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11 pages, 4188 KiB

Open AccessArticle

Optimizing the Band Alignment of the MZO/CdSeTe/CdTe Solar Cell by Varying the Substrate Temperature of MZO Film

by Qiuchen Wu, Ruchun Li, Yufeng Zhang, Kai Huang, Heran Li and Xiangxin Liu

Energies 2024, 17(3), 592; https://doi.org/10.3390/en17030592 - 26 Jan 2024

Cited by 1 | Viewed by 1672

Cadmium telluride (CdTe) photovoltaics is a promising and scalable technology, commanding over 90% of the thin film photovoltaics market. An appropriate window layer is crucial for high-efficiency CdTe solar cells. This study aimed to investigate a representative MgZnO (MZO) window layer and enhance [...] Read more.

Cadmium telluride (CdTe) photovoltaics is a promising and scalable technology, commanding over 90% of the thin film photovoltaics market. An appropriate window layer is crucial for high-efficiency CdTe solar cells. This study aimed to investigate a representative MgZnO (MZO) window layer and enhance device performance. We studied the properties of MZO films with different substrate temperatures and their application in CdSeTe/CdTe solar cells. Despite the high transmittance and wide band gap of MZO film, the device performance of MZO sputtered at room temperature is limited by excessive conduction band offset. Tailoring the substrate temperature for MZO sputtering helps optimize the band alignment of the MZO/CdSeTe interface, contributing to an improvement in the efficiency of CdTe solar cells. Full article

(This article belongs to the Special Issue Advances in Solar Energy Materials and Solar Energy Systems)

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11 pages, 3088 KiB

Open AccessEditor’s ChoiceArticle

Tailoring of the Structural, Optical, and Electrical Characteristics of Sol-Gel-Derived Magnesium-Zinc-Oxide Wide-Bandgap Semiconductor Thin Films via Gallium Doping

by Chien-Yie Tsay, Shih-Ting Chen and Hsuan-Meng Tsai

Materials 2023, 16(19), 6389; https://doi.org/10.3390/ma16196389 - 25 Sep 2023

Cited by 6 | Viewed by 1690

Abstract

The Ga-doped Mg_0.2Zn_0.8O (GMZO) transparent semiconductor thin films were prepared using the sol-gel and spin-coating deposition technique. Changes in the microstructural features, optical parameters, and electrical characteristics of sol-gel-synthesized Mg_0.2Zn_0.8O (MZO) thin films affected by [...] Read more.

The Ga-doped Mg_0.2Zn_0.8O (GMZO) transparent semiconductor thin films were prepared using the sol-gel and spin-coating deposition technique. Changes in the microstructural features, optical parameters, and electrical characteristics of sol-gel-synthesized Mg_0.2Zn_0.8O (MZO) thin films affected by the amount of Ga dopants (0–5 at%) were studied. The results of grazing incidence X-ray diffraction (GIXRD) examination showed that all as-prepared MZO-based thin films had a wurtzite-type structure and hexagonal phase, and the incorporation of Ga ions into the MZO nanocrystals refined the microstructure and reduced the average crystallite size and flatness of surface roughness. Each glass/oxide thin film sample exhibited a higher average transmittance than 91.5% and a lower average reflectance than 9.1% in the visible range spectrum. Experimental results revealed that the optical bandgap energy of the GMZO thin films was slightly higher than that of the MZO thin film; the Urbach energy became wider with increasing Ga doping level. It was found that the 2 at% and 3 at% Ga-doped MZO thin films had better electrical properties than the undoped and 5 at% Ga-doped MZO thin films. Full article

(This article belongs to the Special Issue ZnO Materials: Synthesis, Properties and Applications (Second Volume))

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10 pages, 3968 KiB

Open AccessArticle

Effect of Alkaline Earth Metal on AZrO_x (A = Mg, Sr, Ba) Memory Application

by Ke-Jing Lee and Yeong-Her Wang

Gels 2022, 8(1), 20; https://doi.org/10.3390/gels8010020 - 27 Dec 2021

Cited by 7 | Viewed by 2898

Abstract

Zr can be stabilized by the element selected, such as Mg-stabilized Zr (MSZ), thus providing MSZ thin films with potentially wide applications and outstanding properties. This work employed the element from alkaline earth metal stabilized Zr to investigate the electrical properties of sol–gel [...] Read more.

