bluuebunny/crossref_metadata_2025_split huggingface dataset:
(Invited) Approach to Oxide Tfts with High Mobility & Stability
Authors: Hosono Hideo 
Published: November 2022

Thin film transistors (TFTs) with the channel of amorphous oxide semiconductors (AOSs) represented by amorphous Indium-Gallium-Zinc Oxide (a-IGZO) are now applied to drive pixels of the state-of the art display based on high mobility, good homogeneity, easy fabrication and optical transparency [1]. Recently, larger mobility TFTs are highly demanded for emerging applications such as ultra-high vision and memories. However, there is a critical obstacle to be overcome, i.e., an empirical trade-off rule in oxide TFTs between mobility and stability. Higher mobility TFTs possess less stability to various types of stress (negative bias-thermal stress instability, NBTS, positive bias-thermal stress instability, PBTS, and negative bias-illumination stress instability, NBIS). The Elucidation of origin for this trade-off rule and new approach are required to realize high mobility and high stability TFTs.
We clarify that the origin of this trade-off through comparison in TFTs between IGZO with low mobility and high stability and ITZO with high mobility and low stability. A critical phenomenon was noted during the conventional TFT fabrication; CO-related impurity donates electrons to Indium-Tin-Zinc Oxide (ITZO) with high mobility under the negative bias stress condition but such CO-related impurity effect is negligible in IGZO with lower mobility than ITZO [2]. This finding may be understood by considering that large difference in ECBM determines the transfer of electron generated by adsorbed CO-related species on the back surface of ITZO [3]. Based on this model and this finding, we successfully fabricated the most stable ITZO TFT with a high mobility of 70 cm2/Vs by eliminating CO-related impurity and further passivation; NBTS (-20V, 60 oC, 3600 s, ΔVth: -0.02 V), PBTS (+20 V, 60 oC, 3600 s, ΔVth: 0.12 V) and NBIS (-20V, 15000 lx, 3600s, ΔVth: -1.33 V).
[1] Hosono, H., & Kumomi,K., (ed), Amorphous Oxide Semiconductors: IGZO and Related Materials for Display and Memory (Wiley, 2022); Hosono, H. (2018). How we made the IGZO transistor. Nature Electronics, 1(7), 428-428.
[2]Shiah, Y. S., Sim, K., Ueda, S., Kim, J., & Hosono, H. (2021). Unintended Carbon-Related Impurity and Negative Bias Instability in High-Mobility Oxide TFTs. IEEE Electron Device Letters, 42(9), 1319-1322.
[3] Shiah, Y. S., Sim, K., Shi, Y., Abe, K., Ueda, S., Sasase, M., Kim,J., & Hosono, H. (2021). Mobility–stability trade-off in oxide thin-film transistors. Nature Electronics, 4(11), 800-807.
2D MoS2 Pattern from Sol-Gel-Processed Precursors Using Jet Printer for TFT Application
Authors: Choi Woon-Seop , Can Thi Thu Thuy 
Published: November 2022

Molybdenum disulfide (MoS2) is one of the most studied layered TMDCs due to its excellent optical, electrochemical, and electrical properties. Monolayer MoS2 is a semiconductor with a direct band gap of 1.8 eV, but it has an indirect band gap in its bulk form, and make it possible to use 2D materials in the next generation of switching and optoelectronic devices.
Many research groups have attempted to synthesize MoS2 with different methods to make good MoS2 quality. Mechanical exfoliation has been known as an uncomplicated way for flakes extracted from single crystals. However, several restrictions that method had to come up with were small and random flake size then extreme difficulty in the alignment for device fabrication. Chemical vapor deposition (CVD) have been used to prepare MoS2 thin layers in large scale. Nevertheless, this method demanded vacuum, the use of Mo or MoO3 thin films as precursors included in four-step CVD process for reduction and sulfurization resulted in expensive MoS2 films. Solution based methods, by contrast, is promising for large area formation of controllable MoS2 film with simple equipment, time-saving at low cost. No report has been published using jet printing technology from MoS2 precursor solution but our group.
Therefore, the goal of this research was to develop a new drop-on demand printing method for MoS2 atomic layers based on sol-gel synthesis method. We developed a unique solution process to obtain large-size and uniform MoS2 atomic layers without CVD. The sulfurization process is omitted to simplify the entire process, and wafer-scale and larger-scale synthesis of MoS2 can be achieved by simple thermal treatment. The atomic layers of the synthesized MoS2 were identified as 2 layers, 3 layers, and 5 layers for MoS2 concentrations. MoS2 patterns were made with highly uniform coverage using electrohydrodynamic (EHD)-jet printing for the first time. The EHD jet-printed MoS2 TFTs show good electrical properties of 19.4 cm2 V-1 s-1.
(Invited) Stretchable Sensing Devices Combining Ionic Liquids and Soft Electrodes
Authors: Ota Hiroki 
Published: November 2022

