bluuebunny/crossref_metadata_2025 huggingface dataset:
Photoelectrochemical Characterization of Photosystem I Encapsulated in Nafion
Authors: Baker David R. , Simmerman Richard , Sumner James J , Bruce Barry D , Lundgren Cynthia A.
Published: February 2020

As battlefield technologies continue to become more advanced and energy intensive, there is an increased cost and a higher exposure to hazards when supplying fuels to meet the power demand of these applications. This has created a great need to reduce the amount of energy delivered in the field, and has introduced a need for on-site fuel generation to reduce the logistical burden.

Solar derived fuels are a leading area of research for on-site fuel generation because of the ubiquity of solar energy. The biomimetic approach of converting solar to useful energy, simulating photosynthesis, employs the highly efficient photosynthetic protein Photosystem I (PSI) to reduce water to H2 which would in turn be used to fuel combustion engines or fuel cells. Any device deployed in the field would need to be designed for portable applications. Therefore, a robust and electrochemically active electrode must be developed which allows PSI to access both light and aqueous electrolyte solutions.

This presentation relates recent work with encapsulating PSI and the redox mediator Os(bpy)2Cl2 in a Nafion polymeric film. Because of surface charges in Nafion’s water-filled pores both PSI and Os(bpy)2Cl2 are trapped in the polymer matrix whereas the positively charged methyl viologen (MV) redox mediator is able to diffuse through the film. The films are characterized for their stability and photoelectrochemical performance resulting in their capability to load PSI in the films at very high surface densities. The use of Nafion makes the film more stable than other redox polymers tested, and the high surface densities of PSI opens the door to higher photocurrents.
Analytical Application of Intercalation Processes
Authors: Lipkin Semen M. , Lipkin Mikhail Semenovich , Sedov Andrey Vladimirovich , Onyshko Dmitry Anatolievich
Published: February 2020

An analisys of alloy directly on surface example is interesting for many applications. Electrochemical methods, used in solving this problem, provide variability, low cost, minimal example treatment and informational content of analytic signal.

All the advantages of electrochemical nondestructive alloy analisys can be realized by using appropriate electrode processes. We assume that intercalation is one these processes due to its high sensitivity to host structure composition. It was shown, that pulse chronopotentiometry is the most appropriate method for different intercalation processes.

Use of intercalation process type is determined mainly by nature of analyzed component. So, for metals with high overpotential it is convenient to use anodic intercalation in alkaline electrolytes or reduction of anodic oxide.

For metals with low overpotential (Au, Cu, Ag, Pt) intercalation of water and anions in anodic part of polarization give easy reductive adsorbed complex ions and their inverse reduction is displayed as a horizontal part on chronopotentiometry curve (Fig. 1). A length of such part is proportional to alloy component content, which provides analysis possibility.

Cathodic intercalation of lithium ions from acetonitrile electrolyte makes a basis of carbon determination in steels. Pulse chronopotentiograms of this process (fig. 2) have plato, which length change is proportional to carbon content.

Thus, electrochemical nondestructive alloy analisys on the base of intercalation processes is perspective adaptive method with a much of various tunning-up parameters.
New Trends in Chemistry at Steps Due to Mechanical Stress and Relevance to Design of Catalytic Interfaces
Authors: Francis Michael F , Curtin William A
Published: February 2020

The control and optimization of catalytic processes is a key goal in many technologies. Here, we demonstrate via computation that the application of mechanical stress to late transition metals (LTM) can modify chemisorption energies at stepped surfaces, and thus catalytic activity, in ways not previously envisioned. Specifically, compressive stresses can induce stronger binding of chemical species at steps on LTM surfaces, which is the opposite of the well-established trend found on LTM close-packed surfaces. The mechanism driving this new stress effect is shown to be the mechanical relaxation of the deformed metal during chemisorption, which can be larger, and of the opposite sign, than the electronic effects due to changes in the d-band structure; i.e. the trends predicted by the widely-held “d-band” model are violated. Application of stress can thus simultaneously shift binding energies on steps up (or down) and on terraces down (or up) on the same LTM surface, and potentially increase overall catalytic activity in wide classes of systems.
Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) for In-Situ Analysis of Solid Oxide Electrolysis Cells
Authors: Elder Rachael H , Cumming Denis J , Taylor Rebecca , Hardacre Chris
Published: February 2020

High temperature co-electrolysis of steam and carbon dioxide using a solid oxide cell (SOC) has been shown to be an efficient route to produce syngas (CO + H2), which can then be converted to synthetic fuel. Optimization of co-electrolysis requires detailed understanding of the complex reactions, transport processes and degradation mechanisms occurring in the SOC during operation. Currently, electrochemical measurements are conducted in-situ during electrolysis operation, however many analytical techniques are only used ex-situ, before and/or after electrolysis operation. In some cases the analytical techniques used are destructive (e.g. SEM imaging of the cell microstructure). In order to fully understand and characterize co-electrolysis in SOCs, in-situ monitoring of the reactants, products, and the cell itself are necessary.

