Fluorine-doped Tin Oxide Glass Substrate Research Articles

Precursor-concentration-controlled Morphology of TiO2 Nanorod/Nanoflower Films for Enhanced Photoelectrochemical Water Splitting and Investigating Their Growth Mechanism

Titanium dioxide (TiO2) has been considered as one of the most promising photocatalysts for photoelectrochemical (PEC) water splitting. Therefore, numerous efforts have been devoted to improving its PEC water splitting performance. In this study, TiO2 nanorod/nanoflower (NRF) films with controlled morphology were synthesized on fluorine-doped tin oxide (FTO) glass substrates by following a facile one-step hydrothermal method. The TiO2 NRF films were characterized by X-ray diffraction (XRD), Raman spectroscopy, field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), energy-dispersive X-ray spectrometer (EDS), and ultraviolet-visible (UV-Vis) spectrophotometer. FE-SEM showed that the TiO2 films are composed of a simultaneous growth of a primary layer of TiO2 nanorod arrays (NRAs) and a second layer of TiO2 nanoflowers (NFs). The proposed growth mechanism highlighted the influence of precursor concentration on nucleation sites, affecting the preferred crystallographic plane growth of rutile TiO2 and nanorod alignment on the FTO substrate. Intriguingly, TiO2 NRF films prepared with 1.0 mL of titanium butoxide exhibited a maximum photocurrent density of 3.58 mA.cm−2 at 1.23 V versus (vs.) the reversible hydrogen electrode (RHE), along with a maximum photoconversion efficiency of 0.69%. The enhanced photocurrent density and photoconversion efficiency were attributed to the optimum thickness in the range of 4.52-7.31 µm, which caused the film to be formed with a unique morphology of the primary layer with well-vertically aligned nanorods and the second layer of flowers consisting of numerous rods stacked on top of one another. This study demonstrates the importance of designing semiconductors with 1D nanorod/3D nanoflower structures as high-performance photoelectrodes for PEC water splitting. Copyright © 2024 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

NiO thickness measurement using a rectangular-type Sagnac interferometer as the material transport layer in a perovskite solar cell

This work aims to utilize a phase-shifting technique in a rectangular-type Sagnac interferometer (RTSI) to measure the thickness of a thin film of nickel (II) oxide (NiO) in an electron transport layer (ETL) in perovskite solar cell preparation. The NiO layer is deposited on a fluorine-doped tin oxide (FTO) glass substrate. In the RTSI setup, the signal output from the interferometer is divided into the reference and testing arms using a nonpolarizing beam splitter (NPBS). The balanced photodetectors then detect the signal, with the FTO/NiO layer placed in the testing arm and pure FTO in the reference arm. By analyzing the signal intensities at polarization settings of 0° to 180°, the phase shift and thickness of the NiO layer can be determined. The thickness values of FTO and NiO films obtained through three different phase-shifting algorithms of three-, four-, and five-steps are calculated. The obtained NiO thickness values are validated against scanning electron microscopy (SEM). Finally, by considering the NiO thickness value that exhibits the lowest percentage error compared to one from SEM, it is confirmed that the three-step algorithm is the most suitable scheme for obtaining intensities at 0°, 45°, and 90°. Therefore, the proposed setup shows promise as a replacement for SEM in thickness measurements.

Effect of cerium oxide nanorods growth time on the electrochromic properties of WO3/CeO2 hybrid films

In this study, the cerium oxide nanorods (CeO2) were grown on fluorine-doped tin oxide (FTO) glass substrates by using a hydrothermal process at growth times of 4hrs, 6hrs and 12hrs and annealed at temperature 3500C. The grown samples were characterized by using Scanning electron spectroscopy (SEM), Energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Raman spectroscopy, and UV–Vis spectrometer. Tungsten oxide (WO3) film was deposited, on these hydrothermally grown nanorods (NRs), by using the DC sputtering process to develop WO3/CeO2 hybrid films. From the SEM and XRD analysis, CeO2 nanorods were observed at different growth times, and crystalline structures were observed respectively. The optical transmittance decreases with the increase in synthesis time, mainly due to the increase in nanorods' thickness. The diffusion coefficient of 11.24 × 10−11 cm2/s and the cathodic peak current of −10.1 mA was observed for 12-h WO3/CeO2 films and the coloration efficiency of 12 cm2/C was observed for 4-h WO3/CeO2 hybrid film.

