Special Issue "ZnO Nanowires: Growth, Properties, and Energy Applications"

A special issue of Nanomaterials (ISSN 2079-4991). This special issue belongs to the section "Synthesis, Interfaces and Nanostructures".

Deadline for manuscript submissions: 15 March 2022.

Special Issue Editor

Dr. Vincent Consonni
Website
Guest Editor
Université Grenoble Alpes, CNRS, Grenoble INP, LMGP, 3, parvis Louis Néel 38016 Grenoble, France
Interests: ZnO; compound semiconductor; nanostructures; chemical synthesis; physical deposition techniques; doping; polarity; energy applications

Special Issue Information

Dear Colleagues,

As an abundant and biocompatible compound semiconductor with a high aspect ratio at nanoscale dimensions, ZnO, in the form of nanowires, has emerged as a potential building block in a wide variety of devices. However, there is still a significant need for the exploration of the growth of ZnO nanowires, elucidating and monitoring their fundamental properties, and improving their integration into nanoscale devices, specifically in the field of energy conversion and storage.

This Special Issue will address the following topics: i) growth and nucleation mechanisms of ZnO nanowires using chemical and physical deposition techniques, ii) fundamental properties of ZnO nanowires, including doping, polarity, surfaces, and interfaces, iii) energy applications including photovoltaic cells (i.e., ETA solar cells, dye-sensitized solar cells, quantum dot solar cells, etc.), piezoelectric devices (i.e., nano-generators and pressure/strain sensors), self-powered devices, and batteries.

Dr. Vincent Consonni
Guest Editor

Manuscript Submission Information

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Keywords

  • Chemical deposition techniques
  • Physical deposition techniques
  • Doping
  • Polarity
  • Surface and interfaces
  • Photovoltaic cells
  • Piezoelectric devices
  • Self-powered devices
  • Batteries

Published Papers (8 papers)

