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14 pages, 5943 KiB

Open AccessArticle

Preparation and Optimization of Mn²⁺-Activated Na₂ZnGeO₄ Phosphors: Insights into Precursor Selection and Microwave-Assisted Solid-State Synthesis

by Xiaomeng Wang, Siyi Wei, Jiaping Zhang, Jiaren Du, Yukun Li, Ke Chen and Hengwei Lin

Nanomaterials 2025, 15(14), 1117; https://doi.org/10.3390/nano15141117 - 18 Jul 2025

Viewed by 330

Abstract

Mn²⁺-doped phosphors emitting green light have garnered significant interest due to their potential applications in display technologies and solid-state lighting. To facilitate the rapid synthesis of high-performance Mn²⁺-activated green phosphors, this research optimizes a microwave-assisted solid-state (MASS) method for [...] Read more.

Mn²⁺-doped phosphors emitting green light have garnered significant interest due to their potential applications in display technologies and solid-state lighting. To facilitate the rapid synthesis of high-performance Mn²⁺-activated green phosphors, this research optimizes a microwave-assisted solid-state (MASS) method for the preparation of Na₂ZnGeO₄:Mn²⁺. Leveraging the unique attributes of the MASS technique, a systematic investigation into the applicability of various Mn-source precursors was conducted. Additionally, the integration of the MASS approach with traditional solid-state reaction (SSR) methods was assessed. The findings indicate that the MASS technique effectively incorporates Mn ions from diverse precursors (including higher oxidation states of manganese) into the crystal lattice, resulting in efficient green emission from Mn²⁺. Notably, the photoluminescence quantum yield (PLQY) of the sample utilizing MnCO₃ as the manganese precursor was recorded at 2.67%, whereas the sample synthesized from MnO₂ exhibited a remarkable PLQY of 17.69%. Moreover, the post-treatment of SSR-derived samples through the MASS process significantly enhanced the PLQY from 0.67% to 8.66%. These results underscore the promise of the MASS method as a novel and efficient synthesis strategy for the rapid and scalable production of Mn²⁺-doped green luminescent materials. Full article

(This article belongs to the Section Inorganic Materials and Metal-Organic Frameworks)

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15 pages, 6584 KiB

Open AccessArticle

Defect Engineering and Dopant Properties of MgSiO₃

by Kowthaman Pathmanathan, Poobalasuntharam Iyngaran, Poobalasingam Abiman and Navaratnarajah Kuganathan

Eng 2025, 6(3), 51; https://doi.org/10.3390/eng6030051 - 12 Mar 2025

Cited by 2 | Viewed by 729

Abstract

Magnesium silicate (MgSiO₃) is widely utilized in glass manufacturing, with its performance influenced by structural modifications. In this study, we employ classical and density functional theory (DFT) simulations to investigate the defect and dopant characteristics of MgSiO₃. Our results [...] Read more.

Magnesium silicate (MgSiO₃) is widely utilized in glass manufacturing, with its performance influenced by structural modifications. In this study, we employ classical and density functional theory (DFT) simulations to investigate the defect and dopant characteristics of MgSiO₃. Our results indicate that a small amount of Mg-Si anti-site defects can exist in the material. Additionally, MgO Schottky defects are viable, requiring only slightly more energy to form than anti-site defects. Regarding the solubility of alkaline earth dopant elements, Ca preferentially incorporates into the Mg site without generating charge-compensating defects, while Zn exhibits a similar behavior among the 3D block elements. Al and Sc are promising dopants for substitution at the Si site, promoting the formation of Mg interstitials or oxygen vacancies, with the latter being the more energetically favorable process. The solution of isovalent dopants at the Si site is preferred by Ge and Ti. Furthermore, we analyze the electronic structures of the most favorable doped configurations. Full article

(This article belongs to the Section Materials Engineering)

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14 pages, 4185 KiB

Open AccessArticle

Towards Sustainable Perovskite Solar Cells: Lead-Free High Efficiency Designs with Tin and Germanium

by Marc Al Atem and Yahia Makableh

Eng 2025, 6(2), 38; https://doi.org/10.3390/eng6020038 - 17 Feb 2025

Cited by 2 | Viewed by 1285

Abstract

This study focuses on the development of efficient and environmentally friendly Lead-free Perovskite solar cells (PSCs) using Tin and Germanium as absorber materials. The study was performed using SCAPS-1D simulations (version 3.11) to explore the performance of PSCs. The investigation took into consideration [...] Read more.