Morphological, structural, optical and photocurrent characteristics of Bi(TixMn(1-x))O3 perovskite nanorods grown by hydrothermal synthesis

This study focuses on the hydrothermal synthesis of Bi(TixMn(1-x))O3 (x = 0.3–0.9) perovskite nanorods on fluorine-doped tin oxide glass substrates and investigates the influence of Ti4+ on their morphological, structural, optical properties, and photocatalytic behavior. The high-resolution XPS spectra results have proved that Ti has been properly substituted into the Bi(TixMn(1-x))O3 nanorods. The characterization of morphology reveals a decrease in average diameter from 222 to 115 nm as the Ti concentration increases, while the band-gap energy experiences a slight reduction from 3.158 to 3.132 eV. X-ray and Raman spectroscopy analyses of the Bi(TixMn(1-x))O3 nanorods indicate that Ti ions substitute not only Mn3+ but also Bi3+ ions, leading to structural distortions in the crystal lattice. Moreover, the Bi(TixMn(1-x))O3 systems demonstrate enhanced photocurrent densities at 1.5 V potential, ranging from 3.19 to 5.54 mA/cm2, as the Ti concentration increases. This enhancement can be attributed to the combined effects of increased surface area, accelerating electron transfer at the interface of the electrode, and decreased optical band-gap energy. It is anticipated that this novel system will pave the way for further advancements in the field of photocatalytic water splitting and solar energy conversion applications.

Optimization of the MA/FA Ratio in the Structure of Absorber Layers Based on MA(1-x)FAxPbI3 Perovskites for Stable and Efficient Solar Cells

Herein, we investigate the mixture of methylammonium lead iodide (MAPbI3) and formamidinium lead iodide (FAPbI3). The perovskite films were coated onto fluorine-doped tin oxide (FTO) glass substrates using a spin-coating method, with the spin-coater set at 4,000 rpm for 20 s. We studied the influence of incorporation in MA(1-x) FA(x)PbI3 films. The crystal structure of the perovskite films was characterized using X-ray diffraction (XRD). Optical properties were assessed using UV-Vis spectroscopy with a spectrophotometer, and photoluminescence (PL) was characterized using a He-Cd Si-CCD laser source and a Hamamatsu detector. Images depicting the characteristic morphology of the films were captured with a scanning electron microscope (SEM). Our measurements reveal that the crystallinity of the MAPbI3 thin film improved with the incorporation of FAPbI3. In the case of 70% FAPbI3, the morphology of the MA30FA70PbI3 mixture also improved, exhibiting a rough surface with pores. The optical properties were enhanced, and the mixed thin film demonstrated better stability compared to pure MAPbI3 and FAPbI3 thin films. These film characteristics indicate that the mixtures are particularly suitable for use in photovoltaic applications.

Bifunctional Lead–Iron Oxyfluorides, 3D Cubic PbFeO2f and 2D Layered Pb3Fe2O5F2, Driving Photoelectrochemical and Electrochemical Water-Oxidation

