γ-Ray Irradiation Enables Annealing- and Light-Soaking-Free Solution Processable SnO2 Electron Transport Layer for Inverted Organic Solar Cells

The electrode buffer layer is crucial for high-performance and stable OSCs, optimizing charge transport and energy level alignment at the interface between the polymer active layer and electrode. Recently, SnO2 has emerged as a promising material for the cathode buffer layer due to its desirable properties, such as high electron mobility, transparency, and stability. Typically, SnO2 nanoparticle layers require a postannealing treatment above 150°C in an air environment to remove the surfactant ligands and obtain high-quality thin films. However, this poses challenges for flexible electronics as flexible substrates can't tolerate temperatures exceeding 100°C. This study presents solution-processable and annealing-free SnO2 nanoparticles by employing y-ray irradiation to disrupt the bonding between surfactant ligands and SnO2 nanoparticles. The SnO2 layer treated with y-ray irradiation is used as an electron transport layer in OSCs based on PTB7-Th:IEICO-4F. Compared to the conventional SnO2 nanoparticles that required high-temperature annealing, the y-SnO2 nanoparticle-based devices exhibit an 11% comparable efficiency without postannealing at a high temperature. Additionally, y-ray treatment has been observed to eliminate the light-soaking effect of SnO2. By eliminating the high-temperature postannealing and light-soaking effect, y-SnO2 nanoparticles offer a promising, cost-effective solution for future flexible solar cells fabricated using roll-to-roll mass processing.

Outstanding Fill Factor in Inverted Organic Solar Cells with SnO2 by Atomic Layer Deposition

Transport layers are of outmost importance for thin-film solar cells, determining not only their efficiency but also their stability. To bring one of these thin-film technologies toward mass production, many factors besides efficiency and stability become important, including the ease of deposition in a scalable manner and the cost of the different material's layers. Herein, highly efficient organic solar cells (OSCs), in the inverted structure (n-i-p), are demonstrated by using as electron transport layer (ETL) tin oxide (SnO2) deposited by atomic layer deposition (ALD). ALD is an industrial grade technique which can be applied at the wafer level and also in a roll-to-roll configuration. A champion power conversion efficiency (PCE) of 17.26% and a record fill factor (FF) of 79% are shown by PM6:L8-BO OSCs when using ALD-SnO2 as ETL. These devices outperform solar cells with SnO2 nanoparticles casted from solution (PCE 16.03%, FF 74%) and also those utilizing the more common sol-gel ZnO (PCE 16.84%, FF 77%). The outstanding results are attributed to a reduced charge carrier recombination at the interface between the ALD-SnO2 film and the active layer. Furthermore, a higher stability under illumination is demonstrated for the devices with ALD-SnO2 in comparison with those utilizing ZnO.

High-Throughput Deposition of Recyclable SnO2 Electrodes toward Efficient Perovskite Solar Cells

Chemical bath deposited (CBD) SnO2 is one of the most prevailing electron transport layers for realizing high-efficiency perovskite solar cells (PSCs) so far. However, the state-of-the-art CBD SnO2 process is time-consuming, contradictory to its prospect in industrialization. Herein, a simplified yet efficient method is developed for the fast deposition of SnO2 electrodes by incorporating a concentrated Sn source stabilized by the ethanol ligand with antimony (Sb) doping. The higher concentration of Sn source promotes the deposition rate, and Sb doping improves the hole-blocking capability of the CBD SnO2 layer so that its target thickness can be reduced to further save the deposition time. As a result, the deposition time can be appreciably reduced from 3-4 h to only 5 min while maintaining 95% of the maximum efficiency, indicating the power of the method toward high-throughput production of efficient PSCs. Additionally, the CBD SnO2 substrates are recyclable after removing the upper layers of complete PSCs, and the refurbished PSCs can maintain ≈98% of their initial efficiency after three recycling-and-fabrication processes.

Localized Oxidation Embellishing Strategy Enables High-Performance Perovskite Solar Cells

Perovskite solar cell (pero-SC) has attracted extensive studies as a promising photovoltaic technology, wherein the electron extraction and transfer exhibit pivotal effect to the device performance. The planar SnO2 electron transport layer (ETL) has contributed the recent record power conversion efficiency (PCE) of the pero-SCs, yet still suffers from surface defects of SnO2 nanoparticles which brings energy loss and phase instability. Herein, we report a localized oxidation embellishing (LOE) strategy by applying (NH4 )2 CrO4 on the SnO2 ETL. The LOE strategy builds up plentiful nano-heterojunctions of p-Cr2 O3 /n-SnO2 and the nano-heterojunctions compensate the surface defects and realize benign energy alignment, which reduces surface non-radiative recombination and voltage loss of the pero-SCs. Meanwhile, the decrease of lattice mismatch released the lattice distortion and eliminated tensile stress, contributing to better stability of the devices. The pero-SCs based on α-FAPbI3 with the SnO2 ETL treated by the LOE strategy realized a PCE of 25.72 % (certified as 25.41 %), along with eminent stability performance of T90 >700 h. This work provides a brand-new view for defect modification of SnO2 electron transport layer.

Modeling the Conduction Mechanism in Chemoresistive Gas Sensor Based on Single-Crystalline Sn3O4 Nanobelts: A Phenomenological In Operando Investigation

Investigating the sensing mechanisms in semiconducting metal oxide (SMOx) gas sensors is essential for optimizing their performance across a wide range of potential applications. Despite significant progress in the field, there are still many gaps in comprehending the phenomenological processes occurring in one-dimensional (1D) nanostructures. This article presents the first insights into the conduction mechanism of chemoresistive gas sensors based on single-crystalline Sn3O4 nanobelts using the operando Kelvin Probe technique. From this approach, direct current (DC) electrical resistance and work function changes were simultaneously measured in different working conditions, and a correlation between the conductance and the surface band bending was established. Appropriate modeling was proposed, and the results revealed that the conduction mechanism in the single-crystalline one-dimensional nanostructures closely aligns with the behavior observed in single-crystalline epitaxial layers rather than in polycrystalline grains. Based on this assumption, relevant parameters were further estimated, including Debye length, concentration of free charge carriers, effective density of states in the conduction band, and position of the Fermi level. Overall, this study provides an effective contribution to understanding the role of surface chemistry in the transduction of the electrical signal generated from gas adsorption in single-crystalline one-dimensional nanostructures.

Polymer-Doped SnO2 as an Electron Transport Layer for Highly Efficient and Stable Perovskite Solar Cells

To produce highly efficient and repeatable perovskite solar cells (PSCs), comprehending interfacial loss and developing approaches to ameliorate interfacial features is essential. Nonradiative recombination at the SnO2-perovskite interface in SnO2-based perovskite solar cells (PSCs) leads to significant potential loss and variability in device performance. To improve the quality of the SnO2 electron transport layer, a novel polymer-doped SnO2 matrix, specifically using polyacrylic acid, was developed. This matrix is formed by spin-coating a SnO2 colloidal solution that includes polymers. The polymer aids in dispersing nanoparticles within the substrate and is evenly distributed in the SnO2 solution. As a result of the polymer addition, the density and wetting properties of the SnO2 layer substantially improved. Subsequently, perovskite-based photovoltaic devices comprising SnO2 and Spiro-OMeTAD layers and using (FAPbI3)0.97(MAPbBr3)0.03 perovskite are constructed. These optimized devices exhibited an increased efficiency of 17.2% when compared to the 15.7% power conversion efficiency of the control device. The incorporation of polymers in the electron transport layer potentially enables even better performance in planar perovskite solar cells.