In recent years, a variety of ultra-flexible devices have been proposed. Their applications include wearable devices and soft robots. Among ultra-flexible devices, the devices with stretchablity is attracting attention as next-generation sensing devices. In such devices, ionic liquids can be used as a sensing material. Ionic liquids are polymers in a liquid state and their structure can be easily altered, For example, ionic liquids can be developed reactive to temperature, humidity, light, gases, and many other factors. Furthermore, since they are in a liquid state, they are durable against device stretching. In this study, we report on a stretchable sensing device using ionic liquids. In particular, by using liquid metal and CNT(Carbon nanotube) as electrode materials, we propose a super-stretchable device and a super-flexible device with transparency and high breathability.
<Temperature/humidity/oxygen/optical sensors using liquid metal electrodes> liquid metal was used as electrode, and ionic liquids as a sensing material. Equivalent circuit of the sensors were established based on Nyquist plot The sensor showed stable sensitivity to temperature without hysteresis as shown with a 0.039/°C increase in conductivity, which is quite high compared to other reports. We also show proof of concept for humidity, oxygen gas, and optical sensings using four kinds of ionic liquids, 1-Ethyl-3-methylimidazolium trifluoromethanesulfonate ([EMIM][Otf]), 1-Butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]), 1-Butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([BMPYR][NTf2]) and 1-butyl-3-(4-phenylazobenzyl)imidazolium bis(trifluoromethanesulfonyl)amide ([Azo][NTf2]) for optical sensing. The sensitivity of each ionic liquid to humidity and oxygen differed depending on the ionic liquid. For each type of stimuli, the sensing can be optimized by choosing the proper ionic liquid. In addition, using [Azo][NTf2], we demonstrate optical sensing and memory in this study.
< Transparent and Breathable Ion Gel-based Sensors using CNT> highly transparent, ultra-flexible, and gas-permeable polymer thin-film sensors using ion gels as the sensing material, which demonstrated the capacity for selective detections, were proposed. Particularly, simultaneous and independent sensing of temperature and humidity was demonstrated in this study. The sensors were fabricated using a simple spray coating method on a thin silicone rubber film (around 25 µm thickness). Owing to their thin-film shape, they showed more than 80% visible light transmittance and a higher gas permeability of 58.7 g/m2 h than the human transepidermal water loss. Simultaneous and independent detection of temperature and humidity was achieved with a high sensitivity of 15.9%/°C and 2.5%/percentage of relative humidity, respectively, using two types of gels with ionic liquids.
These results suggest that the easily modifiable nature of ionic liquids contribute to the development of stretchable electronics.
Investigating Oxygen Reduction Reaction Using a Multiscale Modeling Approach for Polymer Electrolyte Membrane Fuel Cell
Authors: White Zakar , Litster Shawn 
Published: November 2022

Cathode catalyst layer (CCL) modeling is an important tool in elucidating the coupled transport-reaction phenomena and optimizing electrode architectures for greater efficiency, power density, and durability and thereby, reducing fuel cell costs. State-of-the-art catalyst use a high surface area carbon black (HSC) that supports platinum (Pt) nanoparticles, where some of the Pt particles reside on the carbon surface and a significant fraction of particles are found in the nm-scale pores of the carbon support. Within the electrode, the catalyst in bound by a polymer electrode binder (i.e., ionomer) that coats the external surface of the catalyst but does not penetrate the internal pores that are filled with liquid water due to capillary condensation. The contact of ionomer with Pt is known to reduce electrocatalytic activity due to site-blocking by the ionomer anion as well as increase the oxygen transport resistance. There is very little prior work on modeling the distinct performance of the internal Pt and the external Pt in contact with the ionomer. Most prior attempts to model CCLs with HSC catalyst supports at the MEA-scale and cell-scale have used an uncoupled approach, that separately considered the transport to the internal and external Pt particles, not considering the combined flux of oxygen through the ionomer film. Thus, the prior uncoupled model could potentially underestimate the oxygen concentration drop through the ionomer film. Here, we have adopted a numerical model of the catalyst that simultaneously considers the transport to the internal and external Pt as well as the different transport properties in the water and ionomer domains in single primary particle of the catalyst. The single spherical catalyst support model is upscaled to a 3D fuel cell model using a parametric linear regression fitting to model the local source/sink terms in the CCL. This multi-scale model is then applied to study the impact of the catalyst morphology.
This material is based upon work supported by the U.S. Department of Energy's Office of Energy Efficiency and Renewable Energy (EERE) under the Fuel Cell Technologies Office, Award Number DE-EE0008822.
Characterizing the Pore Network of Diffusion Media at the Pore Size Scale
Authors: Bozzetti Michele , Berger Anne , Girod Robin , Gasteiger Hubert Andreas , Tileli Vasiliki 
Published: November 2022

