Conductive Oxide Research Articles

Flexible electrochemical sensor based on a ZnO-doped SnO2 heterojunction for simultaneous electrochemical determination of p-aminophenol and acetaminophen

In this work, a novel flexible electrochemical sensor was successfully developed for the simultaneous determination of p-aminophenol and acetaminophen. The sensor is composed of a methanesulfonic acid-treated poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonic acid) film on a poly(ethylene terephthalate) substrate, which has been modified using a zinc oxide-doped tin oxide heterojunction applied through drop-coating (C-ZnO/SnO2-PEDOT/PET). The oxygen vacancies resulting from zinc oxide-doped tin oxide heterojunctions within highly conductive metal oxide nanomaterials enhance mass transfer and synergize seamlessly with methanesulfonic acid-treated electrically conductive dielectric PEDOT/PET films, leading to a substantial improvement in electrochemical activity. Under the optimal conditions, a wider linear range and lower detection limits were shown for p-aminophenol (2–511 μM, LOD=0.437 μM) and acetaminophen (2–591 μM, LOD=0.562 μM). In addition, the sensors demonstrated high accuracy in detecting p-aminophenol and acetaminophen in real samples, with recoveries of 99.36 %-99.60 % and 97.56 %-99.80 %, respectively. Furthermore, the flexible sensors maintained a superior electrochemical response when detecting p-aminophenol and acetaminophen at different bending angles, with relative standard deviations of 0.62 % and 1.68 %, respectively. These findings suggest potential applications for the development of wearable sensors in the future.

Towards sustainable solar cells: unveiling the latest developments in bio-nano materials for enhanced DSSC efficiency

Abstract Fossil fuels—instrumental in powering the nineteenth-century Industrial Revolution—are now under heightened scrutiny due to environmental concerns and carbon emissions. Consequently, there is a global impetus towards achieving carbon-neutral energy production, with solar energy emerging as a cornerstone in this transition. Over the past three decades, dye-sensitized solar cells (DSSCs) have gained increasing prominence due to their unique advantages. This review elucidates several crucial elements essential to DSSC construction, notably bio-nano materials, prized for their structural flexibility, cost-effectiveness and high molar absorption coefficient. It delves into the intricate relationship between molecular structure and DSSC performance, showcasing significant advancements with light-to-power conversion efficiencies reaching 11%. A comprehensive analysis of the photovoltaic performance of DSSCs utilizing bio-nano-based dyes offers invaluable insights into the state of this rapidly evolving industry. Key components under scrutiny include transparent conductive oxide (TCO) layers, physical techniques for metal oxide deposition onto TCO thin films, diverse dye variants and foundational knowledge of components ripe for growth and enhancement. Moreover, the review outlines the latest breakthroughs in the field, providing glimpses into the current status of prototype DSSCs.

Promoting Thermal Conductivity of Alumina-Based Composite Materials by Systematically Incorporating Modified Graphene Oxide

Small amounts of thermally conductive graphene oxide (GO) and modified GO are systematically introduced as a second filler to thermal interface materials (TIMs) consisting of alumina (Al2O3) particles and polydimethylsiloxane (PDMS). The surface of GO is covalently linked with an organic moiety, octadecylamine (ODA), to significantly improve the miscibility and dispersity of GO across the TIM matrix. Subsequently, two series of PDMS-Al2O3 composite TIMs are manufactured as a function of GO and ODA-GO content (0.25 wt%–2.5 wt%) to understand the effect of these second additives. The incorporation of GO into the Al2O3-PDMS composite materials generally increases the thermal conductivity (TC), ranging from 18% to 29%. Conversely, the use of ODA-GO further enhances the overall performance of TIMs (22–54%) by facilitating the dispersion degree of GO across the composite matrix. The great improvement in TC is presumably related to the formation of conductive pathways by uniformly integrating 2D-type GO flakes across spherical Al2O3 particle networks. The ability to simply regulate the polarity of the thermally conductive second filler can provide an idea for designing cost-effective and practical TIM-2-type pads that can be commercially applicable in between an integrated heat spreader and a heat sink.

Titanium Silicide: A Promising Candidate of Recombination Layer for Perovskite/Tunnel Oxide Passivated Contact Silicon Two-Terminal Tandem Solar Cells.

