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Showing papers on "Amorphous solid published in 2021"


Book
01 Feb 2021
TL;DR: In this article, the current use and challenges of thin-film silicon solar cells, including conductivities and doping, the properties of microcrystalline silicon (the role of the internal electric field, shunts, series resistance problems, light trapping), tandem and multijunction solar cells (a-Si:H/a -Si: H tandems, triple-junction amorphous cells, micro-crystaline-amorphous or “micromorph” Tandems), module production (deposition of thinfilm layers, substrate materials,
Abstract: This chapter covers the current use and challenges of thin-film silicon solar cells, including conductivities and doping, the properties of microcrystalline silicon (the role of the internal electric field, shunts, series resistance problems, light trapping), tandem and multijunction solar cells (a-Si:H/a-Si:H tandems, triple-junction amorphous cells, microcrystalline–amorphous or “micromorph” tandems), module production (deposition of thin-film layers, substrate materials, laser scribing, cell interconnection, and module encapsulation), and module performance.

230 citations



Journal ArticleDOI
TL;DR: In this paper, the authors considered the application of the dopant CeO2 with different concentration on the efficiency of gamma radiation shielding by telluride glasses of type (0.5-x)TeO2-0.25MoO-1.25Bi2O3-xCeO2.

171 citations


Journal ArticleDOI
06 Jan 2021-Nature
TL;DR: In this paper, a machine learning model is used to predict the electronic properties of amorphous silicon, showing that polyamorphic low-and high-density regions are found to coexist, rather than appearing sequentially.
Abstract: Structurally disordered materials pose fundamental questions1–4, including how different disordered phases (‘polyamorphs’) can coexist and transform from one phase to another5–9. Amorphous silicon has been extensively studied; it forms a fourfold-coordinated, covalent network at ambient conditions and much-higher-coordinated, metallic phases under pressure10–12. However, a detailed mechanistic understanding of the structural transitions in disordered silicon has been lacking, owing to the intrinsic limitations of even the most advanced experimental and computational techniques, for example, in terms of the system sizes accessible via simulation. Here we show how atomistic machine learning models trained on accurate quantum mechanical computations can help to describe liquid–amorphous and amorphous–amorphous transitions for a system of 100,000 atoms (ten-nanometre length scale), predicting structure, stability and electronic properties. Our simulations reveal a three-step transformation sequence for amorphous silicon under increasing external pressure. First, polyamorphic low- and high-density amorphous regions are found to coexist, rather than appearing sequentially. Then, we observe a structural collapse into a distinct very-high-density amorphous (VHDA) phase. Finally, our simulations indicate the transient nature of this VHDA phase: it rapidly nucleates crystallites, ultimately leading to the formation of a polycrystalline structure, consistent with experiments13–15 but not seen in earlier simulations11,16–18. A machine learning model for the electronic density of states confirms the onset of metallicity during VHDA formation and the subsequent crystallization. These results shed light on the liquid and amorphous states of silicon, and, in a wider context, they exemplify a machine learning-driven approach to predictive materials modelling. Machine learning models enable atomistic simulations of phase transitions in amorphous silicon, predict electronic fingerprints, and show that the pressure-induced crystallization occurs over three distinct stages.

145 citations


Journal ArticleDOI
31 Mar 2021-Nature
TL;DR: In this paper, an atomic electron tomography reconstruction method was developed to determine the 3D atomic positions of an amorphous solid using a multi-component glass-forming alloy as proof of principle.
Abstract: Amorphous solids such as glass, plastics and amorphous thin films are ubiquitous in our daily life and have broad applications ranging from telecommunications to electronics and solar cells1-4 However, owing to the lack of long-range order, the three-dimensional (3D) atomic structure of amorphous solids has so far eluded direct experimental determination5-15 Here we develop an atomic electron tomography reconstruction method to experimentally determine the 3D atomic positions of an amorphous solid Using a multi-component glass-forming alloy as proof of principle, we quantitatively characterize the short- and medium-range order of the 3D atomic arrangement We observe that, although the 3D atomic packing of the short-range order is geometrically disordered, some short-range-order structures connect with each other to form crystal-like superclusters and give rise to medium-range order We identify four types of crystal-like medium-range order-face-centred cubic, hexagonal close-packed, body-centred cubic and simple cubic-coexisting in the amorphous sample, showing translational but not orientational order These observations provide direct experimental evidence to support the general framework of the efficient cluster packing model for metallic glasses10,12-14,16 We expect that this work will pave the way for the determination of the 3D structure of a wide range of amorphous solids, which could transform our fundamental understanding of non-crystalline materials and related phenomena

