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Nanomaterials
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2D Nanostructures for Optoelectronic and Green Energy Devices
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2D Nanostructures for Optoelectronic and Green Energy Devices

A special issue of Nanomaterials (ISSN 2079-4991).

Deadline for manuscript submissions: closed (31 July 2022) | Viewed by 30703

Printed Edition Available!
A printed edition of this Special Issue is available here.

Special Issue Editors

Prof. Dr. Jung-Inn Sohn

E-Mail Website
Guest Editor
Division of Physics and Semiconductor Science, Dongguk University-Seoul, Seoul 04620, Republic of Korea
Interests: novel nanomaterials and hierarchical nanoarchitecture; nano(opto)electronics; energy generation and storage
Prof. Dr. Sangyeon Pak

E-Mail Website
Guest Editor
School of Electronic and Electrical Engineering, Hongik University, Seoul 04066, Korea
Interests: 2D materials; CVD; heterostructures; electronics; optoelectronics; sensors; energy-related devices

Special Issue Information

Dear Colleagues,

Two-dimensional (2D) materials and nanostructures have attracted significant attention due to their excellent mechanical properties, unique electrical and optical properties, large surface-to-volume ratio, and chemical and environmental stability. These properties open a vast range of possible applications ranging from optoelectronics and electronics to energy conversion and saving applications. With the extensive catalogue of available 2D materials, ranging from metallic layers to semiconductors and insulators, their applications in functional devices hold great promise in science and technology.

The scope of this issue, therefore, ranges from synthesis, characterization and modification of 2D nanostructures to their practical device applications in optoelectronics and green-energy-related devices. This Special Issue focuses on designing 2D nanostructures and engineering their fundamental and interface properties for enhancing the performance of various devices.

Prof. Dr. Jung-Inn Sohn
Prof. Dr. Sangyeon Pak
Guest Editors

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 submissions that pass pre-check are 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. 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

  • 2D materials
  • Surface modifications
  • Interface engineering
  • Heterostructures
  • Electronic devices
  • Optoelectronic devices
  • Catalysts and photocatalysts
  • Nanogenerator
  • Supercapacitor and batteries
  • Solar cells/LEDs

Published Papers (11 papers)

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Editorial

Jump to: Research, Review

2 pages, 172 KiB  
Editorial
2D Nanostructures for Optoelectronic and Green Energy Devices
by Sangyeon Pak and Jung-Inn Sohn
Nanomaterials 2023, 13(6), 1070; https://doi.org/10.3390/nano13061070 - 16 Mar 2023
Viewed by 1083
Abstract
Two-dimensional (2D) materials and nanostructures have gathered significant attention due to their excellent mechanical properties [...] Full article
(This article belongs to the Special Issue 2D Nanostructures for Optoelectronic and Green Energy Devices)