Synthesis and Characterization of the Zinc-Oxide: Tin-Oxide Nanoparticle Composite and Assessment of Its Antibacterial Activity: An In Vitro Study

Introduction Nanoparticles (NPs) have been widely used for biomedical applications. Various methods of synthesis of NPs have been performed and the sol-gel technique is one of the most common and feasible methods. ZnO and SnO2 NPs are widely used due to their interesting properties and versatile medical applications. The present study aimed to synthesize a composite of ZnO- SnO2 NPs and evaluate its structural, morphological, and antibacterial properties. Materials and methods ZnO-SnO2 NPs were prepared via the sol-gel technique. The morphological study was performed by scanning electron microscopy (SEM) imaging, the structural study was performed by X-ray diffraction (XRD) analysis, and chemical studies were performed by Fourier transform infrared spectroscopy (FT-IR) and energy-dispersive X-ray spectroscopy (EDAX). Antibacterial properties of the NPs were assessed by the agar diffusion test and the area of bacterial growth that was inhibited was measured under high and low concentrations of the NPs. Results The SEM analysis confirmed the irregular shape and elemental composition of the synthesized NPs. The purity of the NPs was confirmed by the EDAX spectrum, which indicates the weight percentages of the elements in the NPs as follows: Sn-53.8%, Zn-12.5%, O-29.1%, and C-4.7%. The chemical bonds between the NPs were confirmed by Fourier transform infrared spectroscopy. XRD analysis confirmed the high degree of crystallinity of the NPs and orthorhombic structure of SnO2 and the hexagonal structure of ZnO. The zone of inhibition against S. aureus, S. mutans, and E. coli for low concentrations of the NPs was 24 mm, 26 mm, and 30 mm and for high concentrations of the NPs it was 26 mm, 28 mm, and 31mm and these values were similar to the control antibiotics.  Conclusion ZnO- SnO2 NPs were successfully prepared by the sol-gel method. The presence of NPs was confirmed and successfully characterized. The prepared NPs had a good antimicrobial effect against the tested pathogens.

Carboxymethylcellulose/Agar-Based Multifunctional Films Incorporated with Zn-Doped SnO2 Nanoparticles for Active Food Packaging Application

SnO2 and Zn-SnO2 nanoparticles were prepared by chemical precipitation, and the rutile phase of SnO2 was confirmed through X-ray diffraction studies. X-ray photoelectron spectroscopy (XPS) confirmed the doping of SnO2 with Zn and elucidated the surface chemistry before and after doping. The average sizes of SnO2 and Zn-SnO2 nanoparticles determined using TEM were 3.96 ± 0.85 and 3.72 ± 0.9 nm, respectively. UV-visible and photoluminescence spectrophotometry were used to evaluate the optical properties of SnO2 and Zn-SnO2 nanoparticles, and their energy gaps (Eg) were 3.8 and 3.9 eV, respectively. The antibacterial activity of these nanoparticles against Salmonella enterica and Staphylococcus aureus was evaluated under dark and light conditions. Antibacterial activity was higher in light, showing the highest activity (99.5%) against S. enterica. Carboxymethylcellulose (CMC)/agar-based functional composite films were prepared by adding different amounts of SnO2 and Zn-SnO2 nanoparticles (1 and 3 wt % of polymers). The composite film showed significantly increased UV barrier properties while maintaining the mechanical properties, water vapor barrier, and transparency compared to the neat CMC/agar film. These composite films showed significant antibacterial activity; however, the Zn-SnO2-added film showed stronger antibacterial activity (99.2%) than the SnO2-added film (15%).

Influence of NF3 Plasma-Treated HfO2 Gate Insulator Surface on Tin Oxide Thin-Film Transistors

We studied the impact of NF3 plasma treatment on the HfO2 gate insulator of amorphous tin oxide (a-SnOx) thin-film transistors (TFTs). The plasma treatment was for 0, 10, or 30 s. The HfO2 insulator demonstrated a slightly higher breakdown voltage, whereas the capacitance value remained almost constant (~150 nF/cm2). The linear mobility slightly increased from ~30 to ~35 cm2/Vs when the treatment time increased from 0 to 10 s, whereas a 30 s-treated TFT demonstrated a decreased mobility of ~15 cm2/Vs. The subthreshold swing and the threshold voltage remained in the 100-120 mV/dec. range and near 0 V, respectively. The hysteresis dramatically decreased from ~0.5 V to 0 V when a 10 s treatment was applied, and the 10 s-treated TFT demonstrated the best stability under high current stress (HCS) of 100 μA. The analysis of the tin oxide thin film crystallinity and oxygen environment demonstrated that the a-SnOx remained amorphous, whereas more metal-oxygen bonds were formed with a 10 s NF3 plasma treatment. We also demonstrate that the density of states (DOS) significantly decreased in the 10 s-treated TFT compared to the other conditions. The stability under HCS was attributed to the HfO2/a-SnOx interface quality.

Properties of tin oxide films grown by atomic layer deposition from tin tetraiodide and ozone

Polycrystalline SnO2 thin films were grown by atomic layer deposition (ALD) on SiO2/Si(100) substrates from SnI4 and O3. Suitable evaporation temperatures for the SnI4 precursor as well as the relationship between growth per cycle and substrate temperature were determined. Crystal growth in the films in the temperature range of 225-600 °C was identified. Spectroscopic analyses revealed low amounts of residual iodine and implied the formation of single-phase oxide in the films grown at temperatures above 300 °C. Appropriateness of the mentioned precursor system to the preparation of SnO2 films was established.

Two-Dimensional Synergistic Interfacial Orientation on Tin Oxide-Reinforced Cobalt Carbonate Hydroxide Heterostructures for High-Performance Energy Storage

A hierarchical cobalt carbonate hydroxide (CCH) nanostructure with outstanding electrochemical kinetics and structural stability for energy storage is largely unknown. Herein, we report tin oxide-functionalized CCH surface-enabled unique two-dimensional (2D) interlayered heterostructures that promote high conductivity with more electroactive sites to maximize redox reactions. A simple electrodeposition technique was utilized to construct the hierarchical 2D CCH electrode, while a surface-reinforced method was employed to fabricate the 2D interlayered SnO on CCH. The fabricated SnO@CCH-8 electrode showed a maximum areal capacity of 720 mC cm-2 (specific capacitance of 515 F g-1) at a current density of 1 mA cm-2 in 3 M KOH electrolyte. The obtained results indicate that the synergetic effect of SnO in the CCH network delivers an efficient charge transfer pathway to achieve high-performance energy storage. Moreover, SnO@CCH-8//AC was devised as a hybrid supercapacitor (HSC), ensuring a maximum specific capacitance of 129 F g-1 and maximum specific energy and power of 40.25 W h kg-1 and 9000 W kg-1, respectively, with better capacitance retention (94%) even beyond 10,000 cycles. To highlight the excellent performance in real-time studies, the HSC was constructed using a coin cell and displayed to power 21 light-emitting diodes (LEDs).

Rational Design of a Chemical Bath Deposition Based Tin Oxide Electron-Transport Layer for Perovskite Photovoltaics

Chemical bath deposition (CBD) is widely used to deposit tin oxide (SnOx ) as an electron-transport layer in perovskite solar cells (PSCs). The conventional recipe uses thioglycolic acid (TGA) to facilitate attachments of SnOx particles onto the substrate. However, nonvolatile TGA is reported to harm the operational stability of PSCs. In this work, a volatile oxalic acid (OA) is introduced as an alternative to TGA. OA, a dicarboxylic acid, functions as a chemical linker for the nucleation and attachment of particles to the substrate in the chemical bath. Moreover, OA can be readily removed through thermal annealing followed by a mild H2 O2 treatment, as shown by FTIR measurements. Synergistically, the mild H2 O2 treatment selectively oxidizes the surface of the SnOx layer, minimizing nonradiative interface carrier recombination. EELS (electron-energy-loss spectroscopy) confirms that the SnOx surface is dominated by Sn4+ , while the bulk is a mixture of Sn2+ and Sn4+ . This rational design of a CBD SnOx layer leads to devices with T85 ≈1500 h, a significant improvement over the TGA-based device with T80 ≈250 h. The champion device reached a power conversion efficiency of 24.6%. This work offers a rationale for optimizing the complex parameter space of CBD SnOx to achieve efficient and stable PSCs.