As part of the UK-wide £5.7m 4CU project (A Comprehensive, Coordinated Programme for Carbon Capture and Utilisation Research) we are developing a suite of in-situ characterization techniques for high temperature SOC operation. In this paper we report the use of DRIFTS (Diffuse Reflectance Infrared Fourier Transform Spectroscopy) to probe the reactions occurring during dry CO2 electrolysis and co-electrolysis.

The design and commissioning of the rig for in-situ characterization will be presented, along with a discussion on the challenges of spectroscopic access to the areas of interest of an SOC operating at high temperature. Infrared spectra showing CO adsorption on Ni-YSZ powdered catalyst and electrode surfaces will be presented.
Electrochemical Desulfurization of Dibenzothiophene Sulfone in Sodium Fluoride/Acetonitrile
Authors: González-Perea Mario , Dorantes-García Valentín , Dávila-Jiménez M. M. , Elizalde-González Ma. de la Paz
Published: February 2020

The oxidative and reductive desulfurization using electrochemical techniques has attracted much attention in the last decade because mild temperature and conditions are needed [1, 2]. It is known that the dibenzothiophene (DBT) can be progressively oxidized to a sulfoxide dibenzothiophene (DBTO) and dibenzothiophene sulfone (DBTO2). However, the electrochemical oxidation and reduction DBTO2 in a liquid-liquid two-phase system of aqueous NaF/acetonitrile has not been reported. The analysis by Fourier Transformed Infrared Spectroscopy (FTIR) showed partial removal of sulfur from DBTO2 placed in the electrolytic medium at 18.6 ppm or 108 ppm. The FTIR spectrum of the samples diluted in KBr after cathodic electrolysis at -8.0 V on Pt or Ti as cathode and Pt as anode in an undivided cell showed the absence of the characteristic bands of DBTO2: 1288 cm-1, 1166 cm-1 and 758 cm-1. This suggests a transformation of DBTO2 with the electrochemical treatment (Fig. 1). The oxidation and reduction products of DBTO2 were analyzed by GC-MS and LC-MS.

Figure 1 FTIR spectra of DBTO2 before electrochemical treatment (a) and after cathodic treatment using Pt electrode (b and c). IR spectra of the acetonitrile (b) and the aqueous (c) phases.
Electrochemical Investigation of Nitinol/Tantalum Hybrid Surfaces Modiﬁed with Phosphonic Acid Derivatives
Authors: Mekhalif Zineb , Maho Anthony , Devillers Sébastien , Vanhooland Annelies , Delhalle Joseph
Published: February 2020

Nitinol, a nickel and titanium alloy in quasi-equiatomic proportions, is used in numerous biomedical applications due to its remarkable mechanical characteristics, its resistance towards corrosion and good biocompatibility. Further research to reinforce osseointegrative abilities and barrier properties towards external aggressive agents are still needed.

In this context, electrochemical methods can be used to generate protective and functional surface coatings on Nitinol substrates with a good level of control and versatility. Specifically here are considered the elaboration of a structured thin layer on Nitinol plates by electrodeposition of tantalum and its subsequent modification by the self-assembly of phosphonic acid derivatives to consolidate corrosion protection and bioactivity features.

Electrochemical techniques are also used to assess and study the different deposited layers. Cyclic voltammetry, polarization curves, free potential measurements, and scanning electrochemical microscopy experiments are performed to qualitatively and quantitatively evaluate electron and mass transfers at the interface, as well as corrosion resistance properties. Spectroscopic (XPS) and microscopic (SEM) analyses complete the characterization process regarding chemical nature and morphology aspects.
Surface Modification of Mg Alloys for Controlled Biodegradation Behavior
Authors: Virtanen Sannakaisa
Published: February 2020

Mg based materials are in the focus of interest to be used as biodegradable metals, for biomedical applications where the device is only required for a certain time of healing. However, the corrosion behavior of today’s alloys is for many targeted applications too fast. Therefore, in addition to design of novel alloys, research is searching for biocompatible coatings and surface modifications of Mg alloys. The surface modification should at the same time optimize the corrosion behavior and the biological performance.