Introduction Photoelectrochemical water splitting has attracted attention as a method of generating solar fuel such as hydrogen gas to be useful as a renewable energy carrier and a clean fuel of an internal‐combustion engine. For water oxidation of the half reaction in the water splitting, mixed-anion compounds have appeared as good candidates of the catalyst. In the mixed-anion compounds, a metal center is coordinated by several kind of anionic species. This environment induces their wide variety of physical and chemical properties not to be realized in single anion counterparts. The mixed-anion compounds possess visible-light responsibility and can utilize sunlight efficiently, therefore, which have fascinated photocatalyst researchers. The reason why they absorb visible light is the narrow bandgap with less electronegative anion species than oxygen. However, they are not very stable for photoelectrochemical water-oxidation because photogenerated holes oxidize the anion species except for oxygen in the compounds and cause degradation. Recently, we have reported an oxyfluoride Pb2Ti2O5.4F1.2 as a stable photoanode material that absorbs visible light at wavelengths up to ~500 nm.1 Oxyfluoride containing O2− and F− anions in the same phase is an example of the mixed-anion compounds. The other anion F− is less oxidized than O2−. Thus, the Pb2Ti2O5.4F1.2 photoanode showed essential stability toward the degradation by photogenerated holes exceptionally. However, this is the sole example of a visible-light-responsive oxyfluoride photoanode. Development of a new oxyfluoride photoanode absorbing visible light is important to gain the insight for water oxidation using the oxyfluorides. In the present work, another type of lead-iron oxyfluorides, PbFeO2F and Pb3Fe2O5F2, are applied to water oxidation as not only a photoanode but also an electrocatalyst.2,3 The lead-iron oxyfluoride, PbFeO2F, drives photoelectrochemical water-oxidation in visible light up to ~600 nm. In addition, this oxyfluoride functions as the electrocatalyst for water oxidation.2 In the electrochemical water-oxidation, another Pb3Fe2O5F2 shows higher performance for water oxidation than PbFeO2F. It seems that the crystal structure of two-dimensional layered perovskite Pb3Fe2O5F2 influences the superior performance to three-dimensional cubic perovskite PbFeO2F.3 Results and Discussion PbFeO2F and Pb3Fe2O5F2 powder were synthesized through a solid-state reaction and that in the evacuated glass tube, respectively.2,3 They were deposited on a fluorine-doped tin oxide (FTO) glass substrate by using electrophoresis method. The PbFeO2F or Pb3Fe2O5F2/FTO electrode was subjected to post-necking treatment to deposit TiO2 layer (TiO2/PbFeO2F or Pb3Fe2O5F2/FTO electrode), followed by electrodeposition of cobalt phosphate (Co-Pi) cocatalyst (Co-Pi/TiO2/PbFeO2F or Pb3Fe2O5F2/FTO electrode). Linear-sweep voltammetry for the as-prepared electrodes was conducted under intermittent visible-light irradiation (>400 nm) in 0.1 M K3PO4 solution (Figure 1A). The PbFeO2F/FTO electrode exhibited no photocurrent response. By contrast, a slight photocurrent response was observed for the TiO2/PbFeO2F/FTO electrode because of mainly improved interparticle conductivity in the electrode. Furthermore, a clear anodic photocurrent was observed for the Co-Pi/TiO2/PbFeO2F/FTO electrode. The Co-Pi cocatalyst, known as a water-oxidation promoter, improved the charge transfer at the electrode/water interface and charge separation in the electrode. Meanwhile, the Co-Pi/TiO2/PbFeO2F/FTO electrode exhibited an anodic photocurrent in visible light with longer wavelengths than ~600 nm. These tendencies were like those of Pb3Fe2O5F2 electrodes though the photocurrent were slightly higher than the PbFeO2F electrodes (Figure 1A, right). On contrary to the photoelectrochemical water-oxidation, a clear difference was observed when using those lead-iron oxyfluorides as an electrocatalyst. Under dark conditions, controlled-potential electrolysis with non-modified PbFeO2F and Pb3Fe2O5F2/FTO electrode was performed at +1.7 V vs. RHE (Figure 1B). The evolved O2 was detected by GC analysis in the measurement. The amount of that was almost one-fourth of electrons flowed during the electrolysis, which means the water oxidation was the major path for the electrochemical reaction. Besides, Pb3Fe2O5F2/FTO electrode showed 8 times higher activity than PbFeO2F. That reason has not been revealed but the difference is likely to be attributed to two-dimensional layered perovskite Pb3Fe2O5F2 and three-dimensional cubic perovskite PbFeO2F. References Hirayama, H. Nakata, H. Wakayama, S. Nishioka, T. Kanazawa, R. Kamata, Y. Ebato, K. Kato, H. Kumagai, A. Yamakata, K. Oka and K. Maeda, Solar-Driven Photoelectrochemical Water Oxidation over an n-Type Lead-Titanium Oxyfluoride Anode, J. Am. Chem. Soc., 141, 17158 (2019).Mizuochi, K. Izumi, Y. Inaguma and K. Maeda, A bifunctional lead–iron oxyfluoride, PbFeO2F, that functions as a visible-light-responsive photoanode and an electrocatalyst for water oxidation, RSC Adv., 11, 25616 (2021).Mizuochi, K. Oka, Y. Inaguma and K. Maeda, A two-dimensional perovskite oxyfluoride Pb3Fe2O5F2 as a catalyst for electrochemical oxidation of water to oxygen, Sustain. Energy Fuels, 6, 2423 (2022). Figure 1