This study proposes a titanium silicide (TiSi2) recombination layer for perovskite/tunnel oxide passivated contact (TOPCon) 2-T tandem solar cells as an alternative to conventional transparent conductive oxide (TCO)-based recombination layers. TiSi2 was formed while TiO2 was made by oxidizing a Ti film deposited on the p+-Si layer. The reaction formation mechanism was proposed based on the diffusion theory supported by experimental results. The optical and electrical properties of the TiSi2 layer were optimized by controlling the initial Ti thicknesses (5-100 nm). With the initial Ti of 50 nm, the lowest reflectance and highly ohmic contact between the TiO2 and p+-Si layers with a contact resistivity of 161.48 mΩ·cm2 were obtained. In contrast, the TCO interlayer shows Schottky behavior with much higher contact resistivities. As the recombination layer of TiSi2 and the electron transport layer of TiO2 are formed simultaneously, the process steps become simpler. Finally, the MAPbI3/TOPCon tandem device yielded an efficiency of 16.23%, marking the first reported efficiency for a device including a silicide-based interlayer.

Concurrent Crystallization Mechanism Leading to Low Temperature Percolation of LAGP Glass-Ceramic Electrolyte.

Sintering of ceramic electrolytes (CE) is the most efficient way to obtain a dense, all ceramic solid-state battery with oxide-based materials. However, the high temperature required for this process leads to detrimental reactivity between CE and the active material. Crystalline ceramics are necessary for highly conductive oxide materials. Still, thermomechanical properties of glass-phase materials can be used to obtain a denser and more conductive CE. Glass-phase CE can be produced with Nasicon-type CE. Here, Li1.5Al0.5Ge1.5(PO4)3 (LAGP) glass is used as a model to investigate the formability, densification, and conduction properties upon crystallization. A complete study of the crystallization mechanism is first performed to fully understand how a high conductivity of 6.3 × 10-5 S·cm-1 at 30 °C with 92% relative density is obtained at a sintering temperature of only 550 °C without pressure. This is approximately 200 °C below the usual sintering temperature of LAGP. X-ray diffraction is then used to calculate the amount of crystalline phase as a function of time. A combined study of reaction kinetics and conductivity evolution reveals an autocatalytic nucleation effect, which produces an early crystallization pathway. Density is studied to quantify the ability of the glass to flow during the crystallization process.

High-Pressure Polymorphism in Silver Ferrite Delafossite, AgFeO2.

The delafossites are a class of layered metal oxides that are notable for being able to exhibit optical transparency alongside an in-plane electrical conductivity, making them promising platforms for the development of transparent conductive oxides. Pressure-induced polymorphism offers a direct method for altering the electrical and optical properties in this class, and although the copper delafossites have been studied extensively under pressure, the silver delafossites remain only partially studied. We report two new high-pressure polymorphs of silver ferrite delafossite, AgFeO2, that are stabilized above ∼6 and ∼14 GPa. In situ X-ray diffraction and vibrational spectroscopy measurements are used to examine the structural changes across the two phase transitions. The high-pressure structure between 6 and 14 GPa is assigned as a monoclinic C2/c structure that is analogous to the high-pressure phase reported for AgGaO2. Nuclear resonant forward scattering reveals no change in the spin state or valence state at the Fe3+ site up to 15.3(5) GPa.

Enhanced thermoelectric performance of W18O49/ZnO composite for waste heat recovery with induced high weighted mobility

Zinc Oxide (ZnO) exhibits a significant Seebeck coefficient, making it a promising candidate for thermoelectric energy harvesting. This study explores composite materials comprising xW18O49/(1-x)ZnO fabricated through conventional sintering at 1150°C, with x varying from 0 to 0.3. Incorporating a highly conductive secondary phase into the ZnO matrix enhances conductivity by 28 times, reaching 111.4 Scm−1 at 800°C, while maintaining 83 % of the pristine sample's Seebeck coefficient. Notably, the power factor improves to 3.8 mWK−2m−1 for the x = 0.1 sample, representing a 19 times heightening over unmodified ZnO ceramic. Additionally, these composites exhibit high weight mobility, indicating rapid electronic responses. As a result, the ZT value increases by 500 %, reaching 0.15 at 800°C for the x = 1 sample. This study presents a novel approach to fabricating high-power-factor thermoelectric materials by integrating highly conductive oxides into matrices with large Seebeck coefficients.