128 citations


Journal ArticleDOI
TL;DR: In this paper, a defect-enhanced amorphous Co-Mn binary oxides with enhanced defect were fabricated by a facile self-redox approach to improve the catalytic activity for propane oxidation.
Abstract: Cobalt-manganese composite oxides have high-activity potential for catalytic oxidation of volatile organic compounds (VOCs). However, low defect content and poor oxygen mobility of the spinel structure make it difficult to efficiently activate C H bonds of propane at low-temperature. Herein, novel amorphous Co-Mn binary oxides with enhanced defect were fabricated by a facile self-redox approach. Highly defective amorphous Co Mn binary oxides with low-temperature reducibility, weak Mn O bond strength and good mobility of the surface lattice oxygen remarkably improved the catalytic activity for propane oxidation. Highly defective amorphous Co1Mn3Ox catalyst showed the best catalytic activity for propane mineralization and the T90 was 207℃ under high space velocity (18 000 mL·g−1 h−1). Moreover, in situ spectroscopy technologies were utilized to explore the structure-activity relationship and the degradation mechanism of propane oxidation under real reaction condition. Significantly, as an effective defect engineering strategy, amorphous binary oxides exhibit excellent activity and can provide some enlightenments for developing efficient VOCs catalysts.

112 citations


Journal ArticleDOI
TL;DR: In this article, the structure of monolayer amorphous carbon has been determined by atomic-resolution imaging, which reveals the complete absence of long-range periodicity and a threefold-coordinated structure with a wide distribution of bond lengths, bond angles, and five-, six-, seven-and eight-member rings.
Abstract: Bulk amorphous materials have been studied extensively and are widely used, yet their atomic arrangement remains an open issue. Although they are generally believed to be Zachariasen continuous random networks, recent experimental evidence favours the competing crystallite model in the case of amorphous silicon. In two-dimensional materials, however, the corresponding questions remain unanswered. Here we report the synthesis, by laser-assisted chemical vapour deposition, of centimetre-scale, free-standing, continuous and stable monolayer amorphous carbon, topologically distinct from disordered graphene. Unlike in bulk materials, the structure of monolayer amorphous carbon can be determined by atomic-resolution imaging. Extensive characterization by Raman and X-ray spectroscopy and transmission electron microscopy reveals the complete absence of long-range periodicity and a threefold-coordinated structure with a wide distribution of bond lengths, bond angles, and five-, six-, seven- and eight-member rings. The ring distribution is not a Zachariasen continuous random network, but resembles the competing (nano)crystallite model. We construct a corresponding model that enables density-functional-theory calculations of the properties of monolayer amorphous carbon, in accordance with observations. Direct measurements confirm that it is insulating, with resistivity values similar to those of boron nitride grown by chemical vapour deposition. Free-standing monolayer amorphous carbon is surprisingly stable and deforms to a high breaking strength, without crack propagation from the point of fracture. The excellent physical properties of this stable, free-standing monolayer amorphous carbon could prove useful for permeation and diffusion barriers in applications such as magnetic recording devices and flexible electronics.

111 citations


Journal ArticleDOI
TL;DR: In this article, high-density single-atom catalysts for an oxygen evolution reaction (OER) supported by CoOx amorporation have been proposed for renewable energy storage.
Abstract: Developing efficient electrocatalysts for an oxygen evolution reaction (OER) is important for renewable energy storage. Here, we design high-density Ir single-atom catalysts supported by CoOx amorp...