Cathodic arc deposition of nanocrystalline titanium nitride thin film on fluorine doped tin oxide coated glass substrate: Crystal structural, microstructural, mechanical, optical and electrical properties

The nanocrystalline titanium nitride (TiN) films were deposited on fluorine doped tin oxide (FTO) coated glass substrates for the first time by cathodic arc deposition. The crystalline phase and orientation, growth morphology, surface roughness, hardness, scratch adhesion, electrical resistivity, optical absorption and bandgap of the TiN films were investigated. The GI-XRD confirmed the formation of cubic TiN and crystallographic orientation growth. The 2150 nm thick TiN film showed (111) orientation due to columnar growth patterns, while the 650 nm TiN film formed with the (200) orientation. The grain size of TiN films was 50–200 nm by FESEM and AFM analyses, and it was formed as elongated nanocrystals of 65–125 nm width and 120–250 nm lengths. The microhardness of the 650, 1000 and 2150 nm TiN thin films was measured to be 836, 943 and 1281 HV0.05 respectively. The scratch adhesion test demonstrated a good adhesive strength up to a critical load of 10 N and beyond the delamination occurred. The electrical resistivity of TiN film found to vary with thickness, the 650 nm TiN film showed a low resistivity of 16 × 10-6 Ω cm, which is comparable with the electrical resistivity of platinum and magnetron sputtered TiN film. The UV-Vis-NIR diffused reflectance spectroscopic studies of the TiN thin film showed a sharp absorption at 448 nm due to plasmon absorption and Tauc plot showed direct band gap of 2.1 eV. The results demonstrated that cathodic arc deposited nanocrystalline TiN thin film deposited on FTO glass substrate can be used as counter electrode for dye sensitized solar cell (DSSC) applications.

A polyaniline/polyvinyl acetate composite film electrode for highly sensitive electrochemical sensing of pH

The electrochemical performances of three types of polyaniline (PANI)-based films developed as pH-sensing electrodes were evaluated and compared. PANI emeraldine base (PANI-EB), PANI emeraldine salt (PANI-ES), and PANI-ES/polyvinyl acetate (PVAc) composite films were spin coated on fluorine-doped tin oxide (FTO) glass substrates to fabricate pH-sensing electrodes. The surface morphology, wetting properties, and electrochemical properties were characterized and compared. Unprotonated PANI-EB films had a regular structure with residual flakes, whereas protonated PANI-ES and PANI-ES/PVAc films exhibited globular and porous structures, respectively. All PANI-based films adhered well to the FTO substrate. Water contact angles indicated the hydrophobic characteristic of the PANI-EB films and the hydrophilicity of the PANI-ES films, which could affect their stability in buffered solutions of different pH. The PANI-ES/PVAc films exhibited improved stability because of the hydrophobic PVAc. The PANI-ES/PVAc electrodes exhibited a significantly higher pH sensitivity of 100 mV pH−1 than those of the single-component PANI-EB and PANI-ES electrodes (57 and 65 mV pH−1, respectively) in the pH range of 3.0–8.0, which could be attributed to the non-equilibrium protonation/deprotonation of nitrogen atoms in the PANI structure. Moreover, the PANI-ES/PVAc electrodes also exhibited good reproducibility and selectivity to H+ over certain other ions and molecules (e.g., glucose).

Antireflection effect of high haze FTO for improving short circuit current density of perovskite solar cells

The optical properties of fluorine-doped tin oxide (FTO) coated glass substrates will limit the short circuit current density (Jsc), thus the power conversion efficiency (PCE) of perovskite solar cells (PSCs). This work compares the transmittance, reflectance, haze, and surface roughness of different FTO glass substrates. Then the performance of the PSCs, which were fabricated on these substrates, is discussed. The analysis indicates that higher haze FTO glass substrates with higher surface roughness are effective for the reduction of light reflection from NiOx-deposited FTO substrates/perovskite interfaces, leading to higher Jsc and thus the higher PCE of the PSCs. The antireflection effect is attributed to light absorption by the perovskite layer via multiple reflections due to the very rough FTO surface texture.