The presentation will present recents efforts in Mg alloy surface modification. One of the simplest approaches is biomimetic formation of conversion coatings in simulated body fluids. Such layers can significantly slow down dissolution, and can be beneficial for cell adhesion on Mg surfaces. Other approaches currently under investigation are surface functionalization by protein coatings and control of surface wettability by organic monolayers on morphologically-modified Mg surfaces. In addition, we will discuss the preparation and performance of biodegradable polymer coatings on Mg surfaces. Critical issues such as long-term corrosion protection or coating adhesion will be addressed.
Selective Detection by Dpv of Benserazide and Levodopa in Pharmaceutical Preparates
Authors: Dávila Martín Marino , Ruíz Patricia , Elizalde Maria De la Paz
Published: February 2020

For the detection of some important biological substances by electrochemical methods the carbon modified electrodes have been widely used [1-3]. The aim of this work was to study the simultaneous detection of benserazide and levodopa in pharmaceutical tablets of MADOPAR® by the voltammetric method using a modified C-PVC electrode. The preparation and modification of the C-PVC electrode was performed according to the previously reported method [4]. The tablet extract in presence of excipients of MADOPAR® in phosphates buffer pH 7.4 was used for the measurements without pretreatment. The electrochemical experiment by VDP of the MADOPAR®extract using the C-PVC modified electrode showed good defined oxidation peaks for benserazide at 24 mV and levodopa at 141 mV. The oxidation current was proportional to the volume of the extract in the buffer solution (Fig.1). The presence of an excess of ascorbic acid (140 µM) did not affect the detection of benserazide and levodopa. The modified C-PVC electrode can be used for the simultaneous determination of benserazide and levodopa in some real samples at different pH values of buffer solutions.

References

[1] J.B. Raoof, R. Ojani, M. Amiri-Aref, M. Baghayeri; Sens. Actuators, B. 166–167 (2012) 508–518.

[2] EB Sakineh, B Hadi, KM Hassan, SN Somayeh, SN Vahhab, R Sara; J Anal Meth Chem 2012 (2012) 1-8.

[3] Mu Naushad, VK Gupta, SM Wabaidur, ZA Alothman; Int J Electrochem Sci. 8 (2013) 297-311.

[4] P.Ruiz-G, M.P. Elizalde-G, M.M Davila, Esp. Pat., Appl. P201430231 (2014).

Acknowledgments

We acknowledge the financial support of CUVyTT-BUAP under project No.014.
Ionic Liquid Structure in Thin Films
Authors: Anaredy Radhika S , Lucio Anthony J , Shaw Scott K
Published: February 2020

Understanding molecular structure and organization of a fluid’s surface layers is important to control many heterogeneous electrochemical processes. Ionic liquids present an exciting opportunity to examine surface confined thin fluid films and extended interfacial systems that may prove useful for electrochemical applications. This work explores the behavior of thin (1-20 nm) ionic liquid films and bulk IL interfaces in contact with air and noble metal substrates. Thin IL films are introduced by a highly controlled emersion process. Bulk interfaces are prepared by immersing the metal electrode into an IL solution. Data from ellipsometry, vibrational spectroscopy, contact angle, and electrochemical measurements are reported for the thin films and bulk solution / metal interfaces. Results correlate film and interfacial thickness and molecular structure with the chemical nature of the IL components and substrates. We will be particularly interested in future studies showing the effects of common 'contaminents' (i.e. water) on IL instrfacial structure. Descriptors will include chemical interactions i.e. hydrophobic forces, hydrogen bonding, van der Waals, electrostatics, etc. These studies inform work in IL electrochemistry, IL modified materials, and new fabrication methods for tailored surfaces which are urgently desired.
Selective Precipitation Strategies for Isolating Metallofullerenes
Authors: Stevenson Steven
Published: February 2020

We are interested in developing novel, non-chromatographic approaches to purify endohedral metallofullerenes. The goal of new separation science is to isolate gram-scale quantities of pure endohedrals. Another motivation for investigating non-HPLC separations is avoiding the time and expense of purification techniques relying exclusively on HPLC for the entire isolation process. In this presentation, we discuss our improvements in finding chemical methods which selectively precipitate metallofullerenes using our Lewis acid approach.
Surrounding Media Sensitive Photoluminescence of Boron-Doped Graphene Quantum Dots
Authors: Fan Louzhen
Published: February 2020

Graphene is a zero-bandgap semiconductor, no optical luminescence is observed in pristine graphene. A bandgap, however, can be engineered into graphene quantum dots (GQDs) due to quantum confinement and edge effects. As a result, luminescent GQDs have attracted great attention as one of highly promising nanomaterials due to their exceptional advantages of low cytotoxicity, excellent solubility, stable photoluminescence (PL), fine biocompatibility as well as low-cost.[
1
] Above these fascinating merits in GQDs distinguish themselves from traditional fluorescent materials, making them perfect alternatives for numerous exciting applications: bioimaging,[
2
] fluorescence sensors,[
3
[ fuel cells,[
4
] photovoltaic devices.[
5]

