Large Voltage Research Articles

Inhibition of BK channels by GABAb receptors enhances intrinsic excitability of layer 2/3 vasoactive intestinal polypeptide-expressing interneurons in mouse neocortex.

GABAb receptors (GABAbRs) affect many signalling pathways, and hence the net effect of the activity of these receptors depends upon the specific ion channels that they are linked to, leading to different effects on specific neuronal populations. Typically, GABAbRs suppress neuronal activity in the cerebral cortex. Previously, we found that neocortical parvalbumin-expressing cells are strongly inhibited through GABAbRs, whereas somatostatin interneurons are immune to this modulation. Here, we employed in vitro whole-cell patch-clamp recordings to study whether GABAbRs modulate the activity of vasoactive intestinal polypeptide-expressing interneurons (VIP-INs) in layer (L) 2/3 of the mouse primary somatosensory cortex. Utilizing machine learning algorithms (hierarchical clustering and principal component analysis), we revealed that one VIP-IN cluster (about 68% of all VIP-INs) was sensitive to GABAbR activation. Paradoxically, when recordings were performed in standard conditions with high extracellular Ca2+ level, GABAbRs indirectly inhibited the activity of large conductance voltage- and calcium-activated potassium (BK) channels and reduced GABAaR-mediated inhibition, leading to an increase in intrinsic excitability of these interneurons. However, a classical inhibitory effect of GABAbRs on L2/3 VIP-INs was observed in modified artificial cerebrospinal fluid with physiological (low) Ca2+ concentration. Our results are essential for a deeper understanding of mechanisms underlying the modulation of cortical networks. KEY POINTS: Layer 2/3 vasoactive intestinal polypeptide-expressing interneurons (VIP-INs) in the mouse somatosensory cortex cluster into three electrophysiological types differentially sensitive to GABAb receptors (GABAbRs). The majority of VIP-INs (type 1, about 68% of all VIP-INs) are regulated through pre- and postsynaptic GABAbRs, while a subset of these interneurons (types 2 and 3) is controlled only presynaptically. The net effect of GABAbR activation on VIP-IN excitability depends on [Ca2+] in artificial cerebrospinal fluid. When [Ca2+] is high (2.5mM), GABAbRs indirectly inhibit BK channels and reduce GABAaR inhibition leading to increased intrinsic excitability of type 1 VIP-INs. When [Ca2+] is low (1mM), which is more physiological, BK channels do not regulate the intrinsic excitability of VIP-INs and thus postsynaptic GABAbRs canonically decrease the intrinsic excitability of type 1 VIP-INs.

A Large Voltage Responsivity Pyroelectric Sensor Based on Hot-Pressed Lead Zirconate Titanate Ceramic

In this article, hot-pressed PZT ceramics were used as a sensitive element material and made into a pyroelectric chip. Three current mode sensors were fabricated using a pyroelectric chip of different thicknesses (80 μm, 40 μm, and 30 μm). The voltage responsivity of sensors reached the order of magnitude of 105. The size effect resulting from varying the thickness was studied. The results indicate that as the thickness decreases, the performance significantly increases. When the modulation frequency is 10 Hz, the specific detectivity of the sensor with a 30 μm PZT ceramic pyroelectric chip reaches 5.3 × 108 cm·Hz1/2/W.

Magnetic‐Field Induced Charge Accumulation in Scalable Magnetoelectric PVDF‐TrFE/Ni Composite Devices

AbstractThis study investigates the direct magnetoelectric effect in thin film composites comprising a 550 nm thick poly(vinylidene fluoride‐trifluoroethylene) (PVDF‐TrFE) layer spin‐coated onto a 500 µm thick Ni foil substrate. Direct measurements of charge accumulation on dot capacitors with Au top electrodes, induced by the rotation of Ni magnetization from in‐plane to out‐of‐plane orientation by an applied magnetic field, reveal pronounced magnetoelectric coupling. Polarization differences between in‐plane and out‐of‐plane magnetization states of up to (13.8 ± 0.8) × 10−4 µC cm−2 are derived from charge measurements. This corresponds to a maximum open circuit voltage difference of up to 75 ± 6 mV and a magnetoelectric coupling coefficient with respect to magnetization changes of 310 ± 27 mVA−1. Finite element simulations using COMSOL Multiphysics corroborate experimental findings, indicating near‐independence of generated polarizations and open circuit voltages when lateral capacitor dimensions are reduced into the nanometer range. Simulations of nanoscale pillar devices on rigid substrates, employing materials with optimized piezoelectric and magnetostrictive parameters, predict the potential for generating large open circuit voltage differences exceeding 2 V, highlighting the prospects of such devices for spintronic applications.

