Tin-doped Indium Oxide Electrodes Research Articles

Mixed Potential Sensors for the Detection of Hydrogen Leaks from Geologic Reservoirs

Large-scale hydrogen (H2) geologic storage presents a viable alternative to surface storage that is both safer and more economical. One option being considered by DOE is H2 storage in salt formations. These formations have been successfully used for gas storage for decades due to their extremely low permeability and may see significant investment as the US ramps up its R&D efforts in this field. New Mexico has a unique advantage in that bedded salt formations are located strategically in areas where excess energy production can be harnessed for hydrogen production. However, bedded salt is more permeable than domal salt, necessitating sensor deployment to monitor H2 containment. Robust sensors that can provide early leakage detection will be an essential component of the safety of H2 operating facilities. In a LANL-funded Mission Foundations Research (MFR) project, we prepared several zirconia-based mixed potential hydrogen sensors utilizing a tin-doped indium oxide electrode for H2 leak detection to test its stability in subsurface environments. Previous electrochemical sensor work has shown this type of sensor in a hydrogen safety sensor role represents a significant improvement over currently available sensors as it has an extremely stable baseline and limited cross sensitivity to other gaseous compounds.1 The feasibility of this technology will be demonstrated through a hydrogen permeation experiment to measure rates of underground hydrogen permeation between boreholes drilled underground at the DOE Waste Isolation Pilot Plant (WIPP) site. This experiment will (1) establish the use of this novel sensor in geologic H2 storage applications and (2) investigate the feasibility of H2 storage in bedded rock salt. Acknowledgement This research is supported by the Los Alamos National Laboratory, Laboratory Directed Research and Development (LDRD) Office, Missions Foundation Research Charter (Debora Wagner Program Manager). References E. L. Brosha, C. J. Romero, D. Poppe, T. L. Williamson, C. R. Kreller, R. Mukundan, R. S. Glass, and A. S. Wu, “Field Trials Testing of Mixed Potential Electrochemical Hydrogen Safety Sensors at Commercial California Hydrogen Filling Stations,” Journal of the Electrochemical Society 164 (13) B681-B689 (2017).

Effect of dimensional confinement on the memristive properties of the perovskite-inspired novel CuxAgBiI4+x halide compound

Low dimensional halide perovskite materials have shown significant performance enhancement in memristor devices. In search of highly stable and robust perovskites, several perovskite-inspired structures are proposed. This present study demonstrates the fabrication of novel lead-free all-inorganic CuxAgBiI4+x (x = 1 or 2) as the active material sandwiched between gold and indium doped tin oxide electrodes. Initial studies revealed that the memristor devices consisting of two-dimensional Cu2AgBiI6 have higher current on/off ratio as compared to the three-dimensional CuAgBiI5. This is ascribed to the elevated Schottky barrier at the Au/Cu2AgBiI6 interface as suggested by ultraviolet photoelectron spectroscopy, which resulted low current in the high resistance state (HRS) of the device. Kelvin probe force microscopy shows that the charge accumulation property is similar in both the materials although the CuAgBiI5 possesses less vacancies. However, the high switching window of the Cu2AgBiI6-based device succeeded in retaining the stable on/off ratio in the cycling endurance. Artificial synaptic characterizations have been carried out in the Cu2AgBiI6 based device due to low HRS current. The device could mimic paired-pulsed facilitation, transition from short-term to long-term potentiation and thus establishes the fact that low dimensional perovskite-type materials possess great potential for memristor application.

Buried-Metal-Grid Electrodes for Efficient Parallel-Connected Perovskite Solar Cells.

