bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrolytes Based on Binary-Redox Couples for High Voltage Dye-Sensitized Solar Cells
Authors: Nath Narayan Chandra Deb , Jeong In Soo , Kim Jaecheon Chandra Deb , Kim Chulwoo Chandra Deb , Lee Jae-Joon
Published: February 2020

We prepared the interhalogen and halogen-pseudohalogen based electrolytes with multiple redox couples for high voltage dye-sensitized solar cells (DSSCs) and it was characterized by different electrochemical techniques. It was found that the additional interhalogen or halogen-pseudohalogen based redox systems, (I-, Br-)/I2Br- or (I-, SCN-)/I2(SCN)- can be formed by both chemically and electrochemically. The electrochemical redox potential for these both couples is more positive than that of conventional iodide-triiodide system while the redox reaction involved with these ions were essentially comparable to that of I-/I3
- in the conventional DSSC. Therefore, the formation of these redox couples produces extra redox states at more positive potential than I-/I3
- couple, which contributed to increase the open circuit voltage (V
oc) of DSSCs by shifting positively the equilibrium potential of solution phase. The interhalogen based redox couple increased open circuit voltage (V
oc) significantly regardless of sensitizing dyes, which corresponded to 14% higher overall power conversion efficiency (h) compared to that with conventional iodine based redox couple. However, the degree of potential shift, so the corresponding V
oc, can be controlled by adjusting the ratio of the concentrations of these redox species in the solution phase. This study is offering a very promising strategy to develop a novel electrolyte of which the energy level can be controlled by introducing an additional redox species with more positive potentials without compromising the rate of regeneration of dyes.
Dependence of Dark Processes on Film Thickness in Dye Sensitized Solar Cells
Authors: Garcia Rodrigo , Villanueva Julio , Escalante Renán , Heredia Beatriz , Oskam Gerko
Published: February 2020

The development of new sources of energy that can be economically viable and environmentally friendly is, nowadays, one of the most important goals in scientific research. Dye Sensitized Solar Cells (DSSC) are photoelectrochemical systems that represent an interesting option in the development of new technology in the solar cells field. The analysis of this photolectrochemical system is necessary in order to understand the phenomena that take place into the solar cells, which is the basis to propose improvements for achieving high efficiency solar cells.

There exist several different parameters that directly influence the performance of the solar cells. However, in devising strategies to improve the performance of DSSCs, the effects of dark processes are often overlooked. One of these parameters is the exchange current density in the dark, Jo. The value of Jo is related to the rate constant of the recombination reaction, the film thickness, the order of reactions of electrons and oxidized redox species, and the concentrations of background electrons in the TiO2 and oxidized redox species in the electrolyte. It has been proposed from a theoretically analysis that this exchange current density is more relevant as the thickness of the semiconductor film is increased [1], following the relationship showed in Figure 1.

In this work we study the influence of thickness in different parameters of the cell, such as the short circuit density photocurrent, Jsc, open circuit photovoltage, Voc, the ideality factor, m, and the exchange current density in the dark, Jo. Electrochemical impedance spectroscopy (EIS) measurements were made in order to study the kinetic parameters of the cell. The results show that the exchange current density in the dark, Jo, is proportional to the semiconductor film thickness (Figure 1), as proposed theoretically [1], limiting the performance of the solar cells as the thickness of the semiconductor film is increased, resulting in an optimum thickness around 10 µm. In addition, the diffusion length measurements and collection efficiency values are in good agreement with an optimum film thickness around 10 µm [2].

References.

[1]. K. Zhu, S. Rim, A. J. Frank. Impact of High Charge-Collection Efficiencies and Dark Energy-Loss Processes on Transport, Recombination and Photovoltaic Properties of Dye-Sensitized Solar Cells. J. Phys. Chem. Lett. 2, 1070-1076 (2011).

[2] Renan Escalante-Quijano, Rodrigo Garcia-Rodriguez, Beatriz E. Heredia-Cervera, Nikte Gomez-Ortiz, Julio Villanueva-Cab and Gerko Oskam. Influence of TiO2 Film Thickness on the Performance of Dye Dye-Sensitized Solar Cells: Relation Between Optimum Film Thickness and Electron Diffusion Length. Energy Environ. Focus, 2, 280-286 (2014).
Application of ZnO with Different Morphologies to DSSCs
Authors: Lizama-Tzec Francisco Ivan , Rodriguez-Gattorno Geonel , Pal U. , Oskam Gerko
Published: February 2020

ZnO is an attractive material for the fabrication of dye-sensitized solar cells (DSSCs) related to its good electron transport properties. It can be synthesized with different morphologies relatively easily by methods such as electrodeposition, sol-gel, either using forced hydrolysis or a microwave-assisted method [1].

There is a growing interest in linking the crystallographic planes of the material to performance of the solar cell. In this work, ZnO with different morphologies was obtained by the microwave-assisted technique at pH values of 5.5. 8, 10 and 12, and the materials were applied in the fabrication of DSSCs using the screen printing technique after preparing a paste. The surface area of the powders was characterized by BET, and the deposited ZnO layers were characterized by XRD, TEM and SEM. The cells were characterized by I-V curves and the amount of adsorbed dye was determined by UV-Vis spectrophotometry. It was found that the best cells were obtained with the morphology that resulted in the synthesis at pH 10, where the (100) plane is predominant.

References:

1. N. Morales-Flores, R. Galeazzi, E. Rosendo, T. Díaz, S. Velumani and U. Pal.
Morphology control and optical properties of ZnO nanostructures grown by ultrasonic synthesis.