The NMDAR-BK channelosomes as regulators of synaptic plasticity.

Large conductance voltage- and calcium-activated potassium channels (BK channels) are extensively found throughout the central nervous system and play a crucial role in various neuronal functions. These channels are activated by a combination of cell membrane depolarisation and an increase in intracellular calcium concentration, provided by calcium sources located close to BK. In 2001, Isaacson and Murphy first demonstrated the coupling of BK channels with N-methyl-D-aspartate receptors (NMDAR) in olfactory bulb neurons. Since then, additional evidence has confirmed this functional coupling in other brain regions and highlighted its significance in neuronal function and pathophysiology. In this review, we explore the current understanding of these macrocomplexes in the brain, the molecular mechanisms behind their interactions and their potential roles in neurodevelopmental disorders, paving the way for new treatment strategies.

Solvent Engineering-Enabled Surface Defect Passivation in Cu2ZnSn(S,Se)4 Solar Cells with Low Open-Circuit Voltage Losses and Improved Carrier Lifetime.

The efficiency of earth-abundant kesterite Cu2ZnSn(S,Se)4 (CZTSSe) solar cells has been lagging behind the Shockley-Queisser limit primarily due to the presence of deep-level defects. These deep-level defects cause critical issues such as short carrier diffusion length, significant band tailing, and a large open-circuit voltage (Voc) deficit, ultimately leading to low device efficiency. To address these issues, we propose a post-fabrication defect healing strategy by dip-coating the CZTSSe film in dimethylformamide (DMF) solvent. Immersing the absorber layer in DMF (a polar solvent), neutralizes CuSn antisite defects through chemical bonding and facilitates the formation of a dense, smooth CZTSSe film with larger grain size. Deep-level transient spectroscopy revealed a remarkable increase in carrier diffusion length from 93 nm (control device) to 142 nm (champion device), confirming the beneficial effect of solvent-assisted post-treatment on mitigating CuSn antisite defects. The reduction in defect densities led to a decrease in Voc deficit by up to 289 mV, accompanied by an increased champion device efficiency of 11.4 %. This work highlights the huge potential of the DMF post-treatment strategy for defect healing in CZTSSe solar cells.

Is SiC a Predominant Technology for Future High Power Electronics?: A Critical Review

: Due to the magnificent properties of Silicon Carbide (SiC), such as high saturation drift velocity, large operating temperature, higher cut-off and maximum frequency (fT and fmax), high thermal conductivity and large breakdown voltages (BV), it is desirable for high power electronics. With the latest advancements in semiconductor materials and processing technologies, diverse high-power applications such as inverters, power supplies, power converters and smart electric vehicles are implemented using SiC-based power devices. Especially, SiC MOSFETs are mostly used in high-power applications due totheir capability to achieve lower switching loss, higher switching speed and lower ON resistance than the Si-based (Insulated gate bipolar transistor) IGBTs. In this paper, a critical study of SiC MOSFET architectures, emerging dielectric techniques, mobility enhancement methods and irradiation effects are discussed. Moreover, the roadmap of Silicon Carbide power devices is also briefly summarized.

Direct evaluation of effective hole mobility in multilayer organic light-emitting diodes using the MIS-CELIV technique

Abstract To optimize carrier balance in organic light-emitting diodes (OLEDs), it is crucial to gather data on the charge transport properties of organic semiconductors as measured within a functioning device. In this study, we directly investigated the hole mobility of the N,N′-diphenyl-N,N′-bis(1-naphthyl)-1,1′-biphenyl-4,4′-diamine (α-NPD) layer in multilayer OLEDs with various hole injection layers (HILs). This was achieved using the metal–insulator–semiconductor charge extraction by linearly increasing voltage (MIS-CELIV) technique, which utilized hole accumulation at the α-NPD/8-hydroxyquinoline aluminum (Alq3) interface. Our findings confirmed that hole mobilities evaluated via MIS-CELIV with sufficiently large offset voltages were more reliable, as the space-charge-limited extraction was realized through adequate hole accumulation at the α-NPD/Alq3 interface. Moreover, the hole mobility in the multilayer OLED configuration, as assessed by MIS-CELIV, reflects not only the hole transport properties of the α-NPD layer but also the hole injection properties at the HIL/α-NPD interface.