This study focuses on the development of efficient and environmentally friendly Lead-free Perovskite solar cells (PSCs) using Tin and Germanium as absorber materials. The study was performed using SCAPS-1D simulations (version 3.11) to explore the performance of PSCs. The investigation took into consideration optimizing the electron transport layer’s (ETL) material and thickness, and TiO₂, ZnO, and WO₃ were investigated for this purpose. The current results show that Sn-based PSCs achieved a maximum power conversion efficiency of 23.19% with TiO₂ as the ETL, while Ge-based PSCs reached a power conversion efficiency of 14.83%. Additionally, the ETL doping concentration optimization revealed that the doping concentration had little impact on the device performance. These results emphasize the potential of Sn- and Ge-based PSCs as sustainable alternatives to Lead-based technologies, offering a pathway toward safer and more efficient solar energy solutions. Full article

(This article belongs to the Special Issue Emerging Trends in Materials Engineering for Clean Energy Applications)

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14 pages, 2520 KiB

Open AccessArticle

Tuning the Optical and Electrical Properties of ALD-Grown ZnO Films by Germanium Doping

by Sylvester Sahayaraj, Rafał Knura, Katarzyna Skibińska, Zbigniew Starowicz, Wojciech Bulowski, Katarzyna Gawlińska-Nęcek, Piotr Panek, Marek Wojnicki, Sylwester Iwanek, Łukasz Majchrowicz and Robert Piotr Socha

Materials 2024, 17(12), 2906; https://doi.org/10.3390/ma17122906 - 14 Jun 2024

Cited by 1 | Viewed by 1243

Abstract

In this work, we report on the fabrication of ZnO thin films doped with Ge via the ALD method. With an optimized amount of Ge doping, there was an improvement in the conductivity of the films owing to an increase in the carrier [...] Read more.

In this work, we report on the fabrication of ZnO thin films doped with Ge via the ALD method. With an optimized amount of Ge doping, there was an improvement in the conductivity of the films owing to an increase in the carrier concentration. The optical properties of the films doped with Ge show improved transmittance and reduced reflectance, making them more attractive for opto-electronic applications. The band gap of the films exhibits a blue shift with Ge doping due to the Burstein–Moss effect. The variations in the band gap and the work function of ZnO depend strongly on the carrier density of the films. From the surface studies carried out using XPS, we could confirm that Ge replaces some of the Zn in the wurtzite structure. In the films containing Ge, the concentration of oxygen vacancies is also high, which is somehow related to the poor electrical properties of the films at higher Ge concentrations. Full article

(This article belongs to the Special Issue Current Trends and Future Challenges of Electronic and Photonic Materials)

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14 pages, 4829 KiB

Open AccessArticle

Evaluation of the Electronic Properties of Atomic Layer Deposition-Grown Ge-Doped Zinc Oxide Thin Films at Elevated Temperatures

by Rafał Knura, Katarzyna Skibińska, Sylvester Sahayaraj, Marianna Marciszko-Wiąckowska, Jakub Gwizdak, Marek Wojnicki, Piotr Żabiński, Grzegorz Sapeta, Sylwester Iwanek and Robert P. Socha

Electronics 2024, 13(3), 554; https://doi.org/10.3390/electronics13030554 - 30 Jan 2024

Cited by 2 | Viewed by 1617

Abstract

The aim of this study was to determine the electronic properties of as-deposited ALD-grown Ge-doped zinc oxide thin films annealed at 523 K or 673 K. SEM, EDS, and ellipsometry measurements confirmed that the Ge-doped zinc oxide films with a thickness of around [...] Read more.