Doping carbon materials with heteroatoms can effectively tune their intrinsic properties, thus producing new phenomena and unexpected characteristics. Although veriouse heteroatom-doped carbon materials have been reported, doped GQDs have been much less studied. Herein, we report a facile one-pot electrochemical approach for the synthesis of boron(B) doped GQDs (B-GQDs) with B content of 5.24 at %, in which only borax was used as the electrolyte without any other chemical additives. The as obtained water-soluble B-GQDs feature intriguing tunable fluorescence, act as a Al3+fluorescent sensor, cellular imaging and electrocatalysts for the oxygen reduction reaction. With the existence of borax, they show strong green luminescence with a quantum yield as high as 13%. Significantly, green fluorescent crystals were obtained from evaporating the aqueous solution in the presence of borax at room temperature.

Acknowledgements

This work is supported by NSFC (21073018), the Major Research Plan of NSFC (21233003), Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, Beijing Normal University.

References

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2010, 22, 734-738; b) J. Peng, W. Gao, B. K. Gupta, Z. Liu, R. Romero-Aburto, L. Ge, L. Song, L. B. Alemany, X. Zhan, G. Gao, S. A. Vithayathil, B. A. Kaipparettu, A. A. Marti, T. Hayashi, J.-J. Zhu, Nano Letters
2012, 12, 844-849; c) L. Tang, R. Ji, X. Cao, J. Lin, H. Jiang, X. Li, K. S. Teng, C. M. Luk, S. Zeng, J. Hao, S. P. Lau, ACS Nano
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[2] a) S. Zhu, J. Zhang, C. Qiao, S. Tang, Y. Li, W. Yuan, B. Li, L. Tian, F. Liu, R. Hu, H. Gao, H. Wei, H. Zhang, H. Sun, B. Yang, Chem. Commun.
2011, 47, 6858-6860; b) H. Tao, K. Yang, Z. Ma, J. Wan, Y. Zhang, Z. Kang, Z. Liu, Small
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[3] Y. Dong, G. Li, N. Zhou, R. Wang, Y. Chi, G. Chen, Anal. Chem.
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[4] a) Y. Li, Y. Zhao, H. Cheng, Y. Hu, G. Shi, L. Dai, L. Qu, J. Am. Chem. Soc
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[5] a) Y. Li, Y. Hu, Y. Zhao, G. Shi, L. Deng, Y. Hou, L. Qu, Adv.Mater.
2011, 23, 776-780; b) V. Gupta, N. Chaudhary, R. Srivastava, G. D. Sharma, R. Bhardwaj, S. Chand, J. Am. Chem. Soc.
2011, 133, 9960-9963.
Direct Hybridization of Graphene and Metal Oxide Nanoparticles for High Performance Electrochemical Supercapacitors
Authors: Park Hun , Han Tae Hee
Published: February 2020

Graphene oxide (GO), an oxidized form of graphene, has various advantages in the preparation of functional nanocomposites because it can be easily modified and can be produced in large quantity. Moreover, the reduction of GO sheets produces reduced GO (rGO) sheets, which provide a highly electro-conductive pathway and robust electrochemical reaction sites as an electrode material. Moreover, due to the presence of those functional groups, GO can be utilized as a novel platform for hybrid nanocomposites in chemical synthetic approaches. In this presentation, we demonstrate a straightforward strategy to prepare nanohybrids of rGO-metal oxide nanoparticles, such as SnO2 and Cu2O, via simple solution mixing. When precursor solutions and GO suspension were simply mixed, precursor ions were spontaneously formed into nanoparticles upon the deoxygenation of GO. This method anchored nanoparticles on the rGO sheets, preventing the re-stacking of rGO. Our investigation for the electrocapacitive properties of hybrid electrode showed the highly enhanced performance, compared with rGO-only electrode. Our straightforward route for preparing this graphene-based hybrid provides a high-throughput and scalable strategy to synthesize active electrode materials for highly efficient graphene-based supercapacitors.
(Plenary) High-Performance Photonic BiCMOS – Next Generation More-than-Moore Technology for the Large Bandwidth Era
Authors: Zimmermann Lars
Published: February 2020

It is a remarkable fact that since the advent of cable telephony we observe a continuous growth of network traffic on a global scale. Despite all economic ups and downs, traffic grows steadily, certainly since the advent of the internet about two decades ago. The similarity to Moore’s law of microelectronics has been pointed out several times, and, as a matter of fact this traffic development would not have happened without the unswerving advance of IC technology. Ubiquitous compute power has changed and will keep changing our world, spanning an unprecedented application space encompassing web 3.0, augmented reality, 3D online gaming and virtual worlds, social media etc.