Cobalt nanoparticles decorated hollow N-doped carbon nanospindles enable high-performance lithium-oxygen batteries.

Despite the ultrahigh theoretical energy density and cost-effectiveness, aprotic lithium-oxygen (Li-O2) batteries suffer from slow oxygen redox kinetics at cathodes and large voltage hysteresis. Here, we well-design ultrafine Co nanoparticles supported by N-doped mesoporous hollow carbon nanospindles (Co@HCNs) to serve as efficient electrocatalysts for Li-O2 battery. Benefiting from strong metal-support interactions, the obtained Co@HCNs manifest high affinity for the LiO2 intermediate, promoting formation of ultrathin nanosheet-like Li2O2 with low-impedance contact interface on the Co@HCNs cathode surface, which facilitates the reversible decomposition upon charging. The mesoporous hollow nanospindles can provide abundant electron/ions transport channels to synergistically accelerate the formation and decomposition of discharge products. The Li-O2 battery based on Co@HCNs displays remarkably reduced discharge/charge polarization of 0.92V, impressive rate performance, and stable operation for 250 cycles. This work will provide a new avenue to design advanced oxygen electrocatalysts for high-performance Li-O2 battery.

A Soft Start Method for Doubly Fed Induction Machines Based on Synchronization with the Power System at Standstill Conditions

Due to their exceptional operational versatility, doubly fed induction machines (DFIM) are widely employed in power systems comprising variable renewable energy-based electrical generation sources, such as wind farms and pumped-storage hydropower plants. However, their starting and grid synchronization methods require numerous maneuvers or additional components, making the process challenging. In this paper, a soft start method for DFIM, inspired by the traditional synchronization method of synchronous machines, is proposed. This method involves matching the frequencies, voltages, and phase angles on both sides of the main circuit breaker, by adjusting the excitation through the controlled power converter at standstill conditions. Once synchronization is achieved, the frequency is gradually reduced to the rated operational levels. This straightforward starting method effectively suppresses large inrush currents and voltage sags. The proposed method has been validated through computer simulations and experimental tests, yielding satisfactory results.

Dual-mode arrayed vibration-wind piezoelectric energy harvester

Piezoelectric patches are extensively utilized in sensor technology and energy harvesting owing to their uncomplicated design. This research proposes a dual-mode arrayed piezoelectric energy harvester for the efficient harvesting of vibrational and wind energy from the environment. This research elucidates the structure and operational principle of the dual-mode arrayed vibration-wind piezoelectric energy harvester. The theoretical model of the proposed energy harvester was meticulously derived, followed by a Comsol simulation of its piezoelectric electrical performance, and a Fluent simulation study of the natural wind disturbance flow was established. The wind energy harvesting test bench was constructed to carry out the wind energy harvesting assessment. The vibration tests of the sinusoidal sweep frequency, fixed frequency, and railroad spectrum of the energy harvester were conducted using the shaker. The results indicate that the simulated resonance frequencies nearly align with the measured resonance frequencies, and the large voltage output of the harvester varies from 6 to 20 Hz, enhanced by the coupling effect of the magnet’s restoring force. The feasibility of the energy harvester for energizing low-power consumption devices was validated under the measured rail acceleration. The dual-mode arrayed vibration-wind piezoelectric energy harvester presented in this research offers a solution for the self-powered sensors used in freight train hook force detection and plateau intelligent agriculture.

(Invited) Preparation of Boron-Doped Nanodiamond and Its Application to Aqueous Electrochemical Capacitors