The limited conductivity of existing transparent conducting oxide (TCO) greatly restricts the further performance improvement of perovskite solar cells (PSCs), especially for large-area devices. Herein, buried-metal-grid tin-doped indium oxide (BMG ITO) electrodes are developed to minimize the power loss caused by the undesirable high sheet resistance of TCOs. By burying 140-nm-thick metal grids into ITO using a photolithography technique, the sheet resistance of ITO is reduced from 15.0 to 2.7 Ω sq-1 . The metal step of BMG over ITO has a huge impact on the charge carrier transport in PSCs. The PSCs using BMG ITO with a low metal step deliver power conversion efficiencies (PCEs) significantly better than that of their counterparts with higher metal steps. Moreover, compared with the pristine ITO-based PSCs, the BMG ITO-based PSCs show a smaller PCE decrease when scaling up the active area of devices. The parallel-connected large-area PSCs with an active area of 102.8 mm2 reach a PCE of 22.5%. The BMG ITO electrodes are also compatible with the fabrication of inverted-structure PSCs and organic solar cells. The work demonstrates the great efficacy of improving the conductivity of TCO by BMG and opens up a promising avenue for constructing highly efficient large-area PSCs.

Effect of RF-sputtering temperature of ITO electrodes on the resistive switching behaviour of ITO/RbPbI3/Cu devices

In this work, we deposit Indium doped Tin Oxide (ITO) on a glass substrate using the Radio-Frequency Sputtering technique at different temperatures and studied its structural and optical properties. Various structural, optical, and morphological studies are conducted on the ITO substrates. In addition, we have used these ITO films as conducting electrodes in MIM (metal-insulator-metal) type structures for resistive memory application. A resistive switching memory device based on RbPbI3 with sputtered ITO films as the bottom electrode is fabricated and studied for its electrical performance. It has been found that the device showed the write-once-read-many (WORM) nature at a sputtering temperature of 300 °C with a good OFF/ON ratio. The devices with ITO film sputtered a temperature below 300 °C do not show any switching behavior due to lower conductivity and improper surface morphology.

Extraction, chemical, and dual-functional memory and threshold resistive switching characteristics of Elaeodendron buchananii extract

This work presents a study on the electrical properties of plant materials, which is a fascinating area of research. These materials show promising potential in mitigating the exponential increase in electronic waste by enabling the development of eco-friendly electronic devices that can biodegrade. This research article showcases findings on the extraction, chemical analysis, and dual-functional memory and threshold resistive switching of extracts from the Elaeodendron buchananii plant. We report threshold switching with impressive ON/OFF ratio of >103, a retention time of ≥103, and endurance of 20 cycles, for the sandwich type device consisting of Elaeodendron buchananii plant extract-based film positioned between silver and indium-doped tin oxide electrodes. After modifying the experimental parameters, specifically by reducing the voltage scan increments to 1mV and increasing the compliance current to 150μA, transition from threshold switching to bipolar memory mode was detected. This particular memory mode exhibited an ON/OFF ratio of 10 and demonstrated very low switching voltages of −0.37V and +0.22V, although for only a limited number of write/erase cycles. The switching mechanism for both the threshold and memory mode can be attributed to the formation of conductive filaments caused by the migration of oxygen vacancies.

Fabrication of Rb2TeI6 thin films for stable, lead-free perovskite photodetector via dry-processed approach

In the vacancy-ordered double perovskite group, rubidium tellurium iodide is a rarely studied material. In this paper, we report the fabrication of Rb2TeI6 thin film via a dry-processed approach. The process includes the chemical vapor deposition of the RbI film, followed by a thermal annealing treatment in TeI4 vapor. The film has a tetragonal structure with good morphology, high absorption coefficient (>105 cm−1 in the 280–620 nm wavelength range), and good stability in ambient air. A photodetector is fabricated by growing a 300 nm-thick Rb2TeI6 film on indium-doped tin oxide electrodes. The Rb2TeI6-based photodetector has 0.87 pA dark current at 5 V bias. Under 450 nm illumination, it shows 1.4 mA/W photoresponsivity, approximately 1010 J photodetectivity, and 16.4 ms/19.2 ms response times with an excellent operational stability. This study not only presents an effective technique for fabricating the Rb2TeI6 perovskite thin film, but also shows its potential for photodetector application.

All-Ceramic Passive Wireless Temperature Sensor Realized by Tin-Doped Indium Oxide (ITO) Electrodes for Harsh Environment Applications.