The aim of this study was to determine the electronic properties of as-deposited ALD-grown Ge-doped zinc oxide thin films annealed at 523 K or 673 K. SEM, EDS, and ellipsometry measurements confirmed that the Ge-doped zinc oxide films with a thickness of around 100 nm and uniform composition were successfully obtained. GI-XRD measurements did not reveal phases other than the expected Wurtzite structure of the ZnO. The electronic properties, i.e., conductivity, charge carrier concentration, and mobility of the films, were evaluated using Hall effect measurements and explained based on corresponding XPS measurements. This work supports the theory that oxygen vacancies act as electron donors and contribute to the intrinsic n-type conductivity of ZnO. Also, it is shown that the effect of oxygen vacancies on the electronic properties of the material is stronger than the effect introduced by Ge doping. Full article

(This article belongs to the Special Issue Section Collection Series: Recent Advances in Optoelectronics from Lab to Industry)

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10 pages, 1847 KiB

Open AccessCommunication

Theoretical Study of Doping in GaOOH for Electronics Applications

by Masaya Ichimura

Electron. Mater. 2023, 4(4), 148-157; https://doi.org/10.3390/electronicmat4040013 - 10 Nov 2023

Viewed by 1746

Abstract

GaOOH, having a bandgap of 4.7–4.9 eV, can be regarded as one of several ultrawide-bandgap (UWBG) semiconductors, although it has so far mainly been used as a precursor material of Ga₂O₃. To examine the possibility of valence control and [...] Read more.

GaOOH, having a bandgap of 4.7–4.9 eV, can be regarded as one of several ultrawide-bandgap (UWBG) semiconductors, although it has so far mainly been used as a precursor material of Ga₂O₃. To examine the possibility of valence control and application in electronics, impurity levels in GaOOH are investigated using the first-principles density-functional theory calculation. The density values of the states of a supercell including an impurity atom are calculated. According to the results, among the group 14 elements, Si is expected to introduce a shallow donor level, i.e., a free electron is introduced. On the other hand, Ge and Sn introduce a localized state about 0.7 eV below the conduction band edge, and thus cannot act as an effective donor. While Mg and Ca can introduce a free hole and act as a shallow acceptor, Zn and Cd introduce acceptor levels away from the valence band. The transition metal elements (Fe, Co, Ni, Cu) are also considered, but none of them are expected to act as a shallow dopant. Thus, the results suggest that the carrier concentration can be controlled if Si is used for n-type doping, and Mg and Ca for p-type doping. Since GaOOH can be easily deposited using various chemical techniques at low temperatures, GaOOH will potentially be useful for transparent electronic devices. Full article

(This article belongs to the Special Issue Metal Oxide Semiconductors for Electronic Applications)

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17 pages, 5536 KiB

Open AccessArticle

Device Simulation of Highly Stable and 29% Efficient

{F A}_{0.75} {M A}_{0.25} {S n}_{0.95} {G e}_{0.05} I_{3}

-Based Perovskite Solar Cell

by Hussein Sabbah and Zaher Abdel Baki

Nanomaterials 2023, 13(9), 1537; https://doi.org/10.3390/nano13091537 - 3 May 2023

Cited by 10 | Viewed by 2405

Abstract

A new type of perovskite solar cell based on mixed tin and germanium has the potential to achieve good power conversion efficiency and extreme air stability. However, improving its efficiency is crucial for practical application in solar cells. This paper presents a quantitative [...] Read more.

A new type of perovskite solar cell based on mixed tin and germanium has the potential to achieve good power conversion efficiency and extreme air stability. However, improving its efficiency is crucial for practical application in solar cells. This paper presents a quantitative analysis of lead-free FA_0.75MA_0.25Sn_0.95Ge_0.05I₃ using a solar cell capacitance simulator to optimize its structure. Various electron transport layer materials were thoroughly investigated to enhance efficiency. The study considered the impact of energy level alignment between the absorber and electron transport layer interface, thickness and doping concentration of the electron transport layer, thickness and defect density of the absorber, and the rear metal work function. The optimized structures included poly (3,4-ethylenedioxythiophene)polystyrene sulfonate (PEDOT:PSS) as the hole transport layer and either zinc oxide (ZnO) or zinc magnesium oxide (Zn_0.7Mg_0.3O) as the electron transport layer. The power conversion efficiency obtained was 29%, which was over three times higher than the initial structure. Performing numerical simulations on FA_0.75MA_0.25Sn_0.95Ge_0.05I₃ can significantly enhance the likelihood of its commercialization. The optimized values resulting from the conducted parametric study are as follows: a short-circuit current density of 30.13 mA·cm⁻²), an open-circuit voltage of 1.08 V, a fill factor of 86.56%, and a power conversion efficiency of 28.31% for the intended solar cell. Full article