Advances in Nano Research, Vol. 1, No. 1 (2013) 59-70.

Figure 1: SEM images of the different morphologies of the ZnO nanomaterials
New Redox Mediators for Quantum Dot Sensitized Solar Cells
Authors: Haring Andrew J , Morris Amanda J
Published: February 2020

Quantum dot sensitized solar cell (QDSSC) performance has more than doubled in just 3 years of research. However, one remaining limiting factor is the redox mediator electrolyte that completes the circuit by transferring electrons from the counter electrode to the photoanode. Optimum redox mediators must efficiently reduce II-VI semiconductor quantum dots (CdS/CdSe), while maintaining redox potentials sufficiently positive (>0.3 V vs NHE) to realize open circuit voltages higher than the state-of -the-art QDSSCs. A series of Mn complexes have been developed that meet both requirements. Open circuit voltages around 1V have been achieved, much higher than the 0.6V currently obtained with the common sulfide/polysulfide redox mediator. The efficiency increased approximately 50% above equivalent cells made with a cobalt trisbipyridine redox mediator.
Evaluation of ALD-Grown Metal Oxide Tunnel Junction Layer for Organic Tandem Cells
Authors: Kim Minjae , Chambers Conner , Berger Paul R.
Published: February 2020

Since their inception, organic solar cells have been a cynosure of photovoltaic (PV) community, owing to their simplicity, affordability and mass-production capabilities. Research on organic solar cells has been propelled by advances in nanotechnology, polymer synthesis, and semiconductor processing; efforts to achieve high power conversion efficiencies (PCE) through refined device geometry, tailored synthesis and/or combination of new low-bandgap materials, and heuristic process optimization have fructified as ~10 % efficiency in single-junction organic solar cells. Recent PCE enhancement in organic solar cells has mostly attributed to the development of small bandgap materials that extend absorption of the sun into the red and infrared wavelengths.

Utilizing tandem cells comprised of both large and small bandgap sub-cells enables light harvesting of different parts of the solar spectrum to be separately optimized, yielding higher PCE than single junction solar cells. But the challenges in achieving highly efficient organic tandem solar cells include optimal combination of materials for each sub-cell and interconnecting layers between sub-cells that are process compatible. Optimal combination of materials can be achieved by selection of two materials having complementary absorption windows. The interconnecting layer provides electrical and optical coupling between the two sub-cells and plays a key role in the performance of tandem cells. For the design of the interconnecting layer, electrical, optical, chemical and structural characteristics should be considered. Ideally, it should effectively facilitate charge transport between two sub-cells. Moreover, high transmittance and negligible absorption in the spectral region where two sub-cells absorb is desirable. Last but not least, the interconnecting layer should be designed to survive the subsequent solution coating and provide conformal surface coating for tandem cells with solution processed top cells.

Here we evaluate some of candidate metal oxides for tunnel junction layers for organic tandem solar cells. Metal oxides are grown by Atomic Layer Deposition (ALD) for thin defect-free conformal layer to circumvent miscibility issues and negligible absorption. Normal and inverted interfaces are examined. The influence of annealing under different conditions and methods will be presented. Tunneling properties are qualified by J-V characteristics and optical properties evaluated by UV-Vis are contrasted to suggest optimal design tradeoffs of tunnel junctions for solution processed organic tandem solar cells.
Ambient-Pressure XPS Study of GeO2/Ge(100) and SiO2/Si(100) at Controlled Relative Humidity
Authors: Arima Kenta , Kawai Yoshie , Minoura Yuya , Saito Yusuke , Mori Daichi , Oka Hiroshi , Kawai Kentaro , Hosoi Takuji , Liu Zhi , Watanabe Heiji , Morita Mizuho
Published: February 2020

Germanium (Ge) is a promising channel material for electronic devices in the next generation because it has higher mobilities for both holes and electrons than those of Si. Germanium oxide (GeO2) is one of the key materials in Ge-based transistors. However, GeO2 is permeable and soluble in water. This implies that GeO2 films will react with water vapor in air. In this study, water growth on ultrathin GeO2 films on a Ge(100) substrate and their effect on the electronic properties of GeO2 films are investigated using in-situ X-ray photoelectron spectroscopy. In addition, the wetting property of GeO2/Ge is compared with that of more familiar SiO2/Si.

In-situ XPS[1] measurements were performed at beamline 9.3.2 of the Advanced Light Source (ALS), of the Lawrence Berkeley National Laboratory.[2]A differentially pumped electrostatic lens system separates the analysis chamber from a hemispherical photoelectron spectrometer. Water vapor was introduced up to a pressure of 1.0 Torr while the sample temperature was controlled from room temperature to around -5°C by a chiller. This enabled us to control relative humidity from 0 % to around 15 %.

A simple estimation from O1s and Ge3d (or Si2p) indicates that thicker water layers are formed on GeO2 than on SiO2 at RH higher than 10-4%. Namely, the water thickness reaches one monolayer on SiO2 at 10% whereas it is two or three monolayers in the case of GeO2. We also find that the energy separation between Ge4+ and Ge0+ signals in Ge3d spectra increases more drastically at RH higher than 10-4% than that between Si4+ and Si0+ signals in Si2p spectra. This means that GeO2 films are charged more positively than SiO2 above the critical RH. We present two possibilities for the positive charging of the ultrathin GeO2 films in the presence of water vapor. One simple explanation is positive charging of the oxide with adsorbed water molecules by X-ray irradiation. The other explanation is that water-related species emit electrons to the Ge bulk and positive charges are created in GeO2, which may be the cause of the reported negative shift of the flatband voltage in Ge-based MOS capacitors with air-exposed GeO2.[3]

[1] M. Salmeron and R. Schlögl, Surf. Sci. Rep. 63, 169-199 (2008).