Research

Jump to: Editorial, Review

11 pages, 2372 KiB  
Article
Tuning Schottky Barrier of Single-Layer MoS2 Field-Effect Transistors with Graphene Electrodes
by A-Rang Jang
Nanomaterials 2022, 12(17), 3038; https://doi.org/10.3390/nano12173038 - 01 Sep 2022
Cited by 4 | Viewed by 1610
Abstract
Two–dimensional materials have the potential to be applied in flexible and transparent electronics. In this study, single-layer MoS2 field-effect transistors (FETs) with Au/Ti–graphene heteroelectrodes were fabricated to examine the effect of the electrodes on the electrical properties of the MoS2 FETs. [...] Read more.
Two–dimensional materials have the potential to be applied in flexible and transparent electronics. In this study, single-layer MoS2 field-effect transistors (FETs) with Au/Ti–graphene heteroelectrodes were fabricated to examine the effect of the electrodes on the electrical properties of the MoS2 FETs. The contact barrier potential was tuned using an electric field. Asymmetrical gate behavior was observed owing to the difference between the MoS2 FETs, specifically between the MoS2 FETs with Au/Ti electrodes and those with graphene electrodes. The contact barrier of the MoS2 FETs with Au/Ti electrodes did not change with the electric field. However, the contact barrier at the MoS2–graphene interface could be modulated. The MoS2 FETs with Au/Ti–graphene electrodes exhibited enhanced on/off ratios (~102 times) and electron mobility (~2.5 times) compared to the MoS2 FETs with Au/Ti electrodes. These results could improve the understanding of desirable contact formation for high-performance MoS2 FETs and provide a facile route for viable electronic applications. Full article
(This article belongs to the Special Issue 2D Nanostructures for Optoelectronic and Green Energy Devices)
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7 pages, 1324 KiB  
Article
Controlled p-Type Doping of MoS2 Monolayer by Copper Chloride
by Sangyeon Pak
Nanomaterials 2022, 12(17), 2893; https://doi.org/10.3390/nano12172893 - 23 Aug 2022
Cited by 10 | Viewed by 1961
Abstract
Electronic devices based on two-dimensional (2D) MoS2 show great promise as future building blocks in electronic circuits due to their outstanding electrical, optical, and mechanical properties. Despite the high importance of doping of these 2D materials for designing field-effect transistors (FETs) and [...] Read more.
Electronic devices based on two-dimensional (2D) MoS2 show great promise as future building blocks in electronic circuits due to their outstanding electrical, optical, and mechanical properties. Despite the high importance of doping of these 2D materials for designing field-effect transistors (FETs) and logic circuits, a simple and controllable doping methodology still needs to be developed in order to tailor their device properties. Here, we found a simple and effective chemical doping strategy for MoS2 monolayers using CuCl2 solution. The CuCl2 solution was simply spin-coated on MoS2 with different concentrations under ambient conditions for effectively p-doping the MoS2 monolayers. This was systematically analyzed using various spectroscopic measurements using Raman, photoluminescence, and X-ray photoelectron and electrical measurements by observing the change in transfer and output characteristics of MoS2 FETs before and after CuCl2 doping, showing effective p-type doping behaviors as observed through the shift of threshold voltages (Vth) and reducing the ON and OFF current level. Our results open the possibility of providing effective and simple doping strategies for 2D materials and other nanomaterials without causing any detrimental damage. Full article
(This article belongs to the Special Issue 2D Nanostructures for Optoelectronic and Green Energy Devices)
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9 pages, 4885 KiB  
Article
Transparent Heat Shielding Properties of Core-Shell Structured Nanocrystalline CsxWO3@TiO2
by Luomeng Chao, Changwei Sun, Jiaxin Li, Miao Sun, Jia Liu and Yonghong Ma
Nanomaterials 2022, 12(16), 2806; https://doi.org/10.3390/nano12162806 - 16 Aug 2022
Cited by 2 | Viewed by 1334
Abstract
Nanocrystalline tungsten bronze is an excellent near-infrared absorbing material, which has a good potential application in the field of transparent heat shielding materials on windows of automobiles or buildings, but it exhibits serious instability in the actual environment, which hinders its further application. [...] Read more.
Nanocrystalline tungsten bronze is an excellent near-infrared absorbing material, which has a good potential application in the field of transparent heat shielding materials on windows of automobiles or buildings, but it exhibits serious instability in the actual environment, which hinders its further application. In this paper, we coated the CsxWO3 nanoparticles with TiO2 to prepare core-shell structured CsxWO3@TiO2, and its crystal structure and optical properties were studied. The results show that the surface of CsxWO3 nanoparticles is coated with a layer of TiO2 particles with the size of several nanometers, and the shell thickness can be adjusted by the amount of Ti source. The measurement of optical properties illustrates that TiO2-coated CsxWO3 exhibits good stability in actual environment, and its transparent heat shielding performance will decrease with the increase in TiO2 shell thickness. This work provides a new route to promote the applications of tungsten bronze as heat shielding materials. Full article
(This article belongs to the Special Issue 2D Nanostructures for Optoelectronic and Green Energy Devices)
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9 pages, 1715 KiB  
Article
Observation of Strong Interlayer Couplings in WS2/MoS2 Heterostructures via Low-Frequency Raman Spectroscopy
by Ki Hoon Shin, Min-Kyu Seo, Sangyeon Pak, A-Rang Jang and Jung Inn Sohn
Nanomaterials 2022, 12(9), 1393; https://doi.org/10.3390/nano12091393 - 19 Apr 2022
Cited by 7 | Viewed by 4737
Abstract
Van der Waals (vdW) heterostructures based on two-dimensional (2D) transition metal dichalcogenides (TMDCs), particularly WS2/MoS2 heterostructures with type-II band alignments, are considered as ideal candidates for future functional optoelectronic applications owing to their efficient exciton dissociation and fast charge transfers. [...] Read more.