Effect of transparent conductive layers on the functionality of liquid crystal devices: Comparison of AZO, FTO and ITO

The integration of highly transparent and highly conductive layers plays a crucial role in the advancement of various next-generation optoelectronic technologies. Here, we demonstrate a comparison of optical, electrical and wettability properties of Aluminum-doped Zinc Oxide (AZO) deposited by Atomic Layer Deposition Technique (ALD) with commercially available Fluorine-doped Tin Oxide (FTO) and Indium-doped Tin Oxide (ITO) Transparent Conductive Oxide (TCO) layers. Their impact on the electro-optical modulation behavior when applied in Liquid Crystal (LC) device assemblies are compared and discussed. The AZO layers performance prove that are fully competitive to the commercial FTO and ITO layers and verify the high demand for the next generation indium tin oxide (ITO)-free technology.

Indium-free nonmetal and Nb co-doped anatase TiO2 transparent conductive oxide materials for photovoltaic applications: From first-principles calculations to macroscopic simulation

Various researchers have attempted to design indium-free transparent conductive materials. This study first employed density functional theory combined with the Hubbard U parameter to predict the photoelectric properties of nonmetal (B, C, N, F, P, and S) and Nb co-doped anatase TiO2. The results indicate that Ti0.875Nb0.125O1.96875N0.03125, Ti0.9375Nb0.0625O1.96875F0.03125, Ti0.875Nb0.125O1.96875P0.03125 and Ti0.9375Nb0.0625O1.96875S0.03125 possess characteristics of n-type semiconductors with high transmittance, exceptional thermal stability and wide bandgap. Notably, Ti0.9375Nb0.0625O1.96875S0.03125 exhibits optimal electronic conductivity due to its lower effective mass and higher electron concentration. Then, we used the SCAPS-1D solar cell simulation software to simulate the macroscopic characteristics of the MASnI3-based perovskite solar cell with Ti0.9375Nb0.0625O1.96875S0.03125 transparent conductive oxide layer based on the microscopic properties computed at the density functional theory level. A maximum efficiency of 27.17 % is obtained by regulating the thickness, electron affinity, and defect density of Ti0.9375Nb0.0625O1.96875S0.03125 layer and the thickness of MASnI3 absorber layer. The findings highlight the tremendous potential of Ti0.9375Nb0.0625O1.96875S0.03125 as an indium-free transparent conductive oxide candidate material for photovoltaic applications.

Zirconium Oxynitride Thin Films for Photoelectrochemical Water Splitting.

Transition metal oxynitrides are a promising class of functional materials for photoelectrochemical (PEC) applications. Although these compounds are most commonly synthesized via ammonolysis of oxide precursors, such synthetic routes often lead to poorly controlled oxygen-to-nitrogen anion ratios, and the harsh nitridation conditions are incompatible with many substrates, including transparent conductive oxides. Here, we report direct reactive sputter deposition of a family of zirconium oxynitride thin films and the comprehensive characterization of their tunable structural, optical, and functional PEC properties. Systematic increases of the oxygen content in the reactive sputter gas mixture enable access to different crystalline structures within the zirconium oxynitride family. Increasing oxygen contents lead to a transition from metallic to semiconducting to insulating phases. In particular, crystalline Zr2ON2-like films have band gaps in the UV-visible range and are n-type semiconductors. These properties, together with a valence band maximum position located favorably relative to the water oxidation potential, make them viable photoanode candidates. Using chopped linear sweep voltammetry, we indeed confirm that our Zr2ON2 films are PEC-active for the oxygen evolution reaction in alkaline electrolytes. We further show that high-vacuum annealing boosts their PEC performance characteristics. Although the observed photocurrents are low compared to state-of-the-art photoanodes, these dense and planar thin films can offer a valuable platform for studying oxynitride photoelectrodes, as well as for future nanostructuring, band gap engineering, and defect engineering efforts.

