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9 pages, 1182 KiB

Open AccessArticle

Preparation and Characterization of Quinoxaline-Pyrene-Based Conjugated Copolymers for Organic Photovoltaic Devices

by Bakhet A. Alqurashy, Bader M. Altayeb, Sulaiman Y. Alfaifi, Majed Alawad, Ahmed Iraqi and Imran Ali

Coatings 2020, 10(11), 1098; https://doi.org/10.3390/coatings10111098 - 16 Nov 2020

Cited by 3 | Viewed by 2030

Abstract

In this study, two novel conjugated polymers, poly(4,5,9,10-tetrakis((2-ethylhexyl)oxy]pyrene-alt-2,3-bis(3-(octyloxy)phenyl)-5,8-di(2-thienyl)-6,7-difluoroquinoxaline) (PPyQxff) and poly(4,5,9,10-tetrakis((2-ethylhexyl)oxy)pyren-alt-2,3-bis(3-(octyloxy)phenyl)-5,8-di(2-thienyl)quinoxaline) (PPyQx), consisting of quinoxaline units with and without fluorine substituents, as electron-accepting moieties and pyrene flanked with dithienyl units as electron-donating moieties were prepared via Stille polymerization reactions for use as electron [...] Read more.

In this study, two novel conjugated polymers, poly(4,5,9,10-tetrakis((2-ethylhexyl)oxy]pyrene-alt-2,3-bis(3-(octyloxy)phenyl)-5,8-di(2-thienyl)-6,7-difluoroquinoxaline) (PPyQxff) and poly(4,5,9,10-tetrakis((2-ethylhexyl)oxy)pyren-alt-2,3-bis(3-(octyloxy)phenyl)-5,8-di(2-thienyl)quinoxaline) (PPyQx), consisting of quinoxaline units with and without fluorine substituents, as electron-accepting moieties and pyrene flanked with dithienyl units as electron-donating moieties were prepared via Stille polymerization reactions for use as electron donor materials in bulk heterojunction (BHJ) solar cells. PPyQxff and PPyQx were characterized by X-ray powder diffraction (XRD), gel permeation chromatography (GPC), thermogravimetric analysis (TGA), cyclic voltammetry (CV), UV−VIS absorption, and nuclear magnetic resonance (NMR) spectroscopy. PPyQxff and PPyQx revealed excellent solution processability in common organic solvents. PPyQxff and PPyQx presented decomposition temperatures above 300 °C. The inclusion of F atoms to the quinoxaline moiety made a slight reduction in the highest occupied molecular orbital (HOMO) level, relative to the unfluorinated polymer, but had no impact on the lowest unoccupied molecular orbital (LUMO) level. PPyQxff and PPyQx exhibited similar physical properties with strong and broad absorbance from 400 to 700 nm and an optical band-gap energy of 1.77 eV. The X-ray powder diffraction study indicated that PPyQxff possessed a reduced π–π stacking distance relative to PPyQx. Full article

(This article belongs to the Special Issue Advances in Functional Materials and Devices for Semiconductor and Energy Applications)

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7 pages, 2732 KiB

Open AccessArticle

Zn-Al Layered Double Hydroxide Thin Film Fabricated by the Sputtering Method and Aqueous Solution Treatment

by Jaehwan Shin, Kyunghwan Kim and Jeongsoo Hong

Coatings 2020, 10(7), 669; https://doi.org/10.3390/coatings10070669 - 13 Jul 2020

Cited by 8 | Viewed by 4301

Abstract

Zn-Al layered double hydroxides (LDHs) were synthesized herein via a simple process. First, Al-doped ZnO film was deposited onto a glass substrate using the facing target sputtering system. Successful synthesis of the Zn–Al LDH was achieved via a treatment process using an aqueous [...] Read more.