SnO2-Based Memory Device with Filamentary Switching Mechanism for Advanced Data Storage and Computing

In this study, we fabricate a Pt/TiN/SnOx/Pt memory device using reactive sputtering to explore its potential for neuromorphic computing. The TiON interface layer, formed when TiN comes into contact with SnO2, acts as an oxygen vacancy reservoir, aiding the creation of conductive filaments in the switching layer. Our SnOx-based device exhibits remarkable endurance, with over 200 DC cycles, ON/FFO ratio (>20), and 104 s retention. Set and reset voltage variabilities are impressively low, at 9.89% and 3.2%, respectively. Controlled negative reset voltage and compliance current yield reliable multilevel resistance states, mimicking synaptic behaviors. The memory device faithfully emulates key neuromorphic characteristics, encompassing both long-term potentiation (LTP) and long-term depression (LTD). The filamentary switching mechanism in the SnOx-based memory device is explained by an oxygen vacancy concentration gradient, where current transport shifts from Ohmic to Schottky emission dominance across different resistance states. These findings exemplify the potential of SnOx-based devices for high-density data storage memory and revolutionary neuromorphic computing applications.

Recent Advances of Doped SnO2 as Electron Transport Layer for High-Performance Perovskite Solar Cells

Perovskite solar cells (PSCs) have garnered considerable attention over the past decade owing to their low cost and proven high power conversion efficiency of over 25%. In the planar heterojunction PSC structure, tin oxide was utilized as a substitute material for the TiO2 electron transport layer (ETL) owing to its similar physical properties and high mobility, which is suitable for electron mining. Nevertheless, the defects and morphology significantly changed the performance of SnO2 according to the different deposition techniques, resulting in the poor performance of PSCs. In this review, we provide a comprehensive insight into the factors that specifically influence the ETL in PSC. The properties of the SnO2 materials are briefly introduced. In particular, the general operating principles, as well as the suitability level of doping in SnO2, are elucidated along with the details of the obtained results. Subsequently, the potential for doping is evaluated from the obtained results to achieve better results in PSCs. This review aims to provide a systematic and comprehensive understanding of the effects of different types of doping on the performance of ETL SnO2 and potentially instigate further development of PSCs with an extension to SnO2-based PSCs.

The Role of SnO2 Processing on Ionic Distribution in Double-Cation-Double Halide Perovskites

Moving toward a future of efficient, accessible, and less carbon-reliant energy devices has been at the forefront of energy research innovations for the past 30 years. Metal-halide perovskite (MHP) thin films have gained significant attention due to their flexibility of device applications and tunable capabilities for improving power conversion efficiency. Serving as a gateway to optimize device performance, consideration must be given to chemical synthesis processing techniques. Therefore, how does common substrate processing techniques influence the behavior of MHP phenomena such as ion migration and strain? Here, we demonstrate how a hybrid approach of chemical bath deposition (CBD) and nanoparticle SnO₂ substrate processing significantly improves the performance of (FAPbI₃)_0.97(MAPbBr₃)_0.03 by reducing micro-strain in the SnO₂ lattice, allowing distribution of K⁺ from K-Cl treatment of substrates to passivate defects formed at the interface and produce higher current in light and dark environments. X-ray diffraction reveals differences in lattice strain behavior with respect to SnO₂ substrate processing methods. Through use of conductive atomic force microscopy (c-AFM), conductivity is measured spatially with MHP morphology, showing higher generation of current in both light and dark conditions for films with hybrid processing. Additionally, time-of-flight secondary ionization mass spectrometry (ToF-SIMS) observed the distribution of K⁺ at the perovskite/SnO₂ interface, indicating K⁺ passivation of defects to improve the power conversion efficiency (PCE) and device stability. We show how understanding the role of ion distribution at the SnO₂ and perovskite interface can help reduce the creating of defects and promote a more efficient MHP device.

1D Narrow-Bandgap Tin Oxide Materials: Systematic High-Resolution TEM and Raman Analysis

We demonstrate for the first time the structure identification and narrow-bandgap property of 1D hybridized SnO/SnO₂ nanoparticles derived from the calcination of a single-source precursor, i.e., tin(II) oxalate. Systematic Raman analysis together with high-resolution TEM (HR-TEM) measurements of the tin oxide samples were carried out by changing the calcination temperatures. These data revealed the simultaneous formation of 1D SnO/SnO₂ in the rod particles that grew in air. It was also found that Sn(II) can be introduced by changing the concentration of Sn(II) salt in the precursor synthesis and the maximum temperature in calcination. Particles measuring 20~30 nm were sintered to produce tin oxide nanorods including tin monoxide, SnO. Photoabsorption properties associated with the formation of the SnO/SnO₂ nanocomposites were also investigated. Tauc plots indicate that the obtained tin oxide samples had a lower bandgap of 2.9~3.0 eV originating from SnO in addition to a higher bandgap of around 3.5~3.7 eV commonly observed for SnO₂. Such 1D SnO_x/SnO₂ hybrids via tin oxalate synthesis with this optical property would benefit new materials design for photoenergy conversion systems, such as photocatalysts.

Synthesis of PMMA Microspheres with Tunable Diameters: Evaluation as a Template in the Synthesis of Tin Oxide Coatings

The synthesis of polymethyl methacrylate (PMMA) spheres with different sizes has been a challenge. PMMA has promise for future applications, e.g., as a template for preparing porous oxide coatings by thermal decomposition. Different amounts of SDS as a surfactant are used as an alternative to control PMMA microsphere size through the formation of micelles. The objectives of the study were twofold: firstly, to determine the mathematical relationship between SDS concentration and PMMA sphere diameter, and secondly, to assess the efficacy of PMMA spheres as templates for SnO₂ coating synthesis and their impact on porosity. The study used FTIR, TGA, and SEM techniques to analyze the PMMA samples, and SEM and TEM techniques were used for SnO₂ coatings. The results showed that PMMA sphere diameter could be adjusted by varying the SDS concentration, with sizes ranging from 120 to 360 nm. The mathematical relationship between PMMA sphere diameter and SDS concentration was determined with a y = ax^b type equation. The porosity of SnO₂ coatings was found to be dependent on the PMMA sphere diameter used as a template. The research concludes that PMMA can be used as a template to produce oxide coatings, such as SnO₂, with tunable porosities.

Improving Hazardous Gas Detection Behavior with Palladium Decorated SnO2 Nanobelts Networks

Transparent Conductive Oxides (TCOs) have been widely used as sensors for various hazardous gases. Among the most studied TCOs is SnO₂, due to tin being an abundant material in nature, and therefore being accessible for moldable-like nanobelts. Sensors based on SnO₂ nanobelts are generally quantified according to the interaction of the atmosphere with its surface, changing its conductance. The present study reports on the fabrication of a nanobelt-based SnO₂ gas sensor, in which electrical contacts to nanobelts are self-assembled, and thus the sensors do not need any expensive and complicated fabrication processes. The nanobelts were grown using the vapor-solid-liquid (VLS) growth mechanism with gold as the catalytic site. The electrical contacts were defined using testing probes, thus the device is considered ready after the growth process. The sensorial characteristics of the devices were tested for the detection of CO and CO₂ gases at temperatures from 25 to 75 °C, with and without palladium nanoparticle deposition in a wide concentration range of 40-1360 ppm. The results showed an improvement in the relative response, response time, and recovery, both with increasing temperature and with surface decoration using Pd nanoparticles. These features make this class of sensors important candidates for CO and CO₂ detection for human health.

