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Solution-Processed Metal Oxide Nanostructures for Carrier Transport

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A special issue of Nanomaterials (ISSN 2079-4991). This special issue belongs to the section "Nanophotonics Materials and Devices".

Deadline for manuscript submissions: closed (31 August 2022) | Viewed by 12778

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Special Issue Editor

Dr. Sheng-Hsiung Yang

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Institute of Lighting and Energy Photonics, College of Photonics, National Yang Ming Chiao Tung University (NYCU), Tainan 71150, Taiwan
Interests: ionic conjugated polymers; metal oxide thin films, nanoparticles, and nanorod arrays; perovskite materials; organic light-emitting diodes (OLEDs); polymer solar cells; quantum-dot light-emitting diodes (QLEDs); perovskite solar cells (PSCs) and light-emitting diodes (PeLEDs)
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Dear Colleagues,

Metal oxide semiconductors represent a unique class of materials that show prominent optoelectronic applications today. Typical p-type metal oxides, such as vanadium oxide (VO_x), nickel oxide (NiO_x), and cobalt oxide (CoO_x), have the advantages of high hole mobility, superior stability, and solution processibility. On the other hand, several representative n-type metal oxide materials, including zinc oxide (ZnO), titanium dioxide (TiO₂), and tin dioxide (SnO₂), show benefits in device performance due to their high electron mobility, long-term stability, solution-processing capability, and relatively high abundance on earth. In addition to thin films, metal oxides with specific nanostructures such as nanoparticles, nanowires, nanorods, nanotubes, nanosheets, nanowalls, and nanoflowers, have also been developed to increase the active surface area. These nanostructures are achievable via solution processes to reduce production cost and to expand research diversity. Nanostructured metal oxides are especially useful for carrier transport in miscellaneous devices, including organic light emitting diodes, polymer solar cells, perovskite photovoltaics, perovskite light emitting diodes, quantum-dot light emitting diodes, and organic/inorganic hybrid transistors and sensors.

This Special Issue of Nanomaterials is open to manuscripts concerning synthesis, characterization, and especially carrier transport abilities of metal oxide thin films and nanostructures in working devices. Potential topics include but are not limited to:

Hole transport metal oxides such as VO_x, NiO_x, CoO_x, etc.;
Electron transport metal oxides such as ZnO, TiO₂, SnO₂, etc.;
Preparation and characterization of metal oxide thin films and nanostructures;
Utilization of nanostructured metal oxides as carrier transport layers in miscellaneous devices.

Dr. Sheng-Hsiung Yang
Guest Editor

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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. Nanomaterials 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 2900 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

metal oxide semiconductors
solution processibility
nanostructures
organic optoelectronics
perovskite photovoltaics and light-emitting diodes
quantum-dot light-emitting diodes
transistors and sensors

Published Papers (6 papers)

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Editorial

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3 pages, 176 KiB

Open AccessEditorial

Solution-Processed Metal Oxide Nanostructures for Carrier Transport

by Sheng-Hsiung Yang

Nanomaterials 2023, 13(8), 1331; https://doi.org/10.3390/nano13081331 - 11 Apr 2023

Cited by 2 | Viewed by 939

Abstract

Metal oxide semiconductors represent a unique class of materials that show prominent optoelectronic applications nowadays [...] Full article

(This article belongs to the Special Issue Solution-Processed Metal Oxide Nanostructures for Carrier Transport)

Research

Jump to: Editorial

14 pages, 2626 KiB

Open AccessArticle

Organic–Inorganic Hybrid Device with a Novel Deep-Blue Emitter of a Donor–Acceptor Type, with ZnO Nanoparticles for Solution-Processed OLEDs

by Seokwoo Kang, Raveendra Jillella, Sunwoo Park, Sangshin Park, Joo Hwan Kim, Dakyeung Oh, Joonghan Kim and Jongwook Park

Nanomaterials 2022, 12(21), 3806; https://doi.org/10.3390/nano12213806 - 28 Oct 2022