Water management by gas diffusion media and electrodes is a fundamental aspect of the performance of electrochemical cells including proton exchange membrane (PEM) fuel cells. In these devices, product liquid water blocks part of the available space for reactants flow, leading to mass transport losses and lowering of the performance1. Pores saturation has been observed with different experimental techniques for GDL substrates, however a detailed saturation process at the pore size scale of the microporous layer (MPL) is necessary. Previously, it was suggested that large pore network domains are responsible for an enhanced water evacuation2, however, possible existence of narrow size constrictions could still limit water evacuation. In this work, we detail the benefits of three-dimensional imaging of the pore network at the typical MPL pore size scale, i.e. the sub-micrometre scale, which is achieved by focused ion beam scanning electron microscope (FIB-SEM) nanotomography.
Two different MPL designs were analysed: an acetylene black based MPL, named Li100, and a vapor grown carbon fiber (VGCF) based MPL, the latter showing better performance under high relative humidity conditions2,
3. FIB-SEM tomography volumes in Fig. 1a-b were used to observe the relative distribution of larger pore domains and narrower pore constrictions. By removing narrower sized pores from the network and analysing the connections of large pore domains, we show the existence of a characteristic size for pore constrictions below which the pore network is well connected. This characteristic size is depicted by the red line in Fig. 1c-d, which plots the fraction of connected pores as a function of their minimum size. Constrictions size values for the two MPL designs were further validated with mercury intrusion experiments, since constrictions affect all the intrusions by capillary pressure, such as water flow in hydrophobic MPLs.
The calculated parameters, which are representative of the connections between large pore domains, open up new perspectives on the prediction of gas diffusion under realistic conditions. The approach allows evaluation of the effects of alternatively removing larger and narrower pore domains, to understand the saturation-driven tortuosity in different MPL structures.

J. Shen, L. Xu, H. Chang, Z. Tu, and S. H. Chan, Energy Conversion and Management, 207, 112537 (2020).

C. Simon, D. Kartouzian, D. Müller, F. Wilhelm, and H. A. Gasteiger, Journal of The Electrochemical Society, 164, F1697–F1711 (2017).

C. Simon, J. Endres, B. Nefzger-Loders, F. Wilhelm, and H. A. Gasteiger, Journal of The Electrochemical Society, 166, F1022–F1035 (2019).

Figure 1
An Innovative Approach to Design and Optimize Flow Field Pattern of Polymer Electrolyte Membrane Fuel Cell
Authors: Tsukamoto Takayuki , Takayama Tsutomu , Miyamoto Yuhei , Komiyama Keisuke , Yoneda Masakazu 
Published: November 2022

To increase power density of polymer electrolyte membrane fuel cells (PEMFCs), further optimization and downsizing of cell and stack design are necessary.
To support cell and stack design, we have been developing a three-dimensional (3D) PEMFC simulator P-Stack [1]. P-Stack can estimate power generation performance in good agreement with experimental results, and can clarify relationships between the performance and internal states depending on cell designs, operation conditions, and material properties [1]. Although 3D PEMFC simulations are powerful means, preparing 3D model is very time consuming, thus it was difficult to explore various cell designs.
In the present study, we have developed a new modeling technology for PEMFC flow fields. In this technology (Figure (a)), flow fields of anode and cathode gases are drawn by lines in 2D canvas. Properties of the lines such as width, depth and wall angle are given, then it automatically generate 3D model for anode/cathode flow fields and bipolar plates, coolant flow field, seal, gasket and MEA. Power generation performance of the 3D model can be estimated by P-Stack continuously. In addition, the line properties, vertex positions, and the number of repeat can be parametrized, enabling the parametric study of cell design.
In this technology, pressure and flow rate distributions can be calculated by a network model based on Darcy’s law [1], without generating 3D model. As shown in Figure (b), the result is in good agreement with computational fluid dynamics (CFD) calculation of 3D model. Although the CFD calculation takes several hours using 32 parallel processes, the calculation of the network model is finished within several seconds using single process. In similar manner, it can calculate flow rate distribution of cells in the stacking axis. Since the execution time per one case is very short, it can be combined with optimization by genetic algorithm (GA).
In the presentation, we will talk about a result of the parametric study and optimization for more practical cell design. Influence of flow field design on power generation performance and internal states will be discussed.

