Critical Performance Parameters Research Articles

Methyl ammonium iodide via novel PECVD process for the growth of 2-step vacuum based perovskite (MAPbI3) thin films

MAPbI3 thin films were grown via 2-step vacuum based processes by depositing methyl ammonium iodide (MAI) layer as first step using plasma enhanced chemical vapour deposition (PECVD) technique and then depositing lead iodide (PbI2) layer over it as second step using RF-sputtering technique. To the best of our knowledge MAI layer was deposited for the first time by PECVD technique. MAI solution for PECVD process and PbI2 target for sputtering process were made to deposit these two layers under optimized plasma conditions for the growth of MAPbI3 thin films. Characterization techniques like UV-Vis-NIR spectroscopy and Photoluminescence spectroscopy were performed to study the optical properties. Powder-XRD (PXRD) and glancing incidence XRD (GIXRD) were performed to study structural properties. SEM and cross-SEM were performed for morphological study to view top-view and cross-sectional view of the deposited MAPbI3 perovskite thin film. Perovskite thin films deposited on silicon wafer have been used as perovskite/silicon heterojunction photodiode exhibiting critical performance parameters such as rectifying ratio of 1.58 × 104 at 1.0 V, photo-sensitivity value 7.46 × 102 at light intensity 100 mw/cm2 without biasing.

Heterogeneous Catalyst as a Functional Substrate Governing the Shape of Electrochemical Precipitates in Oxygen-Fueled Rechargeable Batteries.

Lithium-oxygen batteries have the potential to become the most eminent solution for future energy storage with their theoretical energy density exceeding all existing batteries. However, the insulating and insoluble discharge product (lithium peroxide; Li2O2) impairs practical application. Conventional catalyst designs based on the electronic structure and interfacial charge transfer descriptors have not been able to overcome these limitations due to Li2O2. Herein, we revisit the role of heterogeneous catalysts as substrates to regulate Li2O2 growth and the formation of solid/solid reaction interfaces. We demonstrate that controlled solid/solid interfacial structure design is a critical performance parameter beyond the inherent electronic structure. In particular, the Cu2O substrate in this study induces a homogeneous deposition of Pd atoms, which leads to well-controlled growth of Li2O2 resolving mass and charge transport limits (i.e., the bottleneck of oxygen reduction/evolution reactions), thus improving reversibility, capacity, and durability of the cells by dissipating electrochemical and mechanical stress. We thus verified the essential role of solid/solid interfaces to regulate the nucleation and growth process of Li2O2 in lithium-oxygen batteries.

Association of Gene Variants with Seasonal Variation in Muscle Strength and Aerobic Capacity in Elite Skiers.