Fabrication and processing of bacterial cellulose/silver nanowire composites as transparent, conductive, and flexible films for optoelectronic applications

AbstractThis work reports on the engineering and fabrication of transparent, conductive, and flexible films made as a composite of bacterial cellulose microfibers (BMF), a polymer (either PVA or PEO), and silver nanowires (AgNWs) as viable and cost‐effective replacements to commercial indium‐tin oxide (ITO) and fluorine‐doped tin oxide (FTO) transparent conductors. The studies conducted indicate that the optical and mechanical properties of BMF‐polymer substrates are tuneable by varying the ratio of BMF to polymer. An optimized ratio of 70:30 of BMF to polymer was established for BMF‐PVA and BMF‐PEO composites. The optimized composite films were coated with varying amounts of AgNWs. As the AgNW loading increased, the deposition density of AgNW networks increased, while the sheet resistance and optical transmittance decreased. The optimum AgNW loading was determined at 0.20 mg for both composite films. The BMF‐PVA‐AgNW film displayed transmittance between 81% and 71% and an average resistivity of 9.462 ± 0.588 Ω/sq while the BMF‐PEO‐AgNW films showed transmittance between 73% and 65% and an average resistivity of 9.388 ± 0.1.375 Ω/sq. These properties compared well to that of commercial ITO and FTO glass substrates. The findings promote cellulose‐based composites as low‐cost, lightweight, and durable substrates for optoelectronic applications.

Effects of Heat Treatment in Air Atmosphere on Dip Coating Deposited CdS Thin Films for Photo Sensor Applications

Objective: In this report, photo sensitive materials with enhanced charge carriers have been prepared using dip coating technique. Methods: Cadmium sulphide (CdS) is N-type semiconductor compound belonging to II-VI group. CdS nanoparticles were synthesized using non-aqueous chemical method and characterized by ultraviolet-visible (UV-Vis) absorption spectroscopy, photoluminescence (PL) and transmission electron microscopy. CdS films were deposited on fluorine doped tin oxide (FTO) glass slides using dip coating method at different dip times and heat treated in air and analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive analysis by X-rays (EDAX), mapping and atomic force microscopy (AFM). Results: Quantum confinement effect was observed in UV-Vis absorption spectra of CdS nanoparticles. Quenching of luminescence intensity and blue shift at smaller wavelengths were observed in PL spectra. Presence of highly dense rectangular shaped grains in CdS films and increment in particle sizes with increase in dip time were shown by AFM images. Selected area electron diffraction images showed ring patterns indicating polycrystalline nature of CdS nanoparticles. Increase in crystallite size and decrease in crystal defects by heat treatment in air and increment in grain size with increase in dip time were shown by SEM images. XRD analysis of CdS films showed polycrystalline nature. Conclusion: In previous work, preparation of dip coating deposited CdS films on FTO glass substrates for optoelectronic device applications such as photo sensors has not been reported. In this study, I-V characteristics of heterojunctions under dark and illumination conditions were discussed. Experimental results obtained in our study and their comparison with previous reports were also discussed.

Growth of quasi-1 dimensional (Bi1−x Sb x )2S3 nanowires on fluorine-doped tin oxide glass substrate by vapor transport

(Bi1−x Sb x )2S3 solid solution nanowires () are grown on fluorine-doped tin oxide (FTO) glass via physical vapor transport. The compositions were controlled by varying the Sb2S3 source temperature (300 °C–453 °C) by changing the upstream locations of the Sb2S3 source in the furnace while keeping the Bi2S3 source at the center of the furnace (497 °C). Defect-free nanowires with phase-pure orthorhombic and quasi-1 dimensional crystal structures were grown under a modified vapor–solid mechanism affected by FTO at initial growth stage. The aspect ratios of the nanowires reached the minimum at composition As the Sb2S3 source approached the Bi2S3 source, x increased owing to the increase in the Sb2S3 source temperature. x/(1-x), which is proportional to the evaporation flux of the Sb2S3 source, could be well-fitted with a thermally activated equation with an apparent activation energy ( ). However, at the distance between the Sb2S3 and Bi2S3 sources, with the Sb2S3 source at temperatures higher than 410 °C, the compositions reduced despite the increased Sb2S3 evaporation flux. Such retrograde behavior was confirmed by high-resolution transmission electron microscopy, x-ray diffraction, and micro-Raman studies. This retrograde behavior is ascribed to the loss due to the reaction of gaseous Sb species with the Bi2S3 source.