References

[1] T. Tsukamoto, T. Aoki, H. Kanesaka, T. Taniguchi, T. Takayama, H. Motegi, R. Takayama, S. Tanaka, K. Komiyama, M. Yoneda, J. Power Sources 488 (2021) 229412

Figure 1
Multiwalled Carbon Nanotube-Filled Polymer Composites for Direct Injection Molding of Bipolar Plates
Authors: Kypta Chadwick J , Young Brian A , Santamaria Anthony , Hollinger Adam S 
Published: November 2022

Fuel cell bipolar plates are commonly fabricated from graphite and stainless steel, however machining intricate channels into these materials can be a costly and time-consuming process. For this reason, we are exploring injection molding of polymer composite bipolar plates. Polymer composites offer the potential for lightweight, low-cost plates [1]. Several factors impact the ability of a polymer composite to conduct electricity. The geometry, filler weight percentage, dispersion, and the physical properties of the fillers are important in forming an electrical pathway through the composite. In this study, polymer composites based on nylon were injection molded with different weight percentages of conductive filler. Initially, carbon fiber was added to nylon at weight percentages ranging from 10 to 50%. Results show that the percolation threshold for carbon fiber in nylon occurs around 25 wt%. While carbon fiber loadings beyond 50 wt% would further increase conductivity, the increased viscosity of the polymer blends can inhibit proper injection molding.
Multiwalled carbon nanotubes were then added to the direct injection-molded nylon/carbon fiber composites to investigate the synergistic effects of multiple conductive fillers [2]. By introducing carbon nanotubes into the polymer matrix, the nanotubes act as a bridge between the carbon fibers. SEM images show that the MWCNTs fill the void between each fiber due to their smaller size and their ease of dispersion. This bridging creates more conductive pathways within the composite, thereby increasing the electrical conductivity. Samples with MWCNTs reached conductivities nearing the United States Department of Energy technical target for bipolar plate conductivity (> 100 S/cm).

Mighri, F.; Huneault, M. A.; Champagne, M. F., Electrically conductive thermoplastic blends for injection and compression molding of bipolar plates in the fuel cell application. Polymer Engineering and Science 2004,
44 (9), 1755-1765.

Zameroski, R.; Kypta, C. J.; Young, B. A.; Sanei, S. H. R.; Hollinger, A. S., Mechanical and Electrical Properties of Injection-Molded MWCNT-Reinforced Polyamide 66 Hybrid Composites. Journal of Composites Science 2020,
4 (4), 14.

Figure 1
High Volume Fuel Cell Stack Manufacturing
Authors: Swider-Lyons Karen , Ramani Manikandan , Carlstrom Chuck , Lawler John , Owejan Jon 
Published: November 2022

Plug Power is a world leader in fuel cell stack and fuel cell systems manufacturing, with over 50,000 fuel cells in the field for materials handling and stationary power applications. Plug Power is using this success to develop new markets in range-extenders for delivery vans, heavy duty vehicles, and aerospace. The rapid growth of Plug Power’s fuel cell technology has brought new challenges with high volume manufacturing. An individual cell needs to be made in less than 5 seconds, and then sealed and stacked rapidly and reproducibly.
This talk will review some of the general approaches that Plug Power is taking toward high-volume stack manufacturing. We will also review two programs funded by the U.S. Department of Energy on high volume manufacturing, and novels ways toward low cost, high volume manufacturing.
Setting Development Targets for Fuel Cells and Systems for Heavy-Duty Trucks Using a Comprehensive Model-Based Approach
Authors: Watanabe Takao , Shibata Masao , Fukaya Norihiro , Nagai Tomoyuki , Suzuki Takahisa 
Published: November 2022

