Crystalline SnO2 Research Articles

Low-Temperature Presynthesized Crystalline Tin Oxide for Efficient Flexible Perovskite Solar Cells and Modules.

Organic-inorganic metal halide perovskite solar cells (PSCs) have been emerging as one of the most promising next generation photovoltaic technologies with a breakthrough power conversion efficiency (PCE) over 22%. However, aiming for commercialization, it still encounters challenges for the large-scale module fabrication, especially for flexible devices which have attracted intensive attention recently. Low-temperature processed high-performance electron-transporting layers (ETLs) are still difficult. Herein, we present a facile low-temperature synthesis of crystalline SnO2 nanocrystals (NCs) as efficient ETLs for flexible PSCs including modules. Through thermal and UV-ozone treatments of the SnO2 ETLs, the electron transporting resistance of the ETLs and the charge recombination at the interface of ETL/perovskite were decreased. Thus, the hysteresis-free highly efficient rigid and flexible PSCs were obtained with PCEs of 19.20 and 16.47%, respectively. Finally, a 5 × 5 cm2 flexible PSC module with a PCE of 12.31% (12.22% for forward scan and 12.40% for reverse scan) was fabricated with the optimized perovskite/ETL interface. Thus, employing presynthesized SnO2 NCs to fabricate ETLs has showed promising for future manufacturing.

Mesoscopic Oxide Double Layer as Electron Specific Contact for Highly Efficient and UV Stable Perovskite Photovoltaics.

The solar to electric power conversion efficiency (PCE) of perovskite solar cells (PSCs) has recently reached 22.7%, exceeding that of competing thin film photovoltaics and the market leader polycrystalline silicon. Further augmentation of the PCE toward the Shockley-Queisser limit of 33.5% warrants suppression of radiationless carrier recombination by judicious engineering of the interface between the light harvesting perovskite and the charge carrier extraction layers. Here, we introduce a mesoscopic oxide double layer as electron selective contact consisting of a scaffold of TiO2 nanoparticles covered by a thin film of SnO2, either in amorphous (a-SnO2), crystalline (c-SnO2), or nanocrystalline (quantum dot) form (SnO2-NC). We find that the band gap of a-SnO2 is larger than that of the crystalline (tetragonal) polymorph leading to a corresponding lift in its conduction band edge energy which aligns it perfectly with the conduction band edge of both the triple cation perovskite and the TiO2 scaffold. This enables very fast electron extraction from the light perovskite, suppressing the notorious hysteresis in the current-voltage ( J-V) curves and retarding nonradiative charge carrier recombination. As a result, we gain a remarkable 170 mV in open circuit photovoltage ( V oc) by replacing the crystalline SnO2 by an amorphous phase. Because of the quantum size effect, the band gap of our SnO2-NC particles is larger than that of bulk SnO2 causing their conduction band edge to shift also to a higher energy thereby increasing the V oc. However, for SnO2-NC there remains a barrier for electron injection into the TiO2 scaffold decreasing the fill factor of the device and lowering the PCE. Introducing the a-SnO2 coated mp-TiO2 scaffold as electron extraction layer not only increases the V oc and PEC of the solar cells but also render them resistant to UV light which forebodes well for outdoor deployment of these new PSC architectures.

Preparation, characterizations, and antibacterial properties of Cu/SnO2 nanocomposite bilayer coatings

A nano-bilayer structure consisting of copper and SnO2 nanocomposites was prepared by a magnetron sputtering method. A nano-SnO2 thin layer with a thickness of 52 nm was achieved on quartz glass. A nano-copper layer was then deposited on top of the SnO2 thin layer by the sputtering method. The thickness of the nano-copper layer was approximately 7 nm, such that the SnO2 layer was not only completely covered by the copper layer but it also resulted in transparent bilayer films. Post-annealing was carried out at 400°C in air for 1 h to obtain a crystalline SnO2 phase and simultaneously the copper layer was oxidized to CuO. Sputtered nanocomposites of CuO/SnO2 bilayer films showed a synergistic effect toward E. coli inactivation under indoor light exposure. A possible mechanism for the synergistic effect with respect to the antibacterial properties of CuO/SnO2 bilayer nanocomposites has been proposed. Incorporating CuO onto the SnO2 layer achieves photocatalyst works under indoor light and provides an antimicrobial function even under a dark environment by the antimicrobial property of CuO itself. Reported CuO/SnO2 sputter coating can be useful to apply, for instance, to electric devices such as touch panel displays in a hospital in order to reduce hospital-acquired infections (HAIs).