Cited by 2 | Viewed by 1726

Abstract

Two new deep-blue emitters with bipolar properties based on an organoboron acceptor and carbazole donor were newly synthesized: 2-(9H-carbazol-9-yl)-5-(2,12-di-tert-butyl-5,9-dioxa-13b-boranaphtho [3,2,1-de]anthracen-7-yl)-5H-benzo[b]carbazole (TDBA-BCZ) and 5-(2,12-di-tert-butyl-5,9-dioxa-13b-boranaphtho [3,2,1-de]anthracen-7-yl)-8-phenyl-5,8-dihydroindolo[2,3-c]carbazole (TDBA-PCZ). The two emitters showed deep-blue and real-blue photoluminescence emission in their solution and film states, respectively. The doped spin-coated films were prepared using synthesized materials and showed a root-mean-square roughness of less than 0.52 nm, indicating excellent surface morphology. The doped devices, fabricated via a solution process using TDBA-BCZ and TDBA-PCZ as the dopants, showed electroluminescence peaks at 428 and 461 nm, corresponding to the Commission Internationale de L’éclairage (CIE) coordinates of (0.161, 0.046) and (0.151, 0.155), respectively. The external quantum efficiency (EQE)/current efficiency (CE) of the solution-processed forward devices, with TDBA-BCZ and TDBA-PCZ as dopants, were 7.73%/8.67 cd/A and 10.58%/14.24 cd/A, respectively. An inverted OLED device fabricated using rod-shaped ZnO nanoparticles as an electron injection layer showed a CE of 1.09 cd/A and an EQE of 0.30%. Full article

(This article belongs to the Special Issue Solution-Processed Metal Oxide Nanostructures for Carrier Transport)

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15 pages, 5671 KiB

Open AccessFeature PaperArticle

Preparation of Nickel Oxide Nanoflakes for Carrier Extraction and Transport in Perovskite Solar Cells

by Chih-Yu Chang, You-Wei Wu, Sheng-Hsiung Yang and Ibrahim Abdulhalim

Nanomaterials 2022, 12(19), 3336; https://doi.org/10.3390/nano12193336 - 25 Sep 2022

Cited by 2 | Viewed by 1893

Abstract

Hole transport layers (HTLs) with high conductivity, charge extraction ability, and carrier transport capability are highly important for fabricating perovskite solar cells (PSCs) with high power conversion efficiency and device stability. Low interfacial recombination between the HTL and perovskite absorber is also crucial to the device performance of PSCs. In this work, we developed a three-stage method to prepare NiO_x nanoflakes as the HTL in the inverted PSCs. Due to the addition of the nanoflake layer, the deposited perovskite films with larger grain sizes and fewer boundaries were obtained, implying higher photogenerated current and fill factors in our PSCs. Meanwhile, the downshifted valence band of the NiO_x HTL improved hole extraction from the perovskite absorber and open-circuit voltages of PSCs. The optimized device based on the NiO_x nanoflakes showed the highest efficiency of 14.21% and a small hysteresis, which outperformed the NiO_x thin film as the HTL. Furthermore, the device maintained 83% of its initial efficiency after 60 days of storage. Our results suggest that NiO_x nanoflakes provide great potential for constructing PSCs with high efficiency and long-term stability. Full article

(This article belongs to the Special Issue Solution-Processed Metal Oxide Nanostructures for Carrier Transport)

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21 pages, 11139 KiB

Open AccessFeature PaperArticle

Enhanced Luminance of CdSe/ZnS Quantum Dots Light-Emitting Diodes Using ZnO-Oleic Acid/ZnO Quantum Dots Double Electron Transport Layer

by Da Young Lee, Hong Hee Kim, Ji-Hyun Noh, Keun-Yong Lim, Donghee Park, In-Hwan Lee and Won Kook Choi

Nanomaterials 2022, 12(12), 2038; https://doi.org/10.3390/nano12122038 - 14 Jun 2022

Cited by 2 | Viewed by 2198

Abstract

The widely used ZnO quantum dots (QDs) as an electron transport layer (ETL) in quantum dot light-emitting diodes (QLEDs) have one drawback. That the balancing of electrons and holes has not been effectively exploited due to the low hole blocking potential difference between the valence band (VB) (6.38 eV) of ZnO ETL and (6.3 eV) of CdSe/ZnS QDs. In this study, ZnO QDs chemically reacted with capping ligands of oleic acid (OA) to decrease the work function of 3.15 eV for ZnO QDs to 2.72~3.08 eV for the ZnO-OA QDs due to the charge transfer from ZnO to OA ligands and improve the efficiency for hole blocking as the VB was increased up to 7.22~7.23 eV. Compared to the QLEDs with a single ZnO QDs ETL, the ZnO-OA/ZnO QDs double ETLs optimize the energy level alignment between ZnO QDs and CdSe/ZnS QDs but also make the surface roughness of ZnO QDs smoother. The optimized glass/ITO/PEDOT:PSS/PVK//CdSe/ZnS//ZnO-OA/ZnO/Ag QLEDs enhances the maximum luminance by 5~9% and current efficiency by 16~35% over the QLEDs with a single ZnO QDs ETL, which can be explained in terms of trap-charge limited current (TCLC) and the Fowler-Nordheim (F-N) tunneling conduction mechanism. Full article