Boron-doped diamond (BDD) is known to be a functional electrode material that can be used in various electrochemical applications such as sensitive electroanalysis and efficient electrolysis, based on the unique electrochemical properties including wide potential window and low background current, as well as extreme physical/chemical stabilities. Usually, BDD electrodes are prepared by deposition of a polycrystalline BDD thin film on a conductive substrate. In this form, the specific surface area is too small to be used as an electrochemical capacitor. Thus, we have developed boron-doped nanodiamond (BDND) powder as a conductive diamond powder with a large specific surface area. BDND exhibits wider potential window in aqueous electrolytes than activated carbon (AC). Therefore, the BDND is expected to be used for an electrode material of aqueous EDLC with a large cell voltage.Nanodiamond powder (primary particle size: 4 nm) was used as a substrate material for BDND. BDD was deposited on the agglomerate of dry nanodiamond powder via microwave plasma-assisted chemical vapor deposition (CVD). The as-deposited BDND was then treated by air oxidation at 425 °C to minimize sp2 carbon components to obtain BDND. Test electrode was prepared by casting an ink containing BDND on a glassy carbon disk electrode as a current collector. For an EDLC pouch cell, BDND paste containing PVDF binder was applied on the both sides of a titanium sheet current collector to form an electrode. Two electrodes with a separator in between was put in a plastic bag and aqueous electrolyte was poured in the bag to form a pouch cell.The BDND was found to show a relatively large specific surface area of 650 m2 g−1 and good conductivity of ~1 S cm−1. CV in 1 M H2SO4 at the BDND test electrode in a three-electrode configuration showed a wide potential window of 3 V, which was significantly wider than that of an AC test electrode (1.5 V). In a symmetric two-electrode system, cell voltage of a CV in 1 M H2SO4 was found to be larger at the BDND electrode (1.8 V) than at the AC electrode (0.8 V). Therefore, wide potential window of the BDND was confirmed to be useful for creation of an aqueous EDLC with a large cell voltage. In addition, the use of saturated NaClO4 as an electrolyte was shown to be effective for an extremely large cell voltage of 2.8 V, which can further enlarge the energy and power densities of an aqueous EDLC. CV of BDND/saturated NaClO4 system exhibited a high energy density of 20 Wh kg−1 and a high power density of 104 W kg−1. Similar charge-discharge properties were also shown at EDLC pouch cells with BDND/concentrated NaClO4 system.

Dual Side Passivation Strategy with Multifunctional Organic Molecules for High Performance Wide Bandgap Perovskite Solar Cells

Perovskite-based tandem solar cells have received great attention, however, the wide bandgap (WBG) perovskite solar cell (PSC) used as the top layer still faces issues to overcome, including large open-circuit voltage (V OC) loss and halide segregation. Over the years, small organic molecules have been introduced at the interfaces between perovskite and charge transport layers to mitigate V OC losses, by passivating interfacial defects. Herein, we propose novel multifunctional organic molecules, i.e., octylammonium (OA) and N-methylsulfanilic acid (NMSA), at the top and bottom sides of perovskite light absorbing layer. We investigated the distinct roles of OA and NMSA components and examined the effects of passivation depending on the position of interfacial treatment such as bottom, top and dual sides of perovskite. It is observed that V OC deficits decreased from 0.58 V to 0.44 V, leading to the increase of the power conversion efficiency (PCE) from 16.24% to 19.83% for the 1.77 eV WBG PSCs. Furthermore, we demonstrate that halide segregation is significantly suppressed. The optimized WBG PSC maintained 98.9% of its initial PCE after 3300 seconds under 1-sun illumination, demonstrating enhanced maximum power point tracking stability. This study contributes to the development of next-generation high-performance PSCs, providing a deeper understanding of interfacial defect engineering.

Boost efficiency with buffer and bottom stack optimization in Cu2BaSn(S,Se)4 solar cells by simulation

Cu2BaSn(S,Se)4 is gaining tremendous attention as a potential absorber due to its non-toxicity, earth abundance, and low antisite defects opposing Cu2ZnSn(S,Se)4. However, the highest experimental efficiency of 6.17 % is achieved with the device structure Al:ZnO/Mg:ZnO/Zn1-xCdxS/Cu2BaSn(S,Se)4/Mo where the drawback is large open circuit voltage (VOC) loss stemming from the large cliff at the absorber/buffer interface and back contact recombination. Therefore, finding a suitable non-toxic buffer with modification of the bottom stack is crucial. In this regard, Cu2BaSn(S,Se)4 solar cells based on diverse buffers are numerically simulated using SCAPS-1D with Ni as back contact and introducing back surface field (BSF) at the absorber/Ni interface. At first, a baseline model validating the experimental efficiency is designed. The application of Ni enhanced efficiency to 7.92 % due to the formation of ohmic contact. Further, it is improved to 9.91 % with anti-reflection coating. Afterward, a total of 780 solar cells were designed with six buffer and eight BSF combinations by optimizing the absorber, buffer, and interface properties where the highest efficiency of 28.11 % with incredible fill factor (90 %) and less VOC loss (0.24 V) is accomplished for the Al:ZnO/Mg:ZnO/TiO2/Cu2BaSn(S,Se)4/CuI/Ni solar cell. Further, the importance of BSF is analyzed via energy band diagrams, Mott-Schottky and Nyquist plots. The outcomes disclosed that the BSF greatly influences the energy band alignment, built-in potential, depletion width, and recombination resistance of solar cells, underscoring its significance in improving performance. Overall, the present work proposes an efficient strategy to modify the device configuration of Cu2BaSn(S,Se)4 solar cells to enhance their efficiency.