[2] M.E. Grass, P.G. Karlsson, F. Aksoy, M. Lundqvist, B. Wannberg, B.S. Mun, Z. Hussain and Z. Liu, Rev. Sci. Instrum. 81, 053106 (2010).

[3] A. Mura, I. Hideshima, Z. Liu, T. Hosoi, H. Watanabe and K. Arima, J. Phys. Chem. C 117, 165-171 (2013).
Graphene and 2-Dimensional Materials for Nanoelectronics Applications
Authors: Lemme Max Christian
Published: February 2020

Graphene science and technology has evolved substantially over the past 10 years. It is now entering a phase, where researchers and industry start to collaborate more closely on applications and to address issues of scalability and manufacturability. In addition to the semimetal graphene, recent years have seen the emergence of a number of related two-dimensional materials. These include insulators such as hexagonal boron nitride, semiconducting transition metal dichalcogenides (TMDs) like molybdenum disulfide (MoS2) or tungsten diselenide (WSe2) or silicene and germanene, similar in structure but less stable than graphene.

The talk will focus on graphene-based hot electron transistors (Graphene Base Transistors, GBTs) for analog radio frequency applications [1], [2]. The operating principle of GBTs is based on vertical current flow by quantum mechanical tunneling through an insulating barrier (Figure 1). The current (red arrow) can be controlled over several orders of magnitude by a base electrode made of graphene (Figure 2). The advantage of graphene over a metal base electrode is its ultimate thinness while maintaining good conductivity. If the barrier materials are optimized, GBTs have the potential to reach cut off frequencies (fT) on the order of 1 THz [3].

In the second part of the talk, options for optoelectronic devices based on 2D materials will be discussed. These include photodetectors / phototransistors made from graphene [4], where the photoresponse can be tuned by the voltage applied to a gate. In addition, photodiodes based on MoS2/silicon heterojunctions will be discussed.

[1] W. Mehr, J. C. Scheytt, J. Dabrowski, G. Lippert, Y.-H. Xie, M. C. Lemme, M. Ostling, and G. Lupina, “Vertical Transistor with a Graphene Base,” IEEE Electron Device Lett., vol. 33, pp. 691–693, 2012.

[2] S. Vaziri, G. Lupina, C. Henkel, A. D. Smith, M. Östling, J. Dabrowski, G. Lippert, W. Mehr, and M. C. Lemme, “A Graphene-based Hot Electron Transistor,” Nano Lett., vol. 13, p. 1435−1439, 2013.

[3] F. Driussi, P. Palestri, and L. Selmi, “Modeling, simulation and design of the vertical Graphene Base Transistor,” Microelectron. Eng., vol. 109, pp. 338–341, Sep. 2013.

[4] M. C. Lemme, F. H. L. Koppens, A. L. Falk, M. S. Rudner, H. Park, L. S. Levitov, and C. M. Marcus, “Gate-Activated Photoresponse in a Graphene pn Junction,” Nano Lett., vol. 11, pp. 4134–4137, 2011.
Fabrication and Characteristic of Wrinkled Stiff Thin Films on Elastomeric Substrates by Surface Treatments
Authors: Lim Sang Chul , Koo Jae Bon , Park Chan Woo , Oh Ji Young , Jung Soon-Won , Na Bock Soon , Lee Sang Seok , Chu Hye Yong
Published: February 2020

The wrinkle process comprises stretching of a soft elastic polydimethylsiloxane PDMS substrate1,2 and subsequent oxygen plasma treatment, resulting in a hard SiO2-like (SiOx-) layer on the surface.3

The PDMS system of choice for the presented process is Sylgard 184(DOW corning) which is usually applied in a 10:1 ratio (w/w) of siloxane and curing agent and requires a thermal curing step. These were treated on one side with oxygen plasma for 5, 10, 15 min to create a nanoscale silica skin, thus presenting identical surface chemistry in all experiments. This paper presents a cost-effective and simple method to form wrinkled stiff SiOx thin films on polydimethylsiloxane (PDMS) substrates at room temperature by oxygen plasma on pre-strained PDMS. The orientation of the generated structures was always perpendicular to the pre-stretched direction and the pitch of the structure could be adjusted ranging from 1.1 μm to 3 μm by controlling the strength of the pre-stretched strain and the thickness of the surface metal film. Upon relaxation, highly controlled and regular wrinkling of the silica skin resulted. Bi-layer substrates under uniaxial compression exhibit micron-scale features that can impart mechanical flexibility in functional electronic devices including interconnects, transistors and solar cells.

Systemic studies have been conducted to understand the dependence of the wavy profile on the PDMS pre-strain, UV/O exposure time, and PDMS modulus. The mechanics analysis has been verified to be quantitatively or qualitatively accurate by experimental comparisons. The wrinkled SiOx/PDMS system is stretchable and provides a wavy mold for stretchable electrodes. The constant electrical resistance during mechanical stretching shows the stretchability of this system. In this study, the metal thin film/contoured substrate is stretchable and has been demonstrated as stretchable electrical conductors.