In this work, an all-ceramic passive wireless inductor–capacitor (LC) resonator was presented for stable temperature sensing up to 1200 °C in air. Instead of using conventional metallic electrodes, the LC resonators are modeled and fabricated with thermally stable and highly electroconductive ceramic oxide. The LC resonator was modeled in ANSYS HFSS to operate in a low-frequency region (50 MHz) within 50 × 50 mm geometry using the actual material properties of the circuit elements. The LC resonator was composed of a parallel plate capacitor coupled with a planar inductor deposited on an Al2O3 substrate using screen-printing, and the ceramic pattern was sintered at 1250 °C for 4 h in an ambient atmosphere. The sensitivity (average change in resonant frequency with respect to temperature) from 200–1200 °C was ~170 kHz/°C. The temperature-dependent electrical conductivity of the tin-doped indium oxide (ITO, 10% SnO2 doping) on the quality factor showed an increase of Qf from 36 to 43 between 200 °C and 1200 °C. The proposed ITO electrodes displayed improved sensitivity and quality factor at elevated temperatures, proving them to be an excellent candidate for temperature sensing in harsh environments. The microstructural analysis of the co-sintered LC resonator was performed using a scanning electron microscope (SEM) which showed that there are no cross-sectional and topographical defects after several thermal treatments.

Low-temperature UV irradiation of carbon/AgNWs counter electrodes for inexpensive flexible dye-sensitized solar cells

Here, we report an inexpensive and highly catalytic carbon/AgNWs counter electrode for flexible dye-sensitized solar cells (DSSCs). In order to reduce the process time, an organic surfactant is added to disperse the carbon composites. Then, a uniform catalytic layer can deposit on the silver nanowire (AgNW) transparent conductive electrode. Ultimately, a low temperature UV irradiation post-treatment is proposed to clean the surface of the catalytic layer. Through the electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) curve and Tafel curve, it can be established that this carbon/AgNWs counter electrode exhibits high catalytic activity than that of Pt/ tin-doped indium oxide (ITO) electrode. In addition, the current density–voltage characteristic curves also prove that the as-assembled DSSC has a superior photoelectrical conversion efficiency.

Controlled synthesis of luminescent ZnS nanosheets with high piezoelectric performance for designing mechanical energy harvesting device

For the first time, single-step fabrication of two-dimensional nanosheets of zinc sulfide (ZnS) was achieved employing flexible aluminum (Al) foil substrate using hydrothermal technique at 140 °C for ∼4 h. Indium doped Tin Oxide (ITO) coated on PET (Polyethylene Terephthalate) substrate and ZnS deposited Al foil as a top and bottom electrodes were used to fabricate a piezoelectric device. To generate an electric potential, the top ITO electrode was tapped on the ZnS nanosheets. The open-circuit voltage, VOC of ∼400 mV was obtained and analyzed for ZnS nanosheets based nanogenerator with gentle finger taping. However, the highest output for the single nanogenerator was found to be ∼600 mV by applying toe pressure. Additionally, switching polarity and superposition experiments were utilized to confirm the nanogenerator's performance, with the findings confirming piezo-electric voltage output. This study investigates the new potential for a ZnS-based high-efficient energy harvester that can scavenge biomechanical energy for next-generation flexible self-powered electronics devices as well as a good replacement for ZnO nanosheets in 2D nanostructured based nanogenerator devices due to its simple single-step production process, low cost, and high output gain.

Reversible Electrodeposition of Ni and Cu for Dynamic Windows

Reversible metal electrodeposition is a promising method for constructing dynamic windows with electronically switchable transparency. Through the reduction of lighting, heating, and cooling costs, these windows reduce energy consumption. Here, we design new electrolytes for reversible metal electrodeposition on tin-doped indium oxide electrodes based on the co-electrodeposition of Ni and Cu. We determined that synergistic effects between Ni and Cu facilitate spectroelectrochemical reversibility in contrast to the individual electrodeposition of these metals. The most reversible electrolytes contain chloride to improve electrodeposition kinetics and sulfamate ions to prevent the formation of dendrites. In addition to improving the color neutrality of the electrodeposits, nickel sulfamate in the electrolytes serves as a source of sulfamate ions that is soluble without added acid. After investigating the functions of the different electrolyte components, we then evaluated the performance of 25 cm2 two-electrode Ni-Cu dynamic windows.