3D Hierarchically Structured Tin Oxide and Iron Oxide-Embedded Carbon Nanofiber with Outermost Polypyrrole Layer for High-Performance Asymmetric Supercapacitor

Herein, unique three-dimensional (3D) hierarchically structured carbon nanofiber (CNF)/metal oxide/conducting polymer composite materials were successfully synthesized by combinations of various experimental methods. Firstly, base CNFs were synthesized by carbonization of electrospun PAN/PVP fibers to attain electric double-layer capacitor (EDLC) characteristics. To further enhance the capacitance, tin oxide (SnO₂) and iron oxide (Fe₂O₃) were coated onto the CNFs via facile hydrothermal treatment. Finally, polypyrrole (PPy) was introduced as the outermost layer by a dispersion polymerization method under static condition to obtain 3D-structured CNF/SnO₂/PPy and CNF/Fe₂O₃/PPy materials. With each synthesis step, the morphology and dimension of materials were transformed, which also added the benign characteristic for supercapacitor application. For the practical application, as-synthesized CNF/SnO₂/PPy and CNF/Fe₂O₃/PPy were applied as active materials for supercapacitor electrodes, and superb specific capacitances of 508.1 and 426.8 F g^-1 (at 1 A g^-1) were obtained (three-electrode system). Furthermore, an asymmetric supercapacitor (ASC) device was assembled using CNF/SnO₂/PPy as the positive electrode and CNF/Fe₂O₃/PPy as the negative electrode. The resulting CNF/SnO₂/PPy//CNF/Fe₂O₃/PPy device exhibited excellent specific capacitance of 101.2 F g^-1 (at 1 A g^-1). Notably, the ASC device displayed a long-term cyclability (at 2000 cycles) with a retention rate of 81.1%, compared to a CNF/SnO₂//CNF/Fe₂O₃ device of 70.3% without an outermost PPy layer. By introducing the outermost PPy layer, metal oxide detachment from CNFs were prevented to facilitate long-term cyclability of electrodes. Accordingly, this study provides an effective method for manufacturing a high-performance and stable supercapacitor by utilizing unique 3D hierarchical materials, comprised of CNF, metal oxide, and conducting polymer.

Enhanced Performance of WO3/SnO2 Nanocomposite Electrodes with Redox-Active Electrolytes for Supercapacitors

For effective supercapacitors, we developed a process involving chemical bath deposition, followed by electrochemical deposition and calcination, to produce WO₃/SnO₂ nanocomposite electrodes. In aqueous solutions, the hexagonal WO₃ microspheres were first chemically deposited on a carbon cloth, and then tin oxides were uniformly electrodeposited. The synthesized WO₃/SnO₂ nanocomposite was characterized by XRD, XPS, SEM, and EDX techniques. Electrochemical properties of the WO₃/SnO₂ nanocomposite were analyzed by cyclic voltammetry, galvanostatic charge-discharge tests, and electrochemical impedance spectroscopy in an aqueous solution of Na₂SO₄ with/without the redox-active electrolyte K₃Fe(CN)₆. K₃Fe(CN)₆ exhibited a synergetic effect on the electrochemical performance of the WO₃/SnO₂ nanocomposite electrode, with a specific capacitance of 640 F/g at a scan rate of 5 mV/s, while that without K₃Fe(CN)₆ was 530 F/g. The WO₃/SnO₂ nanocomposite catalyzed the redox reactions of [Fe(CN)₆]³/[Fe(CN)₆]^4- ions, and the [Fe(CN)₆]^3-/[Fe(CN)₆]^4- ions also promoted redox reactions of the WO₃/SnO₂ nanocomposite. A symmetrical configuration of the nanocomposite electrodes provided good cycling stability (coulombic efficiency of 99.6% over 2000 cycles) and satisfied both energy density (60 Whkg^-1) and power density (540 Wkg^-1) requirements. Thus, the WO₃/SnO₂ nanocomposite prepared by this simple process is a promising component for a hybrid pseudocapacitor system with a redox-flow battery mechanism.

Novel Sb-SnO2 Electrode with Ti3+ Self-Doped Urchin-Like Rutile TiO2 Nanoclusters as the Interlayer for the Effective Degradation of Dye Pollutants

Stable and efficient SnO₂ electrodes are very promising for effectively degrading refractory organic pollutants in wastewater treatment. In this regard, we firstly prepared Ti³⁺ self-doped urchin-like rutile TiO₂ nanoclusters (TiO_2-x NCs) on a Ti mesh substrate by hydrothermal and electroreduction to serve as an interlayer for the deposition of Sb-SnO₂ . The TiO_2-x NCs/Sb-SnO₂ anode exhibited a high oxygen evolution potential (2.63 V vs. SCE) and strong ⋅OH generation ability for the enhanced amount of absorbed oxygen species. Thus, the degradation results demonstrated its good rhodamine B (RhB), methylene blue (MB), alizarin yellow R (AYR), and methyl orange (MO) removal performance, with the rate constant increased 5.0, 1.9, 1.9, and 4.7 times, respectively, compared to the control Sb-SnO₂ electrode. RhB and AYR degradation mechanisms are also proposed based on the results of high-performance liquid chromatography coupled with mass spectrometry and quenching experiments. More importantly, this unique rutile interlayer prolonged the anode lifetime sixfold, given its good lattice match with SnO₂ and the three-dimensional concave-convex structure. Consequently, this work paves a new way for designing the crystal form and structure of the interlayers to obtain efficient and stable SnO₂ electrodes for addressing dye wastewater problems.

Spectromicroscopy Studies of Silicon Nanowires Array Covered by Tin Oxide Layers

The composition and atomic and electronic structure of a silicon nanowire (SiNW) array coated with tin oxide are studied at the spectromicroscopic level. SiNWs are covered from top to down with a wide bandgap tin oxide layer using a metal-organic chemical vapor deposition technique. Results obtained via scanning electron microscopy and X-ray diffraction showed that tin-oxide nanocrystals, 20 nm in size, form a continuous and highly developed surface with a complex phase composition responsible for the observed electronic structure transformation. The "one spot" combination, containing a chemically sensitive morphology and spectroscopic data, is examined via photoemission electron microscopy in the X-ray absorption near-edge structure spectroscopy (XANES) mode. The observed spectromicroscopy results showed that the entire SiNW surface is covered with a tin(IV) oxide layer and traces of tin(II) oxide and metallic tin phases. The deviation from stoichiometric SnO₂ leads to the formation of the density of states sub-band in the atop tin oxide layer bandgap close to the bottom of the SnO₂ conduction band. These observations open up the possibility of the precise surface electronic structures estimation using photo-electron microscopy in XANES mode.

Room Temperature Humidity Tolerant Xylene Sensor Using a Sn-SnO2 Nanocomposite

Xylene is one of the representative indoor pollutants, even in ppb levels, that affect human health directly. Due to the non-polar and less reactive nature of xylene, its room temperature detection is challenging. This work demonstrates a metallic tin-doped Sn-SnO₂ nanocomposite under controlled pH conditions via a simple solvothermal route. The Sn nanoparticles are uniformly distributed inside the SnO₂ nanospheres of ∼70 nm with a high specific surface area of 118.8 m²/g. The surface of the Sn-SnO₂ nanocomposite exhibits strong affinity toward benzene, toluene, ethylbenzene, and xylene (BTEX) compared to other polar volatile organic compounds (VOCs) such as ethanol, acetone, isopropyl alcohol, formaldehyde, and chloroform tested in this study. The sensor's response is highest for xylene among BTEX molecules. Under ambient room temperature conditions, the sensor exhibits a linear response to xylene in the 1-100 ppm range with a sensitivity of ∼255% at 60 ppm within ∼1.5 s and recovers in ∼40 s. The sensor is hardly affected by humidity variations (40-70%), leading to enhanced reliability and repeatability under dynamic environmental conditions. The meso and microporous nanosphere morphology act as a nanocontainer for non-polar VOCs to diffuse inside the nanostructures, providing easy accessibility. The metallic Sn increases the affinity for less reactive xylene at room temperature. Thus, the nanocatalytic Sn-SnO₂ nanocomposite is an active gas/VOC sensing material and provides an effective solution for sensing major indoor pollutants under humid conditions.

Synthesis, Structural and Sensor Properties of Nanosized Mixed Oxides Based on In2O3 Particles

The paper considers the relationship between the structure and properties of nanostructured conductometric sensors based on binary mixtures of semiconductor oxides designed to detect reducing gases in the environment. The sensor effect in such systems is determined by the chemisorption of molecules on the surface of catalytically active particles and the transfer of chemisorbed products to electron-rich nanoparticles, where these products react with the analyzed gas. In this regard, the role is evaluated of the method of synthesizing the composites, the catalytic activity of metal oxides (CeO₂, SnO₂, ZnO), and the type of conductivity of metal oxides (Co₃O₄, ZrO₂) in the sensor process. The effect of oxygen vacancies present in the composites on the performance characteristics is also considered. Particular attention is paid to the influence of the synthesis procedure for preparing sensitive layers based on CeO₂-In₂O₃ on the structure of the resulting composites, as well as their conductive and sensor properties.