Ordered Mesoporous Tin Oxide Semiconductors with Large Pores and Crystallized Walls for High-Performance Gas Sensing.

Owing to their distinct chemical and physical properties, mesoporous metal oxide semiconductors have shown great application potential in catalysis, electrochemistry, energy conversion, and energy storage. In this study, mesoporous crystalline SnO2 materials have been synthesized through an evaporation-induced co-assembly (EICA) method using poly(ethylene oxide)-b-polystyrene diblock copolymers as the template, tin chlorides as the tin sources, and tetrahydrofuran as the solvent. By controlling conditions of the co-assembly process and employing a carbon-supported thermal treatment strategy, highly ordered mesoporous SnO2 materials with a hexagonal mesostructure (space group P63/mmc) and crystalline pore walls can be obtained. The mesoporous SnO2 is employed for fabricating gas sensor nanodevices which exhibit an excellent sensing performance toward H2S with high sensitivity (170, 50 ppm) and superior stability, owing to its high surface area (98 m2/g), well-connected mesopores of ca. 18.0 nm, and high density of active sites in the crystalline pore walls. The chemical mechanism study reveals that both SO2 and SnS2 are generated during the gas sensing process on the SnO2-based sensors.

Properties of a single SnO2:Zn2SnO4 – Functionalized nanowire based nanosensor

Tin oxide nanowires (SnO2 NWs) exhibit large potential for applications in sensor and detector technology. Using a flame transport synthesis method, high-quality single crystalline SnO2 nanowires (NWs) with Zn2SnO4 dots functionalized surface were synthesized on a large scale. The individual SnO2:Zn2SnO4 nanowire based ultraviolet photodetector and ethanol vapors nanosensors were fabricated by contacting an individual nanowire to pre-patterned Au electrodes via a FIB/SEM system. The photodetector structure exhibited excellent photoconductive performance in terms of high response to the 375nm ultraviolet light irradiation, ultra-fast response and recovery time at different temperatures (25–300K). It also showed a long term stability and reliability. The n-type semiconducting behavior of the SnO2:Zn2SnO4, forms an excellent material for fabricating highly sensitive and rapid responding sensors, which will enable the development of high-performance multi-functional devices.

Rapid and scalable synthesis of crystalline tin oxide nanoparticles with superior photovoltaic properties by flame oxidation

Abstract

The formation of layers of porous crystalline tin dioxide from a composite on the basis of multiwalled carbon-nanotube arrays

A new method for the synthesis of porous crystalline tin-dioxide (SnO2) layers from composites on the basis of multiwalled carbon nanotubes (MWCNTs) and nonstoichiometric amorphous tin oxide (MWCNT/SnO x ) is proposed. An MWCN/SnO x composite layer produced by magnetron sputtering is annealed in air atmosphere at 500°C for 30 min. A homogeneous porous layer comprised of crystalline SnO2 spherical particles with a size of about 0.1 μm is obtained as a result. In the process of annealing, nearly all the amount of carbon is removed in the form of gaseous oxides (only a small amount remains in the upper part of the porous SnO2 layer). The structural defectiveness of nanotube walls, which increases because of the magnetron deposition of tin, plays a crucial role in the carbon oxidation and destruction of MWCNTs.