Van der Waals (vdW) heterostructures based on two-dimensional (2D) transition metal dichalcogenides (TMDCs), particularly WS2/MoS2 heterostructures with type-II band alignments, are considered as ideal candidates for future functional optoelectronic applications owing to their efficient exciton dissociation and fast charge transfers. These physical properties of vdW heterostructures are mainly influenced by the interlayer coupling occurring at the interface. However, a comprehensive understanding of the interlayer coupling in vdW heterostructures is still lacking. Here, we present a detailed analysis of the low-frequency (LF) Raman modes, which are sensitive to interlayer coupling, in bilayers of MoS2, WS2, and WS2/MoS2 heterostructures directly grown using chemical vapor deposition to avoid undesirable interfacial contamination and stacking mismatch effects between the monolayers. We clearly observe two distinguishable LF Raman modes, the interlayer in-plane shear and out-of-plane layer-breathing modes, which are dependent on the twisting angles and interface quality between the monolayers, in all the 2D bilayered structures, including the vdW heterostructure. In contrast, LF modes are not observed in the MoS2 and WS2 monolayers. These results indicate that our directly grown 2D bilayered TMDCs with a favorable stacking configuration and high-quality interface can induce strong interlayer couplings, leading to LF Raman modes. Full article
(This article belongs to the Special Issue 2D Nanostructures for Optoelectronic and Green Energy Devices)
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13 pages, 4544 KiB  
Article
Optical Mode Tuning of Monolayer Tungsten Diselenide (WSe2) by Integrating with One-Dimensional Photonic Crystal through Exciton–Photon Coupling
by Konthoujam James Singh, Hao-Hsuan Ciou, Ya-Hui Chang, Yen-Shou Lin, Hsiang-Ting Lin, Po-Cheng Tsai, Shih-Yen Lin, Min-Hsiung Shih and Hao-Chung Kuo
Nanomaterials 2022, 12(3), 425; https://doi.org/10.3390/nano12030425 - 27 Jan 2022
Cited by 3 | Viewed by 3265
Abstract
Two-dimensional materials, such as transition metal dichalogenides (TMDs), are emerging materials for optoelectronic applications due to their exceptional light–matter interaction characteristics. At room temperature, the coupling of excitons in monolayer TMDs with light opens up promising possibilities for realistic electronics. Controlling light–matter interactions [...] Read more.
Two-dimensional materials, such as transition metal dichalogenides (TMDs), are emerging materials for optoelectronic applications due to their exceptional light–matter interaction characteristics. At room temperature, the coupling of excitons in monolayer TMDs with light opens up promising possibilities for realistic electronics. Controlling light–matter interactions could open up new possibilities for a variety of applications, and it could become a primary focus for mainstream nanophotonics. In this paper, we show how coupling can be achieved between excitons in the tungsten diselenide (WSe2) monolayer with band-edge resonance of one-dimensional (1-D) photonic crystal at room temperature. We achieved a Rabi splitting of 25.0 meV for the coupled system, indicating that the excitons in WSe2 and photons in 1-D photonic crystal were coupled successfully. In addition to this, controlling circularly polarized (CP) states of light is also important for the development of various applications in displays, quantum communications, polarization-tunable photon source, etc. TMDs are excellent chiroptical materials for CP photon emitters because of their intrinsic circular polarized light emissions. In this paper, we also demonstrate that integration between the TMDs and photonic crystal could help to manipulate the circular dichroism and hence the CP light emissions by enhancing the light–mater interaction. The degree of polarization of WSe2 was significantly enhanced through the coupling between excitons in WSe2 and the PhC resonant cavity mode. This coupled system could be used as a platform for manipulating polarized light states, which might be useful in optical information technology, chip-scale biosensing and various opto-valleytronic devices based on 2-D materials. Full article
(This article belongs to the Special Issue 2D Nanostructures for Optoelectronic and Green Energy Devices)
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10 pages, 3186 KiB  
Article
Hierarchically Assembled Plasmonic Metal-Dielectric-Metal Hybrid Nano-Architectures for High-Sensitivity SERS Detection
by Puran Pandey, Min-Kyu Seo, Ki Hoon Shin, Young-Woo Lee and Jung Inn Sohn
Nanomaterials 2022, 12(3), 401; https://doi.org/10.3390/nano12030401 - 26 Jan 2022
Cited by 8 | Viewed by 2618
Abstract
In this work, we designed and prepared a hierarchically assembled 3D plasmonic metal-dielectric-metal (PMDM) hybrid nano-architecture for high-performance surface-enhanced Raman scattering (SERS) sensing. The fabrication of the PMDM hybrid nanostructure was achieved by the thermal evaporation of Au film followed by thermal dewetting [...] Read more.
In this work, we designed and prepared a hierarchically assembled 3D plasmonic metal-dielectric-metal (PMDM) hybrid nano-architecture for high-performance surface-enhanced Raman scattering (SERS) sensing. The fabrication of the PMDM hybrid nanostructure was achieved by the thermal evaporation of Au film followed by thermal dewetting and the atomic layer deposition (ALD) of the Al2O3 dielectric layer, which is crucial for creating numerous nanogaps between the core Au and the out-layered Au nanoparticles (NPs). The PMDM hybrid nanostructures exhibited strong SERS signals originating from highly enhanced electromagnetic (EM) hot spots at the 3 nm Al2O3 layer serving as the nanogap spacer, as confirmed by the finite-difference time-domain (FDTD) simulation. The PMDM SERS substrate achieved an outstanding SERS performance, including a high sensitivity (enhancement factor, EF of 1.3 × 108 and low detection limit 10−11 M) and excellent reproducibility (relative standard deviation (RSD) < 7.5%) for rhodamine 6G (R6G). This study opens a promising route for constructing multilayered plasmonic structures with abundant EM hotspots for the highly sensitive, rapid, and reproducible detection of biomolecules. Full article
(This article belongs to the Special Issue 2D Nanostructures for Optoelectronic and Green Energy Devices)
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11 pages, 2536 KiB  
Article
A Redox-Mediator-Integrated Flexible Micro-Supercapacitor with Improved Energy Storage Capability and Suppressed Self-Discharge Rate