(This article belongs to the Special Issue The Development of Sustainable Nanomaterials for Green Energy Applications)

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11 pages, 2679 KiB

Open AccessArticle

Achieving Persistent Luminescence Performance Based on the Cation-Tunable Trap Distribution

by Tao Wang, Rui Li, Mengya Zhang, Panlai Li and Zhijun Wang

Materials 2022, 15(24), 9083; https://doi.org/10.3390/ma15249083 - 19 Dec 2022

Cited by 2 | Viewed by 1711

Abstract

Deep-red persistent luminescence (PersL) materials have promising applications in fluorescence labeling and tracking. PersL spectral range and PersL duration are considered to be the key factors driving the development of high-performance deep-red PersL materials. To address these two key issues, the performance of [...] Read more.

Deep-red persistent luminescence (PersL) materials have promising applications in fluorescence labeling and tracking. PersL spectral range and PersL duration are considered to be the key factors driving the development of high-performance deep-red PersL materials. To address these two key issues, the performance of PersL materials was continually optimized by doping with cations (Si⁴⁺ and Al³⁺ ions), relying on the material of Li₂ZnGe₃O₈:Cr³⁺ from the previous work of our group, and a 4.8-fold increase in PersL radiation spectrum intensity and more than twice the PersL duration was achieved (PersL duration up to 47 h). Ultimately, the obtained PersL materials are used to demonstrate their potential use in multi-level anti-counterfeiting, tracking and localization, respectively. This study provides a unique and novel entry point for achieving high-performance PersL materials by optimizing the PersL material host to modulate the electronic structure. Full article

(This article belongs to the Special Issue Recent Advances in Rare Earth Luminescent Materials)

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17 pages, 3224 KiB

Open AccessArticle

High-Efficiency Electron Transport Layer-Free Perovskite/GeTe Tandem Solar Cell: Numerical Simulation

by Mostafa M. Salah, Abdelhalim Zekry, Mohamed Abouelatta, Ahmed Shaker, Mohamed Mousa, Fathy Z. Amer, Roaa I. Mubarak and Ahmed Saeed

Crystals 2022, 12(7), 878; https://doi.org/10.3390/cryst12070878 - 21 Jun 2022

Cited by 20 | Viewed by 4750

Abstract

The primary purpose of recent research has been to achieve a higher power conversion efficiency (PCE) with stable characteristics, either through experimental studies or through modeling and simulation. In this study, a theoretical analysis of an efficient perovskite solar cell (PSC) with cuprous [...] Read more.

The primary purpose of recent research has been to achieve a higher power conversion efficiency (PCE) with stable characteristics, either through experimental studies or through modeling and simulation. In this study, a theoretical analysis of an efficient perovskite solar cell (PSC) with cuprous oxide (Cu₂O) as the hole transport material (HTM) and zinc oxysulfide (ZnOS) as the electron transport material (ETM) was proposed to replace the traditional HTMs or ETMs. In addition, the impact of doping the perovskite layer was investigated. The results show that the heterostructure of n-p PSC without an electron transport layer (ETL) could replace the traditional n-i-p structure with better performance metrics and more stability due to reducing the number of layers and interfaces. The impact of HTM doping and thickness was investigated. In addition, the influence of the energy gap of the absorber layer was studied. Furthermore, the proposed PSC without ETL was used as a top sub-cell with germanium-telluride (GeTe) as a bottom sub-cell to produce an efficient tandem cell and boost the PCE. An ETL-free PSC/GeTe tandem cell is proposed for the first time to provide an efficient and stable tandem solar cell with a PCE of 45.99%. Finally, a comparison between the performance metrics of the proposed tandem solar cell and those of other recent studies is provided. All the simulations performed in this study are accomplished by using SCAPS-1D. Full article

