversion efficiency of DSSCs based on open-ended [...] Read more.

Dye-sensitized solar cells (DSSCs) were fabricated with closed- or open-ended freestanding TiO₂ nanotube arrays as photoelectrodes that were decorated with carbon materials and large TiO₂ nanoparticles (NPs) to enhance energy conversion efficiency. The energy conversion efficiency of DSSCs based on open-ended freestanding TiO₂ nanotube arrays increased from 4.47% to 5.39%, compared to the DSSCs based on closed-ended freestanding TiO₂ nanotube arrays. In DSSCs based on the open-ended freestanding TiO₂ nanotube arrays, the energy conversion efficiency with carbon materials increased from 5.39% to 6.19% due to better electron transport, and that with a scattering layer from 5.39% to 6.24% due to more light harvesting compared to the DSSCs without carbon materials or scattering layer. Moreover, the energy conversion efficiency of DSSCs based on the open-ended freestanding TiO₂ nanotube arrays with both carbon materials and scattering layer increased from 5.39% to 6.98%, which is an enhancement of 29.50%. In DSSCs based on the TiO₂ nanotube arrays, the carbon materials can improve electron transport by π-π conjugation, and the large TiO₂ NPs can enhance the capacity to light-harvest by scattering. Full article

(This article belongs to the Special Issue New Developments in Nanomaterials for Energy Storage and Conversions)

► Show Figures

Graphical abstract

11 pages, 2433 KB

Open AccessArticle

Dual Functionalized Freestanding TiO₂ Nanotube Arrays Coated with Ag Nanoparticles and Carbon Materials for Dye-Sensitized Solar Cells

by Ho-Sub Kim, Myeung-Hwan Chun, Jung Sang Suh, Bong-Hyun Jun and Won-Yeop Rho

Appl. Sci. 2017, 7(6), 576; https://doi.org/10.3390/app7060576 - 2 Jun 2017

Cited by 19 | Viewed by 5075

Abstract

Highly ordered, freestanding TiO₂ nanotube arrays (TiO₂ NTAs) were prepared using an electrochemical method. The barrier layer was etched to open the bottom of each array, aptly named “open-ended TiO₂ NTAs”. These arrays were coated with silver nanoparticles (Ag NPs) [...] Read more.

Highly ordered, freestanding TiO₂ nanotube arrays (TiO₂ NTAs) were prepared using an electrochemical method. The barrier layer was etched to open the bottom of each array, aptly named “open-ended TiO₂ NTAs”. These arrays were coated with silver nanoparticles (Ag NPs) and/or carbon materials to enhance electron generation and transport. The energy conversion efficiency of the resulting dye-sensitized solar cells (DSSCs) with open-ended freestanding TiO₂ NTAs, when coated with Ag NPs, increased from 5.32% to 6.14% (by 15%) due to plasmonic interactions. Meanwhile, coating the open-ended freestanding TiO₂ NTAs with carbon materials increased the energy conversion efficiency from 5.32% to 6.07% (by 14%), due to π-π conjugation. When the Ag NPs and carbon materials were simultaneously applied to the open-ended freestanding TiO₂ NTAs, the energy conversion efficiency increased from 5.32% to 6.91%—an enhancement of 30%, due to the additive effects of plasmonics and π-π conjugation. Full article

(This article belongs to the Special Issue Clean Energy and Fuel (Hydrogen) Storage)

► Show Figures

Graphical abstract

11 pages, 2202 KB

Open AccessCommunication

Ag Nanoparticle–Functionalized Open-Ended Freestanding TiO₂ Nanotube Arrays with a Scattering Layer for Improved Energy Conversion Efficiency in Dye-Sensitized Solar Cells

by Won-Yeop Rho, Myeung-Hwan Chun, Ho-Sub Kim, Hyung-Mo Kim, Jung Sang Suh and Bong-Hyun Jun

Nanomaterials 2016, 6(6), 117; https://doi.org/10.3390/nano6060117 - 15 Jun 2016

Cited by 26 | Viewed by 7592

Abstract

Dye-sensitized solar cells (DSSCs) were fabricated using open-ended freestanding TiO₂ nanotube arrays functionalized with Ag nanoparticles (NPs) in the channel to create a plasmonic effect, and then coated with large TiO₂ NPs to create a scattering effect in order to improve [...] Read more.

Dye-sensitized solar cells (DSSCs) were fabricated using open-ended freestanding TiO₂ nanotube arrays functionalized with Ag nanoparticles (NPs) in the channel to create a plasmonic effect, and then coated with large TiO₂ NPs to create a scattering effect in order to improve energy conversion efficiency. Compared to closed-ended freestanding TiO₂ nanotube array–based DSSCs without Ag or large TiO₂ NPs, the energy conversion efficiency of closed-ended DSSCs improved by 9.21% (actual efficiency, from 5.86% to 6.40%) with Ag NPs, 6.48% (actual efficiency, from 5.86% to 6.24%) with TiO₂ NPs, and 14.50% (actual efficiency, from 5.86% to 6.71%) with both Ag NPs and TiO₂ NPs. By introducing Ag NPs and/or large TiO₂ NPs to open-ended freestanding TiO₂ nanotube array–based DSSCs, the energy conversion efficiency was improved by 9.15% (actual efficiency, from 6.12% to 6.68%) with Ag NPs and 8.17% (actual efficiency, from 6.12% to 6.62%) with TiO₂ NPs, and by 15.20% (actual efficiency, from 6.12% to 7.05%) with both Ag NPs and TiO₂ NPs. Moreover, compared to closed-ended freestanding TiO₂ nanotube arrays, the energy conversion efficiency of open-ended freestanding TiO₂ nanotube arrays increased from 6.71% to 7.05%. We demonstrate that each component—Ag NPs, TiO₂ NPs, and open-ended freestanding TiO₂ nanotube arrays—enhanced the energy conversion efficiency, and the use of a combination of all components in DSSCs resulted in the highest energy conversion efficiency. Full article

(This article belongs to the Special Issue Nanostructured Solar Cells)

► Show Figures

Figure 1

Search Results (8)

Further Information

Guidelines

MDPI Initiatives

Follow MDPI

Saved Queries

Search Filter Reset All

Years

Feature Papers

Subjects

Journals

Article Types

Countries / Regions

Search Results (8)

Further Information

Guidelines

MDPI Initiatives

Follow MDPI