Looking at the infrastructure underlying all these developments we soon realize that long haul traffic and its growth merely reflect the tip of the iceberg. There is an emerging planetary realm of warehouse-scale data centers hosting a growing fraction of global computing and data storage. Traffic between user and data center is surpassed by traffic created inside the data center leading to Petabit/sec aggregate bandwidth requirements. This inside data center traffic feeds hundreds of individual user services that shape the cloud from the point of view of consumers, therefore stimulating additional traffic in radio access networks, fiber-to-the-home and other networks.

The technology most needed to sustain this positive feedback growth is the interconnect engine. And without any doubt, optical solutions intimately integrated with electronics will be required to satisfy the demand of bandwidth, energy-per-bit, and cost. Eventually, large bandwidth will become ubiquitous. With the migration of photonic systems to ever shorter distances, scalable photonic-electronic IC technologies become a necessity.

At this point it is important to keep in mind that photonic functionality such as reception or transmission can be integrated and the required footprint can shrink. However, photonics cannot shrink anymore by orders of magnitude, simply due to the wavelength used. Therefore, required voltage swings remain similar to discrete solutions, while the ability to go to maximum speed beyond 50Gbit/sec is very important.

Here exists a sweet spot for next generation More-than-Moore technologies, such as high-performance photonic BiCMOS. Going beyond the concept of present More-than-Moore technologies, photonic BiCMOS combines 2 high-performance technology sub-modules (high –performance HBTs and photonics) with a baseline CMOS process. The added complexity pays off with a full set of photonic features fit for broad-band optoelectronic system integration. We shall present IHP’s perspective on a photonic More-than-Moore technology, joining most advanced HBT technology with high-speed photonic devices for electronic-photonic sub-systems for next generation communication networks.
The Use of Dopants for Defect Monitoring for Silicon-Germanium Ultra-High Vaccuum Chemical Vapor Deposition
Authors: Hazbun Ramsey , Hart John , Nakos James , Siegel Dean , Funch Christopher , Kaushal Vikas , Hazel David Scott , Kolodzey James
Published: February 2020

Si and SiGe epitaxy via UHVCVD requires an extremely clean and oxide free substrate but has the advantage of allowing low temperature epitaxy (LTE). In-situ bake-off of thin native oxides is possible at high temperatures, but is not an option for low temperature epitaxy. As a result, LTE processes are sensitive to surface preparation and the duration between oxide removal and epitaxy growth. Traditional techniques for observing interfacial contamination, such as secondary ion mass spectroscopy, are not easily integrated into a fabrication line. In addition, the off-line measurements of monitor wafers cannot detect contamination soon enough before the product wafers have gone through extensive further processing. A new monitor has been developed and demonstrated for observing the contamination of the substrate and process that occurs after the pre-epitaxy cleaning steps. This novel monitor used an ion implanted substrate along with defect etches. The sensitivity of this monitor can be controlled by adjusting the implant dose allowing tailoring to specific process targets and needs. A dilute Secco wet etch and HCl chemical vapor etch were both demonstrated for decorating the dislocation defects caused by interfacial contaminants. Using TEM, these defects were confirmed as originating from the substrate-epitaxy interface. In-line and off-line defect counting systems were then used to quantify the defect density of the novel monitor. These monitors were shown to have sensitivity to defects caused by range of interfacial contaminants. The result of this newly integrated method is a fully line integrated defect monitor using already commonplace equipment and chemicals, that has a rapid turnaround, and that is broadly sensitive to substrate surface contaminants.
Morphological Instability of High Ge Percent SiGe Films Grown by Ultra-High Vacuum Chemical Vapor Deposition
Authors: Hart John , Hazbun Ramsey , Nakos James , Siegel Dean , Funch Chris , Kolodzey James , Harame D. L.
Published: February 2020

The Ge content in SiGe bipolar transistors (HBTs) has been steadily increasing for the past few decades in order to meet higher Fmax targets. Problems exist with higher Ge content films due to the strain from the pseudomorphic growth on Si substrates. In addition to relaxation by misfit dislocation at high Ge contents, SiGe films have been observed to exhibit morphological instability or surfaces waves. This phenomena, known for some time, produces surface corrugations several nm in height that can have detrimental effects on SiGe HBTs. While historic solutions to the problem involved lowering the growth temperature, hot-wall UHVCVD presents a unique challenge due to the inability to quickly change temperatures during growth. In this report, the process parameters including film growth rate, temperature, and H2 pressure will be described in their effect on reducing and eliminating the surface waves. These results will be presented with regards to the total hydrogen coverage of the surface and the adatom mobility during growth.
Epitaxial Transfer Printing of Compound Semiconductor Nanomembranes and Device Applications
Authors: Um Doo-Seung , Lee Youngsu , Lee Hochan , Lim Seongdong , Ko Hyunhyub
Published: February 2020