References

1. J. Genzer and K. Efimenko, Science, 2000, 290, 2130.

2. K. Efimenko and J. Genzer, Adv. Mater., 2001, 13, 1560.

3. M. Ouyang, C. Yuan, R. J. Muisener, A. Boulares and J. T. Koberstein, Chem. Mater., 2000, 12, 1591.
SURMOFs as Ultra-low k Dielectric Thin Films
Authors: Redel Engelbert
Published: February 2020

Here we present a particularly interesting class of surface-anchored (metal-organic frameworks) materials SURMOFs for the fabrication low-k dielectric thin films.

Since these materials are highly porous and the size of their pores are highly adjustable, they can be further functionalized (e.g. with different metal/oxo connectors or clusters linked with various organic linkers) e.g. in order to specifically bind target analytes (optical sensing), to electrically load and unload small ions (optoelectronic applications) inside the metal-organic pores.

In addition, the RI (Refractive Index) as well as the optical properties of SURMOF-materials can be tailored, e.g. through their organic linkers – a fact which makes these materials ideally suited for photonic, optical and low-k dielectric applications.
Plasmonically Targeted Laser Treatment of Human Endothelial Cells
Authors: Muskens Otto L.
Published: February 2020

The potential of small metal nanoparticles for converting resonant light into local heat has given rise to new applications in biomedicine [1]. While many studies focus on destructive laser hyperthermia of malignant cancer cells, the impact of photothermal therapies using plasmonic nanoparticles on healthy, primary human cells is of interest for controlling biological functions and for combined, dual-action treatments. Here, we present results on the controlled laser treatment of human endothelial cells (HUVECs) using oligo-ethylene glycol (OEG-)coated nanoparticles, which are either specifically targeted using peptide-functionalization, or which are nonspecifically taken up by the cells without further functionalization [2-4]. Peptide-functionalized nanoparticles were found to specifically bind to VEGF-receptors in the cell membrane [2]. Subsequent laser treatment at mild conditions of up to 30 W/cm2laser intensity resulted in partially reversible damage of the cellular membrane. A remarkable recovery of cells was found within 24 hours following treatment [3]. For non-functionalized nanoparticles, combined ICP-OES analysis and numerical modeling indicated that irreversible cell apoptosis was caused by collective heating effects over the illumination spot (Fig. 1, left panel) [3]. It is argued that the multiscale effects of nanoparticle hyperthermia range from single nanoparticles to collective heating of macroscopic areas, and on time scales from picoseconds to seconds, are an important factor in designing effective nanoparticle treatments. New studies explore plasmonic laser treatment on in-vitro angiogenesis, the organisation of endothelial cells into a network of microvessels (Fig.1, right panel).

[1]
Dreaden, E. C., Alkilany, A. M., Huang, X., Murphy, C. J., and El-Sayed, M. A., Chem. Soc. Rev., 41, 2740-2779 (2012); Barreto, J. A., O'Malley, W., Kubeil, M., Graham, B., Stephan, H., Spiccia, L., Adv. Mater., 23, H18-H40 (2011).

[2] Bartczak D, Sanchez-Elsner T., Louafi F., Millar T., Kanaras A. G., Small 7, 388–394 (2011).

[3] D. Bartczak, O. L. Muskens, T. M. Millar, T. Sanchez-Elsner, A. G. Kanaras, Nano Lett. 11, 1358-1363 (2011).

[4] D. Bartczak, O. L. Muskens, S. Nitti, T. Sanchez-Elsner, T. M. Millar, and A. G. Kanaras, Small 8, 122-130 (2012).

Figure 1 (left panel) Calculated temperature increase caused by a single nanoparticle (left) and integrated over the 500mm illumination spot (right) [4]. (right panel) In-vitro angiogenesis of HUVECs in a MDA cancer-cell medium.
Properties of Garnet Ceramic Scintillators
Authors: Setlur Anant A , Murphy James , Lyons Robert
Published: February 2020

Garnet-based ceramics have applications as downconverters in LED lighting, laser media, and as scintillators for the detection of high energy photons. In this presentation, we will discuss the properties of Ce3+-doped garnet ceramics within the context of their applicability in computerized tomography (CT) scanners. CT scintillator requirements are different versus those for PET and applications that require energy resolution due to the need to reducing both afterglow at various timeframes and radiation damage while having reduced transparency requirements. Therefore, we will discuss how we can modify garnet composition and processing in order to meet some of these requirements. These modifications in process and composition can also give some insight towards some of the potential defects that are responsible for worse (or better) garnet scintillators. Finally, we will address some of the potential paths for future research and development.
Luminescent Characteristics of Fluorescent Organic Pigments Doped Recycled Polyethylene Thin Films Deposited by Ultrasonic Spray Technique at Low Temperature
Authors: Alarcon-Flores Gilberto , Sanchez-Alarcon Raul Ivan , Carmona-Tellez Salvador , Aguilar-Frutis Miguel Angel , Campos-Arias Martha Patricia , Falcony Ciro
Published: February 2020

Fluorescent organic pigments (FOP´s) doped recycled polyethylene (PE) thin films were synthesized by using the ultrasonic spray technique at low temperature. With the objective of minimizing the environmental impact caused by plastic wastes, a new recycling scheme for the fabrication of luminescent polymeric thin films was designed. The recycled plastic bags of Low Density PolyEthylene (LDPE) were used as hosts for the FOP's. The process consisted of spraying an organic solution of LDPE on glass substrates. Later the FPO`s solution was sprayed on top of the LDPE thin films. Several deposition conditions were varied (deposition time, precursor concentration and substrate temperature) to form homogeneous and uniform films. The substrate temperature was low (180°C) in order to avoid thermal degradation of the polymer, as revealed by infrared spectroscopy. These films were doped with different FOP's. Emissions such as blue light emission (λ=434 nm), orange light emission (λ=503 nm) and green light emission (λ=503nm) were obtained by photoluminescence. These FOP´s were mixed to obtain white light emission polymeric films. The thicknesses were close to 1µ. According to Scanning Electronic Microscopy, the LDPE films consisted of small-superposed clusters and the FOP´s were adhered of them. The optical transmission was shown in the 60-80% range.