Effect of Platinum Ribbons on Photoelectric Efficiencies of Dye-Sensitized Solar Cells

In this study, we fabricate a counter electrode by coating a Pt ribbon onto a fluorine-doped tin oxide glass substrate with a Pt layer. The Pt ribbon gives rise to a protrusive structure of the counter electrode, produced by photolithography, sputtering and lift-off processes. The experimental results reveal that the photoelectric efficiency of the dye-sensitized solar cell (DSSC) with the Pt ribbon (5.32%) is 21% higher than that of the DSSC without a Pt ribbon (4.38%). This infers that Pt ribbons can increase the photoelectric efficiencies of DSSCs. The DSSC with the Pt ribbon has a large photoelectric efficiency of 5.32%, not only because the protrusive structure has specific channels for directional electron transport, but also because of its large surface area. The method that is proposed herein has the advantages of a low production cost and easy fabrication that can be applied to various electrode structures.

Enhanced NH3 Sensing Performance of Mo Cluster-MoS2 Nanocomposite Thin Films via the Sulfurization of Mo6 Cluster Iodides Precursor.

The high-performance defect-rich MoS2 dominated by sulfur vacancies as well as Mo-rich environments have been extensively studied in many fields, such as nitrogen reduction reactions, hydrogen evolution reactions, as well as sensing devices for NH3, which are attributed to the under-coordinated Mo atoms playing a significant role as catalytic sites in the defect area. In this study, the Mo cluster-MoS2 composite was creatively synthesized through a one-step sulfurization process via H2/H2S gas flow. The Mo6 cluster iodides (MIs) coated on the fluorine-doped tin oxide (FTO) glass substrate via the electrophoretic deposition method (i.e., MI@FTO) were used as a precursor to form a thin-film nanocomposite. Investigations into the structure, reaction mechanism, and NH3 gas sensing performance were carried out in detail. The results indicated that during the gas flowing, the decomposed Mo6 cluster iodides played the role of template and precursor, forming complicated Mo cluster compounds and eventually producing MoS2. These Mo cluster-MoS2 thin-film nanocomposites were fabricated and applied as gas sensors for the first time. It turns out that after the sulfurization process, the response of MI@FTO for NH3 gas increased three times while showing conversion from p-type to n-type semiconductor, which enhances their possibilities for future device applications.

The Effect of Transparent Conducting Oxide Films on WO3-based Electrochromic Devices with Conducting Polymer Electrolytes

Over the past few decades, electrochromism has been a prominent topic in energy-saving applications, which is based on the mechanism of altering the optical transmittance of EC materials under the effect of a small applied voltage. Thus, tungsten oxide (WO3) is a significant chemical compound typically applied in electrochromic devices (ECDs) as it is responsible for the optical transmittance variation. In this work, the WO3 films were produced through a sol-gel spin-coating method. The effect of various transparent conducting oxides (TCOs, which are indium-doped tin oxide (ITO), fluorine-doped tin oxide (FTO) glass substrates, and aluminum-doped zinc oxide (AZO)) was investigated in the construction of ECDs. Based on a conducting polymer polypyrene carbonate electrolyte, ITO and aluminum-doped zinc oxide (AZO)-coated glasses were also examined as counter electrodes. The electrode combination employing FTO and ITO as the TCO and counter electrode, respectively, exhibited the most significant coloration efficiency of 72.53 cm2/C. It had coloring and bleaching transmittance of 14% and 56%, respectively, with a large optical modulation of 42%. In addition to that, ECDs with the AZO counter electrode have the advantage of lower intercalation charges compared to ITO and FTO. Hence, this research offers a new avenue for understanding the role of common TCO and counter electrodes in the development of WO3-based ECDs with conducting polymer electrolytes.