Recently, the heterogeneous integration of compound semiconductors on arbitrary substrates has attracted great interests due to their promising applications in high-performance transistors, optoelectronics, and spintronics on flexible and low-cost substrates. The heterogeneous integration of compound semiconductors on arbitrary substrates provides combined advantages of the high performance of compound semiconductors and the well-established, low-cost processing of Si, glass, and flexible substrates. However, the development of simple and efficient strategies for the heterogeneous integration of compound semiconductors on arbitrary substrates still remains a big challenge. Here, we introduce an epitaxial transfer method for the heterogeneous integration of ultrathin III-V nanomembranes on arbitrary substrates. For efficient transfer printing process, we report the fabrication of bio-inspired smart adhesive pads based on microstructured elastomers coated with thermo-responsive polymers, where the adhesion properties can be thermally controlled. In addition, we demonstrate that high-quality InAs nanoribbons are successfully integrated on Si substrates for the fabrication of high-performance field-effect transistors. Furthermore, we demonstrate heterogeneously integration of various types of compound semiconductors on arbitrary substrates for applications in spintronics and photodetectors on heterogeneous substrates.
1D Photonic and Electrochromic Nanomaterials Application
Authors: Redel Engelbert
Published: February 2020

Porous hierarchical and photonic materials assemblies will be presented from a library of different metal oxide nanomaterials and hierarchical multilayer constructions. Potential applications of such materials will be presented, reaching from optical and tune able and porous 1D photonic crystals (PCs) to transparent and conductive oxides (TCOs) porous thin films, white light broad-band bragg reflectors as well as electrochromo-photonic switches. Furthermore, the optical and dielectric properties of single porous SURMOF thin films as well as multilayered photonic SURMOF-Hybrid and electrochromic SURMOF materials will be presented.
Detail Analysis of External Quantum Efficiency Measurement for Tandem Junction Solar Cells
Authors: Cheng Tzu-Huan , Lin Shih-Hung
Published: February 2020

The tandem junction solar cells require accurate external quantum efficiency (EQE) measurement to determine the current match condition for high efficiency approach. The EQE measurement of tandem-junction solar cells requires variation of the bias spectrum and voltage biasing. The optimization of bias spectra and adjusted bias voltage are necessary to minimize a measurement artifact due to the simultaneously measured response of another subcell. Additionally, the shape of the spectral response curve is influenced under certain measurement conditions such as bias light and voltage bias. In this paper, the difference between AC and DC mode EQE measurements are compared and the influence of bias light and voltage biasing in EQE measurement are discussed. The bias light and voltage biasing should be applied for short-circuit condition of the subcell under test. The measurement artifact has been thoroughly discussed by measurement results. Therefore, it is possible to understand the origin of the measurement artifact and to give guidelines for its minimization. The EQE spectra with optimization of bias voltage and bias light to minimize the artifact are confirmed with the IV measurement under illumination. To further improve the accretion of EQE measurement, the heating due to the bias light illumination can be taken into consideration.
Comparison of O2 Plasma Treatment on Porous Low Dielectric Constant Material in Sidewall and Bottom of Trench Structure
Authors: Cheng Yi-Lung , Lin Bing-Hong , Haung Wei-Syuan
Published: February 2020

The degradation induced by oxygen (O2) plasma irradiation to the porous low dielectric constant materials (low-k; k=2.5) has been investigated in this study. The impact in the sidewall and bottom of the trench was compared by designing a special structure to simulate the real trench structure. From the experimental results, the low-k films in both sidewall and bottom of the new-designed trench structure shows a worse electrical performance and reliability after performing O2 plasma treatment. Moreover, the low-k films in the sidewall of the trench structure suffer a less damage in comparison to those samples in the bottom. Furthermore, as the width of the trench is scaled-down, the O2 plasma damage on the sidewall low-k films can be alleviated due to a reduced flux of oxygen active species. While the plasma damage on the bottom low-k films have no impact for trench width effect. Therefore, the scaled trench geometry would not cause more serious degradation for the low-k films under O2 plasma treatment with an identical treatment condition. The blanket film can be used to monitor the plasma damage for the next technology generation since the bottom low-k films have the worse impact under plasma treatment. Furthermore, this new-designed trench structure can easily analyses the low-k material degradation in the sidewall of the trench structure.
Advanced 3D Imaging and Analysis of Lithium Ion Battery Electrodes
Authors: Biton Moshiel , Tariq Farid , Yufit Vladimir , Shearing Paul R , Kishimoto Masashi , Gelb Jeff , Golodnitsky Diana , Peled Emanuel , Brandon Nigel P.
Published: February 2020

Meeting increasing energy demands, storage requirements and energy portability will be expedited through an ability to directly image lithium battery material nano/micro structures at high resolutions in 3D. The performance of the battery is dependent on nano/micro-structure as important reactions often occur at porous electrode interfaces. Furthermore, during processing or operation microstructural evolution may degrade electrochemical performance.