Nano-Confined Tin Oxide in Carbon Nanotube Electrodes via Electrostatic Spray Deposition for Lithium-Ion Batteries

The development of novel materials is essential for the next generation of electric vehicles and portable devices. Tin oxide (SnO₂), with its relatively high theoretical capacity, has been considered as a promising anode material for applications in energy storage devices. However, the SnO₂ anode material suffers from poor conductivity and huge volume expansion during charge/discharge cycles. In this study, we evaluated an approach to control the conductivity and volume change of SnO₂ through a controllable and effective method by confining different percentages of SnO₂ nanoparticles into carbon nanotubes (CNTs). The binder-free confined SnO₂ in CNT composite was deposited via an electrostatic spray deposition technique. The morphology of the synthesized and deposited composite was evaluated by scanning electron microscopy and high-resolution transmission electron spectroscopy. The binder-free 20% confined SnO₂ in CNT anode delivered a high reversible capacity of 770.6 mAh g^-1. The specific capacity of the anode increased to 1069.7 mAh g^-1 after 200 cycles, owing to the electrochemical milling effect. The delivered specific capacity after 200 cycles shows that developed novel anode material is suitable for lithium-ion batteries (LIBs).

Atmospheric Pressure Solvothermal Synthesis of Nanoscale SnO2 and Its Application in Microextrusion Printing of a Thick-Film Chemosensor Material for Effective Ethanol Detection

The atmospheric pressure solvothermal (APS) synthesis of nanocrystalline SnO₂ (average size of coherent scattering regions (CSR)-7.5 ± 0.6 nm) using tin acetylacetonate as a precursor was studied. The resulting nanopowder was used as a functional ink component in microextrusion printing of a tin dioxide thick film on the surface of a Pt/Al₂O₃/Pt chip. Synchronous thermal analysis shows that the resulting semiproduct is transformed completely into tin dioxide nanopowder at 400 °C within 1 h. The SnO₂ powder and the resulting film were shown to have a cassiterite-type structure according to X-ray diffraction analysis, and IR spectroscopy was used to establish the set of functional groups in the material composition. The microstructural features of the tin dioxide powder were analyzed using scanning (SEM) and transmission (TEM) electron microscopy: the average size of the oxide powder particles was 8.2 ± 0.7 nm. Various atomic force microscopy (AFM) techniques were employed to investigate the topography of the oxide film and to build maps of surface capacitance and potential distribution. The temperature dependence of the electrical conductivity of the printed SnO₂ film was studied using impedance spectroscopy. The chemosensory properties of the formed material when detecting H₂, CO, NH₃, C₆H₆, C₃H₆O and C₂H₅OH, including at varying humidity, were also examined. It was demonstrated that the obtained SnO₂ film has an increased sensitivity (the sensory response value was 1.4-63.5) and selectivity for detection of 4-100 ppm C₂H₅OH at an operating temperature of 200 °C.

A Tin Oxide-Coated Copper Foam Hybridized with a Gas Diffusion Electrode for Efficient CO2 Reduction to Formate with a Current Density Exceeding 1 A cm-2

The electrochemical CO₂ reduction reaction (CO₂ RR) is a promising strategy for closing the carbon cycle. Increasing the current density (  J) for CO₂ RR products is a critical requirement for the social implementation of this technology. Herein, nanoscale tin-oxide-modified copper-oxide foam is hybridized with a carbon-based gas-diffusion electrode (GDE). Using the resultant electrode, the J_formate is increased to -1152 mA cm^-2 at -1.2 V versus RHE in 1 m KOH, which is the highest value for CO₂ -to-formate electrolysis. The formate faradaic efficiency (FE_formate ) reaches ≈99% at -0.6 V versus RHE. The achievement of ultra-high-rate formate production is attributable to the following factors: i) homogeneously-modified Sn atoms suppressing H₂ evolution and ii) the hydrophobic carbon nanoparticles on GDEs penetrating the macroporous structure of the foam causing the increase in the thickness of triple-phase interface. Additionally, the FE_formate remains at ≈70% under a high J of -1.0 A cm^-2 for more than 20 h.

Low-Voltage-Driven SnO2-Based H2S Microsensor with Optimized Micro-Heater for Portable Gas Sensor Applications

To realize portable gas sensor applications, it is necessary to develop hydrogen sulfide (H2S) microsensors capable of operating at lower voltages with high response, good selectivity and stability, and fast response and recovery times. A gas sensor with a high operating voltage (>5 V) is not suitable for portable applications because it demands additional circuitry, such as a charge pump circuit (supply voltage of common circuits is approximately 1.8−5 V). Among H2S microsensor components, that is, the substrate, sensing area, electrode, and micro-heater, the proper design of the micro-heater is particularly important, owing to the role of thermal energy in ensuring the efficient detection of H2S. This study proposes and develops tin (IV)-oxide (SnO2)-based H2S microsensors with different geometrically designed embedded micro-heaters. The proposed micro-heaters affect the operating temperature of the H2S sensors, and the micro-heater with a rectangular mesh pattern exhibits superior heating performance at a relatively low operating voltage (3−4 V) compared to those with line (5−7 V) and rectangular patterns (3−5 V). Moreover, utilizing a micro-heater with a rectangular mesh pattern, the fabricated SnO2-based H2S microsensor was driven at a low operating voltage and offered good detection capability at a low H2S concentration (0−10 ppm), with a quick response (<51 s) and recovery time (<101 s).

F-doping-Enhanced Carrier Transport in the SnO2/Perovskite Interface for High-Performance Perovskite Solar Cells

SnO₂ is widely used as the electron transport layer (ETL) in n-i-p perovskite solar cells. However, the deep-level defects at the interface between SnO₂ and the perovskite film will lead to energy loss, reducing the open-circuit voltage. Therefore, the interface optimization is essential to raise the efficiency and enhance the stability of perovskite solar cells. In this work, we introduce NH₄F into the SnO₂ electron transport layers, and the optimized SnO₂ films reduce the interface defect density, improve the charge extraction, and reveal a better energy-level arrangement. Compared to the conventional SnO₂ perovskite solar cell, the average V_oc is improved by 70 mV with the champion efficiency up to 22.12%. Moreover, the unencapsulated F-doped SnO₂ perovskite solar cells show better thermal stability (maintained 86.2%) and humidity stability (maintained 80.8%) after 35 days.

Nanosensor Based on Thermal Gradient and Machine Learning for the Detection of Methanol Adulteration in Alcoholic Beverages and Methanol Poisoning

Methanol, naturally present in small quantities in the distillation of alcoholic beverages, can lead to serious health problems. When it exceeds a certain concentration, it causes blindness, organ failure, and even death if not recognized in time. Analytical techniques such as chromatography are used to detect dangerous concentrations of methanol, which are very accurate but also expensive, cumbersome, and time-consuming. Therefore, a gas sensor that is inexpensive and portable and capable of distinguishing methanol from ethanol would be very useful. Here, we present a resistive gas sensor, based on tin oxide nanowires, that works in a thermal gradient. By combining responses at various temperatures and using machine learning algorithms (PCA, SVM, LDA), the device can distinguish methanol from ethanol in a wide range of concentrations (1–100 ppm) in both dry air and under different humidity conditions (25–75% RH). The proposed sensor, which is small and inexpensive, demonstrates the ability to distinguish methanol from ethanol at different concentrations and could be developed both to detect the adulteration of alcoholic beverages and to quickly recognize methanol poisoning.