102 citations


Journal ArticleDOI
09 Apr 2021-Science
TL;DR: In this article, a route for synthesizing wafer-scale single-crystalline 2H molybdenum ditelluride (MoTe2) semiconductors on an amorphous insulating substrate was reported.
Abstract: The integration of two-dimensional (2D) van der Waals semiconductors into silicon electronics technology will require the production of large-scale, uniform, and highly crystalline films We report a route for synthesizing wafer-scale single-crystalline 2H molybdenum ditelluride (MoTe2) semiconductors on an amorphous insulating substrate In-plane 2D-epitaxy growth by tellurizing was triggered from a deliberately implanted single seed crystal The resulting single-crystalline film completely covered a 25-centimeter wafer with excellent uniformity The 2H MoTe2 2D single-crystalline film can use itself as a template for further rapid epitaxy in a vertical manner Transistor arrays fabricated with the as-prepared 2H MoTe2 single crystals exhibited high electrical performance, with excellent uniformity and 100% device yield

100 citations


Journal ArticleDOI
TL;DR: In this paper, the solid electrolyte interphase (SEI) of Li-metal batteries has been analyzed using ultralow-dosage cryogenic transmission electron microscopy.
Abstract: The solid electrolyte interphase (SEI) dictates the cycling stability of lithium-metal batteries. Here, direct atomic imaging of the SEI's phase components and their spatial arrangement is achieved, using ultralow-dosage cryogenic transmission electron microscopy. The results show that, surprisingly, a lot of the deposited Li metal has amorphous atomic structure, likely due to carbon and oxygen impurities, and that crystalline lithium carbonate is not stable and readily decomposes when contacting the lithium metal. Lithium carbonate distributed in the outer SEI also continuously reacts with the electrolyte to produce gas, resulting in a dynamically evolving and porous SEI. Sulfur-containing additives cause the SEI to preferentially generate Li2 SO4 and overlithiated lithium sulfate and lithium oxide, which encapsulate lithium carbonate in the middle, limiting SEI thickening and enhancing battery life by a factor of ten. The spatial mapping of the SEI gradient amorphous (polymeric → inorganic → metallic) and crystalline phase components provides guidance for designing electrolyte additives.

99 citations


Journal ArticleDOI
Rui Sun1, Yu Bai1, Min Luo1, Meixiu Qu1, Zhenhua Wang1, Wang Sun1, Kening Sun1 
26 Jan 2021-ACS Nano
TL;DR: In this paper, amorphous cobalt phosphide grown on a reduced graphene oxide multi-multi-layer (GOMM) was used for Li-S batteries with a reduced shuttle effect and sluggish redox kinetics.
Abstract: The application of lithium–sulfur (Li–S) batteries is severely hampered by the shuttle effect and sluggish redox kinetics. Herein, amorphous cobalt phosphide grown on a reduced graphene oxide-multi...



Journal ArticleDOI
TL;DR: In this paper, a self-limited growth strategy is proposed to construct CsPbBr3 nanocrystals that are embedded in a transparent amorphous network structure, featuring X-imaging with excellent resolution and fast decay time.
Abstract: Metal halide perovskites are emerging scintillator materials in X-ray detection and imaging. However, the vulnerable structure of perovskites triggers unreliable performance when they are utilized in X-ray detectors under cumulative dose irradiation. Herein, a self-limited growth strategy is proposed to construct CsPbBr3 nanocrystals that are embedded in a transparent amorphous network structure, featuring X-imaging with excellent resolution (≈16.8 lp mm-1 ), and fast decay time (τ = 27 ns). Interestingly, it is found that the performance degradation of the scintillator, caused by the damage from high-dose X-ray irradiation, can be fully recovered after a facile thermal treatment process. This indicates a superior recycling behavior of the explored perovskites scintillator for practical applications. The recoverability of the as-explored scintillator is attributed to the low atom-migration rate in the amorphous network with high-viscosity (1 × 1014 cP). This result highlights the practical settlement of the promising perovskites for long-term, cost-effective scintillator devices.