Zr can be stabilized by the element selected, such as Mg-stabilized Zr (MSZ), thus providing MSZ thin films with potentially wide applications and outstanding properties. This work employed the element from alkaline earth metal stabilized Zr to investigate the electrical properties of sol–gel AZrO_x (A = alkaline earth metal; Mg, Sr, Ba) as dielectric layer in metal-insulator–metal resistive random-access memory devices. In addition, the Hume–Rothery rule was used to calculate the different atomic radii of elements. The results show that the hydrolyzed particles, surface roughness, and density of oxygen vacancy decreased with decreased difference in atomic radius between Zr and alkaline earth metal. The MgZrOx (MZO) thin film has fewer particles, smoother surface, and less density of oxygen vacancy than the SrZrO_x (SZO) and BaZrO_x (BZO) thin films, leading to the lower high resistance state (HRS) current and higher ON/OFF ratio. Thus, a suitable element selection for the sol–gel AZrO_x memory devices is helpful for reducing the HRS current and improving the ON/OFF ratio. These results were obtained possibly because Mg has a similar atomic radius as Zr and the MgO_x-stabilized ZrO_x. Full article

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17 pages, 10640 KiB

Open AccessArticle

Effect of Al and Mg Doping on Reducing Gases Detection of ZnO Nanoparticles

by Soumaya Jaballah, Yazeed Alaskar, Ibrahim AlShunaifi, Imed Ghiloufi, Giovanni Neri, Chaker Bouzidi, Hassen Dahman and Lassaad El Mir

Chemosensors 2021, 9(11), 300; https://doi.org/10.3390/chemosensors9110300 - 24 Oct 2021

Cited by 26 | Viewed by 3529

Abstract

In this work, the main objective is to enhance the gas sensing capability through investigating the effect of Al and Mg doping on ZnO based sensors. ZnO, Mg_1% doped ZnO, Al_5% doped ZnO and (Al_5%, Mg_1%) co-doped ZnO [...] Read more.

In this work, the main objective is to enhance the gas sensing capability through investigating the effect of Al and Mg doping on ZnO based sensors. ZnO, Mg_1% doped ZnO, Al_5% doped ZnO and (Al_5%, Mg_1%) co-doped ZnO nanoparticles (NPs) were synthesized by a modified sol-gel method. The structural characterization showed the hexagonal crystalline structure of the prepared samples. Morphological characterizations confirmed the nanometric sizes of the NPs (27–57 nm) and elemental composition investigation proved the existence of Al and Mg with low concentrations. The optical characterization showed the high absorbance of the synthesized samples in the UV range. The gas sensing performances of the synthesized samples, prepared in the form of thick films, were investigated. Sensing tests demonstrated the high influence of the Al and Mg on the sensing performances towards H₂ and CO gas, respectively. The 5A1MZO-based sensor exhibits high sensitivity and low detection limits to H₂ (<2 ppm) and CO (<1 ppm). It showed a response around 70 (at 250 °C) towards 2000 ppm H₂ and 2 (at 250 °C) towards CO. Full article

(This article belongs to the Special Issue High-Sensitivity and -Selectivity Gas Sensors with Nanoparticles, Nanostructures, and Thin Films)

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19 pages, 2054 KiB

Open AccessArticle

Optical Properties of Magnesium-Zinc Oxide for Thin Film Photovoltaics

by Mohammed A. Razooqi Alaani, Prakash Koirala, Adam B. Phillips, Geethika K. Liyanage, Rasha A. Awni, Dhurba R. Sapkota, Balaji Ramanujam, Michael J. Heben, Stephen K. O’Leary, Nikolas J. Podraza and Robert W. Collins

Materials 2021, 14(19), 5649; https://doi.org/10.3390/ma14195649 - 28 Sep 2021

Cited by 8 | Viewed by 2996

Abstract

Motivated by their utility in CdTe-based thin film photovoltaics (PV) devices, an investigation of thin films of the magnesium-zinc oxide (Mg_xZn_1−xO or MZO) alloy system was undertaken applying spectroscopic ellipsometry (SE). Dominant wurtzite phase MZO thin films with [...] Read more.

Motivated by their utility in CdTe-based thin film photovoltaics (PV) devices, an investigation of thin films of the magnesium-zinc oxide (Mg_xZn_1−xO or MZO) alloy system was undertaken applying spectroscopic ellipsometry (SE). Dominant wurtzite phase MZO thin films with Mg contents in the range 0 ≤ x ≤ 0.42 were deposited on room temperature soda lime glass (SLG) substrates by magnetron co-sputtering of MgO and ZnO targets followed by annealing. The complex dielectric functions ε of these films were determined and parameterized over the photon energy range from 0.73 to 6.5 eV using an analytical model consisting of two critical point (CP) oscillators. The CP parameters in this model are expressed as polynomial functions of the best fitting lowest CP energy or bandgap E₀ = E_g, which in turn is a quadratic function of x. As functions of x, both the lowest energy CP broadening and the Urbach parameter show minima for x ~ 0.3, which corresponds to a bandgap of 3.65 eV. As a result, it is concluded that for this composition and bandgap, the MZO exhibits either a minimum concentration of defects in the bulk of the crystallites or a maximum in the grain size, an observation consistent with measured X-ray diffraction line broadenings. The parametric expression for ε developed here is expected to be useful in future mapping and through-the-glass SE analyses of partial and complete PV device structures incorporating MZO. Full article