Despite their importance, battery electrode microstructures remain poorly understood, limiting current understanding of their failure. Tomographic techniques allow for the direct 3-D imaging and chracterisation of complex microstructures from millimetres down towards nanometers.

Here we present results from 3D x-ray and FIBSEM tomography of battery materials (e.g. Figure 1) down to resolutions of tens of nanometers. Quantitative analysis of critical parameters important for battery materials is evaluated, and these are linked to simulation tools to relate structure to performance characteristics. Both x-ray and FIBSEM tomography can provide this information, facilitating analysis of micro/nano structure, morphology and provide exciting opportunities to study fabrication effects or operating conditions that could cause electrode degradation and failure.

We find this approach is effective in understanding how lithium ion batteries function at high resolutions and consequently that tomography coupled with modeling/experiments can provide new insights into degradation mechanism.

Figure 1 – 3D lithium ion anode structure with MCMB particles
Improved Electrochemical Performance of Silicon Nanowires As Negative Electrode with Metal Coatings
Authors: Baek Seong-Ho , Park Jung-Soo , Kim Jae Hyun
Published: February 2020

In this study, we report the effect of metal coated silicon nanowires (SiNWs) on electrochemical performance as a negative electrode material. We fabricated metal coated SiNWs by using metal assisted chemical etching process. Transmission electron microscopy (TEM) images show that SiNW arrays with silver (Ag) coating on a Si (100) substrate have been successfully prepared in a one-pot process. To investigate the electrochemical performances of Ag-coated SiNWs, coin cells using SiNWs as negative electrodes by the slurry coating method were assembled with Li metal foil as the counter electrode. We show that the rate capability of Ag coated SiNWs is greatly improved compare to bare NWs. Also, the good cycling performances of the Ag-coated SiNWs were clearly observed. The enhanced electrochemical performance is attributed to the improvement of electrical conductivity of SiNWs. Furthermore, we suggest that the Ag layer is exposed to the electrolyte instead of bare Si, and it can prevent solid electrolyte interface (SEI) formation and deterioration of active materials.
Nano-Structured Silicon Derived from Silica Precursors as Anode Material for Lithium Ion Batteries
Authors: Schrandt Matthew , Kolla Praveen , Rhine Wendell , Koodali Ranjit T , Wu James , Lvovich Vadim , Cook Rob , Smirnova Alevtina
Published: February 2020

Silicon is valuable as a high energy density anode material for Li-ion battery applications. However, the high lithium storage capacity leads to extreme volume expansion during lithiation and delithiation that can lead to mechanical deterioration and poor cycle life. To improve cyclability, nano-structured materials can be used to facilitate the volume change without deterioration. By using structured SiO2 precursors, the goal is to reduce SiO2 to Si while maintaining the structure and porosity of SiO2 and thus, mitigating degradation effects during cycling.

Nanostructured Si has been synthesized by Mg vapor reduction from SiO2 precursors [1] (e.g. SiO2 microspheres from 3M, SiO2 aerogel, and mesoporous SiO2 [2]). Following the reduction to Si, the materials were chemically treated in HCl and HF to remove remaining MgO and SiO2 respectively. Figures 1 and 2 confirm the presence of Si in reduced samples and successful removal of MgO and SiO2. TGA/DSC has been used to optimize the reduction time and temperature.

CV data (Figure 3) and cyclability tests (Figure 4) demonstrate a specific capacity of up to 2065 mAh/g with a low charge transfer resistance (Figure 3, inset).

SEM, TEM, BET, EDS, XRD, and Raman spectroscopy data will be presented for SiO2 and reduced Si to describe chemical composition and morphology. Structure dependent electrochemical properties such as impedance spectroscopy, cyclic voltammetry, galvanostatic discharge, and cycle stability will be presented and discussed.

References:

[1] R. Cook, M. Schrandt, P. Kolla, W. Rhine, R. Koodali, A. Smirnova, MRS Online Proceedings Library,1643 (2014).