Surface Morphology of Textured Transparent Conductive Oxide Thin Film Seen by Various Probes: Visible Light, X-rays, Electron Scattering and Contact Probe

Fluorine-doped tin oxide thin films (SnO₂:F) are widely used as transparent conductive oxide electrodes in thin-film solar cells because of their appropriate electrical and optical properties. The surface morphology of these films influences their optical properties and therefore plays an important role in the overall efficiencies of the solar cells in which they are implemented. At rough surfaces light is diffusely scattered, extending the optical path of light inside the active layer of the solar cell, which in term improves light absorption and solar cell conversion efficiency. In this work, we investigated the surface morphology of undoped and doped SnO₂ thin films and their influence on the optical properties of the films. We have compared and analysed the results obtained by several complementary methods for thin-film surface morphology investigation: atomic force microscopy (AFM), transmission electron microscopy (TEM), and grazing-incidence small-angle X-ray scattering (GISAXS). Based on the AFM and TEM results we propose a theoretical model that reproduces well the GISAXS scattering patterns.

Research Progress of p-Type Oxide Thin-Film Transistors

The development of transparent electronics has advanced metal–oxide–semiconductor Thin-Film transistor (TFT) technology. In the field of flat-panel displays, as basic units, TFTs play an important role in achieving high speed, brightness, and screen contrast ratio to display information by controlling liquid crystal pixel dots. Oxide TFTs have gradually replaced silicon-based TFTs owing to their field-effect mobility, stability, and responsiveness. In the market, n-type oxide TFTs have been widely used, and their preparation methods have been gradually refined; however, p-Type oxide TFTs with the same properties are difficult to obtain. Fabricating p-Type oxide TFTs with the same performance as n-type oxide TFTs can ensure more energy-efficient complementary electronics and better transparent display applications. This paper summarizes the basic understanding of the structure and performance of the p-Type oxide TFTs, expounding the research progress and challenges of oxide transistors. The microstructures of the three types of p-Type oxides and significant efforts to improve the performance of oxide TFTs are highlighted. Finally, the latest progress and prospects of oxide TFTs based on p-Type oxide semiconductors and other p-Type semiconductor electronic devices are discussed.

Highly Stable SnO2-Based Quantum-Dot Light-Emitting Diodes with the Conventional Device Structure

ZnO-based electron-transporting layers (ETLs) have been universally used in quantum-dot light-emitting diodes (QLEDs) for high performance. The active surface chemistry of ZnO nanoparticles (NPs), however, leads to QLEDs with positive aging and unacceptably poor shelf stability. SnO₂ is a promising candidate for ETLs with less reactivity, but NP agglomeration in nonionic solvents makes the conventional device structure abandoned, resulting in QLEDs with extremely low operational lifetimes. The large barrier for electron injection also limits the electroluminescence efficiency. Here, we report one solution to all the above-mentioned problems. Owing to the strong HO-SnO₂ coordination and the steric effect provided by the hydrocarbon groups, tetramethylammonium hydroxide can stabilize SnO₂ NPs in alcohol, while its intrinsic dipole induces a favorable electronic-level shift for charge injection. The SnO₂-based devices, with the conventional structure, exhibit not only the most efficient electroluminescence among ZnO-free QLEDs but also an operational lifetime (T₉₅) over 3200 h at 1000 cd m^-2, which is comparable with that of state-of-the-art ZnO-based devices. More importantly, the superior shelf stability means that the TMAH-SnO₂ NPs are promising to enable QLEDs with real stability.

Understanding the "Anti-Catalyst" Effect with Added CoOx Water Oxidation Catalyst in Dye-Sensitized Photoelectrolysis Cells: Carbon Impurities in Nanostructured SnO2 Are the Culprit

In 2017, we reported a dye-sensitized, photoelectrolysis cell consisting of fluorine-doped tin oxide (FTO)-coated glass covered by SnO₂ nanoparticles coated with N,N'-bis(phosphonomethyl)-3,4,9,10-perylenediimide (PMPDI) dye and then a photoelectrochemically deposited CoO_x water oxidation catalyst (WOCatalyst), FTO/nano-SnO₂/PMPDI/CoO_x. This system employed nanostructured SnO₂ stabilized by a polyethyleneglycol bisphenol A epichlorohydrin (PEG-BAE) copolymer and other C-containing additives based on a literature synthesis to achieve a higher surface area and thus greater PMPDI dye absorption and resultant light collection. Surprisingly, the addition of the well-established WOCatalyst CoO_x resulted in a decrease in the photocurrent, an unexpected "anti-catalyst" effect. Two primary questions addressed in the present study are (1) what is the source of this "anti-catalyst" effect? and (2) are the findings of broader interest? Reflection on the synthesis of nano-SnO₂ stabilized by PEG-BAE, and the large, ca. 10:1 ratio of C to Sn in synthesis, led to the hypothesis that even the annealing step at 450 °C in of the FTO/SnO₂ anode precursors was unlikely to remove all the carbon initially present. Indeed, residual carbon impurities are shown to be the culprit in the presently observed "anti-catalyst" effect. The implication and anticipated broader impact of the results of answering the two abovementioned questions are also presented and discussed along with a section entitled "Perspective and Suggestions for the Field Going Forward."

Black Phosphorus Quantum Dot-Engineered Tin Oxide Electron Transport Layer for Highly Stable Perovskite Solar Cells with Negligible Hysteresis

An effective combination of smart materials plays an important role in charge transfer and separation for high photoelectric conversion efficiency (PCE) and stable solar cells. Black phosphorus quantum dots (BPQDs) have been revealed as a direct band gap semiconductor with ultrahigh conductivity, which have been explored in the present work as an additive component to a precursor solution of SnO₂ nanoparticles that can effectively improve the performance of SnO₂ electron transport layer (ETL)-based perovskite solar cells. Such a device can yield a high PCE of 21% with the SnO₂/BPQDs mixed ETL, which is higher than those of perovskite solar cells based on SnO₂ single layer (18.2%), BPQDs/SnO₂ bilayer (19.5%), and SnO₂/BPQDs bilayer (20.5%) samples. The mixed samples still possess good stability of more than 90% efficiency after 1000 h under AM 1.5G lamp irradiation and negligible hysteresis. It is found that the strong interaction of BPQDs with SnO₂ can not only modify the defects inherent to the SnO₂ layer but also inhibit the oxidation of BPQDs. This work provides a promising functional material for SnO₂ ETL-based perovskite solar cells and proves that the BPQD-based modification strategy is useful for designing other solar cells with high performance.

Industrially Compatible Fabrication Process of Perovskite-Based Mini-Modules Coupling Sequential Slot-Die Coating and Chemical Bath Deposition

To upscale the emerging perovskite photovoltaic technology to larger-size modules, industrially relevant deposition techniques need to be developed. In this work, the deposition of tin oxide used as an electron extraction layer is established using chemical bath deposition (CBD), a low-cost and solution-based fabrication process. Applying this simple low-temperature deposition method, highly homogeneous SnO₂ films are obtained in a reproducible manner. Moreover, the perovskite layer is prepared by sequentially slot-die coating on top of the n-type contact. The symbiosis of these two industrially relevant deposition techniques allows for the growth of high-quality dense perovskite layers with large grains. The uniformity of the perovskite film is further confirmed by scanning electron microscopy (SEM)/scanning transmission electron microscopy (STEM) analysis coupled with energy dispersive X-ray spectroscopy (EDX) and cathodoluminescence measurements allowing us to probe the elemental composition at the nanoscale. Perovskite solar cells fabricated from CBD SnO₂ and slot-die-coated perovskite show power conversion efficiencies up to 19.2%. Furthermore, mini-modules with an aperture area of 40 cm² demonstrate efficiencies of 17% (18.1% on active area).

Electron Transport Assisted by Transparent Conductive Oxide Elements in Perovskite Solar Cells

Fluorine and indium elements in F-doped SnO₂ (FTO) and Sn-doped In₂ O₃ (ITO), respectively, significantly contribute toward enhancing the electrical conductivity of these transparent conductive oxides. In this study, fluorine was combined with indium to modify the SnO₂ electron transport layer (ETL) through InF₃ . Consequently, the modified perovskite solar cells (PSCs) showe the favorable alignment of energy levels, improved absorption and utilization of light, enhanced interfacial charge extraction, and suppressed interfacial charge recombination. After InF₃ modification, the open circuit voltage (V_oc ) and fill factor (FF) of the PSC were significantly improved, and the photoelectric conversion efficiency (PCE) reached 21.39 %, far exceeding that of the control PSC (19.62 %).