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Research

Article
Optimization of the Sb2S3 Shell Thickness in ZnO Nanowire-Based Extremely Thin Absorber Solar Cells
Nanomaterials 2022, 12(2), 198; https://doi.org/10.3390/nano12020198 - 07 Jan 2022
Viewed by 139
Abstract
Extremely thin absorber (ETA) solar cells made of ZnO/TiO2/Sb2S3 core–shell nanowire heterostructures, using P3HT as the hole-transporting material (HTM), are of high interest to surpass solar cell efficiencies of their planar counterpart at lower material cost. However, no [...] Read more.
Extremely thin absorber (ETA) solar cells made of ZnO/TiO2/Sb2S3 core–shell nanowire heterostructures, using P3HT as the hole-transporting material (HTM), are of high interest to surpass solar cell efficiencies of their planar counterpart at lower material cost. However, no dimensional optimization has been addressed in detail, as it raises material and technological critical issues. In this study, the thickness of the Sb2S3 shell grown by chemical spray pyrolysis is tuned from a couple of nanometers to several tens of nanometers, while switching from a partially to a fully crystallized shell. The Sb2S3 shell is highly pure, and the unwanted Sb2O3 phase was not formed. The low end of the thickness is limited by challenges in the crystallization of the Sb2S3 shell, as it is amorphous at nanoscale dimensions, resulting in the low optical absorption of visible photons. In contrast, the high end of the thickness is limited by the increased density of defects in the bulk of the Sb2S3 shell, degrading charge carrier dynamics, and by the incomplete immersion of the P3HT in the structure, resulting in the poor hole collection. The best ETA solar cell with a short-circuit current density of 12.1 mA/cm2, an open-circuit voltage of 502 mV, and a photovoltaic conversion efficiency of 2.83% is obtained for an intermediate thickness of the Sb2S3 shell. These findings highlight that the incorporation of both the absorber shell and HTM in the core–shell heterostructures relies on the spacing between individual nanowires. They further elaborate the intricate nature of the dimensional optimization of an ETA cell, as it requires a fine-balanced holistic approach to correlate all the dimensions of all the components in the heterostructures. Full article
(This article belongs to the Special Issue ZnO Nanowires: Growth, Properties, and Energy Applications)
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Article
Controlled Fabrication of Quality ZnO NWs/CNTs and ZnO NWs/Gr Heterostructures via Direct Two-Step CVD Method
Nanomaterials 2021, 11(7), 1836; https://doi.org/10.3390/nano11071836 - 15 Jul 2021
Cited by 1 | Viewed by 824
Abstract
A novel and advanced approach of growing zinc oxide nanowires (ZnO NWs) directly on single-walled carbon nanotubes (SWCNTs) and graphene (Gr) surfaces has been demonstrated through the successful formation of 1D–1D and 1D–2D heterostructure interfaces. The direct two-step chemical vapor deposition (CVD) method [...] Read more.
A novel and advanced approach of growing zinc oxide nanowires (ZnO NWs) directly on single-walled carbon nanotubes (SWCNTs) and graphene (Gr) surfaces has been demonstrated through the successful formation of 1D–1D and 1D–2D heterostructure interfaces. The direct two-step chemical vapor deposition (CVD) method was utilized to ensure high-quality materials’ synthesis and scalable production of different architectures. Iron-based universal compound molecular ink was used as a catalyst in both processes (a) to form a monolayer of horizontally defined networks of SWCNTs interfaced with vertically oriented ZnO NWs and (b) to grow densely packed ZnO NWs directly on a graphene surface. We show here that our universal compound molecular ink is efficient and selective in the direct synthesis of ZnO NWs/CNTs and ZnO NWs/Gr heterostructures. Heterostructures were also selectively patterned through different fabrication techniques and grown in predefined locations, demonstrating an ability to control materials’ placement and morphology. Several characterization tools were employed to interrogate the prepared heterostructures. ZnO NWs were shown to grow uniformly over the network of SWCNTs, and much denser packed vertically oriented ZnO NWs were produced on graphene thin films. Such heterostructures can be used widely in many potential applications, such as photocatalysts, supercapacitors, solar cells, piezoelectric or thermal actuators, as well as chemical or biological sensors. Full article
(This article belongs to the Special Issue ZnO Nanowires: Growth, Properties, and Energy Applications)
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Article
Fabrication of Piezoelectric ZnO Nanowires Energy Harvester on Flexible Substrate Coated with Various Seed Layer Structures
Nanomaterials 2021, 11(6), 1433; https://doi.org/10.3390/nano11061433 - 28 May 2021
Cited by 1 | Viewed by 1185
Abstract
Flexible piezoelectric nanogenerators (PENGs) are very attractive for mechanical energy harvesting due to their high potential for realizing self-powered sensors and low-power electronics. In this paper, a PENG that is based on zinc oxide (ZnO) nanowires (NWs) is fabricated on flexible and transparent [...] Read more.