(This article belongs to the Special Issue Advances of Perovskite Solar Cells)

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13 pages, 5964 KiB

Open AccessArticle

Tuning Multicolor Emission of Manganese-Activated Gallogermanate Nanophosphors by Regulating Mn Ions Occupying Sites for Multiple Anti-Counterfeiting Application

by Dangli Gao, Peng Wang, Feng Gao, William Nguyen and Wei Chen

Nanomaterials 2022, 12(12), 2029; https://doi.org/10.3390/nano12122029 - 13 Jun 2022

Cited by 14 | Viewed by 2338

Abstract

The ability to manipulate the luminescent color, intensity and long lifetime of nanophosphors is important for anti-counterfeiting applications. Unfortunately, persistent luminescence materials with multimode luminescent features have rarely been reported, even though they are expected to be highly desirable in sophisticated anti-counterfeiting. Here, [...] Read more.

The ability to manipulate the luminescent color, intensity and long lifetime of nanophosphors is important for anti-counterfeiting applications. Unfortunately, persistent luminescence materials with multimode luminescent features have rarely been reported, even though they are expected to be highly desirable in sophisticated anti-counterfeiting. Here, the luminescence properties of Zn₃Ga₂GeO₈:Mn phosphors were tuned by using different preparation approaches, including a hydrothermal method and solid-state reaction approach combining with non-equivalent ion doping strategy. As a result, Mn-activated Zn₃Ga₂GeO₈ phosphors synthesized by a hydrothermal method demonstrate an enhanced red photoluminescence at 701 nm and a strong green luminescence with persistent luminescence and photostimulated luminescence at 540 nm. While Mn-activated Zn₃Ga₂GeO₈ phosphors synthesized by solid-state reactions combined with a hetero-valent doping approach only exhibit an enhanced single-band red emission. Keeping the synthetic method unchanged, the substitution of hetero-valent dopant ion Li⁺ into different sites is valid for spectral fine-tuning. A spectral tuning mechanism is also proposed. Mn-activated Zn₃Ga₂GeO₈ phosphors synthesized by a hydrothermal approach with multimodal luminescence is especially suitable for multiple anti-counterfeiting, multicolor display and other potential applications. Full article

(This article belongs to the Special Issue Luminescence Nanomaterials and Applications)

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14 pages, 5032 KiB

Open AccessArticle

Defect Chemistry, Sodium Diffusion and Doping Behaviour in NaFeO₂ Polymorphs as Cathode Materials for Na-Ion Batteries: A Computational Study

by Navaratnarajah Kuganathan, Nikolaos Kelaidis and Alexander Chroneos

Materials 2019, 12(19), 3243; https://doi.org/10.3390/ma12193243 - 4 Oct 2019

Cited by 22 | Viewed by 5587

Abstract

Minor metal-free sodium iron dioxide, NaFeO₂, is a promising cathode material in sodium-ion batteries. Computational simulations based on the classical potentials were used to study the defects, sodium diffusion paths and cation doping behaviour in the α- and β-NaFeO₂ polymorphs. [...] Read more.

Minor metal-free sodium iron dioxide, NaFeO₂, is a promising cathode material in sodium-ion batteries. Computational simulations based on the classical potentials were used to study the defects, sodium diffusion paths and cation doping behaviour in the α- and β-NaFeO₂ polymorphs. The present simulations show good reproduction of both α- and β-NaFeO₂. The most thermodynamically favourable defect is Na Frenkel, whereas the second most favourable defect is the cation antisite, in which Na and Fe exchange their positions. The migration energies suggest that there is a very small difference in intrinsic Na mobility between the two polymorphs but their migration paths are completely different. A variety of aliovalent and isovalent dopants were examined. Subvalent doping by Co and Zn on the Fe site is calculated to be energetically favourable in α- and β-NaFeO₂, respectively, suggesting the interstitial Na concentration can be increased by using this defect engineering strategy. Conversely, doping by Ge on Fe in α-NaFeO₂ and Si (or Ge) on Fe in β-NaFeO₂ is energetically favourable to introduce a high concentration of Na vacancies that act as vehicles for the vacancy-assisted Na diffusion in NaFeO₂. Electronic structure calculations by using density functional theory (DFT) reveal that favourable dopants lead to a reduction in the band gap. Full article