Tin Oxide Electron Transport Layers for Air-/Solution-Processed Conventional Organic Solar Cells

Commercialization of organic solar cells (OSC) is imminent. Interlayers between the photoactive film and the electrodes are critical for high device efficiency and stability. Here, the applicability of SnO₂ nanoparticles (SnO₂ NPs) as the electron transport layer (ETL) in conventional OSCs is evaluated. A commercial SnO₂ NPs solution in butanol is mixed with ethanol (EtOH) as a processing co-solvent to improve film formation for spin and slot-die coating deposition procedures. When processed with 200% v/v EtOH, the SnO₂ NPs film presents uniform film quality and low photoactive layer degradation. The optimized SnO₂ NPs ink is coated, in air, on top of two polymer:fullerene-based systems and a nonfullerene system, to form an efficient ETL film. In every case, addition of SnO₂ NPs film significantly enhances photovoltaic performance, from 3.4 and 3.7% without the ETL to 6.0 and 5.7% when coated on top of PBDB-T:PC₆₁BM and PPDT2FBT:PC₆₁BM, respectively, and from 3.7 to 7.1% when applied on top of the PTQ10:IDIC system. Flexible, all slot-die-coated devices, in air, are also fabricated and tested, demonstrating the versatility of the SnO₂ NPs ink for efficient ETL formation on top of organic photoactive layers, processed under ambient condition, ideal for practical large-scale production of OSCs.

Hydrothermal Synthesis of Hierarchical SnO2 Nanostructures for Improved Formaldehyde Gas Sensing

The indoor environment of buildings affects people’s daily life. Indoor harmful gases include volatile organic gas and greenhouse gas. Therefore, the detection of harmful gas by gas sensors is a key method for developing green buildings. The reasonable design of SnO₂-sensing materials with excellent structures is an ideal choice for gas sensors. In this study, three types of hierarchical SnO₂ microspheres assembled with one-dimensional nanorods, including urchin-like microspheres (SN-1), flower-like microspheres (SN-2), and hydrangea-like microspheres (SN-3), are prepared by a simple hydrothermal method and further applied as gas-sensing materials for an indoor formaldehyde (HCHO) gas-sensing test. The SN-1 sample-based gas sensor demonstrates improved HCHO gas-sensing performance, especially demonstrating greater sensor responses and faster response/recovery speeds than SN-2- and SN-3-based gas sensors. The improved HCHO gas-sensing properties could be mainly attributed to the structural difference of smaller nanorods. These results further indicate the uniqueness of the structure of the SN-1 sample and its suitability as HCHO- sensing material.

Characterization of Ti/SnO2 Interface by X-ray Photoelectron Spectroscopy

The Ti/SnO₂ interface has been investigated in situ via the technique of x-ray photoelectron spectroscopy. Thin films (in the range from 0.3 to 1.1 nm) of titanium were deposited on SnO₂ substrates via the e-beam technique. The deposition was carried out at two different substrate temperatures, namely room temperature and 200 °C. The photoelectron spectra of tin and titanium in the samples were found to exhibit significant differences upon comparison with the corresponding elemental and the oxide spectra. These changes result from chemical interaction between SnO₂ and the titanium overlayer at the interface. The SnO₂ was observed to be reduced to elemental tin while the titanium overlayer was observed to become oxidized. Complete reduction of SnO₂ to elemental tin did not occur even for the lowest thickness of the titanium overlayer. The interfaces in both the types of the samples were observed to consist of elemental Sn, SnO₂, elemental titanium, TiO₂, and Ti-suboxide. The relative percentages of the constituents at the interface have been estimated by curve fitting the spectral data with the corresponding elemental and the oxide spectra. In the 200 °C samples, thermal diffusion of the titanium overlayer was observed. This resulted in the complete oxidation of the titanium overlayer to TiO₂ upto a thickness of 0.9 nm of the overlayer. Elemental titanium resulting from the unreacted overlayer was observed to be more in the room temperature samples. The room temperature samples showed variation around 20% for the Ti-suboxide while an increasing trend was observed in the 200 °C samples.

Understanding the Origin of the Hysteresis of High-Performance Solution Processed Polycrystalline SnO2 Thin-Film Transistors and Applications to Circuits

Crystalline tin oxide has been investigated for industrial applications since the 1970s. Recently, the amorphous phase of tin oxide has been used in thin film transistors (TFTs) and has demonstrated high performance. For large area electronics, TFTs are well suited, but they are subject to various instabilities due to operating conditions, such as positive or negative bias stress PBS (NBS). Another instability is hysteresis, which can be detrimental in operating circuits. Understanding its origin can help fabricating more reliable TFTs. Here, we report an investigation on the origin of the hysteresis of solution-processed polycrystalline SnO₂ TFTs. We examined the effect of the carrier concentration in the SnO₂ channel region on the hysteresis by varying the curing temperature of the thin film from 200 to 350 °C. Stressing the TFTs characterized further the origin of the hysteresis, and holes trapped in the dielectric are understood to be the main source of the hysteresis. With TFTs showing the smallest hysteresis, we could fabricate inverters and ring oscillators.

Hydrophilic and Conductive Carbon Nanotube Fibers for High-Performance Lithium-Ion Batteries

Carbon nanotube fiber (CNTF) is a highly conductive and porous platform to grow active materials of lithium-ion batteries (LIB). Here, we prepared SnO₂@CNTF based on sulfonic acid-functionalized CNTF to be used in LIB anodes without binder, conductive agent, and current collector. The SnO₂ nanoparticles were grown on the CNTF in an aqueous system without a hydrothermal method. The functionalized CNTF exhibited higher conductivity and effective water infiltration compared to the raw CNTF. Due to the enhanced water infiltration, the functionalized CNTF became SnO₂@CNTF with an ideal core-shell structure coated with a thin SnO₂ layer. The specific capacity and rate capability of SnO₂@-functionalized CNTF were superior to those of SnO₂@raw CNTF. Since the SnO₂@CNTF-based anode was free of a binder, conductive agent, and current collector, the specific capacity of the anode studied in this work was higher than that of conventional anodes.

One-Step Synthesis of SnO2/Carbon Nanotube Nanonests Composites by Direct Current Arc-Discharge Plasma and Its Application in Lithium-Ion Batteries

Tin dioxide (SnO₂)-based materials, as anode materials for lithium-ion batteries (LIBs), have been attracting growing research attention due to the high theoretical specific capacity. However, the complex synthesis process of chemical methods and the pollution of chemical reagents limit its commercialization. The new material synthesis method is of great significance for expanding the application of SnO₂-based materials. In this study, the SnO₂/carbon nanotube nanonests (SnO₂/CNT NNs) composites are synthesized in one step by direct current (DC) arc-discharge plasma; compared with conventional methods, the plasma synthesis achieves a uniform load of SnO₂ nanoparticles on the surfaces of CNTs while constructing the CNTs conductive network. The SnO₂/CNT NNs composites are applied in LIBs, it can be found that the nanonest-like CNT conductive structure provides adequate room for the volume expansion and also helps to transfer the electrons. Electrochemical measurements suggests that the SnO₂/CNT NNscomposites achieve high capacity, and still have high electrochemical stability and coulombic efficiency under high current density, which proves the reliability of the synthesis method. This method is expected to be industrialized and also provides new ideas for the preparation of other nanocomposites.

Flower-like SnO2 Nanoparticle Biofabrication Using Pometia pinnata Leaf Extract and Study on Its Photocatalytic and Antibacterial Activities

The present study reported biofabrication of flower-like SnO₂ nanoparticles using Pometia pinnata leaf extract. The study focused on the physicochemical characteristics of the prepared SnO₂ nanoparticles and its activity as photocatalyst and antibacterial agent. The characterization was performed by XRD, SEM, TEM, UV-DRS and XPS analyses. Photocatalytic activity of the nanoparticles was examined on bromophenol blue photooxidation; meanwhile, the antibacterial activity was evaluated against Klebsiella pneumoniae, Escherichia coli Staphylococcus aureus and Streptococcus pyogenes. XRD and XPS analyses confirmed the single tetragonal SnO₂ phase. The result from SEM analysis indicates the flower like morphology of SnO₂ nanoparticles, and by TEM analysis, the nanoparticles were seen to be in uniform spherical shapes with a diameter ranging from 8 to 20 nm. SnO₂ nanoparticles showed significant photocatalytic activity in photooxidation of bromophenol blue as the degradation efficiency reached 99.93%, and the photocatalyst exhibited the reusability as the degradation efficiency values were insignificantly changed until the fifth cycle. Antibacterial assay indicated that the synthesized SnO₂ nanoparticles exhibit an inhibition of tested bacteria and showed a potential to be applied for further environmental and medical applications.