High-performance composite transparent electrode composed of ultra-long silver nanowires and antimony-doped tin oxide nanoparticles

Composite transparent conductive electrodes (TCEs) consisting of silver nanowires (AgNWs) and conductive metal oxides are very promising for flexible optoelectronic devices due to their smooth surface morphology and high chemical stability. However, it is still challenging to ensure high optoelectronic performance and long-term stability in practical applications. Here, we solved these problems by coating antimony-doped tin oxide (ATO) nanoparticles dispersion on ultra-long AgNWs network using waterborne polyurethane (WPU) binder. Ultra-long nanowires occupy less wire-wire junctions and space than short nanowires, thus increasing the optoelectronic performance and flexibility of the composite TCE. WPU improves the adhesion and stability of ATO nanoparticles to the substrate and AgNWs network. The fabricated composite TCE showed a low sheet resistance of 11.9 Ω sq−1, good optical transmittance of 83% at 550 nm and a figure of merit (FOM) of 162 compared to PET/ITO electrode. It also showed excellent mechanical flexibility, adhesion to the substrate and solvent stability. Furthermore, the long-term conductivity was maintained under ambient conditions for 60 days.

Effect of polyvinylpyrrolidone concentration on optical properties of CuCrO2 thin films

In this study, CuCrO2 thin films were fabricated by spin-coating technique on alkali-free glass substrates and a two-step annealing process. The copper-based delafossite CuCrO2 is a p-type transparent conductive oxide that exhibits a wide energy bandgap and excellent stability. To improve the transmittance of CuCrO2 thin films, polyvinylpyrrolidone (PVP) was used as a porogen for preparing thin films with high transmittance and high haze values. The highest transmittance of 73.75% was achieved with 0.5 g of PVP. The bandgaps of prepared CuCrO2 thin films were estimated at 2.82 eV to 3.11 eV. The prepared CuCrO2 thin films had a porous structure and high transmittance. The high potential transmittance of porous CuCrO2 thin films makes them applicable to photovoltaic systems, transistors and touch screens or displays in the future.

Thermal conduction in polycrystalline or amorphous transparent conductive oxide films

With the widespread utilization of transparent conductive oxides (TCO) in various electronic devices, it is beneficial to revisit the fundamentals of heat conduction to formulate a comprehensive physical understanding for thermal properties of TCOs with the aim of improving the thermal design of electronic devices. For degenerate polycrystalline TCO films, both free electrons and phonons act as heat carriers, where free electron contribution can be calculated based on the Wiedemann-Franz law.Interestingly, the phonon thermal conductivity remains almost constant for degenerated polycrystalline TCO films with different dopant concentrations, suggesting the existence of dopant-induced minimum phonon thermal conductivity. For degenerate amorphous TCO film, free electrons act as heat carriers along the conduction path formed by the orbital overlap of cations, which also obey the Wiedemann-Franz law. Moreover, the atomic vibration contribution to thermal conductivity almost keeps unchanged for amorphous TCO films deposited under different conditions, indicating the existence of a minimum thermal conductivity caused by the scattering of vibrational mode due to structural randomness appeared in the bond angle. We anticipate that these fundamental understanding can provide a guide for the discovery of TCO materials with optimized thermal properties.

Zirconium doped indium oxide thin films as transparent electrodes for photovoltaic applications

In this work we report on ultra-thin Zirconium doped In2O3 transparent conductive films grown at room temperature via RF-Magnetron co-sputtering. Samples from 15 nm to 90 nm thick, and low Zr atomic concentration (0.6–0.9 at.%), were annealed at T = 200 °C after the deposition. The phase-transition from amorphous to crystalline, confirmed by XRD measurements, leads to an improvement of both electrical and optical properties. The thinnest film (15 nm) shows electrical resistivity as low as 5 × 10−4 Ωcm, with carrier mobility of 20 cm2V−1s−1, and optical transmittance up to 80 % in visible and near-infrared range. IZrO electrode performances were tested through external quantum efficiency (EQE) measurements on a semi-finite Silicon Heterojunction bi-facial solar cell. The EQE values for 90 nm thick film are comparable to that of standard ITO when IZrO films are implemented as front electrodes. These results suggest that ultra-thin IZrO films may be successfully used to reduce costs and the amount of Indium used in Indium-based transparent conductive oxide layers for solar cells.

Diffusional Electron Transport Coupled to Thermodynamically Driven Electron Transfers in Redox-Conductive Multivariate Metal-Organic Frameworks.

