Special Issue "Solution Synthesis, Processing, and Applications of Semiconducting Nanomaterials"

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

Deadline for manuscript submissions: closed (31 July 2019).

Special Issue Editor

Prof. Dr. Julia W. P. Hsu
Website
Guest Editor
Department of Materials Science and Engineering, University of Texas at Dallas, Richardson, TX 75080, USA
Interests: emergent photovoltaics; solution synthesis of inorganic nanostructures; interfacial phenomena between dissimilar materials; growth and properties of lattice-mismatched semiconductors; scanning probe microscopy and spectroscopy; semiconductor defect characterization; oxide catalysts for NO oxidation; superconductivity; metal-insulator transition; proximity effect

Special Issue Information

Dear Colleagues,

Semiconducting nanomaterials synthesized using solution methods have played important roles in a wide variety of electronic and optical applications, such as solar cells (SCs), light emitting diodes (LEDs), photodetectors, and sensors. The frontiers in synthesis include new compounds, reducing the size of nanomaterials, increasing the crystallinity of nanocrystals, alternative green synthesis methods to reduce waste and energy, and surface functionalization and characterization. Furthermore, great challenges are encountered in processing nanomaterials from suspensions to uniform thin films on different substrates for optoelectronic device applications. While many publications focus on synthesis and applications of solution-based nanomaterials, issues related to processing, e.g., solvent choice, surface compositions and ligands, and deposition methods, are addressed infrequently. This Special Issue solicits submissions on processing of solution-based semiconducting nanomaterials in addition to their synthesis and applications.

Prof. Dr. Julia W. P. Hsu
Guest Editor

Manuscript Submission Information

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Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2000 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

  • Solution synthesis
  • Nanomaterials
  • Oxides
  • Semiconductors
  • Surface composition and ligands
  • Solution processing of films
  • Film optical and electronic properties
  • Green methods for synthesis and processing

Published Papers (11 papers)

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Editorial

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Open AccessEditorial
Solution Synthesis, Processing, and Applications of Semiconducting Nanomaterials
Nanomaterials 2019, 9(10), 1442; https://doi.org/10.3390/nano9101442 - 11 Oct 2019
Abstract
Nanomaterials have contributed to the forefront of materials research in the past two decades, and are used today in sensors, solar cells, light emitting diodes, electronics, and biomedical devices [...] Full article