Grain Boundary Passivation of Wide Bandgap Perovskites using Inorganic Potassium Lead Halides for Tandem Solar Cells

Wide bandgap (WBG) perovskite solar cells (PSCs) are a crucial component in advancing perovskite-based tandem solar cells for absorbing high-energy photons. However, increasing Br to I ratio in WBG perovskites decreases the formation energy, leading to rapid crystallization and small grain size. Consequently, the numerous grain boundaries are formed with charged defects such as vacancies, interstitials, and undercoordinated ions, leading to large open circuit voltage (V OC) deficits and severe halide segregation under continuous light illumination. Therefore, passivating grain boundary defects is essential for achieving high V OC and enhanced stability. Here, we introduce an effective strategy to passivate the grain boundaries with an inorganic protective layer as well as to reduce the density of grain boundaries on perovskite film, by incorporating potassium thiocyanate (KSCN) into I-Br mixed halide WBG perovskites. The incorporation of KSCN into the mixed halide forms band-shaped barriers on the film along the grain boundaries. Meanwhile, the KSCN enlarges the grains of the mixed halide film, which is attributed to the effect of SCN ions, as is well-known. The incorporation of potassium thiocyanate dramatically increases the fill factor and V OC of WBG (1.82 eV) single junction PSCs owing to reduced trap density, achieving a high power conversion efficiency of 18.02%. Furthermore, both operational and shelf stability are improved with retarded light-induced halide segregation. Using the passivated WBG sub-cells, monolithic all-perovskite tandem solar cells are demonstrated.

Separation of Electrochemical Signals By Ohmic Drop between Electrodes Arranged in a Matrix Configuration

1.introduction Combining electrochemical principles and microfabrication techniques can achieve high sensitivity and miniaturization of sensing devices. However, commonly used three-electrode systems increase the number of contacts paid and manufacturing costs with the integration of electrodes. Array electrodes are advantageous as a solution to this problem. Array electrodes share contact pads, making them easy to integrate and suitable for multiple detections. The single-channel array electrode electrochemical system used in this study (Figure 1a) consists of an array electrode as the detection part and a polydimethylsiloxane (PDMS) flow channel as the separation signal part. In previous studies of array electrodes, multi-channel was used to separate the signals, and no attempt was made to achieve the separation of electrochemical signals in the same channel. This study achieved signal separation within a single channel by controlling the ohmic drop. 2.Experimental Figure 1a shows the equipment used in this study. Four working electrode platinum strips and two platinum counter electrodes were formed orthogonally. The silver strip of the reference electrode is inserted between the working and counter electrodes. The polyimide layer opens at the orthogonal intersections. These 8 openings form 8 detectable electrochemical sensing regions.In order to investigate the impact of ohmic voltage drop, a polydimethylsiloxane (PDMS) flow channel was devised. As shown in Figure 1b, the left working electrode was deliberately insulated, leaving only the right working electrode operational. The large ohmic drop case and the small ohmic drop case can be obtained by changing the left and right reference electrodes and counter electrodes.As the working electrodes used for detection are moved away from the reference electrodes, the ohmic drop becomes larger. When the working electrodes used for detection are located away from the reference electrodes, the ohmic drop becomes larger. At this working electrode, oxidation or reduction reactions are difficult to realize because of the large ohmic drop. As a result, the signals at the sensing site used for detection (intersection point) will be separated and detected. To discern the effects of varying ohmic drops, cyclic voltammetry（CV）and differential pulse voltammetry (DPV) data were collected. This involved the systematic replacement of both the left and right reference electrodes as well as the counter electrodes. K4[Fe(CN)6] was used to obtain the peak current and KCl was used as the electrolyte. 3.Result and Discussion Figure 1c shows the differential pulse voltammetry results obtained for the sensing region within the PDMS flow channel. A clear current peak can be seen in the small ohmic drop case, and almost no current change can be observed in the large ohmic drop case. The sensing regions at the intersections have a small ohmic drop and the sensing regions work normally. The non-crossing sensing region is affected by a large ohmic voltage drop and cannot reach the oxidation or reduction potential. In Figure 1d, red line shows the cyclic voltammetry result obtained for the sensing region without the insulating layer on any working electrode. Green line shows the cyclic voltammetry result with the insulating layer on one working electrode (large ohmic drop one). It can be seen that the working electrode at a distance from the reference electrode produces almost no electrochemical signal, as the two results are very similar. Combining these two experiments, we can conclude that it is practicable to use ohmic drop to separate electrochemical signals.The device enables a high degree of integration and simple sample injection. This study provides a new platform for the field of multiplexed detection. Reference 1. Zhang, Huijie, et al. Analytical chemistry 89.11 (2017): 5832-5839.2. Ino, Kosuke, et al. Electrochemistry Communications 77 (2017): 76-80. Figure 1