Background: The training of elite skiers follows a systematic seasonal periodization with a preparation period, when anaerobic muscle strength, aerobic capacity, and cardio-metabolic recovery are specifically conditioned to provide extra capacity for developing ski-specific physical fitness in the subsequent competition period. We hypothesized that periodization-induced alterations in muscle and metabolic performance demonstrate important variability, which in part is explained by gene-associated factors in association with sex and age. Methods: A total of 34 elite skiers (20.4 ± 3.1 years, 19 women, 15 men) underwent exhaustive cardiopulmonary exercise and isokinetic strength testing before and after the preparation and subsequent competition periods of the World Cup skiing seasons 2015-2018. Biometric data were recorded, and frequent polymorphisms in five fitness genes, ACE-I/D (rs1799752), TNC (rs2104772), ACTN3 (rs1815739), and PTK2 (rs7460, rs7843014), were determined with specific PCR reactions on collected DNA. Relative percentage changes of cardio-pulmonary and skeletal muscle metabolism and performance over the two seasonal periods were calculated for 160 data points and subjected to analysis of variance (ANOVA) to identify hypothesized and novel associations between performance alterations and the five respective genotypes and determine the influence of age × sex. A threshold of 0.1 for the effect size (h2) was deemed appropriate to identify relevant associations and motivate a post hoc test to localize effects. Results: The preparation and competition periods produced antidromic functional changes, the extent of which varied with increasing importance for anaerobic strength, aerobic performance, cardio-metabolic efficiency, and cardio-metabolic/muscle recovery. Only peak RER (-14%), but not anaerobic strength and peak aerobic performance, and parameters characterizing cardio-metabolic efficiency, differed between the first and last studied skiing seasons because improvements over the preparation period were mostly lost over the competition period. A number of functional parameters demonstrated associations of variability in periodic changes with a given genotype, and this was considerably influenced by athlete "age", but not "sex". This concerned age-dependent associations between periodic changes in muscle-related parameters, such as anaerobic strength for low and high angular velocities of extension and flexion and blood lactate concentration, with rs1799752 and rs2104772, whose gene products relate to sarcopenia. By contrast, the variance in period-dependent changes in body mass and peak VO2 with rs1799752 and rs2104772, respectively, was independent of age. Likely, the variance in periodic changes in the reliance of aerobic performance on lactate, oxygen uptake, and heart rate was associated with rs1815739 independent of age. These associations manifested at the post hoc level in genotype-associated differences in critical performance parameters. ACTN3 T-allele carriers demonstrated, compared to non-carriers, largely different periodic changes in the muscle-associated parameters of aerobic metabolism during exhaustive exercise, including blood lactate and respiration exchange ratio. The homozygous T-allele carriers of rs2104772 demonstrated the largest changes in extension strength at low angular velocity during the preparation period. Conclusions: Physiological characteristics of performance in skiing athletes undergo training period-dependent seasonal alterations the extent of which is largest for muscle metabolism-related parameters. Genotype associations for the variability in changes of aerobic metabolism-associated power output during exhaustive exercise and anaerobic peak power over the preparation and competition period motivate personalized training regimes. This may help to predict and maximize the benefit of physical conditioning of elite skiers based on chronological characteristics and the polymorphisms of the ACTN3, ACE, and TNC genes investigated here.

Developing Enzyme Immobilization with Fibrous Membranes: Longevity and Characterization Considerations.

Fibrous membranes offer broad opportunities to deploy immobilized enzymes in new reactor and application designs, including multiphase continuous flow-through reactions. Enzyme immobilization is a technology strategy that simplifies the separation of otherwise soluble catalytic proteins from liquid reaction media and imparts stabilization and performance enhancement. Flexible immobilization matrices made from fibers have versatile physical attributes, such as high surface area, light weight, and controllable porosity, which give them membrane-like characteristics, while simultaneously providing good mechanical properties for creating functional filters, sensors, scaffolds, and other interface-active biocatalytic materials. This review examines immobilization strategies for enzymes on fibrous membrane-like polymeric supports involving all three fundamental mechanisms of post-immobilization, incorporation, and coating. Post-immobilization offers an infinite selection of matrix materials, but may encounter loading and durability issues, while incorporation offers longevity but has more limited material options and may present mass transfer obstacles. Coating techniques on fibrous materials at different geometric scales are a growing trend in making membranes that integrate biocatalytic functionality with versatile physical supports. Biocatalytic performance parameters and characterization techniques for immobilized enzymes are described, including several emerging techniques of special relevance for fibrous immobilized enzymes. Diverse application examples from the literature, focusing on fibrous matrices, are summarized, and biocatalyst longevity is emphasized as a critical performance parameter that needs increased attention to advance concepts from lab scale to broader utilization. This consolidation of fabrication, performance measurement, and characterization techniques, with guiding examples highlighted, is intended to inspire future innovations in enzyme immobilization with fibrous membranes and expand their uses in novel reactors and processes.