Artificial Synapse Based on a 2D-SnO2 Memtransistor with Dynamically Tunable Analog Switching for Neuromorphic Computing

A new type of two-dimensional (2D) SnO2 semiconductor-based gate-tunable memristor, that is, a memtransistor, an integrated device of a memristor and a transistor, was demonstrated to advance next-generation neuromorphic computing technology. The polycrystalline 2D-SnO2 memristors derived from a low-temperature and vacuum-free liquid metal process offer several interesting resistive switching properties such as excellent digital/analog resistive switching, multistate storage, and gate-tunability function of resistance switching states. Significantly, the gate tunability function that is not achievable in conventional two-terminal memristors provides the capability to implement heterosynaptic analog switching by regulating gate bias for enabling complex neuromorphic learning. We successfully demonstrated that the gate-tunable synaptic device dynamically modulated the analog switching behavior with good linearity and an improved conductance change ratio for high recognition accuracy learning. The presented gate-tunable 2D-oxide memtransistor will advance neuromorphic device technology and open up new opportunities to design learning schemes with an extra degree of freedom.

Alkali Metal Fluoride-Modified Tin Oxide for n-i-p Planar Perovskite Solar Cells

The practical applications of perovskite solar cells (PSCs) are limited by further improvement of their stability and performance. Additive engineering and interface engineering are promising medicine to cure this stubborn disease. Herein, an alkali metal fluoride as an additive is introduced into the tin oxide (SnO₂) electron transport layer (ETL). The formation of coordination bonds of F^- ions with the oxygen vacancy of Sn⁴⁺ ions decreases the trap-state density and improves the electron mobility; the hydrogen bond interaction between the F ion and amine group (FA⁺) of perovskite inhibits the diffusion of organic cations and promotes perovskite (PVK) stability. Meanwhile, the alkali metal ions (K⁺, Rb⁺, and Cs⁺) permeated into PVK fill the organic cation vacancies and ameliorate the crystal quality of PVK films. Consequently, a SnO₂-based planar PSC exhibits a power conversion efficiency (PCE) of 20.24%, while the PSC modified by CsF achieves a PCE of 22.51%, accompanied by effective enhancement of stability and negligible hysteresis. The research results provide a typical example for low-cost and multifunctional additives in high-performance PSCs.

Effect of NaOH molarities to the microstructure and sodium storage performance of the Sn-MOF derived SnO2microporous rod

In this study, we demonstrated a facile method to prepare a novel SnO₂microporous rod with various microstructures by controlling NaOH molarities in precursor synthesis processes. Four different molarities of NaOH solution (0.005 M, 0.048 M, 0.12 M and 0.5 M) were used together with o-phthalic acid in Sn-MOF synthesis to determine the effect of ligand [o-C₆H₄CO222-] concentration on microstructure evolution. It was found that increasing NaOH molarity can effectively decrease the size of Sn-MOF rods. Then, the SnO₂microporous rods were obtained by calcinating the as-prepared Sn-MOF as microstructures. Under an optimized experimental condition (NaOH molarity of 0.12 M), the SnO₂rods shows a modest initial coulombic efficiency of 61.3% with a high reversible sodium storage capacity of 503 mAh g^-1after 150 cycles at 50 mA g^-1. Moreover, an impressive reversible sodium storage capacity of 206 mAh g^-1can be obtained at long-term cycling performance (800 cycles at current density of 2 A g^-1). Effects of morphologies to electrochemical performances have been further discussed in aspects of intrinsic resistance, pseudocapacitive contribution, surface area and porous structure and microstructural stability, and the enhanced electrochemical performance could be attributed to factors of enhanced pseudocapacitive charge contribution, optimized microstructures, and structural stability, which ensure the SnO₂-0.12 M to have a good rate performance and cyclability. This nanoscale-engineering method adopted here could be a promising path to fabricate SnO₂-based anodes with novel microstructures for sodium storage applications.

Atomic-Layer-Deposited SiOx/SnOx Nanolaminate Structure for Moisture and Hydrogen Gas Diffusion Barriers

High-density SnO_x and SiO_x thin films were deposited via atomic layer deposition (ALD) at low temperatures (100 °C) using tetrakis(dimethylamino)tin(IV) (TDMASn) and di-isopropylaminosilane (DIPAS) as precursors and hydrogen peroxide (H₂O₂) and O₂ plasma as reactants, respectively. The thin-film encapsulation (TFE) properties of SnO_x and SiO_x were demonstrated with thickness dependence measurements of the water vapor transmission rate (WVTR) evaluated at 50 °C and 90% relative humidity, and different TFE performance tendencies were observed between thermal and plasma ALD SnO_x. The film density, crystallinity, and pinholes formed in the SnO_x film appeared to be closely related to the diffusion barrier properties of the film. Based on the above results, a nanolaminate (NL) structure consisting of SiO_x and SnO_x deposited using plasma-enhanced ALD was measured using WVTR (H₂O molecule diffusion) at 2.43 × 10^-5 g/m² day with a 10/10 nm NL structure and time-lag gas permeation measurement (H₂ gas diffusion) for applications as passivation layers in various electronic devices.

Atomic Layer Deposition of Ternary Indium/Tin/Aluminum Oxide Thin Films, Their Characterization and Transistor Performance under Illumination

Multilayered heterostructures comprising of In2 O3 , SnO2 , and Al2 O3 were studied for their application in thin-film transistors (TFT). The compositional influence of tin oxide on the properties of the thin-film, as well as on the TFT characteristics is investigated. The heterostructures are fabricated by atomic layer deposition (ALD) at 200 °C, employing trimethylindium (TMI), tetrakis(dimethylamino)tin (TDMASn), trimethylaluminum (TMA), and water as precursors. After post-deposition annealing at 400 °C the thin-films are found to be amorphous, however, they show a discrete layer structure of the individual oxides of uniform film thickness and high optical transparency in the visible region. Incorporation of only two monolayers of Al2 O3 in the active semiconducting layer the formation of oxygen vacancies can be effectively suppressed, resulting in an improved semiconducting and switching behavior. The heterostacks comprising of In2 O3 /SnO2 /Al2 O3 are incorporated into TFT devices, exhibiting a saturation field-effect mobility (μsat ) of 2.0 cm2  ⋅ V-1  s-1 , a threshold-voltage (Vth ) of 8.6 V, a high current on/off ratio (IOn /IOff ) of 1.0×107 , and a subthreshold swing (SS) of 485 mV ⋅ dec-1 . The stability of the TFT under illumination is also altered to a significant extent. A change in the transfer characteristic towards conductive behavior is evident when illuminated with light of an energy of 3.1 eV (400 nm).

The Heterostructures of CuO and SnOx for NO2 Detection

Controlling environmental pollution is a burning problem for all countries more than ever. Currently, due to the increasing industrialization, the number of days when the limits of air pollutants are over the threshold levels exceeds 80-85% of the year. Therefore, cheap and effective sensors are always welcome. One idea is to combine such solutions with cars and provide real-time information about the current pollution level. However, the environmental conditions are demanding, and thus the developed sensors need to be characterized by the high 3S parameters: sensitivity, stability and selectivity. In this paper, we present the results on the heterostructure of CuO/SnO_x and SnO_x/CuO as a possible approach for selective NO₂ detection. The developed gas sensors exhibited lower operating temperature and high response in the wide range of NO₂ and in a wide range of relative humidity changes. Material characterizations and impedance spectroscopy measurements were also conducted to analyze the chemical and electrical behavior.