Zn-Al layered double hydroxides (LDHs) were synthesized herein via a simple process. First, Al-doped ZnO film was deposited onto a glass substrate using the facing target sputtering system. Successful synthesis of the Zn–Al LDH was achieved via a treatment process using an aqueous solution which contains NO₃⁻ anions. X-ray diffraction analysis confirmed that it was consistent with the previous Zn–Al LDH synthesis experiment data, and the calculated d-value was 9.1 Å. Scanning electron microscopy observations revealed that the as-synthesized sample had a plate-like structure. Full article

(This article belongs to the Special Issue Advances in Functional Materials and Devices for Semiconductor and Energy Applications)

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12 pages, 3847 KiB

Open AccessArticle

Synergistic Design of Anatase–Rutile TiO₂ Nanostructured Heterophase Junctions toward Efficient Photoelectrochemical Water Oxidation

by Sangwoo Lee, A. Young Cho, You Seung Rim, Jun-Young Park and Taekjib Choi

Coatings 2020, 10(6), 557; https://doi.org/10.3390/coatings10060557 - 11 Jun 2020

Cited by 12 | Viewed by 3742

Abstract

Synergistically designing porous nanostructures and appropriate band alignment for TiO₂ heterophase junctions is key to efficient charge transfer, which is crucial in enhancing photoelectrochemical (PEC) water splitting for hydrogen production. Here, we investigate the efficiency of PEC water oxidation in anatase–rutile TiO [...] Read more.

Synergistically designing porous nanostructures and appropriate band alignment for TiO₂ heterophase junctions is key to efficient charge transfer, which is crucial in enhancing photoelectrochemical (PEC) water splitting for hydrogen production. Here, we investigate the efficiency of PEC water oxidation in anatase–rutile TiO₂ nanostructured heterophase junctions that present the type-II band alignment. We specifically prove the importance of a phase alignment in heterophase junction for effective charge separation. The TiO₂ heterophase junctions were prepared by transferring TiO₂ nanotube (TNT) arrays onto FTO substrate with the help of a TiO₂ nanoparticle (TNP) glue layer. The PEC characterization reveals that the rutile (R)-TNT/anatase (A)-TNP heterophase junction has a higher photocurrent density than those of A-TNT/R-TNP junction and anatase or rutile single phase, corresponding to twofold enhanced efficiency. This type-II band alignment of R-TNT/A-TNP for water oxidation, in which photogenerated electrons (holes) will flow from rutile (anatase) to anatase (rutile), enables to facilitate efficient electron-hole separation as well as lower the effective bandgap of heterophase junctions. This work provides insight into the functional role of heterophase junction for boosting the PEC performances of TiO₂ nanostructures. Full article

(This article belongs to the Special Issue Advances in Functional Materials and Devices for Semiconductor and Energy Applications)

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13 pages, 4560 KiB

Open AccessArticle

Effect of Magnetic Field Arrangement of Facing Targets Sputtering (FTS) System on Controlling Plasma Confinement

by Sangmo Kim and Kyung Hwan Kim

Coatings 2020, 10(4), 321; https://doi.org/10.3390/coatings10040321 - 28 Mar 2020

Cited by 11 | Viewed by 5478

Abstract

Conventional sputtering method uses a single cathode with a permanent magnet. Facing targets sputtering (FTS) methods consists of two cathodes. Because of a unique structure, FTS can prepare high quality films with low temperature and low plasma damage. During the film sputtering process, [...] Read more.

Conventional sputtering method uses a single cathode with a permanent magnet. Facing targets sputtering (FTS) methods consists of two cathodes. Because of a unique structure, FTS can prepare high quality films with low temperature and low plasma damage. During the film sputtering process, density and confinement of discharged plasma depend on the arrangement of a permanent magnet in the cathode. In this study, we designed two types of permanent magnet arrangements in the FTS system and the designed permanent magnet was inserted into two cathodes in the FTS system. The system was operated in different permanent magnet conditions, and their discharge voltage and properties of as-grown films were recorded. In the designed FTS, compared to a conventional magnetron sputtering method, the substrate temperature increased to a value under 80 °C, which is relatively low, even though the films’ sputtering process was completed. Full article

(This article belongs to the Special Issue Advances in Functional Materials and Devices for Semiconductor and Energy Applications)

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9 pages, 1686 KiB

Open AccessFeature PaperArticle

Electrical Defect State Distribution in Single Crystal ZnO Schottky Barrier Diodes

by Jinhee Park, You Seung Rim, Pradeep Senanayake, Jiechen Wu and Dwight Streit

Coatings 2020, 10(3), 206; https://doi.org/10.3390/coatings10030206 - 27 Feb 2020

Cited by 10 | Viewed by 3675

Abstract

The characterization of defect states in a hydrothermally grown single crystal of ZnO was performed using deep-level transient spectroscopy in the temperature range of 77–340 K. The native intrinsic defect energy level within the ZnO band gap occurred in the depletion region of [...] Read more.