Electro-chemo-mechanical finite-element model of single-crystal and polycrystalline NMC cathode particles embedded in an argyrodite solid electrolyte

All-solid-state batteries (ASSB) are emerging as a high-performance alternative to Li-ion batteries. However, some technical challenges need to be overcome before commercialization. Understanding and improving the chemo-mechanical behavior is considered one of the fundamental challenges in the development of ASSB. This work develops a continuum-level, two-dimensional finite-element model that predicts electro-chemo-mechanical responses of a cathode particle in contact with, and surrounded by, solid electrolyte. The model incorporates physics such as structural anisotropy, intergranular particle fracture, cathode embrittlement upon lithiation and cycling, and intragranular separation at cathode-electrolyte interfaces. The model results compare electrochemical performance between single-crystal and randomly oriented polycrystalline cathode particles. Additionally, performance is predicted at several operating pressures. The manuscript considers LiXNi0.8Mn0.1Co0.1O2 (NMC811) electrode particles surrounded by Li6PS5Cl (LPSC) solid-state electrolyte. The model aims to inform the design of microstructures and operating conditions that limit or prevent mechanical damage during electrochemical cycling of all-solid-state batteries. The results indicate the superior performance of single-crystal NMC811 particles with smaller sizes and higher applied pressure. The highest degradation is predicted in the first cycle. Particle size is identified as a critical parameter for composite electrode performance.

Structural behavior of steel dowel-reinforced cross-laminated bamboo and timber beams

Cross-laminated bamboo and timber (CLBT) products exemplify the efficient utilization of bamboo and timber resources, demonstrating excellent potential in sustainable structural engineering. The significant difference in mechanical properties between high-density engineered bamboo and low-density timber laminations leads to premature in-plane delamination failure and loss of ductility and energy absorption for CLBT members subjected to out-of-plane loading. This study demonstrated that vertically-driven steel dowels significantly enhanced the layer combination efficiency and addressed the above problems of CLBT. A comparison of measured critical mechanical performance parameters was presented, systematically characterizing the structural behavior of CLBT beams with steel dowels. Steel dowels in CLBT were more effective than those in cross-laminated timber at resisting high in-plane shear stress and exhibiting the progressive failure phenomenon. Although steel dowels slightly reduced the bending stiffness in some specimens, they increased the ductility and energy absorption performance, particularly in CLBT. This study provides a potential solution for improving the structural behavior of CLBT members subjected to out-of-plane loads under high in-plane shear stress conditions.

A comprehensive investigation of a water and energy-based waste integrated system: Techno-eco-environmental-sustainability aspects

In this work, a novel biomass gasifier combined energy system was offered for potable water, heating load, and power generation. The system included a gasifier, an S–CO2 cycle, a combustor, a domestic water heater, and thermal desalination unit. The plant was evaluated from various aspects, i.e., energetic, energetic, exergo-economic, sustainability, and environmental. To this aim, modeling of the suggested system was conducted by EES software; then, a parametric inquiry was carried out to detect the critical performance parameters, considering an environmental impact indicator. The results showed that the freshwater rate, Levelized CO2 emissions, total cost, and sustainability index of 21.19 kg s−1, 0.563 t.MWh−1, 13.13 $.GJ−1, and 1.53 were acquired, each. Moreover, the combustion chamber is a major fount in the irreversibility of the system. Besides, the energetic and exergetic efficiencies were computed at 89.51% and 40.87%. Overall, the offered water and energy-based waste system showed great functionality in terms of thermodynamic, economic, sustainability, and environmental standpoints by enhancing the gasifier temperature.