Flexible piezoelectric nanogenerators (PENGs) are very attractive for mechanical energy harvesting due to their high potential for realizing self-powered sensors and low-power electronics. In this paper, a PENG that is based on zinc oxide (ZnO) nanowires (NWs) is fabricated on flexible and transparent Polydimethylsiloxane (PDMS) substrate. The ZnO NWs were deposited on two different seed layer structures, i.e., gold (Au)/ZnO and tin-doped indium-oxide (ITO)/ZnO, using hydrothermal synthesis. Along with the structural and morphological analyses of ZnO NWs, the electrical characterization was also investigated for ZnO NWs-based flexible PENGs. In order to evaluate the suitability of the PENG device structure, the electrical output performance was studied. By applying a periodic mechanical force of 3 N, the ZnO NWs-based flexible PENG generated a maximum root mean square (RMS) voltage and average power of 2.7 V and 64 nW, respectively. Moreover, the comparison between the fabricated device performances shows that a higher electrical output can be obtained when ITO/ZnO seed layer structure is adopted. The proposed ZnO NWs-based PENG structure can provide a flexible and cost-effective device for supplying portable electronics. Full article
(This article belongs to the Special Issue ZnO Nanowires: Growth, Properties, and Energy Applications)
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Article
Low-Temperature Growth of ZnO Nanowires from Gravure-Printed ZnO Nanoparticle Seed Layers for Flexible Piezoelectric Devices
Nanomaterials 2021, 11(6), 1430; https://doi.org/10.3390/nano11061430 - 28 May 2021
Viewed by 1453
Abstract
Zinc oxide (ZnO) nanowires (NWs) are excellent candidates for the fabrication of energy harvesters, mechanical sensors, and piezotronic and piezophototronic devices. In order to integrate ZnO NWs into flexible devices, low-temperature fabrication methods are required that do not damage the plastic substrate. To [...] Read more.
Zinc oxide (ZnO) nanowires (NWs) are excellent candidates for the fabrication of energy harvesters, mechanical sensors, and piezotronic and piezophototronic devices. In order to integrate ZnO NWs into flexible devices, low-temperature fabrication methods are required that do not damage the plastic substrate. To date, the deposition of patterned ceramic thin films on flexible substrates is a difficult task to perform under vacuum-free conditions. Printing methods to deposit functional thin films offer many advantages, such as a low cost, low temperature, high throughput, and patterning at the same stage of deposition. Among printing techniques, gravure-based techniques are among the most attractive due to their ability to produce high quality results at high speeds and perform deposition over a large area. In this paper, we explore gravure printing as a cost-effective high-quality method to deposit thin ZnO seed layers on flexible polymer substrates. For the first time, we show that by following a chemical bath deposition (CBD) process, ZnO nanowires may be grown over gravure-printed ZnO nanoparticle seed layers. Piezo-response force microscopy (PFM) reveals the presence of a homogeneous distribution of Zn-polar domains in the NWs, and, by use of the data, the piezoelectric coefficient is estimated to be close to 4 pm/V. The overall results demonstrate that gravure printing is an appropriate method to deposit seed layers at a low temperature and to undertake the direct fabrication of flexible piezoelectric transducers that are based on ZnO nanowires. This work opens the possibility of manufacturing completely vacuum-free solution-based flexible piezoelectric devices. Full article
(This article belongs to the Special Issue ZnO Nanowires: Growth, Properties, and Energy Applications)
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Article
Environment-Friendly Zinc Oxide Nanorods-Grown Cellulose Nanofiber Nanocomposite and Its Electromechanical and UV Sensing Behaviors
Nanomaterials 2021, 11(6), 1419; https://doi.org/10.3390/nano11061419 - 27 May 2021
Cited by 1 | Viewed by 1099
Abstract
This paper reports a genuine environment-friendly hybrid nanocomposite made by growing zinc oxide (ZnO) nanorods on cellulose nanofiber (CNF) film. The nanocomposite preparation, characterizations, electromechanical property, and ultraviolet (UV) sensing performance are explained. CNF was extracted from the pulp by combining the 2,2,6,6-tetramethylpiperidine-1-oxyl [...] Read more.
This paper reports a genuine environment-friendly hybrid nanocomposite made by growing zinc oxide (ZnO) nanorods on cellulose nanofiber (CNF) film. The nanocomposite preparation, characterizations, electromechanical property, and ultraviolet (UV) sensing performance are explained. CNF was extracted from the pulp by combining the 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO) oxidation and the aqueous counter collision (ACC) methods. The CNF film was fabricated using doctor blade casting, and ZnO nanorods were grown on the CNF film by seeding and by a hydrothermal method. Morphologies, optical transparency, mechanical and electromechanical properties, and UV sensing properties were examined. The nanocomposite’s optical transparency was more than 80%, and the piezoelectric charge constant d31 was 200 times larger than the CNF film. The UV sensing performance of the prepared ZnO-CNF nanocomposites was tested in terms of ZnO concentration, UV irradiance intensity, exposure side, and electrode materials. A large aspect ratio of ZnO nanorods and a work function gap between ZnO nanorods and the electrode material are essential for improving the UV sensing performance. However, these conditions should be compromised with transparency. The use of CNF for ZnO-cellulose hybrid nanocomposite is beneficial not only for electromechanical and UV sensing properties but also for high mechanical properties, renewability, biocompatibility, flexibility, non-toxicity, and transparency. Full article
(This article belongs to the Special Issue ZnO Nanowires: Growth, Properties, and Energy Applications)
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Article
Dimensional Roadmap for Maximizing the Piezoelectrical Response of ZnO Nanowire-Based Transducers: Impact of Growth Method
Nanomaterials 2021, 11(4), 941; https://doi.org/10.3390/nano11040941 - 07 Apr 2021
Cited by 2 | Viewed by 1078
Abstract