The characterization of defect states in a hydrothermally grown single crystal of ZnO was performed using deep-level transient spectroscopy in the temperature range of 77–340 K. The native intrinsic defect energy level within the ZnO band gap occurred in the depletion region of ZnO Schottky barrier diodes. A major defect level was observed, with a thermal activation energy of 0.27 eV (E3) within the defect state distribution from 0.1 to 0.57 eV below the conduction band minimum. We confirmed the maximum defect concentration to be 3.66 × 10¹⁶ cm⁻³ at 0.27 eV (E3). As a result, we clearly confirmed the distribution of density of defect states in the ZnO band gap. Full article

(This article belongs to the Special Issue Advances in Functional Materials and Devices for Semiconductor and Energy Applications)

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13 pages, 3810 KiB

Open AccessArticle

A New Alternative Electrochemical Process for a Pre-Deposited UPD-Mn Mediated the Growth of Cu(Mn) Film by Controlling the Time during the Cu-SLRR

by Jau-Shiung Fang, Yu-Fei Sie, Yi-Lung Cheng and Giin-Shan Chen

Coatings 2020, 10(2), 164; https://doi.org/10.3390/coatings10020164 - 11 Feb 2020

Cited by 1 | Viewed by 1834

Abstract

A layer-by-layer deposition is essential for fabricating the Cu interconnects in a nanoscale-sized microelectronics because the gap-filling capability limits the film deposition step coverage on trenches/vias. Conventional layer-by-layer electrochemical deposition of Cu typically works by using two electrolytes, i.e., a sacrificial Pb electrolyte [...] Read more.

A layer-by-layer deposition is essential for fabricating the Cu interconnects in a nanoscale-sized microelectronics because the gap-filling capability limits the film deposition step coverage on trenches/vias. Conventional layer-by-layer electrochemical deposition of Cu typically works by using two electrolytes, i.e., a sacrificial Pb electrolyte and a Cu electrolyte. However, the use of a Pb electrolyte is known to cause environmental issues. This study presents an Mn monolayer, which mediated the electrochemical growth of Cu(Mn) film through a sequence of alternating an underpotential deposition (UPD) of Mn, replacing the conventionally used UPD-Pb, with a surface-limited redox replacement (SLRR) of Cu. The use of the sacrificial Mn monolayer uniquely provides redox replacement by Cu²⁺ owing to the standard reductive potential differences. Repeating the sequence of the UPD-Mn followed by the SLRR-Cu enables Cu(Mn) film growth in an atomic layer growth manner. Further, controlling the time of open circuit potential (OCP) during the Cu-SLRR yields a technique to control the content of the resultant Cu(Mn) film. A longer OCP time caused more replacement of the UPD-Mn by the Cu²⁺, thus resulting in a Cu(Mn) film with a higher Cu concentration. The proposed layer-by-layer growth method offers a wet, chemistry-based deposition capable of fabricating Cu interconnects without the use of the barrier layer and can be of interest in microelectronics. Full article

(This article belongs to the Special Issue Advances in Functional Materials and Devices for Semiconductor and Energy Applications)

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8 pages, 2410 KiB

Open AccessFeature PaperArticle

Improvement of Electrical Performance by Neutron Irradiation Treatment on IGZO Thin Film Transistors

by Sera Kwon, Jongin Hong, Byung-Hyuk Jun and Kwun-Bum Chung

Coatings 2020, 10(2), 147; https://doi.org/10.3390/coatings10020147 - 06 Feb 2020

Cited by 3 | Viewed by 2736

Abstract

The effects of the neutron irradiation treatment on indium-gallium-zinc oxide (IGZO) are investigated as a function of the neutron irradiation time. With an increase in neutron irradiation time, the oxygen vacancies associated the oxygen deficient states increase, and both shallow and deep band [...] Read more.