(Invited) Organic Floating-Gate Transistors for Printable Nonvolatile Memory and Optoelectronic Device Applications

There has been considerable interest in the development of nonvolatile memories using organic materials owing to their potential use in flexible and printed electronic devices. In recent years, organic field-effect transistors (OFETs) having floating-gate structures as the charge storage layer have attracted increasing interest because they allow achieving large threshold voltage (Vth ) shifts and a relatively long retention time with a simple device configuration. However, the fabrication of floating-gate OFET memories by solution processes is generally difficult because it often suffers from the mixing of soluble organic materials at their interfaces. In previous studies, we have developed solution-processable floating-gate OFET memories by using top-gate/bottom-contact OFETs based on polymer semiconductors and the vertical phase separation behavior in the solution-processed composite film of a polymer insulator (PMMA or polystyrene) and a soluble small-molecule semiconductor (TIPS-pentacene) [1-3]. Here, I report the memory characteristics of solution-processed floating-gate OFET memories using a typical p-type polymer semiconductor of polythiophenes (P3HT and PBTTT) and an ambipolar polymer semiconductor based on diketopyrrolopyrrole (DPP) and their usefulness for the development of printable nonvolatile memories and image sensing devices with high functionality.Figure 1(a) shows the typical structure of our memory devices. Since a variety of orthogonal solvents are available for polymer semiconductors, the organic charge storage layer composed of PMMA and TIPS-pentacene molecules can be deposited onto the semiconductor layer by spin coating using butyl acetate. During thermal annealing at 100 ºC, TIPS-pentacene molecules segregate to the upper side of the composite film through vertical phase separation, and floating-gate electrodes consisting of TIPS-pentacene and organic tunneling layers are simultaneously formed by solution processes.Figure 1(b) shows the energy band diagram of the P3HT-based organic FET memory during the programming process. Because P3HT has a shallow LUMO level compared to the work function of the Au source-drain electrodes, the P3HT FET memory shows only a negligible Vth shift when programmed in the dark. Under light illumination, the device exhibits a large Vth shift of over 30 V by storing photogenerated electrons into TIPS-pentacene floating gates. To investigate the applicability of the OFET memories to large-area image sensors, the imaging of a black and white pattern using the recorded drain currents of the memory array under light illumination has been demonstrated [Fig. 1(c)]. We also found that P3HT FET memories with organic semiconductor floating gates exhibit light-intensity dependent synaptic characteristics when programmed under red light, enabling the enhancement of the functionality of organic image sensors.In contrast to OFET memories based on polythiophenes, DPP-DTT FET memories can be programmed in the dark because of the deep LUMO level and good electron transport property of DPP-DTT. It was also found that the electrical characteristics of DPP-DTT TFT memory devices depend on the difference of work function of source-drain and gate electrodes and tuning the energy level difference enables ambipolar carrier trapping and good retention characteristics [Fig. 1(d)]. The DPP-DTT FET memories having hole trapping characteristics also achieve NAND-like memory operations as memory devices are connected in series.