Well-Dispersive Polypyrrole and MoSe2 Embedded in Multiwalled Carbon Nanotube@Reduced Graphene Oxide Nanoribbon Electrocatalysts as the Efficient Counter Electrodes in Rigid and Plastic Dye-Sensitized Solar Cells

In this study, a core–shell structured multiwall carbon nanotube@reduced graphene oxide nanoribbon (MWCNT@rGNR) was prepared by the facile unzipping of MWCNTs with mild conditions to synthesize the composites of the MWCNT@rGNR and polypyrrole (PPy) or MoSe2, which were used as the electrocatalysts for the counter electrodes (CEs) in dye-sensitized solar cells (DSSCs). The transmission electron microscopy image of the MWCNT@rGNR showed a graphene sheet structure found on both sides of the MWCNTs, indicating a central core of the MWCNTs and its shell of the rGNR. The obtained MWCNT@rGNR functionalized with PPy or MoSe2 was envisaged to have the advantages of both component, that are the unique electronic structure of the MWCNT@rGNR and the synergistic effects of conductive PPy or electrocatalytically active MoSe2, respectively. The DSSCs with PPy/MWCNT@rGNR0.3 and MoSe2/MWCNT@rGNR0.3 showed comparable efficiency (photoelectric conversion efficiency, PCE = 7.48 and 8.34%, respectively), short-circuit current (Isc = 17.97 and 17.11 mA cm–2, respectively), and open-circuit voltage (Voc = 0.80 and 0.84 V, respectively) without any loss of the fill factor (FF = 0.52 and 0.58, respectively) as compared to the cell fabricated using a standard Pt electrode. The PCE of a standard Pt CE was 7.70% with an Isc of 16.09 mA cm–2, Voc of 0.76 V, and FF of 0.63. According to the results of the electrochemical measurements, composites with PPy or MoSe2 showed better electrocatalytic activity, higher redox-active surface area, and extremely large heterogeneous electron transfer rate constant. The plastic devices assembled with the PPy/MWCNT@rGNR0.3 and MoSe2/MWCNT@rGNR0.3 coated on a flexible plastic substrate (indium tin oxide-coated polyethylene naphthalate; ITO/PEN)exhibited impressive PCEs of 4.61 and 5.25%, respectively, comparable to those coated on the rigid fluorine-doped tin oxide glass substrate. This work presented a facile low-temperature method to fabricate high-performance MWCNT@rGNR composite-based CEs to make them applicable to large-scale plastic DSSCs.

Electrodeposition of Gold Nanoparticles from a Low Electrolyte Concentration for Ethanol Electrooxidation

In this research, the spherical gold nanoparticles (AuNPs) were successfully synthesized over fluorine-doped tin oxide glass (FTO) substrate from an additive-free and low-concentration electrolyte. Based on the field emission scanning electron microscopy micrograph, the AuNPs tend to agglomerate and form spherical particles with protrusions outward. The electrochemical impedance spectroscopy shows that Au/FTO has a lower charge transfer resistance than the substrate, indicating catalytic reactivity of the AuNPs. The cyclic voltammetry measurement exhibits an oxidation peak current at about 1.83 mA/cm2, showing a high catalytic response of AuNPs on ethanol electrooxidation.

THE PROPERTIES OF SONICATED IMMERSION GROWN HEMATITE FILMS AT VARIOUS ANNEALING TEMPERATURES

In this research, hematite (α-Fe2O3) film was synthesised to study the effect of annealing temperature on its crystallinity, optical and electrical properties. Through a sonicated solution immersion technique, hematite films were deposited on a fluorine-doped tin oxide (FTO) glass substrate. In the synthesis process, 0.2 M ferric chloride (FeCl3·6H2O) was used as a precursor, 0.2 M urea (NH2CONH2) as the stabilizer, and de-ionized (DI) water as a solvent to produce 200 ml of aqueous solution. During the annealing treatment, we varied the temperatures at 350 ºC, 450 ºC and 500 ºC. The X-ray diffraction (XRD) pattern revealed the presence of peaks of 2θ angles between 20° to 90°, corresponding to (104), (110), (214), (125) and (128) planes, which exhibited crystalline structures of rhombohedral with diffraction peaks of hematite phase (α-Fe2O3). Optical characterisations showed that the transmittances of all samples were close to 100% in the high wavelength level of the visible light region, which is close to the infrared spectrum. Absorption of hematite samples was found to be more than 0.6 a.u. in the low wavelength level of the visible light region close to the ultraviolet spectrum and close to 0 in the high wavelength level of the visible light region close to the infrared spectrum. A sample with an annealing temperature of 500 °C has the lowest transmission and the highest absorbance in the visible region due to dim pigments in the hematite film.