(This article belongs to the Special Issue Solution-Processed Metal Oxide Nanostructures for Carrier Transport)

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17 pages, 7735 KiB

Open AccessArticle

A Morphological Study of Solvothermally Grown SnO₂ Nanostructures for Application in Perovskite Solar Cells

by Zhuldyz Yelzhanova, Gaukhar Nigmetova, Damir Aidarkhanov, Bayan Daniyar, Bakhytzhan Baptayev, Mannix P. Balanay, Askhat N. Jumabekov and Annie Ng

Nanomaterials 2022, 12(10), 1686; https://doi.org/10.3390/nano12101686 - 15 May 2022

Cited by 8 | Viewed by 2694

Abstract

Tin(IV) oxide (SnO₂) nanostructures, which possess larger surface areas for transporting electron carriers, have been used as an electron transport layer (ETL) in perovskite solar cells (PSCs). However, the reported power conversion efficiencies (PCEs) of this type of PSCs show a large variation. One of the possible reasons for this phenomenon is the low reproducibility of SnO₂ nanostructures if they are prepared by different research groups using various growth methods. This work focuses on the morphological study of SnO₂ nanostructures grown by a solvothermal method. The growth parameters including growth pressure, substrate orientation, DI water-to-ethanol ratios, types of seed layer, amount of acetic acid, and growth time have been systematically varied. The SnO₂ nanomorphology exhibits a different degree of sensitivity and trends towards each growth factor. A surface treatment is also required for solvothermally grown SnO₂ nanomaterials for improving photovoltaic performance of PSCs. The obtained results in this work provide the research community with an insight into the general trend of morphological changes in SnO₂ nanostructures influenced by different solvothermal growth parameters. This information can guide the researchers to prepare more reproducible solvothermally grown SnO₂ nanomaterials for future application in devices. Full article

(This article belongs to the Special Issue Solution-Processed Metal Oxide Nanostructures for Carrier Transport)

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22 pages, 11081 KiB

Open AccessArticle

Double Perovskite LaFe_1−xNi_xO₃ Coated with Sea Urchin-like Gold Nanoparticles Using Electrophoresis as the Photoelectrochemical Electrode to Enhance H₂ Production via Surface Plasmon Resonance Effect

by Hsiang-Wei Tsai and Yen-Hsun Su

Nanomaterials 2022, 12(4), 622; https://doi.org/10.3390/nano12040622 - 12 Feb 2022

Cited by 4 | Viewed by 2157

Abstract

The surface plasmon resonance (SPR) effect and the hetero-junction structure play crucial roles in enhancing the photocatalytic performances of catalysts for the water-splitting reaction. In this study, a series of double perovskites LaFe_1−xN_ixO₃ was synthesized. LaFe_1−xN_ixO₃ particles were then decorated with sea urchin-like Au nanoparticles (NPs) with the average size of approximately 109.83 ± 8.48 nm via electrophoresis. The d-spacing became narrow and the absorption spectra occurred the redshift phenomenon more when doping increasing Ni mole concentrations for the raw LaFe_1−xN_ixO₃ samples. From XPS analysis, the Ni atoms were inserted into the lattice of the matrix, resulting in the defect of the oxygen vacancy, and NiO and Fe₂O₃ were formed. This hybrid structure was the ideal electrode for photoelectrochemical hydrogen production. The photonic extinction of the Au-coated LaFe_1−xNi_xO₃ was less than 2.1 eV (narrow band gap), and the particles absorbed more light in the visible region. According to the Mott–Schottky plots, all the LaFe_1−xN_ixO₃ samples were the n-type semiconductors. Moreover, all the band gaps of the Au-coated LaFe_1−xN_ixO₃ samples were higher than 1.23 eV (H⁺/H₂). Then, the hot electrons from the Au NPs were injected via the SPR effect, the coupling effect between LaFe_1−xN_ixO₃ and Au NPs, and the more active sites from Au NPs into the conduction band of the semiconductor, improving the hydrogen efficiency. The H₂ efficiency of the Au-coated LaFe_1−xNi_xO₃ measured in ethanol was approximately ten times larger than the that of Au-coated LaFe_1−xNi_xO₃ measured in 1-butanol at any testing temperature because ohmic and kinetic losses occurred in the latter solvent. Thus, the activation energies of ethanol at any testing temperature were smaller. The maximum real H₂ production was up to 43,800 μmol g⁻¹ h⁻¹ in ethanol. The redox reactions among metal ions, OH*, and oxides were consecutively proceeded under visible light illumination. Full article

(This article belongs to the Special Issue Solution-Processed Metal Oxide Nanostructures for Carrier Transport)

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