(Digital Presentation) Clarification Using Jarzynski’s Equality for Three Unexplained Experimental Results in SOFCs Using Sm-Doped Ceria Electrolytes Based on Wagner’s Equation

A solid oxide fuel cell (SOFC) converts chemical energy from a fuel gas, such as hydrogen or methane, to electrical energy. In yttria-stabilized zirconia (YSZ) films, only oxygen ions are carriers; thus, these films are often used as electrolytes. In these cases, the open-circuit voltage (OCV = 1.15 V at 1073 K) is equal to the Nernst voltage (Vth = 1.15 V at 1073 K).Samaria-doped ceria (SDC) has a higher ionic conductivity than YSZ. Therefore, SDC films are potential electrolyte candidates. However, when SDC electrolytes are used in SOFCs, the OCV at 1073 K is only 0.80 V. This voltage loss can be explained by Wagner’s equation.Numerous subsequent models have been created based on Wagner’s equation. The current-voltage relationship can be calculated with the cathode and anode polarization voltage losses using the Riess model [1]. Furthermore, Duncan and Wachsman developed a nonlinear model [2]; this model could also be used to clarify the equilibration process.According to the Riess model, the OCV should decrease during electrode degradation. However, experimentally, the OCV does not change during electrode degradation [3]. The change in the equilibration of the thick SDC electrolytes with respect to a change in the anode gas has not yet been clarified using the model of Duncan and Wachsman. Experimentally, when a very thick (6.6 mm) SDC electrolyte is used, the OCV can reach 0.80 V in only 5 minutes [4]. According to Weppner, the corresponding delay in the electron diffusion current should be more than 2080 minutes [5].We proposed a current-independent anode voltage loss (1.15 V-0.80 V=0.35 V) [6]. Since large leakage currents in the SDC electrolytes do not occur, our explanations appear to deviate from Wagner’s equation. However, we noted that the lack of large leakage currents in the SDC electrolytes is only a side effect. When an SDC electrolyte experiences a large anode voltage loss (0.35 V), the leakage current is very low. This phenomenon is called the “anode shielding effect” [7].The ionic activation energy of the SDC electrolyte is 0.7 eV (0.35 V×2e=0.7 eV). During the ion hopping processes in the SDC electrolytes, the work done by ions on the surrounding lattice structure is 0.7 eV. Thus, the ions should regain 0.7 eV after hopping. However, when many electrons are present in the hopping path, the hopping process becomes very complex.Jarzynski’s equality is defined by the Helmholtz energy [8]. Here, the ionic activation energy must be defined as the Gibbs energy. During the ion hopping processes, the PVs change, and the maximum PVs are equal to the ionic activation energies. The above two experimental results occur when the final PVs during the work loss are unchanged and isothermal process under the same temperature of the heat reservoir. Since the ΔPVs are zero, Jarzynski’s equality can be used.In our third experiment, the cell used contained a 500-mm thick polished YSZ electrolyte on the cathode side, which is in direct contact with a 970-mm thick polished SDC electrolyte on the anode side. The measured OCV was 819 mV at 1073 K; this value was clearly higher than 800 mV [9]. The ionic activation energy of the YSZ electrolyte was 1.1 eV. In this case, the final PVs during the work loss were unchanged, but the final PVs before the work loss were changed from 1.1 eV to 0.8 eV. Since the ΔPVs were not zero, the voltage for compensation (Vcomp) due to the change in activation energy is as follows:Vconp = kBT/2e×ln(1.1 eV/0.7 eV) (1)The value of 19 mV (819 mV-800 mV=19 mV) was small. However, this value can be increased using any other electrolyte instead of YSZ.Consequently, the three unexplained experimental results can be explained by Jarzynski’s equality.

Highly Ionic Conductive Polymer Interlayer for Garnet-Type Solid Electrolyte to Improve Energy Storage Performance of All-Solid-State-Batteries

Garnet-type Li6.4La3Zr1.4Ta0.6O12 (LLZTO) has been spotlighted as a promising solid-state-electrolyte for all-solid-state lithium metal batteries (ASSBs) due to high ionic conductivity, superior chemical stability against Li metal, and broad window potential (0~5 V versus Li/Li+). However, an insufficient solid-solid contact between the electrode and electrolyte brings about high interface resistance, low Coulombic efficiency, and large voltage polarization during cycling. To overcome these challenges, it is a desirable tactic to introduce an ionic conductive polymer interlayer such as novel modified polyethylene oxide (PEO). Herein, we fabricated ASSB structures that employed polyoxanorbornene-based bottlebrush polymers with PEO side chains as interlayers between the cathode and the electrolyte layer. This polymer exhibits semi-crystallinity and showcases high ionic conductivity (~0.63 mS cm-1) at room temperature due to the presence of the polyoxanorbornene backbone, which acts as an additional ion conductive agent alongside the PEO side chain, thus overcoming typical conductivity issues associated with using PEO-based materials. The resultant ASSB composed of the highly conductive polymer (HCP) interlayer demonstrates outstanding electrochemical performance including an improved specific capacity, rate performance, and cycling stability at room temperature, compared to the PEO interlayer. We will disclose data both describing the functional materials used as well as the performance of the test cells that were assembled.