Acknowledgments

The authors acknowledge the financial support from SIP-IPN and CONACyT through the scientific research projects (Grant Nos. 20140458, 20140459, 20131915, 20130236, 20130153, 20121399, 129227).
Visualization of Mg2+ Electrochemical Insertion/Deinsertion into MnO2: Ex-Situ TEM Study
Authors: Song Jaehee , Noked Malachi , Lee Sang Bok
Published: February 2020

Magnesium-ion (Mg-ion) rechargeable batteries are perhaps one of the most promising candidates that could potentially replace the current lithium ion battery technology. While the low cost and stability of magnesium make the Mg-ion battery an attractive technology, the divalent charge of Mg2+ ion brings in several significant scientific questions: How the divalent charge of Mg2+ affects their insertion/deinsertion behaviors? How far can Mg2+ ions penetrate into the bulk of the electrode material? One of the best ways to answer these questions is to visualize the Mg2+ insertion/deinsertion to/from the electrode material.

In this work, we visualized the process of the electrochemical insertion and deinsertion of Mg2+ into a MnO2 nanowire electrode by utilizing transmission electron microscopy (TEM) technique and electron energy loss spectroscopy (EELS). MnO2 nanowires were electrochemically grown within an aluminum anodized oxide (AAO) template. The obtained free-standing MnO2 nanowire array showed well-ordered, uniform structure and excellent contact with the current collector. These features of electrodeposited MnO2 nanowire electrode are beneficial for various imaging analyses as they would provide consistent results throughout the measurements. Moreover, this MnO2 nanowire electrode does not require conductive additives or a polymer binder solution to fabricate the electrode, therefore clear images of the nanowire samples can be obtained with no interferences from such additives.

From the ex-situ TEM energy dispersive X-ray spectroscopy (EDS) analysis, we found that the Mg2+ insertion is mostly confined to the surface of MnO2 nanowires. In order to observe the distribution of Mg2+ ions within the MnO2 nanowire in more detail, the discharged MnO2 nanowire array was sliced via microtome and its cross-section was analyzed by EELS. The EELS analysis on the cross-section of the discharged MnO2 nanowire showed that Mg2+ is also found at the center of the MnO2 nanowire, but at a lower degree than the surface. Moreover, we found that almost all of the inserted Mg2+ is retracted after charging the MnO2 electrode. This work not only presents interesting Mg2+ insertion/deinsertion behavior with MnO2, but also provides a systematic method that can be applied for the analysis of other cation/electrode systems.
Oxidative Stable Cu
3
Sn Nanoparticles for Novel Electrode Fabrication Using Pressure Under Ambient Condition
Authors: Cho Sanghun , Lim Keon-Hee , Yoo Jeeyoung , Park Si Yun , Park Youngmin , Kim Youn Sang
Published: February 2020

Manufacturing methods of conductive electrode is essential technology for printable electronics such as radio frequency identification tags (RFID), thin film transistor (TFT), ultra high frequency antennas and solar cell. Various fabrication methods of electrodes for printable electronics have been suggested to screen printing, gravure printing and inkjet printing. However, these methods have difficulties to the control of printing pressure, thickness, nozzle blocking, viscosity of ink and coffee ring effect. New technique for electrode for printable electronics needs to perform at room temperature and ambient condition.

In addition, copper nanoparticles are good prospective candidate to replace high cost silver because of low-cost, abundant deposit and high conductivity. However, copper nanoparticles have the limitation which is highly oxidative materials and these drawbacks limited practical printing process. To overcome these limitations, conductive materials for electrodes requires high oxidative stable nanoparticles and low cost materials. In this study, we synthesized high oxidative stable, conductive Cu3Sn Nanoparticles and fabricated electrode by pressure assisted method at room temperature and ambient condition.

Prepared Cu3Sn nanoparticles were confirmed using X-ray diffraction (XRD) and Energy Dispersive X-ray Spectrum (EDS) with High Angle Annular Dark-Field Scanning TEM (HAADF-STEM). Measurement of electrical conductivity was carried out with the 4-point probe methods depending on various value of pressure. The conductive electrodes were obtained by pressure at 530MPa and showed electrical resistivity of less than 19.8 µΩ cm. Electrical resistivity of fabricated electrodes is similar to that of bulk Cu3Sn material (8.8. µΩ•cm). This result is caused by numerous and three dimensional contact of each conductive nanoparticle. To investigate the contact of each nanoparticle, Cross-sectional TEM analysis of pressed nanoparticles was performed. Also, we analyzed oxidation stability of nanoparticles by XRD and change of conductivity during 4 weeks in harsh condition (50% RH, at 25 oC). XRD and conductivity variation results showed no significant degradation. From these results, Cu3Sn nanoparticles have highly stable against air oxidation.