Journal ArticleDOI
TL;DR: In this paper, two types of free-standing nitrogen-doped amorphous Zn-carbon multichannel fibers are synthesized as multifunctional hosts for lithium accommodation.
Abstract: The application of lithium metal anodes for practical batteries is still impeded by safety issues and low Coulombic efficiency caused mainly by the uncontrollable growth of lithium dendrites. Herein, two types of free-standing nitrogen-doped amorphous Zn-carbon multichannel fibers are synthesized as multifunctional hosts for lithium accommodation. The 3D macroporous structures endow effectively reduced local current density, and the lithiophilic nitrogen-doped carbon and functional Zn nanoparticles serve as preferred deposition sites with low nucleation barriers to guide uniform lithium deposition. As a result, the developed anodes exhibit remarkable electrochemical properties in terms of high Coulombic efficiency for more than 500 cycles at various current densities from 1 to 5 mA cm-2 , and symmetric cells show long-term cycling duration over 2000 h. Moreover, full cells based on the developed anode and a LiFePO4 cathode also demonstrate superior rate capability and stable cycle life.



Journal ArticleDOI
TL;DR: In this article, a hybrid heterogeneous nanostructure of crystalline and amorphous phases was proposed to improve the fatigue resistance of NiTi-based shape memory alloys.
Abstract: Many established, but also potential future applications of NiTi-based shape memory alloys (SMA) in biomedical devices and solid-state refrigeration require long fatigue life with 107–109 duty cycles1,2. However, improving the fatigue resistance of NiTi often compromises other mechanical and functional properties3,4. Existing efforts to improve the fatigue resistance of SMA include composition control for coherent phase boundaries5–7 and microstructure control such as precipitation8,9 and grain-size reduction3,4. Here, we extend the strategy to the nanoscale and improve fatigue resistance of NiTi via a hybrid heterogenous nanostructure. We produced a superelastic NiTi nanocomposite with crystalline and amorphous phases via severe plastic deformation and low-temperature annealing. The as-produced nanocomposite possesses a recoverable strain of 4.3% and a yield strength of 2.3 GPa. In cyclic compression experiments, the nanostructured NiTi micropillars endure over 108 reversible-phase-transition cycles under a stress of 1.8 GPa. We attribute the enhanced properties to the mutual strengthening of nanosized amorphous and crystalline phases where the amorphous phase suppresses dislocation slip in the crystalline phase while the crystalline phase hinders shear band propagation in the amorphous phase. The synergy of the properties of crystalline and amorphous phases at the nanoscale could be an effective method to improve fatigue resistance and strength of SMA. Increasing the fatigue life of shape memory alloys often compromises other mechanical properties such as yield strength and plastic deformation behaviour. Introducing a mixed nanostructure of crystalline and amorphous phases can enable superelasticity in NiTi micropillars with recoverable strain of 4.3%, yield strength of 2.3 GPa and 108 reversible-phase transition cycles under a stress of 1.8 GPa.

Journal ArticleDOI
Chengying Guo1, Yanmei Shi1, Siyu Lu2, Yifu Yu1, Bin Zhang1 
TL;DR: In this paper, a review of the progress in amorphous electrocatalysts for water splitting is presented, which aims to provide a guide for designing and developing Amorphous nanomaterials with a fascinating electrocatalysistic water splitting performance.

Journal ArticleDOI
TL;DR: In this article, the axial chiral chromophores were incorporated into polymer chains via radical cross-linked polymerization to achieve circularly polarized organic phosphorescence (CPP) from amorphous copolymers.
Abstract: Organic optoelectronic functional materials featuring circularly polarized emission and persistent luminescence represent a novel research frontier and show promising applications in data encryption, displays, biological imaging, and so on. Herein, we present a simple and universal approach to achieve circularly polarized organic phosphorescence (CPP) from amorphous copolymers by the incorporation of axial chiral chromophores into polymer chains via radical cross-linked polymerization. Our experimental data reveal that copolymers (R/S)-PBNA exhibit a maximum CPP efficiency of 30.6% and the largest dissymmetric factor of 9.4 × 10-3 and copolymers (R/S)-PNA show the longest lifetime of 0.68 s under ambient conditions. Given the CPP property of these copolymers, their potential applications in multiple information encryption and displays are demonstrated, respectively. These findings not only lay the foundation for the development of amorphous polymers with superior CPP but also expand the outlook of room-temperature phosphorescent materials.