Influence of the Pt nanoscale interlayer on stability and electrical property of Ti/Pt/Sb-SnO2 electrode: A synergetic experimental and computational study

The Ti/Pt/Sb-SnO2 electrodes with nanoscale Pt interlayers were fabricated by pyrolytic coating combining with magnetron sputtering method. The effects of introducing Pt interlayer were evaluated by physicochemical and electrochemical measurements. We calculated the texture coefficients of SnO2 crystals growing on Ti and Ti/Pt substrates according to the XRD data, and found the SnO2 crystalline grains growing on Ti and Ti/Pt having the different preferred orientations. Hence, we used the first-principles method building three kinds of supercells along diverse preferred orientations (110), (101) and (211) to simulate three types SnO2 crystalline grains. The computation results indicated the conductivity of supercell built along the (101) face was better than that of (211) face supercell. Furthermore, electrochemical tests such as linear sweep voltammetry (LSV), chronopotentiometry and electrochemical impedance spectroscopy (EIS) had been carried out on the Ti/Pt/Sb-SnO2 electrodes. We also discussed the changes of oxygen evolution overpotential and charge transfer resistant on the Ti/Pt/Sb-SnO2 electrodes in a physical perspective.

Thin Films of Tin Oxide Nanosheets Used as the Electron Transporting Layer for Improved Performance and Ambient Stability of Perovskite Photovoltaics

Inorganic semiconducting metal oxide electron transporting layers (ETLs) with tailored nanostructures have the potential to yield efficient perovskite solar cells (PSCs) with improved stability and reduced hysteresis. Here, a simple and facile hydrothermal protocol is demonstrated for the growth of crystalline SnO2 nanosheet (SNS) thin films with excellent optical and photoelectrical properties. When applied as ETLs, the SNS enhances light harvesting, boosts charge collection, reduces hysteresis and improves the ambient stability. Moreover, optimization of the interfacial properties between the SNS and the perovskite layer by the introduction of a C60 interlayer results in better energy level alignment, decreasing charge recombination and thus prolonging the electron lifetime and improving the open‐circuit voltage (Voc). Therefore, the efficient conventional n‐i‐p PSCs based on C60‐modified SNS ETLs have almost hysteresis‐free behavior, with a champion power conversion efficiency, PCE, of 18.31% and a stabilized PCE over 18.00%. The SNS‐based PSC exhibits respectable ambient stability retaining over 90% of its initial efficiency after being stored in air at room temperature for 500 h without encapsulation. Such robust SNS ETLs pave the way to low‐cost and stable PSCs with high efficiency, less hysteresis, and long‐term stability.

Influence of SnO2 Orientation on Electrocatalytic Activities of Pt/SnO2 Model Electrodes for Methanol Oxidation

As an electrocatalyst in fuel cells, carbon-supported platinum (Pt/C) catalysts are widely used, but there are some problems in the degradation of carbon support and CO poisoning of Pt surface. To mitigate these problems, oxides supports are considered to be an alternative support for Pt catalysts. Oxide supports have some advantages to improve the long-term stability and the CO tolerance of electrocatalysts, but the detailed mechanism of oxide supports has not yet been unveiled. In this study, we fabricated Pt/SnO2 model electrodes with controlling SnO2 crystalline orientation.Pulsed laser deposition (PLD) technique was used for fabricating the SnO2 support oxides. Single crystals of aluminum and titanium oxides were used as a support for SnO2 thin film fabrication. Platinum nanoparticles were deposited on SnO2 film with the arc plasma deposition. Fabricated model electrodes were characterized with X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy. Electrochemical measurements were performed in an aqueous solution with methanol and perchloric acid. CO stripping voltammetry was also carried out to investigate CO tolerance of model electrodes.XRD patters show SnO2 thin films had surface orientation of (101), (100), and (110). XPS spectra also show the deposited Pt nanoparticles were metallic and had identical positive shift (~ 0.3 eV). The activities for methanol oxidation were in the following order: Pt/SnO2 (101) > Pt/SnO2 (100) > Pt/SnO2 (110). CO stripping voltammograms also showed similar activities for CO oxidation. Detailed influence and mechanism of surface orientation on catalytic activities will be discussed in the meeting.