Composite films based on copper nanoparticles and nickel phthalocyanine as electrochemical sensors for serotonin detection

Electrochemical sensors for detecting neurotransmitters have been extensively explored owing to the versatility and low cost of electrochemical techniques. Although serotonin (5-HT) is a very important neurotransmitter, very few studies have investigated its electrochemical detection. Herein, the use of layer-by-layer (LbL) films, containing layers of copper nanoparticles alternating with nickel phthalocyanine in indium-doped tin-oxide electrodes, for electrochemically detecting 5-HT is proposed. Copper nanoparticles were synthesized and characterized based on size, zeta potential, and spectroscopic behavior in the ultraviolet–visible (UV–Vis) region. Subsequently, the films were produced and characterized by UV–Vis spectroscopy and cyclic voltammetry. The electrochemical response of the films was evaluated as a function of the supporting electrolyte, number of adsorbed layers, material adsorption sequence, stability, electrochemical mechanism, and other parameters. In the electrochemical detection of serotonin, the developed material exhibited high sensitivity and specificity for 5-HT compared to some interferents such as ascorbic acid, hydrogen peroxide, cysteine, sulfamethoxazole, and aspartic acid. The results showed a 400% increase in the current densities of the film in the presence of 20 µmol•L−1 of 5-HT. The electrochemical signal recorded for 5-HT was unaffected even in the presence of ascorbic acid at the same concentration. The sensor exhibited a linear response over a wide concentration range (0.35–135 µmol•L−1) and a low detection limit (0.13 µmol•L−1) for 5-HT. Furthermore, the developed electrode enables successive 5-HT analyses without requiring new films. The material reported herein is promising for 5-HT electrochemical analysis in biological samples.

Organic Semiconductors for Optically Triggered Neural Interfacing: The Impact of Device Architecture in Determining Response Magnitude and Polarity

The use of organic semiconductor devices as photocapacitors is an innovation with promising applications in neural interface technologies, particularly for retinal prosthetics. Here we report the characterization of four distinct photocapacitor device architectures that were fabricated by depositing ultra-thin layers of poly-3-hexylthiophene and C60 fullerene in various combinations on tin-doped indium oxide (ITO) electrodes. We used electrophysiological recordings to measure the intrinsic photoresponse at 470 nm, and also to determine light-induced voltage perturbations in electrolyte solutions interfaced with these semiconductors. We also determined the light-induced intracellular voltage changes in co-cultured sensory neurons. Electrochemical impedance spectroscopy was used to establish the photocapacitive response mechanism of the intracellular changes upon illumination. The largest amplitude photocapacitive response was elicited from a neuron/acceptor-donor bilayer/ITO device architecture, whilst reversing the donor and acceptor layer order enabled a neuron response of the opposite polarity. The photoresponse in the neuron/acceptor/donor/ITO bilayer device configuration was significantly enhanced in both amplitude and time duration by electrical grounding of the indium tin oxide layer. We describe the advantages and limitations of each configuration of these device and discuss pathways towards the creation of optically triggered neural interfaces that do not require an external electrical power supply.

Lattice Constant Effect on Diffracted Transmission of ITO Periodic Nanostructures and Improvement of the Light Extraction Efficiency of Light-Emitting Diodes.

We studied the effects of the lattice pitch of indium-doped tin oxide (ITO) periodic nanostructures on the diffracted transmission to improve the light extraction efficiency of light-emitting diodes (LEDs). Periodic hexagonal ITO nanopillars with lattice constants of 600, 800, 1050, 1200, and 1600 nm were fabricated on ITO electrodes. We found that the light extraction efficiency strongly depended on the lattice constant. The LEDs with a lattice constant of 800 nm ITO nanopillars showed an increase in light extraction of 83%. In addition, their electrical properties were not degraded compared to conventional LEDs. The dependence of the extraction efficiency on the lattice constant was also calculated using a 3D finite-difference time-domain (FDTD) method, and this dependence was in good agreement with the experimental measurements. The transmission of each diffraction order and with the total transmission of ITO nanopillars with different lattice constants were calculated using the FDTD method to investigate the enhancement effect.