The effects of the neutron irradiation treatment on indium-gallium-zinc oxide (IGZO) are investigated as a function of the neutron irradiation time. With an increase in neutron irradiation time, the oxygen vacancies associated the oxygen deficient states increase, and both shallow and deep band edge states below the conduction band also increase. Moreover, the conduction band offset continuously decreases because of the increase in the oxygen vacancies with increasing the neutron irradiation time. In IGZO TFTs with the neutron irradiation time for 10 s, superior device performance demonstrates such as the lower threshold voltage, higher field effect mobility, smaller sub-threshold gate swing, larger on-off current ratio, and improved bias stability, comparing those of other IGZO TFTs. Full article

(This article belongs to the Special Issue Advances in Functional Materials and Devices for Semiconductor and Energy Applications)

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16 pages, 7810 KiB

Open AccessArticle

The Effect of the Indium(III) Phthalocyanine Chloride Films on the Behavior of Flexible Devices of Flat and Disperse Heterojunction

by María Elena Sánchez-Vergara, Raquel Carrera-Téllez, Paulina Smith-Ruiz, Citlalli Rios and Roberto Salcedo

Coatings 2019, 9(10), 673; https://doi.org/10.3390/coatings9100673 - 17 Oct 2019

Cited by 4 | Viewed by 4149

Abstract

By means of flat-heterojunction structures based on small semiconductor molecules (MSCs), an analysis of the indium(III) phthalocyanine chloride (In(III)PcCl) film as a constituent of optoelectronic devices was performed. The study included the behavior of In(III)PcCl playing three different roles: a donor species, an [...] Read more.

By means of flat-heterojunction structures based on small semiconductor molecules (MSCs), an analysis of the indium(III) phthalocyanine chloride (In(III)PcCl) film as a constituent of optoelectronic devices was performed. The study included the behavior of In(III)PcCl playing three different roles: a donor species, an electronic acceptor, and a hole layer carrier. The flat-heterojunction structures were prepared by vacuum deposition method that permits a controlled layer-by-layer growth of high purity films. The investigated structures were characterized by scanning electron microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDS), UV-vis spectroscopy and optical bandgaps were obtained by Tauc’s and Cody’s methods. As the structures exhibit a large spectral absorption in the visible range, they were incorporated into flat-heterojunction devices based on flexible and rigid substrates. However, during the synthesis of those structures, the disperse heterojunction arrangement was found and indeed it showed to be more efficient than the initial flat-heterojunction. In order to complement these results, disperse heterojunction arrangement structure as well as its bandgap value were obtained by DFT calculations. Finally, the electronic behavior of both fabricated devices, disperse heterojunction and flat-heterojunction were compared. Full article

(This article belongs to the Special Issue Advances in Functional Materials and Devices for Semiconductor and Energy Applications)

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10 pages, 3673 KiB

Open AccessArticle

Boron and Nitrogen Co-Doped Porous Carbons Synthesized from Polybenzoxazines for High-Performance Supercapacitors

by Lijun Bai, Yanping Ge and Lizhong Bai

Coatings 2019, 9(10), 657; https://doi.org/10.3390/coatings9100657 - 11 Oct 2019

Cited by 17 | Viewed by 3287

Abstract

Boron and nitrogen co-doped porous carbons (BNPC-X) were synthesized from boron-containing polybenzoxazines through carbonization and chemical activation, where X represents the weight ratio of boric acid to benzoxazine resin. The as-prepared BNPC-X were characterized by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, [...] Read more.