The development of redox-conductive metal-organic frameworks (MOFs) and the fundamental understanding of charge propagation through these materials are central to their applications in energy storage, electronics, and catalysis. To answer some unresolved questions about diffusional electron hopping transport and redox conductivity, mixed-linker MOFs were constructed from two statistically distributed redox-active linkers, pyromellitic diimide bis-pyrazolate (PMDI) and naphthalene diimide bis-pyrazolate (NDI), and grown as crystalline thin films on conductive fluorine-doped tin oxide (FTO). Owing to the distinct redox properties of the linkers, four well-separated and reversible redox events are resolved by cyclic voltammetry, and the mixed-linker MOFs can exist in five discrete redox states. Each state is characterized by a unique spectroscopic signature, and the interconversions between the states can be followed spectroscopically under operando conditions. With the help of pulsed step-potential spectrochronoamperometry, two modes of electron propagation through the mixed-linker MOF are identified: diffusional electron hopping transport between linkers of the same type and a second channel that arises from thermodynamically driven electron transfers between linkers of different types. Corresponding to the four redox events of the mixed-linker MOFs, four distinct bell-shaped redox conductivity profiles are observed at a steady state. The magnitude of the maximum redox conductivity is evidenced to be dependent on the distance between redox hopping sites, analogous to the situation for apparent electron diffusion coefficients, Deapp, that are obtained in transient experiments. The design of mixed-linker redox-conductive MOFs and detailed studies of their charge transport properties present new opportunities for future applications of MOFs, in particular, within electrocatalysis.

Fabrication and Characterization of Nanostructured Tin doped Indium Oxide Coatings by the Instrument of Spray Pyrolysis

Nanostructured indium tin oxide (ITO) coating is one of the transparent conductive oxides (TCO) materials utilized as a transparent electrode. Due to its high demand in various applications like liquid crystal displays, touch screens, light emitting devices, and solar cells, ITO coatings have garnered significant research attention, owing to their excellent properties of high visible light transmittance and low resistance. Nanostructured coating of tin -doped Indium Oxide (ITO) was fabricated on glass slides utilizing the instrument of chemical spray pyrolysis (CSP), with varying levels of Sn-doping at 0, 3, 6, and 9 wt%. The effect of tin content on the many physical characteristics of the resulting coatings has been examined. The analysis of x-ray diffraction (XRD) displayed the characteristic orientations. The coatings have a polycrystalline cubic lattice structure along (400) as the preferred growth direction. Morphological measurements indicate that the samples possess a highly uniform surface and the grain size for the ITO samples is 100 nm displaying a nanostructure for all samples. The optical transmittance was measured over 75% for coating with tin content equal to 0wt%, while the transmittance of the Sn-doped films can range from 78% to 84% at 700 nm and the values of the direct bandgap were measured as 3.6, 3.65, 3.675, and 3.7eV for Sn doping 0, 3, 6, and 9 wt% respectively. In the visible area, the nanostructured ITO coatings exhibit elevated values of transmittance which makes them suitable for various optoelectronic applications such as window materials in solar cells. The results indicate a desirable reduction in the electrical resistivity with rising the number of carriers per unit volume and mobility with increasing tin content in the samples. The minimum electrical resistivity and maximum carrier concentration were achieved for ITO coating with tin content equal to 9wt%. The incorporation of Sn dopant significantly changes the overall electrical properties of indium oxide films, this is favorable for transparent conducting oxide.

FSS based high gain optically transparent MIMO antenna for Sub-6 GHz 5G mid-band applications

A novel optically transparent Multi Input Multi Output (MIMO) antenna design positioned on a Frequency-Selective Surface (FSS) for gain improvement while maintaining a simple fabrication procedure. Transparent conductive materials inherently exhibit higher sheet impedance due to lower conductivity, resulting in decreased antenna gain and radiation efficiency. To address this limitation, an optically transparent FSS is incorporated beneath the MIMO structure to improve radiation characteristics. Utilizing a Malinex substrate and a conductive silver oxide sheet, the 4-element MIMO design achieves both transparency and MIMO operability. The operational bandwidth spans from 3.09 GHz to 3.7 GHz, with a percentage bandwidth of 17.96 %, ensuring port isolation of over 20 dB. With the presence of the FSS, a consistent gain enhancement of approximately 3.46 dBi is achieved, with an average gain within the band reaching 4.56 dBi. The proposed design employs a simplified fabrication process while addressing aesthetic concerns and providing a solution to the existing issue of low gain in conductive metal oxide-based transparent antennas.