In conclusion, we synthesized high oxidative stable, conductive Cu3Sn Nanoparticles and fabricated electrode by pressure assisted method at room temperature and ambient condition. The Cu3Sn nanoparticles were stable in air due to the low Gibbs free energy and have very low price. Pressure assisted method promotes the contact of each particle which induce low electrical resistivity at room temperature and ambient condition. We believe that Cu3Sn nanoparticles and pressure assisted method for fabrication of electrode make a great contribution to TFTs, Solar Cell and RFID for electronics.
Studies on Dielectric Properties of Annealed Reactively Co-Sputtered Bcn Thin Films
Authors: Prakash Adithya , Sundaram Kalpathy B
Published: February 2020

The main concern in the Ultra Large Scale Integrated (ULSI) semiconductor devices is the reduction of signal propagation delay. This delay ( ) is the product of electrical resistance of wiring metal and the parasitic capacitance of the Inter dielectric layer (IDL). The motivation behind the boron carbon nitride (BCN) ternary compounds is their similarities in the structure and difference in properties between graphite and hexagonal boron nitride (h-BN). Both theoretical calculations and experimental studies show that BCN compounds exhibit excellent mechanical, optical and electrical properties [1], [2]. It has been reported that the addition of carbon atoms to BN films is effective in reducing the dielectric constant. Also the structure of BCN film has a strong impact on dielectric constant [3]. The BCN deposition by chemical vapor deposition (CVD) has been reported [4], but in this work reactive co-sputtering is performed to deposit BCN thin films. The co-sputtering helps in the creation of films which gives more freedom to vary the composition when compared to single target sputtering. Thickness uniformity and the film quality are better when using co-sputtering.

In this work, we are depositing BCN thin films on oxidized silicon wafer substrates using two targets namely B4C and BN using RF power and DC power respectively at different N2/Ar gas flow ratios. A thin film of titanium (Ti) was deposited on it and another layer of Aluminum was deposited on top of the titanium layer to form a metal/insulator/semiconductor (MIS) device. This titanium layer acts as the barrier layer against the aluminum migration into BCN at higher temperatures during annealing. The dielectric constant value was found from capacitance-voltage (C-V) characteristics.

REFERENCES

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[2] A. Perrone, A.P. Caricato, A. Luches, M. Dinescu, C. Ghica, V. Sandu, A.Andrei , Appl. Surf. Sci., 133 (1998), p. 239

[3] T.Sugino, Y. Etou, T. Tai, Jpn. and H. Mori, Appl. Phys. Lett. 80, 649 (2002)

[4] J. Yu and E. G. Wang, Appl. Phys. Lett. 74, 2848 (1999)
Unique Layered Tin Oxide Structure Via Buffered Anodization
Authors: Mohri Nils Erich Karl , Tremel Wolfgang
Published: February 2020

The electrochemical anodization of various metals (e.g., Al [1], Ti [2] and Fe [3]) is able to generate a great variety of nanostructures. In the last decade, these new nanomaterials have received intensive interest due to their high technological potential in many applications such as photocatalysts for organic degradation [4], self-cleaning substrates [5] and solar cell electrodes [6, 7].

Tin dioxide (SnO2) is an n-type semiconductor used as solid-state gas sensor [8] and oxidation catalyst [9]. It also has the potential to function as high capacity anode material for lithium-ion batteries [10]. Jeun et al. [11] synthesized irregular nanoporous tin oxide films in 0.3 M oxalic acid solution at 6 V and used it as a gas sensor material.

Anodization of tin in oxalic acid solutions at an applied voltage of above 5 V produces highly porous tin oxide structures. Lower applied voltages, as investigated by Yang et. Al [12], result in a passivation of the surface by precipitation of tin-oxalate.

We investigated the use of a buffer solution to prevent the precipitation of tin oxalate unto the surface. This enabled us to anodize tin at lower applied voltages resulting in a completely new tin / tin dioxide layer structure.

After optimizing the parameters, we investigated the growth mechanism and various chemical, physical and biological applications of this new structure.

Literature:

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Structural and Chemical Transformations in Li2MnO3
Authors: Persson Kristin Aslaug , Lee Eunseok
Published: February 2020

Li2MnO3is a critical component in the family of the so-called `Li-excess' materials, which are attracting attention as advanced cathode materials for Li-ion batteries. We present first-principle calculations to investigate the electrochemical activity and structural stability of stoichiometric LixMnO3(0 < x < 2) as a function of Li content. We find that the Li2MnO3 structure is electrochemically activated above 4.5 V on delithiation and that charge neutrality in the bulk of the material is mainly maintained by anion oxidization. While oxygen vacancy formation is found to be thermodynamically favorable for x < 1, the activation barriers for O migration remain high throughout the Li composition range, impeding any significant oxygen release from the bulk of the compound. Furthermore, we show that, defect layered structures, where some Mn resides in the Li layer, become thermodynamically favorable at lower Li content (x < 1), indicating a strong tendency towards local spinel-like domain transformation. Concurrently, the calculated energy barriers for Mn migration from the Mn-layer into the Li-layer suggests a Li2MnO3 structural instability for x < 0:5. Based on our observations, we suggest a critical phase transformation path for forming nuclei of spinel-like domains within the matrix of the original layered structure. We also show that formation of defect layered structures during the first charge manifests in a significant depression of the voltage profile on the first discharge, providing a possible background for the observed `voltage fade' of the Li-excess materials.
Hydrogenated TiO2 Nanotubes as High-Power Anode Materials for Lithium-Ion Batteries
Authors: Eom Ji-Yong , Yun Ju-Ho , Yoo Seung-Eul , Ryu Won-Hee , Lim Sung-Jin , Kwon HyukSang
Published: February 2020

Titanium oxide (TiO2) has received much attention as the most promising alternative to the conventional graphite anode of Li-ion batteries for high energy and power. The performance of TiO2 anode for Li-ion batteries depends strongly on the crystalline phase, the morphology, and the porosity of the structure. The nanostructured TiO2 materials, such as nanoparticles, nanorods, nanowires, and nanotubes have been studied to improve the performance of TiO2 anode. Recently, it was reported that the hydrogenated TiO2, called a ‘black TiO2’ nanostructures are more attractive for photovoltaics, photocatalysis, and supercapacitors owing to their narrower bandgap (less than typical 3 eV value) and relatively high electrical conductivity.