Journal ArticleDOI
TL;DR: In this article, the authors demonstrate enhancement-mode field effect transistors by an atomic-layer-deposited (ALD) amorphous In2O3 channel with thickness down to 0.7 nm.
Abstract: In this work, we demonstrate enhancement-mode field-effect transistors by an atomic-layer-deposited (ALD) amorphous In2O3 channel with thickness down to 0.7 nm. Thickness is found to be critical on the materials and electron transport of In2O3. Controllable thickness of In2O3 at atomic scale enables the design of sufficient 2D carrier density in the In2O3 channel integrated with the conventional dielectric. The threshold voltage and channel carrier density are found to be considerably tuned by channel thickness. Such a phenomenon is understood by the trap neutral level (TNL) model, where the Fermi-level tends to align deeply inside the conduction band of In2O3 and can be modulated to the bandgap in atomic layer thin In2O3 due to the quantum confinement effect, which is confirmed by density function theory (DFT) calculation. The demonstration of enhancement-mode amorphous In2O3 transistors suggests In2O3 is a competitive channel material for back-end-of-line (BEOL) compatible transistors and monolithic 3D integration applications.

Journal ArticleDOI
TL;DR: Electrochemical analysis and theoretical modeling demonstrate that the interface layer provides fast ion transport path and plays a key role in achieving high and stable ionic conductivity for PEOm -Li21 Si5 composite solid electrolyte.
Abstract: To achieve high ionic conductivity for solid electrolyte, an artificial Li-rich interface layer of about 60 nm thick has been constructed in polymer-based poly(ethylene oxide)-lithium bis(trifluoromethanesulfonyl)imide composite solid electrolyte (briefly noted as PEOm ) by adding Li-based alloys. As revealed by high-resolution transmission electron microscopy and electron energy loss spectroscopy, an artificial interface layer of amorphous feature is created around the Li-based alloy particles with the gradient distribution of Li across it. Electrochemical analysis and theoretical modeling demonstrate that the interface layer provides fast ion transport path and plays a key role in achieving high and stable ionic conductivity for PEOm -Li21 Si5 composite solid electrolyte. The PEOm -5%Li21 Si5 composite electrolyte exhibits an ionic conductivity of 3.9 × 10-5 S cm-1 at 30 °C and 5.6 × 10-4 S cm-1 at 45 °C. The LiFePO4 | PEOm -5%Li21 Si5 | Li all-solid-state batteries could maintain a stable capacity of 129.2 mA h g-1 at 0.2 C and 30 °C after 100 cycles, and 111.3 mA h g-1 after 200 cycles at 0.5 C and 45 °C, demonstrating excellent cycling stability and high-rate capability.

Journal ArticleDOI
TL;DR: In this article, the recent successes and current challenges of amorphous inorganic semiconductor-based materials for applications in solar cells, photoelectrocatalysis, and photocatalysis are addressed.
Abstract: Amorphous inorganic semiconductors have attracted growing interest due to their unique electrical and optical properties that arise from their intrinsic disordered structure and thermodynamic metastability. Recently, amorphous inorganic semiconductors have been applied in a variety of new technologies, including solar cells, photoelectrocatalysis, and photocatalysis. It has been reported that amorphous phases can improve both efficiency and stability in these applications. While these phenomena are well established, their mechanisms have long remained unclear. This review first introduces the general background of amorphous inorganic semiconductor properties and synthesis. Then, the recent successes and current challenges of amorphous inorganic semiconductor-based materials for applications in solar cells, photoelectrocatalysis, and photocatalysis are addressed. In particular, we discuss the mechanisms behind the remarkable performances of amorphous inorganic semiconductors in these fields. Finally, we provide insightful perspectives into further developments for applications of amorphous inorganic semiconductors.