(This article belongs to the Special Issue Thin Films: Growth, Characterization, and Optoelectronic Device Applications)

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8 pages, 835 KiB

Open AccessArticle

Effects of Thermal Annealing on the Properties of Zirconium-Doped Mg_xZn_1−XO Films Obtained through Radio-Frequency Magnetron Sputtering

by Wen-Yen Lin, Feng-Tsun Chien, Hsien-Chin Chiu, Jinn-Kong Sheu and Kuang-Po Hsueh

Membranes 2021, 11(5), 373; https://doi.org/10.3390/membranes11050373 - 20 May 2021

Cited by 4 | Viewed by 3135

Abstract

Zirconium-doped Mg_xZn_1−xO (Zr-doped MZO) mixed-oxide films were investigated, and the temperature sensitivity of their electric and optical properties was characterized. Zr-doped MZO films were deposited through radio-frequency magnetron sputtering using a 4-inch ZnO/MgO/ZrO₂ (75/20/5 wt%) target. Hall measurement, [...] Read more.

Zirconium-doped Mg_xZn_1−xO (Zr-doped MZO) mixed-oxide films were investigated, and the temperature sensitivity of their electric and optical properties was characterized. Zr-doped MZO films were deposited through radio-frequency magnetron sputtering using a 4-inch ZnO/MgO/ZrO₂ (75/20/5 wt%) target. Hall measurement, X-ray diffraction (XRD), transmittance, and X-ray photoelectron spectroscopy (XPS) data were obtained. The lowest sheet resistance, highest mobility, and highest concentration were 1.30 × 10³ Ω/sq, 4.46 cm²/Vs, and 7.28 × 10¹⁹ cm⁻³, respectively. The XRD spectra of the as-grown and annealed Zr-doped MZO films contained Mg_xZn_1−xO(002) and ZrO₂(200) coupled with Mg(OH)₂(101) at 34.49°, 34.88°, and 38.017°, respectively. The intensity of the XRD peak near 34.88° decreased with temperature because the films that segregated Zr⁴⁺ from ZrO₂(200) increased. The absorption edges of the films were at approximately 348 nm under 80% transmittance because of the Mg content. XPS revealed that the amount of Zr⁴⁺ increased with the annealing temperature. Zr is a potentially promising double donor, providing up to two extra free electrons per ion when used in place of Zn²⁺. Full article

(This article belongs to the Special Issue Thin-Film Transistors)

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13 pages, 31718 KiB

Open AccessCommunication

Efficient PbS Quantum Dot Solar Cells with Both Mg-Doped ZnO Window Layer and ZnO Nanocrystal Interface Passivation Layer

by Hao Ren, Ao Xu, Yiyang Pan, Donghuan Qin, Lintao Hou and Dan Wang

Nanomaterials 2021, 11(1), 219; https://doi.org/10.3390/nano11010219 - 15 Jan 2021

Cited by 12 | Viewed by 4272

Abstract

In this paper, a Mg-doped ZnO (MZO) thin film is prepared by a simple solution process under ambient conditions and is used as the window layer for PbS solar cells due to a wide n-type bandgap. Moreover, a thin layer of ZnO nanocrystals [...] Read more.

In this paper, a Mg-doped ZnO (MZO) thin film is prepared by a simple solution process under ambient conditions and is used as the window layer for PbS solar cells due to a wide n-type bandgap. Moreover, a thin layer of ZnO nanocrystals (NCs) was deposited on the MZO to reduce carrier recombination at the interface for inverted PbS quantum dot solar cells with the configuration Indium Tin Oxides (ITO)/MZO/ZnO NC (w/o)/PbS/Au. The effect of film thickness and annealing temperature of MZO and ZnO NC on the performance of PbS quantum dot solar cells was investigated in detail. It was found that without the ZnO NC thin layer, the highest power conversion efficiency(PCE) of 5.52% was obtained in the case of a device with an MZO thickness of 50 nm. When a thin layer of ZnO NC was introduced between MZO and PbS quantum dot film, the PCE of the champion device was greatly improved to 7.06% due to the decreased interface recombination. The usage of the MZO buffer layer along with the ZnO NC interface passivation technique is expected to further improve the performance of quantum dot solar cells. Full article