Research

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Open AccessArticle
Mg Doped CuCrO2 as Efficient Hole Transport Layers for Organic and Perovskite Solar Cells
Nanomaterials 2019, 9(9), 1311; https://doi.org/10.3390/nano9091311 - 13 Sep 2019
Cited by 2
Abstract
The electrical and optical properties of the hole transport layer (HTL) are critical for organic and halide perovskite solar cell (OSC and PSC, respectively) performance. In this work, we studied the effect of Mg doping on CuCrO2 (CCO) nanoparticles and their performance [...] Read more.
The electrical and optical properties of the hole transport layer (HTL) are critical for organic and halide perovskite solar cell (OSC and PSC, respectively) performance. In this work, we studied the effect of Mg doping on CuCrO2 (CCO) nanoparticles and their performance as HTLs in OSCs and PSCs. CCO and Mg doped CCO (Mg:CCO) nanoparticles were hydrothermally synthesized. The nanoparticles were characterized by various experimental techniques to study the effect of Mg doping on structural, chemical, morphological, optical, and electronic properties of CCO. We found that Mg doping increases work function and decreases particle size. We demonstrate CCO and Mg:CCO as efficient HTLs in a variety of OSCs, including the first demonstration of a non-fullerene acceptor bulk heterojunction, and CH3NH3PbI3 PSCs. A small improvement of average short-circuit current density with Mg doping was found in all systems. Full article
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Open AccessArticle
Tailoring IGZO Composition for Enhanced Fully Solution-Based Thin Film Transistors
Nanomaterials 2019, 9(9), 1273; https://doi.org/10.3390/nano9091273 - 06 Sep 2019
Cited by 4
Abstract
Solution-processed metal oxides have been investigated as an alternative to vacuum-based oxides to implement low-cost, high-performance electronic devices on flexible transparent substrates. However, their electrical properties need to be enhanced to apply at industrial scale. Amorphous indium-gallium-zinc oxide (a-IGZO) is the most-used transparent [...] Read more.
Solution-processed metal oxides have been investigated as an alternative to vacuum-based oxides to implement low-cost, high-performance electronic devices on flexible transparent substrates. However, their electrical properties need to be enhanced to apply at industrial scale. Amorphous indium-gallium-zinc oxide (a-IGZO) is the most-used transparent semiconductor metal oxide as an active channel layer in thin-film transistors (TFTs), due to its superior electrical properties. The present work evaluates the influence of composition, thickness and ageing on the electrical properties of solution a-IGZO TFTs, using solution combustion synthesis method, with urea as fuel. After optimizing the semiconductor properties, low-voltage TFTs were obtained by implementing a back-surface passivated 3-layer In:Ga:Zn 3:1:1 with a solution-processed high-к dielectric; AlOx. The devices show saturation mobility of 3.2 cm2 V−1 s−1, IOn/IOff of 106, SS of 73 mV dec−1 and VOn of 0.18 V, thus demonstrating promising features for low-cost circuit applications. Full article
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Open AccessArticle
Preparation of CuCrO2 Hollow Nanotubes from an Electrospun Al2O3 Template
Nanomaterials 2019, 9(9), 1252; https://doi.org/10.3390/nano9091252 - 03 Sep 2019
Cited by 1
Abstract
A hollow nanostructure is attractive and important in different fields of applications, for instance, solar cells, sensors, supercapacitors, electronics, and biomedical, due to their unique structure, large available interior space, low bulk density, and stable physicochemical properties. Hence, the need to prepare hollow [...] Read more.
A hollow nanostructure is attractive and important in different fields of applications, for instance, solar cells, sensors, supercapacitors, electronics, and biomedical, due to their unique structure, large available interior space, low bulk density, and stable physicochemical properties. Hence, the need to prepare hollow nanotubes is more important. In this present study, we have prepared CuCrO2 hollow nanotubes by simple approach. The CuCrO2 hollow nanotubes were prepared by applying electrospun Al2O3 fibers as a template for the first time. Copper chromium ions were dip-coated on the surface of electrospun-derived Al2O3 fibers and annealed at 600 °C in vacuum to form Al2O3-CuCrO2 core-shell nanofibers. The CuCrO2 hollow nanotubes were obtained by removing Al2O3 cores by sulfuric acid wet etching while preserving the rest of original structures. The structures of the CuCrO2-coated Al2O3 core-shell nanofibers and CuCrO2 hollow nanotubes were identified side-by-side by X-ray diffraction, field emission scanning electron microscopy, and transmission electron microscopy. The CuCrO2 hollow nanotubes may find applications in electrochemistry, catalysis, and biomedical application. This hollow nanotube preparation method could be extended to the preparation of other hollow nanotubes, fibers, and spheres. Full article
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Open AccessArticle
Resistive Switching Characteristics of HfO2 Thin Films on Mica Substrates Prepared by Sol-Gel Process
Nanomaterials 2019, 9(8), 1124; https://doi.org/10.3390/nano9081124 - 04 Aug 2019
Cited by 7
Abstract
The resistive switching (RS) characteristics of flexible films deposited on mica substrates have rarely been reported upon, especially flexible HfO2 films. A novel flexible Au/HfO2/Pt/mica resistive random access memory device was prepared by a sol-gel process, and a Au/HfO2 [...] Read more.