Povećanje efikasnosti guseničnog vozila optimizacijom prenosnih odnosa i strategije promene stepena prenosa

Introduction/purpose: Tracked vehicles play a vital role across various domains, from military operations to construction and agriculture. This study focuses on improving the efficiency of tracked vehicles by optimizing both gear ratios and gear-shifting strategies while preserving other performance aspects. Methods: The optimization process involves a genetic algorithm for determining optimal gear ratios, considering performance constraints. Furthermore, the paper introduces a gear-shifting optimization algorithm aimed at enhancing fuel economy to the maximum, while allowing for a valid comparison between two sets of gear ratios. Results: Optimizing gear ratios leads to substantial reductions in fuel consumption, as the engine operates within more efficient regions. Additionally, the optimized gear-shifting strategy further enhances efficiency, resulting in a fuel consumption reduction exceeding 12%, when combined with the optimized gear ratios. Conclusions: This paper offers a direct and robust approach for optimizing powertrain gear ratios and gear-shifting strategies in tracked vehicles. The results demonstrate significant improvements in fuel efficiency without compromising other critical vehicle performance parameters.

Modeling and Simulation of Circuit-Level Nonidealities for an Analog Computing Design Approach With Application to EEG Feature Extraction

This article presents a design approach for the modeling and simulation of ultralow power (ULP) analog computing machine learning (ML) circuits for seizure detection using electroencephalography (EEG) signals in wearable health monitoring applications. In this article, we describe a new analog system modeling and simulation technique to associate power consumption, noise, linearity, and other critical performance parameters of analog circuits with the classification accuracy of a given ML network, which allows to realize a power and performance optimized analog ML hardware implementation based on diverse application-specific needs. We carried out circuit simulations to obtain nonidealities, which are then mathematically modeled for an accurate mapping. We have modeled noise, nonlinearity, resolution, and process variations such that the model can accurately obtain the classification accuracy of the analog computing-based seizure detection system. Noise has been modeled as an input-referred white noise that can be directly added at the input. Device process and temperature variations were modeled as random fluctuations in circuit parameters, such as gain and cut-off frequency. Nonlinearity was mathematically modeled as a power series. The combined system level model was then simulated for classification accuracy assessments. The design approach helps to optimize power and area during the development of tailored analog circuits for ML networks with the ability to potentially trade power and performance goals while still ensuring the required classification accuracy. The simulation technique also enables to determine target specifications for each circuit block in the analog computing hardware. This is achieved by developing the ML hardware model, and investigating the effect of circuit nonidealities on classification accuracy. Simulation of an analog computing EEG seizure detection block shows a classification accuracy of 91%. The proposed modeling approach will significantly reduce design time and complexity of large analog computing systems. Two feature extraction approaches are also compared for an analog computing architecture.

Exploring electromechanical utility of GaAs interdigitated transducers; using finite-element-method-based parametric analysis and experimental comparison

Analysis of interdigitated transducers often relies on phenomenological models to approximate device electrical performance. While these approaches prove essential for signal processing applications, phenomenological models provide limited information on the device’s mechanical response and physical characteristics of the generated acoustic field. Finite element method modeling, in comparison, offers a robust platform to study the effects of the full device geometry on critical performance parameters of interdigitated transducer devices. In this study, we fabricate a surface acoustic wave resonator on semi-insulating GaAs (100), which consists of an interdigitated transducer and acoustic mirror assembly. The device is subsequently modeled using fem software. A vector network analyzer is used to measure the experimental device scattering response, which compares well with the simulated results. The wave characteristics of the experimental device are measured by contact-mode atomic force microscopy, which validates the simulation’s mechanical response predictions. We further show that a computational parametric analysis can be used to optimize device designs for series resonance frequency, effective coupling coefficient, quality factor, and maximum acoustic surface displacement.

Nanometer-Thick Oxide Semiconductor Transistor with Ultra-High Drain Current.