(This article belongs to the Special Issue Nanomaterials and Nanotechnology for Optoelectronics and Photovoltaics)

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14 pages, 3758 KiB

Open AccessArticle

Stability of Quantum-Dot Light Emitting Diodes with Alkali Metal Carbonates Blending in Mg Doped ZnO Electron Transport Layer

by Hyo-Min Kim, Wonkyeong Jeong, Joo Hyun Kim and Jin Jang

Nanomaterials 2020, 10(12), 2423; https://doi.org/10.3390/nano10122423 - 4 Dec 2020

Cited by 6 | Viewed by 4200

Abstract

We report here the fabrication of highly efficient and long-lasting quantum-dot light emitting diodes (QLEDs) by blending various alkali metal carbonate in magnesium (Mg) doped zinc oxide (ZnO) (MZO) electron transport layer (ETL). Alkali metal carbonates blending in MZO, X₂CO₃ [...] Read more.

We report here the fabrication of highly efficient and long-lasting quantum-dot light emitting diodes (QLEDs) by blending various alkali metal carbonate in magnesium (Mg) doped zinc oxide (ZnO) (MZO) electron transport layer (ETL). Alkali metal carbonates blending in MZO, X₂CO₃:MZO, control the band-gap, electrical properties, and thermal stability. This can therefore enhance the operational lifetime of QLEDs. It is found that the conductivity of X₂CO₃:MZO film can be controlled and the thermal stability of ETLs could be improved by X₂CO₃ blending in MZO. The inverted red QLEDs (R-QLEDs) with Cs₂CO₃:MZO, Rb₂CO₃:MZO, and K₂CO₃:MZO ETLs exhibited the operational lifetime of 407 h for the R-QLEDs with Cs₂CO₃:MZO, 620 h with Rb₂CO₃:MZO and 94 h with K₂CO₃:MZO ETLs at T₉₅ with the initial luminance of 1000 cd/m². Note that all red QLEDs showed the high brightness over 150,000 cd/m². But the R-QLEDs with Na₂CO₃:MZO and Li₂CO₃:MZO ETLs exhibited shorter operational lifetime and poor brightness than the R-QLED with pristine MZO ETL. Full article

(This article belongs to the Special Issue Nanomaterials and Nanotechnology for Optoelectronics and Photovoltaics)

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16 pages, 8608 KiB

Open AccessArticle

NH₃ Plasma-Treated Magnesium Doped Zinc Oxide in Biomedical Sensors with Electrolyte–Insulator–Semiconductor (EIS) Structure for Urea and Glucose Applications

by Chun Fu Lin, Chyuan Haur Kao, Chan Yu Lin, Kuan Lin Chen and Yun Hao Lin

Nanomaterials 2020, 10(3), 583; https://doi.org/10.3390/nano10030583 - 23 Mar 2020

Cited by 23 | Viewed by 3985

Abstract

This study compared the sensing characteristics of ZnO (ZO) treated with ammonia (NH₃) plasma for 1 min, 3 min, and 6 min, under the EIS structure. The measurement results revealed that, after 3 min of NH₃ plasma treatment, the Mg-doped [...] Read more.

This study compared the sensing characteristics of ZnO (ZO) treated with ammonia (NH₃) plasma for 1 min, 3 min, and 6 min, under the EIS structure. The measurement results revealed that, after 3 min of NH₃ plasma treatment, the Mg-doped ZnO (MZO) sensing film had a high hydrogen ion sensitivity, linearity, hysteresis, and drift rate of 53.82 mV/pH, 99.04%, 2.52 mV, and 1.75 mV/h, respectively. The sensing film was used with sodium and potassium ion solutions, and it performed satisfactorily in sensing hydrogen ions. Additionally, we investigated the biomedical sensing properties of Mg-doped ZnO (MZO) sensing film with regard to urea, creatinine, and glucose solutions and found that the Mg-doped ZnO (MZO) sensing film treated with NH₃ plasma for 3 min had the best properties for sensing urea, creatinine, and glucose. Specifically, with glucose, the sensing film achieved the best linearity and sensitivity and of 97.87% and 10.73 mV/mM, respectively. The results revealed that the sensing characteristics varied with the processing environment and are useful in the developing biomedical sensing applications with different sensing elements. Full article

(This article belongs to the Section Nanocomposite Materials)

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