The smooth and well-ordered TiO2 nanotubes were synthesized on a Ti disk successfully by anodization in a non-aqueous solution containing fluoride ions. The as-prepared TiO2 nanotubes were annealed to obtain crystalline anatase (A-TiO2 NTs) and hydrogenated TiO2 nanotubes (H-TiO2 NTs) at 450 °C for 2 h in air and hydrogen atmosphere, and then their electrochemical performances were investigated as alternative anode materials for Li-ion batteries.

The initial discharge capacity of the H-TiO2 NTs (0.117 mAh cm-2) was superior to that of the A-TiO2 NTs (0.110 mAh cm-2) and the discharge capacities of the H-TiO2 NTs and A-TiO2 NTs maintained nearly 72 and 44 % at a current density of 10 mA cm-2. In addition, the H-TiO2 NTs (89 %) exhibited much higher the capacity retention than the A-TiO2 NTs (70 %) at the current density of 1 mA cm-2 (~10 C-rate) after 300 cycles, as shown in Figure 1. The H-TiO2 NTs presented smaller the crystallite size and charge transfer resistance (Rc) compared with the A-TiO2 NTs and the oxygen vacancies were formed in the H-TiO2 NTs during hydrogenation, which was proved by the presence of Ti3+ from the XPS analysis.

These results indicate that the insertion and extraction of Li+ through the H-TiO2 NTs were preferable to those through the A-TiO2 NTs, which were probably attributed to the short diffusion length for Li+, innumerable reaction sites, and relatively high electrical conductivity. Therefore, the H-TiO2 NTs exhibited vastly superior the rate capability and capacity retention property during cycling to the A-TiO2 NTs at high current density as anode materials for Li-ion batteries.
Synthesis and Lithium Storage Properties of Novel Flower-like Co3O4
Authors: Liu Peng , Xia Xifeng , Wang Wenjuan , Hao Qingli
Published: February 2020

Cobalt oxide, Co3O4, one of the most important metal oxides and p-type semiconductor, has been found wide spread applications in many important fields, including solar cell photo-catalysts and supercapacitors or lithium-ion batteries. Usually, properties of the material depends on its special morphology. Different morphologies of cobalt oxide such as cubes, sheets, wires and tubes have been synthesized[1][2].

In this work, a novel flower-like Co3O4 has been produced by calcining the precursor, which was obtained through a simple hydrothemal method. The unique hierarchical architecture is able to shorten Li+diffusion paths and accommodate the volume change of the materials during charge/discharge process. Electrochemical evaluation demonstrates its potential application as anode material for lithium ion batteries. Fig. 1 shows the cycle life of cobalt oxide, the inserted picture a and b are the TEM images of precusor and cobalt oxide, respectively.

references：

[1] Lou X W, Deng D, Lee J Y, et al. Advanced Materials, 2008, 20(2): 258-262.

[2] Tian L, Zou H, Fu J, et al. Advanced Functional Materials, 2010, 20(4): 617-623.
Entropy of Cycled and Aged Li-Ion Batteries for Maritime Conditions
Authors: Vie Preben J. S. , Mæhlen Jan Petter , Kirkengen Martin
Published: February 2020

Electrification with Li-ion batteries is a global trend that has been on-going for many years across sectors, driven by a strong decrease in battery prices, increasing energy density and increasing fuel costs. Studies by DNV of the electrification of ships (e.g. Fellowship) have shown a large potential of reduction in energy consumption and emissions of CO2, NOx and particulate matters through electrification [1]. In addition, cost calculations have shown the possibilities for return of investment through electrification within 3 years for some applications, more recent data states even 2 years for other applications [1].

It is well-known that the safety of Li-ion batteries is an important issue. E.g. during over-charge of a Lithium-ion battery, the battery may eventually overheat and cause a thermal runaway which can ignite neighboring cells which have not been overcharged. Internal shorting of the electrodes is also reported to create thermal runaway situations. Based on the large amounts of energy in a 1 MWh Li-ion battery, it is absolutely vital that the safety of the battery system is assured. The degradation and ageing of Li-ion batteries will contribute to additional instability and affect the safety performance of the batteries as well. Hence, knowledge and the ability to predict capacity decay and the battery state of health will be vital information to enable safe and long-life operation of marine battery systems.

In this study commercial Li-ion cells were studied with the entropy spectroscopy technique [2, 3] to establish a State-of-Health indicator for aged cells. The cells tested were Li-ion pouch cells which have been aged for both calendar and cycle life up to 3 years.

For cycle life, the Li-ion cells were evaluated at various temperatures and charge and discharge rates. The calendar life was scrutinized at various temperatures and at different state of charge. The cells were characterized, based on continuous monitoring of capacity and energy content. In addition, periodic capacity and impedance data was recorded for all cells at the same temperature (25 °C) and discharge rate (1C).