High drive current is a critical performance parameter in semiconductor devices for high-speed, low-power logic applications or high-efficiency, high-power, high-speed radio frequency (RF) analogue applications. In this work, we demonstrate an In2O3 transistor grown by atomic layer deposition (ALD) at back-end-of-line (BEOL) compatible temperatures with a record high drain current in planar FET, exceeding 10 A/mm, the performance of which is 2-3 times better than all known transistors with semiconductor channels. A high transconductance reaches 4 S/mm, recorded among all transistors with a planar structure. Planar FETs working ballistically or quasi-ballistically are exploited as one of the simplest platforms to investigate the intrinsic transport properties. It is found experimentally and theoretically that a high carrier density and high electron velocity both contribute to this high on-state performance in ALD In2O3 transistors, which is made possible by the high-quality oxide/oxide interface, the metal-like charge-neutrality-level (CNL) alignment, and the high band velocities induced by the low density-of-state (DOS). Experimental Hall, I-V, and split C-V measurements at room temperature confirm a high carrier density of up to 6-7 × 1013 /cm2 and a high velocity of about 107 cm/s, well-supported by density functional theory (DFT) calculations. The simultaneous demonstration of such high carrier concentration and average band velocity is enabled by the exploitation of the ultrafast pulse scheme and heat dissipation engineering.

A sensitive multimode dot-filtration strip for the detection of Salmonella typhimurium using MoS2@Fe3O4.

Asensitive, accurate, and rapid multimode dot-filtration immunoassay (MDFIA) was established for the detection of Salmonella typhimurium using the intrinsic color, catalytic property, and photothermal effect of magnetic molybdenum disulphide (MoS2@Fe3O4). The critical performance parameters of MDFIA were optimized in detail. The sensitivity of MDFIA can be improved by the catalytic color development and photothermal conversion of MoS2@Fe3O4 with alimit of detection (LOD) of 101CFU·mL-1, which is an order of magnitude lower than direct visual detection (102CFU·mL-1). Besides, the magnetic property of MoS2@Fe3O4 was used for the rapid enrichment and separation of the target allowing detection oftrace concentrations of Salmonella typhimurium. Theselectivity and applicability of the MDFIA were verified in spiked samples, indicating that the established assay may have bright application prospects for the detection and control of foodborne pathogens. A multimode dot-filtration immunoassay was constructed for Salmonella typhimurium rapid detection based on the peroxidase-like activity, magnetic property, and photothermal effect of MoS2@Fe3O4.

AeMg6Ga6S16 (Ae = Ca, Sr, Ba): The First Double Alkaline‐Earth Metal Chalcogenides with Excellent Performances

AbstractInfrared nonlinear optical (IR NLO) crystals are of quite significance in the development of laser technology, yet rationally designing new IR NLO crystal that can satisfy all the property requirements is still a great challenge owing to the incompatibility between large second harmonic generation (SHG) response and wide band gap. Herein, taking AgGaS2 (AGS) as the template and using highly electropositive alkaline‐earth metal cations substituting Ag+ cations, the first examples of double alkaline‐earth (Ae) metal chalcogenide IR NLO crystals, AeMg6Ga6S16 (Ae = Ca, Sr, Ba), are successfully designed and synthesized. Structurally, they possess stable [Mg/GaS]∞ open frameworks, which can accommodate a wide range of cations from the small size of Ca2+ to large Ba2+ cations and all of the resulting compounds melt congruently. More importantly, these materials achieve the optimal balance among the critical performance parameters, including the strong SHG response (≈0.7–0.8 × AGS) and wide band gap (Eg = 3.50–3.54 eV). Theoretical calculations and structure analysis reveal that their superior NLO properties can be attributed to the synergistic contribution of the polarizable MgS6 and GaS4 groups.

Experimental study and numerical simulation for the development of critical performance parameters of eco-friendly Cu2ZnSnS4-based solar cells

This work aims to study the basic Characteristics of CZTS thin films produced by chemical solution process in addition to a numerical study of the CZTS-based solar cells. In this context, eco-friendly and cost effective thin films of CZTS were coated on glass substrates by sol–gel dip-coating method. This method is used to grow crystalline CZTS thin films without sulfidation processes. The structural and optical properties have been carried out by X-ray Diffraction (XRD) and UV/Visible spectroscopy. The oxidation states of CZTS thin film have been studied by, X-ray photoelectron spectroscopy XPS analysis. The performance of CZTS solar cells has been investigated with the simulator SCAPS-1 D. The impact of different parameters like the CZTS absorber layer thickness, the carrier doping density and the operation temperature has been studied to get better understanding of the properties of our cells.