For a carbon-neutral society to be realized, widespread use of fuel cells for transportation applications would be effective. The widespread use of fuel cells, in turn, requires improvements in the durability and energy conversion efficiency when fuel cells are used in high-load, long-time use applications, such as heavy-duty trucks (HDTs), construction machinery, railroads, and ships. Enhancing their durability and efficiency would require improving the performance of fuel cells and appropriately assigning performance targets to the hybrid system configuration, including batteries and radiators, and the control system. However, the performance target for each component remains unclear. This is due to the lack of a comprehensive study to reasonably assign the requisites for each component to achieve the system requirement, such as the durability and fuel economy targets of HDTs.
Few studies have comprehensively proposed how individual components should be developed to satisfy the fuel cell system requirements. Cullen et al [1] discussed the development targets of fuel cell materials from the HDT requirements. Additionally, performance targets of individual components must be set to minimize the total cost, including durability and replacement, total fuel, and initial costs. Furthermore, a comprehensive model that can calculate the total cost of HDTs while accounting for the efficiency degradation due to long time use of fuel cells is also required.
In this study, we propose a procedure to set the development targets of individual components by minimizing the total cost of HDTs. A mathematical model that combines a fuel cell performance model, degradation models, and a power management control model is employed to bridge the gap between the components’ properties and the system performance. Optimization using this model allows candidates to be found for the optimal I-V polarization curve, the system configuration of fuel cell stacks, batteries, and radiators, and their control algorithms. In the presentation, after showing the proposed procedure and the model, the development targets of the polarization curves, system configurations, and control specifications will be discussed.

Reference

[1] D. A. Cullen, et.al, NATURE ENERGY. 6, pp.462-474 (2021).
Crown Ether As a Chemical Stabilizer for Enhanced Cerium Stability and Radical Scavenging in Proton Exchange Membranes
Authors: Agarwal Tanya , Komini Babu Siddharth , Sievert Allen , Park Andrew M , Hopkins Tim , Advani Suresh , Prasad Ajay Krishna , Borup Rod L. 
Published: November 2022

Nafion is one of the standard proton exchange membranes that serves as the electrolyte membrane in fuel cells. However, it has been found to chemically degrade over time due to the generation of harmful peroxide and hydroxyl radicals. Attack by such radicals on the Nafion side chains causes polymer chain unzipping, and the membrane loses its mechanical integrity over time [1]. Cerium is proven to be an effective radical scavenger due to rapid transition between its +3 and +4 oxidation states and regenerates swiftly in the fuel cell environment. However, over time, cerium migrates due to the electrochemical potential, high water flux, and ionic diffusion [2] [3]. To resolve this issue, we functionalized a fraction of the side chains of Nafion with crown ether to complex with cerium and thereby prevent its migration. Crown ether has shown the ability to enhance cerium stability in recent studies [4] [5]. Cerium complex formation with crown ether was studied using UV visible spectroscopy, and enhanced retention was verified by testing drop in cerium concentration in the acidic medium, and migration of cerium under an external potential gradient. Membrane durability testing was conducted to verify that the stabilized membrane indeed shows higher lifetime in fuel cell operation.
[1] F. D. Coms, “The Chemistry of Fuel Cell Membrane Chemical Degradation,” ECS Transactions, 16(2): 235–255 (2008).
[2] S. M. Stewart, D. Spernjak, R. Borup, A. Datye, and F. Garzon, “Cerium Migration through Hydrogen Fuel Cells during Accelerated Stress Testing,” ECS Electrochemistry Letters, 3(4): F19–F22 (2014).
[3] Baker, Andrew M., et al. ''Cerium ion mobility and diffusivity rates in perfluorosulfonic acid membranes measured via hydrogen pump operation.'' Journal of The Electrochemical Society 164.12 (2017): F1272.
[4] Park, Junghwa, Yongman Park, and Dukjoon Kim. ''Chemical stability enhancement of crown ether grafted sulfonated poly (arylene ether ketone) fuel cell membrane by cerium ion fixation.'' Journal of Polymer Science Part A: Polymer Chemistry 57.2 (2019): 101-109.
[5] Tinh, Vo Dinh Cong, and Dukjoon Kim. ''Enhancement of oxidative stability of PEM fuel cell by introduction of HO• radical scavenger in Nafion ionomer.'' Journal of Membrane Science (2020): 118517.