by Sung Min Wi, Jihong Kim, Suok Lee, Yu-Rim Choi, Sung Hoon Kim, Jong Bae Park, Younghyun Cho, Wook Ahn, A-Rang Jang, John Hong and Young-Woo Lee
Nanomaterials 2021, 11(11), 3027; https://doi.org/10.3390/nano11113027 - 11 Nov 2021
Cited by 8 | Viewed by 1853
Abstract
To effectively improve the energy density and reduce the self-discharging rate of micro-supercapacitors, an advanced strategy is required. In this study, we developed a hydroquinone (HQ)-based polymer-gel electrolyte (HQ-gel) for micro-supercapacitors. The introduced HQ redox mediators (HQ-RMs) in the gel electrolyte composites underwent [...] Read more.
To effectively improve the energy density and reduce the self-discharging rate of micro-supercapacitors, an advanced strategy is required. In this study, we developed a hydroquinone (HQ)-based polymer-gel electrolyte (HQ-gel) for micro-supercapacitors. The introduced HQ redox mediators (HQ-RMs) in the gel electrolyte composites underwent additional Faradaic redox reactions and synergistically increased the overall energy density of the micro-supercapacitors. Moreover, the HQ-RMs in the gel electrolyte weakened the self-discharging behavior by providing a strong binding attachment of charged ions on the porous graphitized carbon electrodes after the redox reactions. The micro-supercapacitors with HQ gel (HQ-MSCs) showed excellent energy storage performance, including a high energy volumetric capacitance of 255 mF cm−3 at a current of 1 µA, which is 2.7 times higher than the micro-supercapacitors based on bare-gel electrolyte composites without HQ-RMs (b-MSCs). The HQ-MSCs showed comparatively low self-discharging behavior with an open circuit potential drop of 37% compared to the b-MSCs with an open circuit potential drop of 60% after 2000 s. The assembled HQ-MSCs exhibited high mechanical flexibility over the applied external tensile and compressive strains. Additionally, the HQ-MSCs show the adequate circuit compatibility within series and parallel connections and the good cycling performance of capacitance retention of 95% after 3000 cycles. Full article
(This article belongs to the Special Issue 2D Nanostructures for Optoelectronic and Green Energy Devices)
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8 pages, 7101 KiB  
Communication
Atomic Arrangements of Graphene-like ZnO
by Jong Chan Yoon, Zonghoon Lee and Gyeong Hee Ryu
Nanomaterials 2021, 11(7), 1833; https://doi.org/10.3390/nano11071833 - 14 Jul 2021
Cited by 5 | Viewed by 3196
Abstract
ZnO, which can exist in various dimensions such as bulk, thin films, nanorods, and quantum dots, has interesting physical properties depending on its dimensional structures. When a typical bulk wurtzite ZnO structure is thinned to an atomic level, it is converted into a [...] Read more.
ZnO, which can exist in various dimensions such as bulk, thin films, nanorods, and quantum dots, has interesting physical properties depending on its dimensional structures. When a typical bulk wurtzite ZnO structure is thinned to an atomic level, it is converted into a hexagonal ZnO layer such as layered graphene. In this study, we report the atomic arrangement and structural merging behavior of graphene-like ZnO nanosheets transferred onto a monolayer graphene using aberration-corrected TEM. In the region to which an electron beam is continuously irradiated, it is confirmed that there is a directional tendency, which is that small-patched ZnO flakes are not only merging but also forming atomic migration of Zn and O atoms. This study suggests atomic alignments and rearrangements of the graphene-like ZnO, which are not considered in the wurtzite ZnO structure. In addition, this study also presents a new perspective on the atomic behavior when a bulk crystal structure, which is not an original layered structure, is converted into an atomic-thick layered two-dimensional structure. Full article
(This article belongs to the Special Issue 2D Nanostructures for Optoelectronic and Green Energy Devices)
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10 pages, 3433 KiB  
Article
Vanadium Pentoxide Nanofibers/Carbon Nanotubes Hybrid Film for High-Performance Aqueous Zinc-Ion Batteries
by Xianyu Liu, Liwen Ma, Yehong Du, Qiongqiong Lu, Aikai Yang and Xinyu Wang
Nanomaterials 2021, 11(4), 1054; https://doi.org/10.3390/nano11041054 - 20 Apr 2021
Cited by 28 | Viewed by 3669
Abstract
Aqueous zinc-ion batteries (ZIBs) with the characteristics of low production costs and good safety have been regarded as ideal candidates for large-scale energy storage applications. However, the nonconductive and non-redox active polymer used as the binder in the traditional preparation of electrodes hinders [...] Read more.
Aqueous zinc-ion batteries (ZIBs) with the characteristics of low production costs and good safety have been regarded as ideal candidates for large-scale energy storage applications. However, the nonconductive and non-redox active polymer used as the binder in the traditional preparation of electrodes hinders the exposure of active sites and limits the diffusion of ions, compromising the energy density of the electrode in ZIBs. Herein, we fabricated vanadium pentoxide nanofibers/carbon nanotubes (V2O5/CNTs) hybrid films as binder-free cathodes for ZIBs. High ionic conductivity and electronic conductivity were enabled in the V2O5/CNTs film due to the porous structure of the film and the introduction of carbon nanotubes with high electronic conductivity. As a result, the batteries based on the V2O5/CNTs film exhibited a higher capacity of 390 mAh g−1 at 1 A g−1, as compared to batteries based on V2O5 (263 mAh g−1). Even at 5 A g−1, the battery based on the V2O5/CNTs film maintained a capacity of 250 mAh g−1 after 2000 cycles with a capacity retention of 94%. In addition, the V2O5/CNTs film electrode also showed a high energy/power density (e.g., 67 kW kg−1/267 Wh kg−1). The capacitance response and rapid diffusion coefficient of Zn2+ (~10−8 cm−2 s−1) can explain the excellent rate capability of V2O5/CNTs. The vanadium pentoxide nanofibers/carbon nanotubes hybrid film as binder-free cathodes showed a high capability and a stable cyclability, demonstrating that it is highly promising for large-scale energy storage applications. Full article
(This article belongs to the Special Issue 2D Nanostructures for Optoelectronic and Green Energy Devices)
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Review