Stability of Magnesium Binary and Ternary Compounds for Batteries Determined from First Principles.

Electrochemical stability is a critical performance parameter for the materials used as electrolytes and electrodes in batteries. Using first-principles electronic structure calculations, we have determined the electrochemical stability windows of magnesium binary and ternary spinel compounds. These materials are candidates for protective coatings, solid electrolytes, and cathodes in Mg batteries, which represent a promising sustainable alternative to Li-ion batteries that still dominate the battery market. Furthermore, we have applied and assessed two different criteria for the chemical stability of the compounds. For the spinel materials, we identify the critical role of the ionic radii of the transition metal for the stability of the compounds. In addition, we determine the ion mobility in these materials using a recently developed descriptor. We thus provide guidelines for the choice of promising solid materials for Mg batteries with improved properties.

Reassessment of silicon heterojunction cell performance under operating conditions

Temperature coefficient (TC) is a critical operational parameter for solar modules. Amorphous/crystalline silicon heterojunction (SHJ) solar cell is usually considered as a good choice for installation in hot climates because of its lowest TC amongst silicon solar cells. Recently, we have found that light soaking can activate efficient boron doping in hydrogenated amorphous silicon (a-Si:H), which improves the efficiency of SHJ solar cells by enhanced field effect passivation and declined series resistance. In this study, we further report that high temperature can boost this light-induced doping effect. This implies that SHJ solar cells can generate more electricity than estimated by indoor International Electrotechnical Commission (IEC) standards in light abundant locations with hot climates. As a consequence, a 100 MW solar plant comprising SHJ solar modules will gain an extra income of more than 2 million U.S. dollars in a 25-year operation period. Additionally, for the first time, we demonstrate that the dark conductance of phosphorus-doped a-Si:H (n-a-Si:H) increases more greatly than that of boron-doped a-Si:H (p-a-Si:H) after one-sun illumination. This finding has an important implication for bifacial solar modules.

Microfluidic single-cell scale-down bioreactors: A proof-of-concept for the growth of Corynebacterium glutamicum at oscillating pH values.

In large-scale bioreactors, gradients in cultivation parameters such as oxygen, substrate, and pH result in fluctuating cell environments. pH fluctuations were identified as a critical parameter for bioprocess performance. Traditionally, scale-down systems at the laboratory scale are used to analyze the effects of fluctuating pH values on strains and thus process performance. Here, we demonstrate the application of dynamic microfluidic single-cell cultivation (dMSCC) as a novel scale-down system for the characterization of Corynebacterium glutamicum growth using oscillating pH conditions as a model stress factor. A detailed comparison between two-compartment reactor (two-CR) scale-down experiments and dMSCC was performed for one specific pH oscillation between reference pH 7 (~8 min) and disturbed pH 6 (~2 min). Similar reductions in growth rates were observed in both systems (dMSCC 21% and two-CR 27%) compared to undisturbed cultivation at pH 7. Afterward, systematic experiments at symmetric and asymmetric pH oscillations, between pH ranges of 4-6 and 8-11 and different intervals from 1to 20 min, were performed to demonstrate the unique application range and throughput of the dMSCC system. Finally, the strength of the dMSCC application was demonstrated by mimicking fluctuating environmental conditions of a putative large-scale bioprocess, which is difficult to conduct using two-CRs.