The resistive switching (RS) characteristics of flexible films deposited on mica substrates have rarely been reported upon, especially flexible HfO2 films. A novel flexible Au/HfO2/Pt/mica resistive random access memory device was prepared by a sol-gel process, and a Au/HfO2/Pt/Ti/SiO2/Si (100) device was also prepared for comparison. The HfO2 thin films were grown into the monoclinic phase by the proper annealing process at 700 °C, demonstrated by grazing-incidence X-ray diffraction patterns. The ratio of high/low resistance (off/on) reached 1000 and 50 for the two devices, respectively, being relatively stable for the former but not for the latter. The great difference in ratios for the two devices may have been caused by different concentrations of the oxygen defect obtained by the X-ray photoelectron spectroscopy spectra indicating composition and chemical state of the HfO2 thin films. The conduction mechanism was dominated by Ohm’s law in the low resistance state, while in high resistance state, Ohmic conduction, space charge limited conduction (SCLC), and trap-filled SCLC conducted together. Full article
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Open AccessArticle
Conformational Effects of Pt-Shells on Nanostructures and Corresponding Oxygen Reduction Reaction Activity of Au-Cluster-Decorated NiOx@Pt Nanocatalysts
Nanomaterials 2019, 9(7), 1003; https://doi.org/10.3390/nano9071003 - 11 Jul 2019
Cited by 3
Abstract
Herein, ternary metallic nanocatalysts (NCs) consisting of Au clusters decorated with a Pt shell and a Ni oxide core underneath (called NPA) on carbon nanotube (CNT) support were synthesized by combining adsorption, precipitation, and chemical reduction methods. By a retrospective investigation of the [...] Read more.
Herein, ternary metallic nanocatalysts (NCs) consisting of Au clusters decorated with a Pt shell and a Ni oxide core underneath (called NPA) on carbon nanotube (CNT) support were synthesized by combining adsorption, precipitation, and chemical reduction methods. By a retrospective investigation of the physical structure and electrochemical results, we elucidated the effects of Pt/Ni ratios (0.4 and 1.0) and Au contents (2 and 9 wt.%) on the nanostructure and corresponding oxygen reduction reaction (ORR) activity of the NPA NCs. We found that the ORR activity of NPA NCs was mainly dominated by the Pt-shell thickness which regulated the depth and size of the surface decorated with Au clusters. In the optimal case, NPA-1004006 (with a Pt/Ni of 0.4 and Au of ~2 wt.%) showed a kinetic current (JK) of 75.02 mA cm−2 which was nearly 17-times better than that (4.37 mA cm−2) of the commercial Johnson Matthey-Pt/C (20 wt.% Pt) catalyst at 0.85 V vs. the reference hydrogen electrode. Such a high JK value resulted in substantial improvements in both the specific activity (by ~53-fold) and mass activity (by nearly 10-fold) in the same benchmark target. Those scenarios rationalize that ORR activity can be substantially improved by a syngeneic effect at heterogeneous interfaces among nanometer-sized NiOx, Pt, and Au clusters on the NC surface. Full article
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Open AccessArticle
Investigation on the Selenization Treatment of Kesterite Cu2Mg0.2Zn0.8Sn(S,Se)4 Films for Solar Cell
Nanomaterials 2019, 9(7), 946; https://doi.org/10.3390/nano9070946 - 29 Jun 2019
Cited by 2
Abstract
High-selenium Cu2Mg0.2Zn0.8Sn(S,Se)4 (CMZTSSe) films were prepared on a soda lime glass substrate using the sol–gel spin coating method, followed by selenization treatment. In this work, we investigated the effects of selenization temperature and selenization time on [...] Read more.
High-selenium Cu2Mg0.2Zn0.8Sn(S,Se)4 (CMZTSSe) films were prepared on a soda lime glass substrate using the sol–gel spin coating method, followed by selenization treatment. In this work, we investigated the effects of selenization temperature and selenization time on the crystal quality, and electrical and optical properties of CMZTSSe films. The study on the micro-structure by XRD, Raman, X-ray photoelectron spectroscopy (XPS), and energy-dispersive X-ray spectroscopy (EDS) analysis showed that all CMZTSSe samples had kesterite crystalline structure. In addition, the crystalline quality of CMZTSSe is improved and larger Se takes the site of S in CMZTSSe with the increase of selenization temperature and selenization time. When increasing the selenization temperature from 500 to 530 °C and increasing the annealing time from 10 to 15 min, the morphological studies showed that the microstructures of the films were dense and void-free. When further increasing the temperature and time, the crystalline quality of the films began to deteriorate. In addition, the bandgaps of CMZTSSe are tuned from 1.06 to 0.93 eV through adjusting the selenization conditions. When CMZTSSe samples are annealed at 530 °C for 15 min under Se atmosphere, the crystal quality and optical–electrical characteristics of CMZTSSe will be optimal, and the grain size and carrier concentration reach maximums of 1.5–2.5 μm and 6.47 × 1018 cm−3. Full article
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Open AccessArticle
High-Sensitive Ammonia Sensors Based on Tin Monoxide Nanoshells
Nanomaterials 2019, 9(3), 388; https://doi.org/10.3390/nano9030388 - 07 Mar 2019
Cited by 7
Abstract