An efficient Sb-SnO2-supported IrO2 electrocatalyst for the oxygen evolution reaction in acidic medium

Polymer (acidic) electrolyte membrane water electrolysis suffers from insufficient catalyst activity, high cost of noble metal, and unsatisfactory durability, due to the sluggish reaction kinetics of oxygen evolution reaction and poor stability of catalysts under harsh operating environments. Aiming to enhance the utilization and durability of noble metals, a mesoporous Sb-doped SnO2 material with high surface area and conductivity was synthesized via soft-template method to support IrO2 catalyst. Physical characterization reveals that the as-prepared composite exhibits a rough morphology with the weak crystallinity IrO2 upper layer covering the rutile SnO2 crystalline phase. Electrochemical test for the IrO2-loading-dependant activity finds that both the area-free activity and mass-specific current on the 31 wt% sample are the optimal, meaning the excellent dispersion effect coming from the mesoporous Sb-SnO2 support and the synergy between the catalytic particles and Sb dopant. In addition, the enhancement in mass transfer efficiency and conductivity coming from the porous, IrO2-covered cross-linked morphology and the support-active component interaction, the supported IrO2 with 50 wt% loading marks the maximum normalized charge (227 C g−1 IrO2) and the highest apparent current at 1.75 V. What is more, this composite catalyst with the noble metal oxide coating is much more durable during continuous oxygen evolution procedure under a constant potential of 1.6 V because of the anchor effect from the carrier on the catalyst and a protective effect from the noble metal layer on the non-acid-tolerant support.

True Vapor-Liquid-Solid Process Suppresses Unintentional Carrier Doping of Single Crystalline Metal Oxide Nanowires.

Single crystalline nanowires composed of semiconducting metal oxides formed via a vapor-liquid-solid (VLS) process exhibit an electrical conductivity even without an intentional carrier doping, although these stoichiometric metal oxides are ideally insulators. Suppressing this unintentional doping effect has been a challenging issue not only for metal oxide nanowires but also for various nanostructured metal oxides toward their semiconductor applications. Here we demonstrate that a pure VLS crystal growth, which occurs only at liquid-solid (LS) interface, substantially suppresses an unintentional doping of single crystalline SnO2 nanowires. By strictly tailoring the crystal growth interface of VLS process, we found the gigantic difference of electrical conduction (up to 7 orders of magnitude) between nanowires formed only at LS interface and those formed at both LS and vapor-solid (VS) interfaces. On the basis of investigations with spatially resolved single nanowire electrical measurements, plane-view electron energy-loss spectroscopy, and molecular dynamics simulations, we reveal the gigantic suppression of unintentional carrier doping only for the crystal grown at LS interface due to the higher annealing effect at LS interface compared with that grown at VS interface. These implications will be a foundation to design the semiconducting properties of various nanostructured metal oxides.

Magnetic and antibacterial properties of Zr-doped SnO2 nanopowders

Zirconium doped tin oxide (SnO2:Zr) nanopowders were synthesized by a simple soft chemical route adding various concentrations of zirconyl chloride (0, 5, 10 and 15 wt%). The samples were characterized by techniques like XRD, SEM, TEM, EDX, FTIR spectroscopy, UV–Vis-NIR spectroscopy and photoluminescence spectroscopy. XRD studies confirm that all the samples exhibit rutile tetragonal crystal structure with a strong (1 0 1) preferential growth texture. Hexagonal shaped grains were evinced from the SEM images. Nanosized grains are evinced from the TEM images and EDX spectra confirm the presence of Zr in the doped samples. The bands at 523 and 583 cm−1 observed in the FTIR spectra which are attributed as the characteristics of γ (Sn–OH) terminal bond of the SnO2 crystalline phase confirm the presence of Sn–O in the synthesized samples. The doped samples exhibit ferromagnetic behavior. Enhanced antibacterial activity was observed for the doped samples. The obtained results show that zirconium strongly influenced the structural, morphological, optical, magnetic and antibacterial properties of pure SnO2 nanopowders.