Boron and nitrogen co-doped porous carbons (BNPC-X) were synthesized from boron-containing polybenzoxazines through carbonization and chemical activation, where X represents the weight ratio of boric acid to benzoxazine resin. The as-prepared BNPC-X were characterized by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, element analysis and electrochemical measurements. The results show that the BNPC-0.15 possesses relatively high weight fractions of boron (2.97 wt %) and nitrogen (2.43 wt %), a homogeneous pore distribution, and remarkable electrochemical capacitive performance. It exhibits high specific capacitance (286 F·g⁻¹ at 0.05 A·g⁻¹), excellent rate capability (at A·g⁻¹), and good charge–discharge stability (>92% capacitance retention after 1,000 cycles at 1.0 A·g⁻¹) in 6 M KOH aqueous solution. Full article

(This article belongs to the Special Issue Advances in Functional Materials and Devices for Semiconductor and Energy Applications)

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11 pages, 3240 KiB

Open AccessFeature PaperArticle

Cost-Effective and High-Throughput Plasmonic Interference Coupled Nanostructures by Using Quasi-Uniform Anodic Aluminum Oxide

by Yoonsu Bae, Jiseop Yu, Yeonseok Jung, Donghun Lee and Dukhyun Choi

Coatings 2019, 9(7), 420; https://doi.org/10.3390/coatings9070420 - 30 Jun 2019

Cited by 3 | Viewed by 3978

Abstract

Large-area and uniform plasmonic nanostructures have often been fabricated by simply evaporating noble metals such as gold and silver on a variety of nanotemplates such as nanopores, nanotubes, and nanorods. However, some highly uniform nanotemplates are limited to be utilized by long, complex, [...] Read more.

Large-area and uniform plasmonic nanostructures have often been fabricated by simply evaporating noble metals such as gold and silver on a variety of nanotemplates such as nanopores, nanotubes, and nanorods. However, some highly uniform nanotemplates are limited to be utilized by long, complex, and expensive fabrication. Here, we introduce a cost-effective and high-throughput fabrication method for plasmonic interference coupled nanostructures based on quasi-uniform anodic aluminum oxide (QU-AAO) nanotemplates. Industrial aluminum, with a purity of 99.5%, and copper were used as a base template and a plasmonic material, respectively. The combination of these modifications saves more than 18 h of fabrication time and reduces the cost of fabrication 30-fold. From optical reflectance data, we found that QU-AAO based plasmonic nanostructures exhibit similar optical behaviors to highly ordered (HO) AAO-based nanostructures. By adjusting the thickness of the AAO layer and its pore size, we could easily control the optical properties of the nanostructures. Thus, we expect that QU-AAO might be effectively utilized for commercial plasmonic applications. Full article

(This article belongs to the Special Issue Advances in Functional Materials and Devices for Semiconductor and Energy Applications)

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9 pages, 2658 KiB

Open AccessArticle

Rectifying Characteristics of Thermally Treated Mo/SiC Schottky Contact

by Jeongsoo Hong, Ki Hyun Kim and Kyung Hwan Kim

Coatings 2019, 9(6), 388; https://doi.org/10.3390/coatings9060388 - 15 Jun 2019

Cited by 6 | Viewed by 3854

Abstract

The rectifying characteristics of a Mo/SiC Schottky contact fabricated by facing targets sputtering system were investigated through current–voltage measurement. The Schottky diode parameters were extracted from the forward current–voltage characteristic curve by the Cheung and Cheung method and the Norde method. The as-deposited [...] Read more.

The rectifying characteristics of a Mo/SiC Schottky contact fabricated by facing targets sputtering system were investigated through current–voltage measurement. The Schottky diode parameters were extracted from the forward current–voltage characteristic curve by the Cheung and Cheung method and the Norde method. The as-deposited Mo/SiC Schottky contacts possessed Schottky barrier heights of 1.17 and 1.22 eV, respectively. The Schottky barrier heights of the diodes were decreased to 1.01 and 0.91 eV after annealing at 400 °C for 30 min. The ideality factor was increased from 1.14 and 1.08 to 1.51 and 1.41, respectively. This implies the presence of non-ideal behaviors due to a current transport mechanism other than ideal thermionic emission, and the non-ideal behaviors increased as a result of excessive thermal annealing. In contrast, only a negligible change was observed in the crystallographic characteristics. This result suggests that the reason for the deviation from the ideal rectifying characteristics of the Mo/SiC Schottky contact through the annealing process was the variation in the current transport mechanism, including recombination, tunneling, and/or minority carrier injection. Full article

(This article belongs to the Special Issue Advances in Functional Materials and Devices for Semiconductor and Energy Applications)

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