Ammonia (NH3) is a harmful gas contaminant that is part of the nitrogen cycle in our daily lives. Therefore, highly sensitive ammonia sensors are important for environmental protection and human health. However, it is difficult to detect low concentrations of ammonia [...] Read more.
Ammonia (NH3) is a harmful gas contaminant that is part of the nitrogen cycle in our daily lives. Therefore, highly sensitive ammonia sensors are important for environmental protection and human health. However, it is difficult to detect low concentrations of ammonia (≤50 ppm) using conventional means at room temperature. Tin monoxide (SnO), a member of IV–VI metal monoxides, has attracted much attention due to its low cost, environmental-friendly nature, and higher stability compared with other non-oxide ammonia sensing material like alkaline metal or polymer, which made this material an ideal alternative for ammonia sensor applications. In this work, we fabricated high-sensitive ammonia sensors based on self-assembly SnO nanoshells via a solution method and annealing under 300 °C for 1 h. The as fabricated sensors exhibited the response of 313%, 874%, 2757%, 3116%, and 3757% (∆G/G) under ammonia concentration of 5 ppm, 20 ppm, 50 ppm, 100 ppm, and 200 ppm, respectively. The structure of the nanoshells, which have curved shells that provide shelters for the core and also possess a large surface area, is able to absorb more ammonia molecules, leading to further improvements in the sensitivity. Further, the SnO nanoshells have higher oxygen vacancy densities compared with other metal oxide ammonia sensing materials, enabling it to have higher performance. Additionally, the selectivity of ammonia sensors is also outstanding. We hope this work will provide a reference for the study of similar structures and applications of IV–VI metal monoxides in the gas sensor field. Full article
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Open AccessArticle
Fabrication of Cu2ZnSnS4 (CZTS) Nanoparticle Inks for Growth of CZTS Films for Solar Cells
Nanomaterials 2019, 9(3), 336; https://doi.org/10.3390/nano9030336 - 02 Mar 2019
Cited by 8
Abstract
Cu2ZnSnS4 (CZTS) is a promising candidate material for photovoltaic applications; hence, ecofriendly methods are required to fabricate CZTS films. In this work, we fabricated CZTS nanocrystal inks by a wet ball milling method, with the use of only nontoxic solvents, [...] Read more.
Cu2ZnSnS4 (CZTS) is a promising candidate material for photovoltaic applications; hence, ecofriendly methods are required to fabricate CZTS films. In this work, we fabricated CZTS nanocrystal inks by a wet ball milling method, with the use of only nontoxic solvents, followed by filtration. We performed centrifugation to screen the as-milled CZTS and obtain nanocrystals. The distribution of CZTS nanoparticles during centrifugation was examined and nanocrystal inks were obtained after the final centrifugal treatment. The as-fabricated CZTS nanocrystal inks were used to deposit CZTS precursors with precisely controlled CZTS films by a spin-coating method followed by a rapid high pressure sulfur annealing method. Both the grain growth and crystallinity of the CZTS films were promoted and the composition was adjusted from S poor to S-rich by the annealing. XRD and Raman characterization showed no secondary phases in the annealed film, the absence of the detrimental phases. A solar cell efficiency of 6.2% (open circuit voltage: Voc = 633.3 mV, short circuit current: Jsc = 17.6 mA/cm2, and fill factor: FF = 55.8%) with an area of 0.2 cm2 was achieved based on the annealed CZTS film as the absorber layer. Full article
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Open AccessArticle
Suitability of Copper Nitride as a Wiring Ink Sintered by Low-Energy Intense Pulsed Light Irradiation
Nanomaterials 2018, 8(8), 617; https://doi.org/10.3390/nano8080617 - 14 Aug 2018
Cited by 2
Abstract
Copper nitride particles have a low decomposition temperature, they absorb light, and are oxidation-resistant, making them potentially useful for the development of novel wiring inks for printing circuit boards by means of intense pulsed light (IPL) sintering at low-energy. Here, we compared the [...] Read more.
Copper nitride particles have a low decomposition temperature, they absorb light, and are oxidation-resistant, making them potentially useful for the development of novel wiring inks for printing circuit boards by means of intense pulsed light (IPL) sintering at low-energy. Here, we compared the thermal decomposition and light absorption of copper materials, including copper nitride (Cu3N), copper(I) oxide (Cu2O), or copper(II) oxide (CuO). Among the copper compounds examined, copper nitride had the second highest light absorbency and lowest decomposition temperature; therefore, we concluded that copper nitride was the most suitable material for producing a wiring ink that is sintered by means of IPL irradiation. Wiring inks containing copper nitride were compared with those of wiring inks containing copper nitride, copper(I) oxide, or copper(II) oxide, and copper conversion rate and sheet resistance were also determined. Under low-energy irradiation (8.3 J cm−2), copper nitride was converted to copper at the highest rate among the copper materials, and provided a sheet resistance of 0.506 Ω sq−1, indicating that copper nitride is indeed a candidate material for development as a wiring ink for low-energy intense pulsed light sintering-based printed circuit board production processes. Full article
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Review