(Invited) A Comparative Evaluation of Li, Na, and K-Ion Cathodes

Most cathode materials for Li-ion batteries are layered oxides which are isostructural to LiCoO2. Other structures, such as spinels, olivines, and disordered rocksalts, can also be used as high-capacity cathodes. The latter three structures types create less resource issues as they can function with Fe or Mn as active transition metals, but still may suffer from resource issues related to Li-ion availability.With Na, almost all transition metals form layered structures, providing less expensive and more resource abundant options for Na-ion cathodes, but typical layered cathodes have a large voltage slope which limits the usable energy density. The voltage slope is even larger when K is used as an intercalant in layered materials. I will discuss the origin of the voltage slope in these materials and evaluate whether better cathode options are available for Na and K-ion batteries.

Materials Science Aspects and Performance of High Power Magnetically Ordered Pseudocapacitors

This investigation was motivated by increasing interest in magnetically ordered pseudocapacitor (MOPC) materials for applications in high-power pseudocapacitors and water purification devices. MOPCs exhibit capacitance enhancement due to the magnetohydrodynamic effect and interesting magnetocapacitive effects, which result in influence of charge/magnetization on magnetic/pseudocapacitive properties.Advanced magnetic materials, such as ferrimagnetic spinels, ferrimagnetic hexagonal ferrites and ferromagnetic lanthanum strontium manganates (LSM) were studied. Electrodes with active mass loadings of 40 mg cm-2 were tested in Na2SO4 electrolytes. Chemical precipitation methods, hydrothermal synthesis and high energy ball milling techniques were used for the synthesis of nanoparticles. Capping agents, such as caffeic acid, gallic acid and murexide, were used for synthesis. The chelating groups of the capping agents facilitated their adsorption on particles and the adsorbed capping agents limited particle growth. The use of multifunctional organic capping agents-alkalizers influenced the morphology and phase content of the synthesized materials and facilitated the fabrication of electrodes with enhanced capacitance. In another approach, enhanced capacitance was achieved using redox active dispersants, such as gallocyanine and Celestine Blue, which acted as charge transfer mediators and facilitated charge transfer.Electrochemical testing was performed using cyclic voltammetry, galvanostatic charge-discharge and impedance spectroscopy. Ferrimagnetic spinels, such as CuFe2O4, Fe3O4, γ-Fe2O3, MnFe2O4 showed capacitances of 2.76, 5.82, 3.78 and 2.67 F cm-2, respectively. The high active mass electrodes showed low resistance, which was below 1 Ohm. The large voltage window, high capacitance and low resistance of the electrodes facilitated the fabrication of devices with enhanced power-energy characteristics. The electrodes were used for the fabrication of asymmetric and symmetric devices. A symmetric device, containing two ferrimagnetic MnFe2O4 electrodes showed a capacitance of 0.92 F cm-2. Asymmetric devices showed capacitances in the range of 2.4-3.2 F cm-2 in a voltage window of 1.6V.Ferrimagnetic SrFe12O19 and BaFe12O19 showed capacitances of 1.2 and 1.34 F cm-2, respectively. Good capacitive behavior was linked to beneficial effect of high energy ball milling and the use of efficient dispersant, which also acted as a charge transfer mediator. A remarkably high capacitance of 4.59 F cm-2 was achieved at a low resistance for ferromagnetic LSM electrodes. The electrodes showed good capacitance retention at fast charge-discharge rates and excellent cyclic stability.Magnetic properties of the ferrimagnetic and ferromagnetic materials were analyzed. The charging mechanisms in positive and negative potential ranges were studied. The effect of hard and soft magnetic properties on capacitive behavior was analyzed. The high active mass MOPC electrodes showed good capacitance retention at fast charge-discharge rates and enhanced power-energy characteristics.The MOFC electrodes tested in this work combine advanced charge storage properties, high spontaneous magnetization, low resistance, giant magnetoresistance and other functional properties. The obtained electrodes are promising for energy storage in supercapacitors with enhanced power-energy characteristics for operation at fast charge-discharge rates, capacitive deionization of water devices and novel applications based on magnetocapacitive effects.