1. Vartdal, B.-J. and C. Chryssakis, Potential Benefits of Hybrid Powertrain Systems for Various Ship Types, in International scientific conference on hybrid and electric vehicles, RHEVE 20112011: Rueil-Malmaison, France. p. 12.

2. Reynier, Y., R. Yazami, and B. Fultz, The entropy and enthalpy of lithium intercalation into graphite. Journal of Power Sources, 2003. 119: p. 850-855.

3. Viswanathan, V.V., D. Choi, D. Wang, et al., Effect of entropy change of lithium intercalation in cathodes and anodes on Li-ion battery thermal management. Journal of Power Sources, 2010. 195(11): p. 3720-3729.
Comparative Electrochemical Study of Metal Oxalate As Anode for Lithium Batteries
Authors: Oh Hyo-Jin , Kim Sun-Jae , Myung Seung-Taek
Published: February 2020

Rechargeable lithium ion batteries (LIB) are the most advanced power sources for portable electronic devices, hybrid electric vehicles, transportation sectors and military applications. Metal oxalate is technologically important and functional material, because of its applications for use in energy storage such for Li ion batteries. Thus, these materials have been investigated as alternative negative materials for LIB owing to high capacity (700 ~ 1,000 mAhg-1) based on a conversion mechanism.

Several metals based oxalates with different aspect ratios have been synthesized by hydrothermal reaction of metals (= Ni, Co, Mn) with Na2C2O4 and H2O in the presence of ethylene glycol (EG). Control over the aspect ratios of oxalates were achieved by adjusting the hydrothermal reaction temperature and time.

The electrode was fabricated by mixing 70 wt% active material, 10 wt% carbon black (electronic conductive additive) and polyacrylic acid (PAA, binder) in N-methylpyrrolidinone (20 wt%). A solution of 1 M LiPF6 dissolved in a mixture of ethylene carbonate (EC) and dimethyl carbonate (DMC) (3 : 7 weight ratio) was used as the electrolyte in the cell. Electrochemical test was carried out in coin type cell. Galvanostatic electrochemical charge and discharge test were made between 0V and 3.0V at 100 mAg-1 current at room temperature.

The hydrothermal method is useful to synthesize metal oxalate with particles and crystallization. Nickel and manganese oxalate crystallize in the monoclinic phase, while the cobalt compound adopts the orthorhombic phase.

The as-prepared metal oxalates demonstrate a high performance as anode material for LIB. Among them, nickel oxalate showed a high initial discharge capacity of 1321 mAhg-1. The first charge capacity of the as-prepared electrode at a current density of 100 mAg-1 reach 786 mAhg-1 with good capacity retention.
Failure Mode Analysis of Li-Ion Batteries Using in-Situ Scanning Electron Microscopy
Authors: Hovington Pierre , Lagacé Marin , Marceau Hugues , Clément Daniel , Dontigny Martin , Trottier Julie , Guerfi Abdelbast , Mauger Alain , Julien Christian M , Zaghib Karim
Published: February 2020

High cycle life is a key parameter for any lithium-ion battery technology to obtain a commercial success. In this regard, multiple electrochemical (Impedance, ASI, floating current, etc.) and non-electrochemical techniques (XRD, FT-IR, SEM/TEM, etc.) are used and developed. The most complete techniques involve measurements while the battery is cycling (in-situ experiment). Among them, in-situ SEM/TEM is able to focus on the same region/particle at all steps of the oxidation/reduction process. Hydro-Quebec has developed a complete expertise for in-situ techniques, especially in situ SEM.

Lithium Polymer Battery (LPB), a solid-state battery, is the preferred configuration for SEM in-situ experiment. We present in Figure 1 micrographs taken during in-situ experiments of a Li/PEO-based solid polymer electrolyte (SPE)/Li1.2V3O8 LPB showing the variation in thickness for the Li, SPE and cathode layers with the cell voltage. Only the Li thickness shows an important variation during cycling. The Li plating rate can also be measured. This experiment can clearly be used to better understand the Li plating mechanism.

In figure 2 we present micrographs taken during an in-situ SEM cycling of a Li/PEO-based SPE/SiO cell using backscattered electron signal. We clearly see an important decrease in the beam intensity of the back-scattered electrons (BSE) as a function of the cell voltage as a result of the Si phase transformation upon cycling (upon Li ‘insertion’, the BSE intensity is lower and the particle becomes darker). We also note that a region of the big particle remains white (i.e. the Li+ ions did not have sufficient time to ‘diffuse’ inside their core region). This result explains the rather low capacity observed with such particles, and it gives evidence that the system is out of thermodynamic equilibrium. This in-situ experiment also shows no cracking of the relatively big SiO particles since the voltage was kept higher than 0.1V (stop at the Li22Si7 phase instead of Li22Si5) when compared to previous results [1]. We will also present in-situ SEM of nano-Si particles that did not suffer any cracking, but agglomerate (electrochemical sintering), which results in a more rigid and fractured electrodes [2]

This presentation will also use in-situ SEM to obtain a better understanding of the failure mechanism of new electrode materials, including Li-S.

References:

[1] http://batt.lbl.gov/blog/research-tasks/in-situ-sem-seeing-battery-cycling-in-action/?utm_source=rss&utm_medium=rss&utm_campaign=in-situ-sem-seeing-battery-cycling-in-action

[2] Hovington et al, (2014) ‘in situ Scanning electron microscope study and micriostructural evolution of nano silicon anode for high energy Li-ion batteries’, Journal of Power Sources 248, 457-464