Structural, electrical, and optical properties of F-doped SnO or SnO2 films prepared by RF reactive magnetron sputtering at different substrate temperatures and O2 fluxes

The effects of substrate temperature and O2 flux on structural, electrical, and optical properties of the films prepared by RF reactive magnetron sputtering with SnF2-Sn target have been investigated by X-ray diffraction (XRD), Hall effect measurements, optical transmission spectra, and photoluminescence (PL) spectra. It is found that F-doped SnO films are produced and exhibit amorphous structure at lower O2 fluxes for substrate temperature of RT-300 °C, and window of O2 flux for depositing the films is reduced as substrate temperature increases. F-doped SnO2 (FTO) films are formed at higher O2 fluxes, and they exhibit amorphous state at substrate temperature of RT but crystalline state at substrate temperature of 150 and 300 °C. Furthermore, increasing O2 flux or substrate temperature can promote crystallinity and affect growth orientation for crystalline FTO films. Highly conductive FTO films can be obtained only at suitable O2 fluxes and higher substrate temperatures (150 and 300 °C), at which the films keep crystalline SnO2 structure along with high amount of oxygen vacancy (VO). Increasing substrate temperature from 150 to 300 °C, the resistivity of FTO films cannot be further decreased due to the out-diffusion of F although the film crystallinity improves. Compared with F-doped SnO films, the average transmittance in visible light range and band gap (Eg) of FTO films obviously increase. The FTO films show similar shaped PL spectra that can be attributed to substitutional fluorine (FO) and VO defects in the films, and PL emission intensity increases with increasing O2 flux or substrate temperature due to the improvement of film crystallinity. It is observed that the PL emission characteristics (shape and intensity) of F-doped SnO film are obviously different from FTO films and they have great changes as substrate temperature from RT to 150 °C, but corresponding mechanisms need to further clarify.

Enhancing performances of a resistivity-type hydrogen sensor based on Pd/SnO2/RGO nanocomposites

Palladium/tin oxide/reduced graphene oxide (Pd/SnO2/RGO) nanocomposites with Pd and SnO2 crystalline nanoparticles of high density and uniformity coated on RGO have been synthesized by a two-step reduction process. A novel hydrogen (H2) sensor based on Pd/SnO2/RGO nanocomposites was fabricated by placing Pd/SnO2/RGO nanocomposites onto a pair of gold electrodes. The Pd/SnO2/RGO nanocomposite-based sensor exhibited higher responses than Pd/RGO to H2 because the introduction of SnO2 nanoparticles enhances H2 adsorption and forms a P–N junction with RGO. The sensor shows a high response of 55% to 10 000 ppm H2, and a low detection limit, fast response, good selectivity and repeatability due to a combination effect of the Pd and SnO2 nanoparticles. The studies provide a novel strategy for great potential applications of graphene-based gas sensors.

Low-temperature electrodeposited crystalline SnO2 as an efficient electron-transporting layer for conventional perovskite solar cells

Tin oxide (SnO2) has recently attracted significant research interest for its role functioning as an efficient electron-transporting layer (ETL) due to its higher charge mobility than the commonly used titanium oxide (TiO2) for realizing high-performance perovskite solar cells (PVSCs). However, it is still challenging to develop a facile, low-temperature solution-based (<100oC) processing method to synthesize crystalline SnO2 with desirable charge mobility, which can facilitate its widespread applications in flexible optoelectronic devices. In this work, we utilize an electrochemical deposition technique to prepare SnO2 films at a reduced temperature below 100 oC. The electrodeposition endows the SnO2 film with high crystallinity and conductivity in addition to high transparency across the visible spectrum. Efficient photoluminescence (PL) quenching is observed in the bi-layered SnO2/CH3NH3PbI3 film, manifesting its efficient electron extraction capability from perovskite. Consequently, a conventional n-i-p PVSC using this electrodeposited SnO2 ETL shows a high PCE of 13.88% with negligible hysteresis. This work demonstrates a low-temperature solution-based preparation route for making crystalline SnO2 and its potential for application in large-scale PVSC production.

A facile and one step synthesis of large surface area SnO2 nanorods and its photocatalytic activity

High quality single crystalline SnO2 nanorods (NRs) were successfully synthesized by using novel microwave-irradiation method by using PEG-400 as surfactant. Powder X-ray diffraction (XRD) results reveals that the SnO2 crystalline with tetragonal rutile type structure (space group P42/mnm) have formed directly during the microwave irradiation process. The results are good in agreement with the standard JCPDS data (file no. 41-1445). Transmission electron microscope (TEM) images showed that NRs of about 460–530 nm in length and 55–75 nm in diameter. UV–visible diffusion reflectance spectroscopic (DRS) studies exposed the band gap energies of SnO2 was found to be 3.27 and 2.58 eV for without and with PEG respectively. The photocatalytic activity study showed that the as-synthesized SnO2 NRs were superior photocatalytic performance for the degradation of methylene blue (MB) and rhodamine B (RhB) dye solutions. The samples were further characterized by photoluminescence and energy dispersive spectra analysis.