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8 pages, 4167 KiB

Open AccessArticle

Effect of Ge Nanocrystals on 1.54 μm Photoluminescence Enhancement in Er₂O₃:ZnO and Ge Co-Sputtered Films

by Ranran Fan, Fei Lu and Kaikai Li

Nanomaterials 2017, 7(10), 311; https://doi.org/10.3390/nano7100311 - 11 Oct 2017

Cited by 3 | Viewed by 3811

Abstract

Photoluminescence (PL) of Er and Ge co-doped ZnO films synthesized by radio frequency magnetron co-sputtering was investigated. X-ray diffraction (XRD) patterns showed that the annealing process at 400–800 °C led to the formation of nanocrystal (nc) Ge. Samples containing nc-Ge showed a strong [...] Read more.

Photoluminescence (PL) of Er and Ge co-doped ZnO films synthesized by radio frequency magnetron co-sputtering was investigated. X-ray diffraction (XRD) patterns showed that the annealing process at 400–800 °C led to the formation of nanocrystal (nc) Ge. Samples containing nc-Ge showed a strong visible PL with a peak at 582–593 nm, which was consistent with the calculated energy of the exciton of the ~5 nm-sized nc-Ge, according to the quantum confinement effect. The formation of nc-Ge could greatly enhance the 1.54 μm emission, and it is considered that the 1.54 μm PL enhancement may come from a joint effect of both the energy transfer from nc-Ge to Er³⁺ and the local environment change of Er³⁺. Full article

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4 pages, 265 KiB

Open AccessProceeding Paper

Near Infrared Plasmonic Gas Sensing with Doped Metal Oxide Nanocrystals

by Marco Sturaro, Enrico Della Gaspera, Carlo Cantalini, Massimo Guglielmi and Alessandro Martucci

Proceedings 2017, 1(4), 319; https://doi.org/10.3390/proceedings1040319 - 5 Sep 2017

Cited by 4 | Viewed by 2258

Abstract

In this paper, we demonstrate the application of ZnO doped with gallium (GZO), aluminum (AZO) and germanium (GeZO) nanocrystals as novel plasmonic and chemiresistive sensors for the detection of hazardous gases including hydrogen (H₂) and nitrogen dioxide (NO₂). GZO, [...] Read more.

In this paper, we demonstrate the application of ZnO doped with gallium (GZO), aluminum (AZO) and germanium (GeZO) nanocrystals as novel plasmonic and chemiresistive sensors for the detection of hazardous gases including hydrogen (H₂) and nitrogen dioxide (NO₂). GZO, AZO and GeZO nanocrystals are obtained by non-aqueous colloidal heat-up synthesis with high transparency in the visible range and strong localized surface plasmon resonance (LSPR) in the near IR range, tunable with dopant concentration (up to 20% mol nominal). Thanks to the strong sensitivity of the LSPR to chemical and electrical changes occurring at the surface of the nanocrystals, such optical features can be used to detect the presence of toxic gases. By monitoring the changes in the dopant-induced plasmon resonance in the near infrared, we demonstrate that GZO, AZO and GeZO thin films prepared depositing an assembly of highly doped ZnO colloids are able to optically detect both oxidizing and reducing gases at mild (<100 °C) operating temperatures. Combined optical and electrical measurements show that the dopants within ZnO nanocrystals enhance the gas sensing response compared to undoped ZnO. Full article

(This article belongs to the Proceedings of Proceedings of Eurosensors 2017, Paris, France, 3–6 September 2017)

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