Electrolytes for reversible zinc electrodeposition for dynamic windows

Reversible Zn electrodeposition electrolytes enable dynamic window with electronically tuneable transmission.

High-performing silicon-based germanium Schottky photodetector with ITO transparent electrode* *Project supported by the National Key Research and Development Program of China (Grant No. 2018YFB2200103), the National Natural Science Foundation of China (Grant No. 61474094), and Principal Fund of Minnan Normal University (Grant No. KJ2020006).

A near-infrared germanium (Ge) Schottky photodetector (PD) with an ultrathin silicon (Si) barrier enhancement layer between the indium-doped tin oxide (ITO) electrode and Ge epilayer on Si or silicon-on-insulator (SOI) is proposed and fabricated. The well-behaved ITO/Si cap/Ge Schottky junctions without intentional doping process for the Ge epilayer are formed on the Si and SOI substrates. The Si- and SOI-based ITO/Si cap/Ge Schottky PDs exhibit low dark current densities of 33 mA/cm2 and 44 mA/cm2, respectively. Benefited from the high transmissivity of ITO electrode and the reflectivity of SOI substrate, an optical responsivity of 0.19 A/W at 1550 nm wavelength is obtained for the SOI-based ITO/Si cap/Ge Schottky PD. These complementary metal–oxide–semiconductor (CMOS) compatible Si (or SOI)-based ITO/Si cap/Ge Schottky PDs are quite useful for detecting near-infrared wavelengths with high efficiency.

Electrochemical Characteristics of Azo Dyes Doped Poly(3,4-Ethylenedioxythiophene)

In the present study, the electrosynthesis and the electrochemical characterization of azo dyes doped poly(3,4-ethylenedioxythiophene (PEDOT) were described. PEDOT film was electrochemically deposited onto indium doped tin oxide (ITO) coated/glass electrode, following azo dyes adsorption. The electropolymerized-PEDOT films on ITO glass were doped with various azo dyes; 4-Phenylazo-2-phenyliminomethyl-phenol (PAPM), 4-Phenylazo-2-(p-tolyimino-methyl)-phenol (PATM) and 4-[(2-Hydroxy-5-phenylazo-benzylidene)-amino]-benzenesulfonic acid (HPAB). The structures of azo dyes-doped PEDOT were characterized via cycle voltammograms and electrochemical impedance spectroscopy (EIS). Diverse doping counterions have a significant influence on the electrochemical behaviour of electropolymerized-PEDOT film. The electropolymerized-PEDOT doped by HPAB (PEDOT-HPAB) film possesses higher electrochemical activity than other azo dye-doped PEDOT composites. The main characteristics of PEDOT-azo dyes films contain uniformity, durability, and adherent on ITO electrodes, which are better when it is compared to PEDOT film.

Influence of the Substrate on the Optical and Photo-electrochemical Properties of Monolayer MoS2.