Synthesis of Sr2Nb3O10 nanosheets and their application for growth of thin film using an electrophoretic method

AbstractK(Sr2Nb3)O10 (KSN) ceramic without the secondary phase was obtained from a KSN + 0.05K2O specimen sintered at 1350°C. This ceramic was used as the precursor to synthesize Sr2Nb3O10− (SNO−) nanosheets, because it has a pure KSN phase with a large (002) plane. The SNO− nanosheets were deposited on a Pt/Ti/SiO2/Si substrate using the electrophoresis method at room temperature, and heated at various temperatures to get rid of the organic defects. The crystalline SNO phase without organic defects was formed in film annealed at 600°C. However, when the annealing temperature exceeded 600°C, the Pt electrode became unstable, resulting in degradation of the SNO film. Good electric properties were obtained from the SNO film annealed at 600°C: dielectric constant of 70, dielectric loss of 0.017 at 1.0 MHz, leakage current density of 3.5×10−8 A/cm2 at 0.2 MV/cm, and a breakdown electric field of 0.25 MV/cm.

Comparative analysis of physico-chemical and gas sensing characteristics of two different forms of SnO2 films

In this paper the results of studies of comparative studies on the crystallinity, morphology and chemistry combined with the gas sensor response of two different forms of tin dioxide (SnO2) films prepared by the Rheotaxial Growth and Thermal Oxidation (RGTO) and by the Laser-enhanced Chemical Vapour Deposition (L-CVD) methods, respectively, are presented.For this purpose the X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM) and X-ray Photoelectron spectroscopy (XPS) have been used. XRD studies for both samples show the contribution from the crystalline SnO2 in the cassiterite rutile phase without any evident contribution from the tin oxide (SnO) phase. SEM and AFM studies show that the surface morphology of RGTO and L-CVD SnO2 samples are characterized by grains/nanograins of different size and surface roughness.In turn XPS studies confirm that for both SnO2 samples a slight nonstoichiometry with a relative [O]/[Sn] concentration of 1.8, and slightly different amount of C contamination at the surface of internal grains with relative [C]/[Sn] concentration of 3.5 and 3.2, respectively. This undesired C contamination cannot be ignored because it creates an uncontrolled barrier for the potential gas adsorption at the internal surface of sensor material. This is confirmed by the gas sensor response in NO2 atmosphere of both SnO2 samples because the sensitivity is evidently smaller for RGTO SnO2 with respect to the L-CVD SnO2 samples, whereas the response time showed a completely opposite tendency. It is probably caused by the smaller extension of internal surface and grain dimension with respect to the Debye length, as well as higher C contamination observed for RGTO SnO2 with respect to L-CVD SnO2 samples.

Single crystalline SnO2 thin films grown on m ‐plane sapphire substrate by mist chemical vapor deposition

Tin dioxide (SnO2) thin films, as a candidate for realizing next‐generation electrical and optical devices, were grown on 2‐inch diameter m ‐plane sapphire substrates by mist chemical vapour deposition at atmospheric pressure. The SnO2 thin films were characterized by scanning electron microscope (SEM), atomic force microscope (AFM), X‐ray diffraction (XRD) in θ–2θ and φ scanning modes, and electron backscatter diffraction (EBSD). Although the SEM and AFM images showed a relatively rough surface morphology, it was found from the XRD and EBSD measurements that SnO2 films were epitaxially grown on the substrates under optimised growth condition. Epitaxial growth of SnO2 thin film growth at three typical areas on the substrate was confirmed by the EBSD measurements. It is likely that the single crystalline SnO2 (001) thin film was formed across the 2‐inch sapphire substrate. Finally, the second SnO2 layer was overgrown on the above single crystalline SnO2 thin film, which functioned as a buffer layer. This method which drastically improved surface roughness of the second SnO2 layer.