Journal ArticleDOI
01 Nov 2021-Nature
TL;DR: In this article, the authors successfully synthesized millimetre-sized samples of transparent, nearly pure sp3 amorphous carbon by heating fullerenes at pressures close to the cage collapse boundary.
Abstract: Amorphous materials inherit short- and medium-range order from the corresponding crystal and thus preserve some of its properties while still exhibiting novel properties1,2. Due to its important applications in technology, amorphous carbon with sp2 or mixed sp2–sp3 hybridization has been explored and prepared3,4, but synthesis of bulk amorphous carbon with sp3 concentration close to 100% remains a challenge. Such materials inherit the short-/medium-range order of diamond and should also inherit its superior properties5. Here, we successfully synthesized millimetre-sized samples—with volumes 103–104 times as large as produced in earlier studies—of transparent, nearly pure sp3 amorphous carbon by heating fullerenes at pressures close to the cage collapse boundary. The material synthesized consists of many randomly oriented clusters with diamond-like short-/medium-range order and possesses the highest hardness (101.9 ± 2.3 GPa), elastic modulus (1,182 ± 40 GPa) and thermal conductivity (26.0 ± 1.3 W m−1 K−1) observed in any known amorphous material. It also exhibits optical bandgaps tunable from 1.85 eV to 2.79 eV. These discoveries contribute to our knowledge about advanced amorphous materials and the synthesis of bulk amorphous materials by high-pressure and high-temperature techniques and may enable new applications for amorphous solids. Preparing amorphous phases of carbon with mostly sp3 bonding in bulk is challenging, but macroscopic samples that are nearly pure sp3 are synthesized here by heating fullerenes at high pressure.


Journal ArticleDOI
TL;DR: In this article, the authors demonstrate the disorder-to-order transformation from amorphous polymeric membrane to crystalline COF membrane via monomer exchange, where the replacing monomer is selected based on the chemical and thermodynamical stability of the final framework.
Abstract: Covalent organic framework (COF) membranes hold potential for widespread applicability, but scalable fabrication is challenging. Here, we demonstrate the disorder-to-order transformation from amorphous polymeric membrane to crystalline COF membrane via monomer exchange. Solution processing is used to prepare amorphous membrane and the replacing monomer is selected based on the chemical and thermodynamical stability of the final framework. Reversible imine bonds allow the extraneous monomers to replace the pristine monomers within amorphous membrane, driving the transformation from disordered network to ordered framework. Incorporation of intramolecular hydrogen bonds enables the crystalline COF to imprint the amorphous membrane morphology. The COF membranes harvest proton conductivity up to 0.53 S cm-1 at 80 °C. Our strategy bridges amorphous polymeric and crystalline COF membranes for large-scale fabrication of COF membranes and affords guidance on materials processing.

Journal ArticleDOI
TL;DR: In this paper, in situ straining transmission electron microscopy (TEM) experiments reveal a crystalline-to-amorphous phase transformation in an ultrafine-grained Cantor alloy.
Abstract: The Cantor high-entropy alloy (HEA) of CrMnFeCoNi is a solid solution with a face-centered cubic structure. While plastic deformation in this alloy is usually dominated by dislocation slip and deformation twinning, our in situ straining transmission electron microscopy (TEM) experiments reveal a crystalline-to-amorphous phase transformation in an ultrafine-grained Cantor alloy. We find that the crack-tip structural evolution involves a sequence of formation of the crystalline, lamellar, spotted, and amorphous patterns, which represent different proportions and organizations of the crystalline and amorphous phases. Such solid-state amorphization stems from both the high lattice friction and high grain boundary resistance to dislocation glide in ultrafine-grained microstructures. The resulting increase of crack-tip dislocation densities promotes the buildup of high stresses for triggering the crystalline-to-amorphous transformation. We also observe the formation of amorphous nanobridges in the crack wake. These amorphization processes dissipate strain energies, thereby providing effective toughening mechanisms for HEAs.