Substrates influence the electrical and optical properties of monolayer (ML) MoS2 in field-effect transistors and photodetectors. Photoluminescence (PL) and Raman spectroscopy measurements have shown that conducting substrates can vary the doping concentration and influence exciton decay channels in ML-MoS2. Doping and exciton decay dynamics are expected to play a major role in the efficiency of light-driven chemical reactions, but it is unclear to what extent these factors contribute to the photo(electro)catalytic properties of ML-MoS2. Here, we report spatially resolved PL, Raman, and photo-electrochemical current measurements of 5-10 μm-wide ML-MoS2 triangles deposited on pairs of indium-doped tin oxide (ITO) electrodes that are separated by a narrow insulating quartz channel [i.e., an ITO interdigitated array (IDA) electrode]. Optical microscopy images and atomic force microscopy measurements revealed that the ML-MoS2 triangles lie conformally on the quartz and ITO substrates. The PL spectrum of MoS2 shifts and decreases in intensity in the ITO region, which can be attributed to differences in nonradiative and radiative exciton decay channels. Raman spectra showed no significant peak shifts on the two substrates that would have indicated a substrate-induced doping effect. We spatially resolved the photo-electrochemical current because of hole-induced iodide oxidation and observed that ML-MoS2 produces lower photocurrents in the quartz region than in the ITO region. The correlated PL, Raman, and photocurrent mapping data show that the MoS2/quartz interface diminishes fast nonradiative exciton decay pathways but the photocurrent response in the quartz region is likely limited by inefficient in-plane carrier transport to the ITO electrode because of carrier recombination with S vacancies in MoS2 or charged impurities in the quartz substrate. Nonetheless, the experimental methodology presented herein provides a framework to evaluate substrate engineering strategies to tune the (photo)electrocatalytic properties of two-dimensional materials.

Effects of indium-doped tin oxide film on electrochromic properties under lithium ion guidance

Electrochromic material can change its optical property by the applied low electric field. It has attracted more attention because of its potential application in various fields. In this paper, the simple electrochromic device was manufactured by the indium-doped tin oxide (ITO) glass as the electrochromic layer. The optical transmittance of ITO was modulated by the injection/extraction of Li+. The device can cyclically reversible change between the colorless and colored states by the extracting/inserting of Li+ in the ITO electrode. These finds indicated that ITO can become the potential candidate for electrochromic material with low cost and good coloring efficiency.

Electrochemical immunoassay for the detection of stress biomarkers

A rapid electrochemical immunoassay method was developed to detect and measure stress biomarkers (cortisol and cortisone) in two biological samples (Zebrafish whole-body and artificial saliva). This methodology utilizes an immunoassay approach taking advantage of the lock and key mechanism that is related to the antibody-antigen interaction depending on the reliable immobilization of the antibody labelled with ferrocene tags (Ab-Fc) on a modified tin-doped indium oxide (ITO) electrode using electrochemical instrumentation to build a POC platform. The limit of detection (LOD) obtained for this biosensor was 1.03 pg ml−1 for cortisol and 0.68 pg ml−1 for cortisone, respectively. The correlation coefficient was 0.9852 and 0.9841 for cortisol and cortisone, respectively with a linear concentration from (0-50 ng ml−1) which covers the standard levels of stress hormones in both selected biological samples. The incubation time was investigated and 30 min was found to be the optimum incubation time. This time would be acceptable for the POC system as total process time can be determined within 35 min.

Carbon quantum dot-incorporated nickel oxide for planar p-i-n type perovskite solar cells with enhanced efficiency and stability

Carbon quantum dots (CQDs) have attracted extreme interest as a promising nanocarbon platform for divergence optoelectronics due to their high stability, good dispersibility in solvents, and tunable optical and electronic properties. Herein, planar p-i-n type perovskite solar cells (PSCs) with enhanced efficiency and long-term stability were developed by incorporating CQDs into a nickel oxide (NiO) hole transport layer (HTL). The incorporation of CQDs downshifts the band structure of NiO, leading to good alignment with the work-function of the tin-doped indium oxide (ITO) electrode and the band-edges of the perovskite. The efficient cascade charge transport achieved with the optimized incorporation ratio of CQDs resulted in an enhanced power conversion efficiency (PCE) of 17.02%, compared to that of the PSC fabricated with bare NiO (15.66%), even though they were fabricated in air. The suppressed charge recombination accompanied by restricted charge accumulation curtails the J-V hysteresis, with a reduction from 4.5% to less than 1%. Moreover, long-term stability under atmospheric conditions without any encapsulation was achieved with CQD-incorporated NiO. More than 70% of the initial PCE was retained over 190 h. This work suggests a novel strategy for fabricating solution-processible metal oxide interlayers with highly efficient charge migration for divergence energy conversion devices.