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Open AccessReview
Colloidal Self-Assembly of Inorganic Nanocrystals into Superlattice Thin-Films and Multiscale Nanostructures
Nanomaterials 2019, 9(9), 1243; https://doi.org/10.3390/nano9091243 - 01 Sep 2019
Cited by 1
Abstract
The self-assembly of colloidal inorganic nanocrystals (NCs) offers tremendous potential for the design of solution-processed multi-functional inorganic thin-films or nanostructures. To date, the self-assembly of various inorganic NCs, such as plasmonic metal, metal oxide, quantum dots, magnetics, and dielectrics, are reported to form [...] Read more.
The self-assembly of colloidal inorganic nanocrystals (NCs) offers tremendous potential for the design of solution-processed multi-functional inorganic thin-films or nanostructures. To date, the self-assembly of various inorganic NCs, such as plasmonic metal, metal oxide, quantum dots, magnetics, and dielectrics, are reported to form single, binary, and even ternary superlattices with long-range orientational and positional order over a large area. In addition, the controlled coupling between NC building blocks in the highly ordered superlattices gives rise to novel collective properties, providing unique optical, magnetic, electronic, and catalytic properties. In this review, we introduce the self-assembly of inorganic NCs and the experimental process to form single and multicomponent superlattices, and we also describe the fabrication of multiscale NC superlattices with anisotropic NC building blocks, thin-film patterning, and the supracrystal formation of superlattice structures. Full article
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