[2] D. Zhao, A. Rodriguez, N. M. Dimitrijevic, T. Rajh and R. T. Koodali, J. Physical Chemistry
C, 114, 15728 (2010)
Preparation and Improved Electrochemical Properties of PANI– Li3V2(PO4)3 composite As Cathode Material for Lithium Ion Batteries
Authors: Kim Hyo Sang , Baek Seul Gi , Choi Hyun Jun , Lee Yun Sung
Published: February 2020

Introduction

In recent decades, lithium transition-metal phosphates such as LiMPO4 (M=Fe, Co and Mn) and Li3M2(PO4)3 (M=V, Fe and Ti) have been extensively studied as cathode materials for lithium ion batteries, due to high theoretical capacity, reversibility and better thermal stability than lithium transition metal oxides such as LiCoO2. 1-2

Monoclinic lithium vanadium phosphate, Li3V2(PO4)3, having structure similar to the open framework NASICON with corner shared VO6 octahedra and PO4 tetrahedra contains three independent lithium sites. The poly-anion instead of the O2− ions helps to stabilize the structure and allows a faster ion migration. The reversible cycling of all three lithium ions from Li3V2(PO4)3 would correspond to a theoretical capacity of 197 mAh/g in the voltage range of 3.0-4.8V, which is the highest reported of the phosphates. However, Li3V2(PO4)3 has poor conductivity, which restricts its practical application for lithium ion batteries. Much research has been devoted to increasing its conductivity by controlling particle size, carbon coating and metal doping in the V sites. 3-4

In this study, we tried to improve the electrochemical performance of the Li3V2(PO4)3cathode materials which have poor electronic conductivity by the wet ball-milling method and using PANI as conducting network.

Results and Discussion

Li3V2(PO4)3 particles were uniformly distributed within the PANI, forming a conducting network for easy movement of electrons. The highly porous and amorphous conducting polymer is also responsible for storing additional electrolyte near the surface of the electrode materials as represented in the SEM and TEM given in figure 1. This facilitated the increase in ionic and electronic conductivity, which in turn improved the electrochemical performance of the Li3V2(PO4)3. The content of the conducting polymer was optimized such that the charge-discharge mechanism of Li3V2(PO4)3 was not affected. The capacity retention of the PANI-Li3V2(PO4)3 composites were evaluated under various current rates. A considerable increase in capacity at high current rates was observed for the PANI-Li3V2(PO4)3 composite than the corresponding discharge capacity of pristine Li3V2(PO4)3 (figure 2). At 5C the capacity of PANI-Li3V2(PO4)3 composite was 122 mAh g-1 and the pristine Li3V2(PO4)3 was 102 mAh g-1. The reason behind the improvement in electrochemical properties of the PANI-Li3V2(PO4)3 composite substantiating with the physical and electrochemical studies will be discussed in detail.

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Published: February 2020

The pressing concerns of reducing greenhouse gas emissions and the consumption of non-renewable fossil fuels have led to increased demand for electrochemical energy storage systems with energy densities that far exceed those of the lithium-ion battery. To this end, rechargeable lithium-oxygen (Li-O2) batteries have been the focus of great interest due to their extremely high energy potentiality (up to 2-3 kWh kg-1) because oxygen, the cathode material, is not necessarily stored in the battery, as with convention lithium-ion battery technology, but can be accessed from the environment. However, in practice, the system has presented many scientific and technological challenges since it was introduced in 1996. The decomposition of the organic electrolytes during the discharge and charge processes causes the battery instability and electrolyte depletion. The irregular precipitation of thick film-like or large toroidal-like insoluble discharge product, Li2O2, blocks the void of the O2 cathode and eventually limits the battery performance, including the specific capacity, charge efficiency, and cycle life. The continuous accumulation of Li2CO3 and lithium carboxylates, resulting from side reactions of the Li2O2 and intermediate species, such as LiO2* and O2
-, with the cathode and the electrolyte on cycling, leads to cathode passivation and battery death. The insufficient structural stability of the cathode during Li2O2 formation/decomposition is also a limitation for battery cycle life.

In response, we have designed and fabricated a series of advanced cathodes, which hold many favorable properties including high electronic conductivity, tuned porous structure, and high electrocatlytic activity for both oxygen reduction and evolution reactions, to reduce the discharge/charge overpotentials to alleviate electrolyte decomposition, tailoring the deposition site and morphology of Li2O2 within cathode to enhance the specific capacity, charge efficiency, and cycle life. Finally, a free-standing honeycomb-like palladium-modified hollow spherical carbon deposited onto carbon paper cathode is successfully obtained, which endows a lithium-oxygen battery with high-rate capability (5900 mAh g-1 at a current density of 1.5 A g-1) and long-term (100 cycles at a current density of 300 mA g-1 and a specific capacity limit of 1000 mAh g-1) stability. These superior properties could be explained by the tailored deposition and morphology of the discharge products as well as the alleviated electrolyte decomposition compared with the conventional carbon cathode. The obtained performances provide a promising example and promotethe effort to design more advanced cathode architecture for lithium-oxygen batteries.