Electrodeposition of polyaniline on high electroactive indium tin oxide nanoparticles-modified fluorine doped tin oxide electrode for fabrication of high-performance hybrid supercapacitor

In this study, hierarchical polyaniline (PANI) nanosheets were electrochemically deposited on indium tin oxide nanoparticles coated fluorine-doped tin oxide glass (ITONPs-FTO) substrate from an aqueous solution containing 0.5 M aniline and 1 M H2SO4. The ITONPs provide efficient support with high electroactive surface area in the electrochemical deposition of PANI and produce excellent PANI films. The developed PANI film deposited on the ITONPs-FTO electrode was characterized via field-emission scanning-electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. A hybrid supercapacitor (HSC) was fabricated using the developed PANI deposited ITONPs-FTO as a positrode and the jute sticks derived activated carbon nanosheets coated FTO (JAC-FTO) as a negatrode. Because of its high capacitive performance, unique structures of electrode materials, and optimum operating potential window, the fabricated PANI-ITONPs-FTO//JAC-FTO HSC performed excellently in 0.1 M HCl aqueous electrolyte, delivering a high areal capacitance of 318 mF/cm2 at a 1.0 mA/cm2 current density and exhibit a high energy density of 28 µWh/cm2 at a high power density of 400 µW/cm2. Moreover, the HSC exhibits excellent cyclic stability with ∼ 87% Coulombic efficiency and ∼ 91% capacitance retention after 1000 charge–discharge cycles.

Study of the Optical, Structural and Morphological Properties of Electrodeposited Copper Manganese Sulfide (CuMnS) Thin Films for Possible Device Applications

Semiconductor thin films of CuMnS have been deposited onto conductive fluorine-doped tin oxide (FTO) glass substrate using an electrodeposition method to investigate their properties for possible applications. Copper sulfate, manganese sulfate and Thiourea were precursors used for sources of copper, manganese and sulphur ions respectively. The concentration of manganese ions was varied while keeping deposition voltage and time constant at 0.6 and 100 s, respectively. The films were characterized for optical, structural and morphological properties. The results obtained showed that the absorbance of the films is high in the visible (VIS) and near-infrared (NIR) regions but decreases towards NIR. The films transmittance is low in the VIS but increased in the NIR regions. The extinction coefficient is low in the VIS and NIR regions and decreases as concentration of manganese ion increased. The refractive index is high and initially increased slightly from 4.49 to 4.68 in the mid-VIS region while manganese concentration increased from 0.05 to 0.15 M and then decreased to the value of 2.73 as concentration of manganese ion increased further. The optical conductivity is high throughout the VIS and NIR regions while the optical bandgap energy is in the range of 1.5 to 2.05 eV and increases as manganese ion concentration increased. The XRD analysis showed that the deposited thin films of CuMnS are crystalline with average crystallite size and micro-strain in the range of 15.86 - 24. 45 nm and 3.97×10–3 - 6.13×10–3, respectively. The SEM results showed that the films are composed of particle sizes that are spherical in shape, uniform in sizes and densely packed together and consequently make the film surface rough. These properties exhibited by the films make them good materials for applications in photovoltaic calls, solar control coatings, photothermal applications and many other electronic devices that require high temperatures.
 HIGHLIGHTS
 
 This paper focused on the study of the effect of manganese ion concentration on the chalcogenide semiconductor thin films of CuMnS for possible device applications
 Electrodeposition method was used to fabricate the semiconductor thin films of CuMnS
 Optical, Structural and morphological properties of the thin films were characterized
 The deposited thin films of CuMnS were found to have good applications for photovoltaic cells and other optoelectronic device fabrications
 
 GRAPHICAL ABSTRACT