ZnO nanowires are excellent candidates for energy harvesters, mechanical sensors, piezotronic and piezophototronic devices. The key parameters governing the general performance of the integrated devices include the dimensions of the ZnO nanowires used, their doping level, and surface trap density. However, although the [...] Read more.
ZnO nanowires are excellent candidates for energy harvesters, mechanical sensors, piezotronic and piezophototronic devices. The key parameters governing the general performance of the integrated devices include the dimensions of the ZnO nanowires used, their doping level, and surface trap density. However, although the method used to grow these nanowires has a strong impact on these parameters, its influence on the performance of the devices has been neither elucidated nor optimized yet. In this paper, we implement numerical simulations based on the finite element method combining the mechanical, piezoelectric, and semiconducting characteristic of the devices to reveal the influence of the growth method of ZnO nanowires. The electrical response of vertically integrated piezoelectric nanogenerators (VING) based on ZnO nanowire arrays operating in compression mode is investigated in detail. The properties of ZnO nanowires grown by the most widely used methods are taken into account on the basis of a thorough and comprehensive analysis of the experimental data found in the literature. Our results show that the performance of VING devices should be drastically affected by growth method. Important optimization guidelines are found. In particular, the optimal nanowire radius that would lead to best device performance is deduced for each growth method. Full article
(This article belongs to the Special Issue ZnO Nanowires: Growth, Properties, and Energy Applications)
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Article
Enhanced UV Photoresponsivity of ZnO Nanorods Decorated with Ag2S/ZnS Nanoparticles by Successive Ionic Layer Adsorption and Reaction Method
Nanomaterials 2021, 11(2), 461; https://doi.org/10.3390/nano11020461 - 11 Feb 2021
Viewed by 684
Abstract
Recently, different kinds of energy band structures have been utilized to improve the photoelectric properties of zinc oxide (ZnO). In this work, ZnO nanorods were prepared by the hydrothermal method and then decorated with silver sulfide (Ag2S)/zinc sulfide (ZnS) via two-step [...] Read more.
Recently, different kinds of energy band structures have been utilized to improve the photoelectric properties of zinc oxide (ZnO). In this work, ZnO nanorods were prepared by the hydrothermal method and then decorated with silver sulfide (Ag2S)/zinc sulfide (ZnS) via two-step successive ionic layer adsorption and reaction method. The photoelectric properties of nanocomposites are investigated. The results show that ZnO decorated with Ag2S/ZnS can improve the photocurrent of photodetectors from 0.34 to 0.56 A at bias of 9 V. With the immersion time increasing from 15 to 60 minutes, the photocurrent of photodetectors increases by 0.22 A. The holes in the valence band of ZnO can be transferred to the valence band of ZnS and Ag2S, which promotes the separation and suppresses the recombination of hole-electron pairs generated in ZnO. Moreover, electrons excited by ultraviolet (UV) light in Ag2S can also be injected into the conduction band of ZnO, which causes the photocurrent to increase more than the ZnO photodetector. Full article
(This article belongs to the Special Issue ZnO Nanowires: Growth, Properties, and Energy Applications)
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Article
Efficient Photocatalytic Hydrogen Evolution over TiO2-X Mesoporous Spheres-ZnO Nanorods Heterojunction
Nanomaterials 2020, 10(11), 2096; https://doi.org/10.3390/nano10112096 - 22 Oct 2020
Cited by 3 | Viewed by 832
Abstract
Photocatalytic water splitting into hydrogen is regarded as one of the key solutions to the deterioration of the global environment and energy. Due to the significantly reduced grain boundaries, ZnO nanorods facilitate a fast electron transfer through their smooth tunnels and are well [...] Read more.
Photocatalytic water splitting into hydrogen is regarded as one of the key solutions to the deterioration of the global environment and energy. Due to the significantly reduced grain boundaries, ZnO nanorods facilitate a fast electron transfer through their smooth tunnels and are well suited as a photocatalyst. However, the photocatalytic hydrogen evolution performance of pristine ZnO nanorods is still low due to the high recombination rate of photogenerated electron-hole pairs and the less light absorption. Here, a novel structure about black ZnO nanorods (NRs)/TiO2-X mesoporous spheres (MSs) heterojunction has been prepared and the photocatalytic hydrogen evolution performance has been explored. The photocatalytic activity test results showed that ZnO NRs/TiO2-X MSs exhibited higher catalytic activity than ZnO NRs for hydrogen production. Compared to the pure ZnO NRs photoanode, the photocurrent of ZnO NRs/TiO2-X MSs heterojunction photoanode could reach 0.41 mA/cm2 in view of the expanding spectral response region and effective inhibition of e/h+ recombination at the same condition. Using a relatively integrated experimental investigation and mechanism analysis, we scrutinized that after being treated with NaBH4, TiO2 MSs introduce oxygen vacancies expanding the photocatalytic activity of pure TiO2, and improving conductivity and charge transport capabilities through coating on ZnO NRs. More importantly, the results provide a promising approach in the NRs/MSs composite structure serving as photoanodes for photocatalytic hydrogen production. Full article
(This article belongs to the Special Issue ZnO Nanowires: Growth, Properties, and Energy Applications)
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