Oxidative torrefaction and torrefaction-based biorefining of biomass: a critical review

Torrefaction is a vital pretreatment technology for thermochemical biorefinery applications like pyrolysis, gasification, and liquefaction. Oxidative torrefaction, an economical version of torrefaction, has recently gained much attention in the renewable energy field. Recent literature on inert and oxidative torrefaction was critically reviewed in this work to provide necessary guidance for future research and commercial implementations. The critical performance parameters of torrefaction for thermochemical biorefinery applications, such as solid yield, energy yield, carbon enhancement, higher heating value (HHV) enhancement, and energy-mass co-benefit index (EMCI), were also analyzed. Agricultural waste, woody biomass, and microalgae were considered. The analysis reveals that woody biomass could equally benefit from oxidative or inert torrefaction. In contrast, inert torrefaction was found more suitable for agricultural wastes and microalgae. Using flue gas as the oxidative torrefaction medium and waste biomass as the feedstock could achieve a circular economy, improving the sustainability of oxidative torrefaction for thermochemical biorefineries. The significant challenges in oxidative torrefaction include high ash content in torrefied agricultural waste, the oxidative thermal runaway of fibrous biomass during torrefaction, temperature control, and scale-up in reactors. Some proposed solutions to address these challenges are combined washing and torrefaction pretreatment, balancing oxygen content, temperature, and residence time, depending on the biomass type, and recirculating torrefaction gases.

Review and Techno-Economic Analysis of Emerging Thermo-Mechanical Energy Storage Technologies

Thermo-mechanical energy storage can be a cost-effective solution to provide flexibility and balance highly renewable energy systems. Here, we present a concise review of emerging thermo-mechanical energy storage solutions focusing on their commercial development. Under a unified framework, we review technologies that have proven to work conceptually through project demonstration at a scale above 1 MW by describing the current state of commercial development, quantifying techno-economic parameters, outlining the challenges, and assessing each technology’s potential for commercial viability. The levelized cost of storage for thermo-mechanical energy storage at storage duration between 8 h and 1 week is cheaper than that of lithium-ion batteries and hydrogen storage; however, energy storage for such duration does not pay for itself at the current renewable penetration levels. For medium-term energy storage to be viable, at the realistic storage cost of 15 USD/kWh to 40 USD/kWh, the investment cost for power components should decrease to one-fifth of the current costs. Thermo-mechanical energy storage can be economically viable at the current investment costs in off-grid systems only when the marginal cost of alternative fuel exceeds 100 USD/MWh. We identified the cost ratio (charge power cost/discharge power cost) and the discharge efficiency as the critical technology-related performance parameters. Other external factors such as wind and solar fractions, demand, interconnections, sector coupling, and market structure play an important role in determining the economic feasibility of thermo-mechanical energy storage.

Tunable Capacitive Behavior in Metallopolymer-based Electrochromic Thin Film Supercapacitors.

Volumetric capacitance is a more critical performance parameter for rechargeable power supply in lightweight and microelectronic devices as compared to gravimetric capacitance in larger devices. To this end, we report three electrochromic metallopolymer-based electrode materials containing Fe2+ as the coordinating metal ion with high volumetric capacitance and energy densities in a symmetric two-electrode supercapacitor setup. These metallopolymers exhibited volumetric capacitance up to 866.2 F cm-3 at a constant current density of 0.25 A g-1. The volumetric capacitance (poly-Fe-L2: 544.6 F cm-3 > poly-Fe-L1: 313.8 F cm-3 > poly-Fe-L3: 230.8 F cm-3 at 1 A g-1) and energy densities (poly-Fe-L2: 75.5 mWh cm-3 > poly-Fe-L1: 43.6 mWh cm-3 > poly-Fe-L3: 31.2 mWh cm-3) followed the order of the electrical conductivity of the metallopolymers and are among the best values reported for metal-organic systems. The variation in the ligand structure was key toward achieving different electrical conductivities in these metallopolymers with excellent operational stability under continuous cycling. High volumetric capacitances and energy densities combined with tunable electro-optical properties and electrochromic behavior of these metallopolymers are expected to contribute to high performance and compact microenergy storage systems. We envision that the integration of smart functionalities with thin film supercapacitors would warrant the surge of miniaturized on-chip microsupercapacitors integrated in-plane with other microelectronic devices for wearable applications.