Comprehensive study on catalytic potential of Ti3C2Tx based catalyzer for Dye sensitized solar cells application

Abstract Recently Dye-sensitized solar cells (DSSC) have gained significant research limelight for having exceptional photovoltaic potential. However, DSSC became an underdog solar cell due to the use of an expensive transparent conductive layer (FTO/ITO) along with the use of rare earth element Pt to concoct counter electrode (CE). Thus, an attempt has been made to concoct a Ti3C2-TX MXene-based CE to replace both the transparent conductive layer and CE. Herein, relatively larger with less defective Ti3C2 flakes were produced by the minimally intensive layer delamination method, and physical architecture was investigated by X-ray diffraction (XRD) mapping, Field-emission scanning electron microscope (FE-SEM) and Dynamic light scattering (DLS), respectively. MXene flakes were drop cast on a glass substrate by dispersing it in ethanol, isopropyl alcohol, and deionized water, respectively, and found the least sheet resistance, 14.824 Ω/sq by 4-point probe test, owing to superior adsorption force with the glass substrate. Ethanol solvent facilitates optimum interlamellar spacing to promote fast diffusion and transportation. Further, the study was expanded by introducing it to numerous sintering temperatures to find the best result. The result revealed exceptional sheet resistance of 0.08 Ω/sq for the 120℃ sintered sample, which was encouraged by removing water intercalant and occupying H+. Further, the potential of MXene-based counter electrode’s catalytic activity has been studied through electrochemical impedance spectroscopy, Tafel polarization, and Cyclic voltammogram under iodide and triiodide-based electrolytes. The electrochemical study revealed 120℃ sintered sample superior to 140℃ sintered but comparable to Pt CE. 120℃ sintered Ti3C2-based CE performed exceptional 6.27% power conversion efficiency. Thus, this novel study communicates that Ti3C2-TX is a potential replacement for transparent conductive oxide layer and Pt, frequently used in Dye-sensitized solar cell applications.

Controlled Calcium Oxalate Crystals Obtained by Electrocrystallization on Electrospun Polycaprolactone Fibers Loaded with Zarzaparrilla ( Herreria stellata ).

Calcium oxalate (CaOx) is known to grow on organic matrices and is often associated with the formation of kidney stones. Therefore, it is crucial to understand the nucleation and growth mechanisms. This study investigates the role of electrospun polycaprolactone (PCL)-loaded zarzaparrilla (ZP) (Herreria stellata) in the electrocrystallization (EC) of CaOx. Electrospinning (ES) was used to prepare PCL meshes with random (R) and aligned (A) fiber orientations. CaOx particles were grown directly on conductive tin indium oxide (ITO) glass modified with electrospun ZP-loaded PCL meshes by EC. The CaOx crystals after EC were measured by chronopotentiometry (CP), optical microscopy (OM), scanning electron microscopy (SEM), and X-ray diffraction (XRD), which showed that the ZP additive and PCL fiber orientations are key factors for CaOx nucleation.

HASPIDE: a project for the development of hydrogenated amorphous silicon radiation sensors on a flexible substrate

Hydrogenated amorphous silicon (a-Si:H) is a material with a very good radiation hardness and with the possibility of deposition on flexible substrates like Polyimide (PI). Exploiting these properties, the HASPIDE (Hydrogenated Amorphous Silicon PIxels DEtectors) project has the goal of developing a-Si:H detectors on flexible substrates for beam dosimetry and profile monitoring, neutron detection and space experiments. The detectors for this experiment will be developed in two different structures: the n-i-p diode structure, which has been used up to now for the construction of the planar a-Si:H detectors, and the recently developed charge selective contact structure. In the latter the doped layers (n or p) are replaced with charge selective materials namely electron-selective conductive metal-oxides (TiO2 or Al:ZnO) and hole-selective conductive metal oxides (MoO x ). In this paper preliminary data on the capabilities of these detectors to measure X-ray and electron fluxes will be presented. In particular, the linearity, the sensitivity, the stability and dark current in various conditions will be discussed.