Jump to: Editorial, Research

34 pages, 4016 KiB  
Review
2D Material and Perovskite Heterostructure for Optoelectronic Applications
by Sijia Miao, Tianle Liu, Yujian Du, Xinyi Zhou, Jingnan Gao, Yichu Xie, Fengyi Shen, Yihua Liu and Yuljae Cho
Nanomaterials 2022, 12(12), 2100; https://doi.org/10.3390/nano12122100 - 18 Jun 2022
Cited by 13 | Viewed by 4282
Abstract
Optoelectronic devices are key building blocks for sustainable energy, imaging applications, and optical communications in modern society. Two-dimensional materials and perovskites have been considered promising candidates in this research area due to their fascinating material properties. Despite the significant progress achieved in the [...] Read more.
Optoelectronic devices are key building blocks for sustainable energy, imaging applications, and optical communications in modern society. Two-dimensional materials and perovskites have been considered promising candidates in this research area due to their fascinating material properties. Despite the significant progress achieved in the past decades, challenges still remain to further improve the performance of devices based on 2D materials or perovskites and to solve stability issues for their reliability. Recently, a novel concept of 2D material/perovskite heterostructure has demonstrated remarkable achievements by taking advantage of both materials. The diverse fabrication techniques and large families of 2D materials and perovskites open up great opportunities for structure modification, interface engineering, and composition tuning in state-of-the-art optoelectronics. In this review, we present comprehensive information on the synthesis methods, material properties of 2D materials and perovskites, and the research progress of optoelectronic devices, particularly solar cells and photodetectors which are based on 2D materials, perovskites, and 2D material/perovskite heterostructures with future perspectives. Full article
(This article belongs to the Special Issue 2D Nanostructures for Optoelectronic and Green Energy Devices)
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