Indium Tin Oxide-coated Glass Substrates Research Articles

Improving photovoltaic characteristics of CdS-based hybrid solar cells through Mn incorporation

CdS thin films, both with and without Mn-doping, were grown via chemical bath deposition on indium tin oxide-coated glass substrates for application in hybrid solar cells. X-ray diffraction analysis revealed that Mn doping led to a deterioration in the crystal quality of CdS samples, evidenced by increased microstrain and dislocation density. Mn atoms were interstitially incorporated into the CdS structure, resulting in an expansion of the unit cell volume. Morphological analysis indicated a decrease in grain size from 390 nm to 140 nm for 0 % and 2 % Mn-doped CdS samples, respectively, while maintaining the spherical shape of the CdS thin films. Mn doping also increased the transmittance of CdS thin films, with the highest transparency of 95 % at 580 nm achieved for the 2 % Mn-doped CdS sample. In comparison to undoped CdS (2.38 eV), the band gap of CdS samples initially decreased to 1.84 eV for 1 % Mn doping but significantly increased to 3.03 eV for 2 % Mn-doped CdS. Photoluminescence (PL) data indicated that 2 % Mn-doped CdS thin films exhibited the lowest peak intensity, suggesting that a high concentration of Mn atoms caused non-radiative charge recombination. Additionally, efficient exciton dissociation was observed between CdS:Mn and P3HT:PCBM (poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61-butyric acid methyl ester (PCBM)) layers in the 2 % Mn-doped CdS-based device, as per the PL results. Photovoltaic measurements demonstrated that compared to undoped CdS, 2 % Mn doping increased the power conversion efficiency of the CdS-based device from 0.070 % to 0.202 %, indicating an almost threefold increase in hybrid solar cell efficiency. This improvement is likely attributed to the development of a better interface between the CdS:Mn and P3HT:PCBM layers.

Surface induced effects on the dielectric and optical properties of polymer-stabilized cholesteric liquid crystal composites

Polymer-stabilized cholesteric liquid crystal is one of the most coveted systems in the ever-expanding field of liquid crystal due to its wider potential application in smart windows, optical shutters, tunable lenses, etc. The dispersion of polymer into liquid crystal by introducing a small amount of chiral dopant prepared polymer-stabilized cholesteric liquid crystal. In this work, two samples of polymer- cholesteric liquid crystal were prepared. Surface treatment is applied on one composite while another sample is prepared without any treatment on the indium tin-oxide coated glass substrates. Frequency and temperature-dependent dielectric parameters are observed for both samples. The dielectric studies revealed that after surface treatment, the permittivity of the sample significantly increased. AC conductivity of the sample also increased. The photoluminescence spectra also show improvement in the intensity with the surface-treated sample.

Multilevel resistive switching memory in lead-free double perovskite La_{2}NiFeO_{6} films

Dense and flat La_{2}NiFeO_{6} (LNFO) films were fabricated on the indium tin oxide-coated glass (ITO/glass) substrate by sol–gel method. The bipolar resistive switching behavior (BRS) could be maintained in 100 cycles and remained after 30 days, indicating that the LNFO-based RS device owned good memory stability. Surprisingly, the multilevel RS characteristics were firstly observed in the Au/LNFO/ITO/glass device. The high resistance states (HRSs) and low resistance state (LRS) with the maximum ratio of sim 500 could be remained stably in 900 s and 130 cycles, demonstrating the fine retention and endurance ability of this LNFO-based RS device. The BRS behavior of Au/LNFO/ITO/glass devices primarily obeyed the SCLC mechanism controlled by oxygen vacancies (OVs) dispersed in the LNFO layer. Under the external electric field, injected electrons were captured or discharged by OVs during trapping or detrapping process in the LNFO layer. Thus, the resistive state switched between HRS and LRS reversibly. Moreover, the modulation of Schottky-like barrier formed at the Au/LNFO interface was contributed to the resistive states switchover. It was related to the change in OVs located at the dissipative region near the Au/LNFO interface. The multilevel RS ability of LNFO-based devices in this work provides an opportunity for researching deeply on the high density RS memory in lead-free double perovskite oxides-based devices.

Flat variable liquid crystal diffractive spiral axicon enabling perfect vortex beams generation

A transparent variable diffractive spiral axicon (DSA) based on a single LC cell is presented. The manufactured DSA can be switched between 24 different configurations, 12 convergent and 12 divergent, where the output angle is varied as a function of the applied topological charge. The active area of the device is created using a direct laser writing technique in indium-tin oxide coated glass substrates. Liquid crystal is used to modulate the phase of the incoming beam generating the different DSA configurations. The DSA consists in 24 individually driven transparent spiral shaped electrodes, each introducing a specific phase retardation. In this article, the manufacture and characterization of the tunable DSA is presented and the performance of the DSA is experimentally demonstrated and compared to the corresponding simulations.

Connecting electrical current conduction and Urbach energy in doped BiFeO3 thin-films

The present study explores the influence of Co2+ and Mn4+ ions on the optical and electrical properties of bismuth ferrite thin films prepared on indium tin oxide-coated glass substrates. In particular, a correlation between the Urbach energy tails and the current conduction is established. Doping-dependent variations in Urbach energy tail widths, optical bandgap energies and J-V curves of the fabricated films are investigated. The Urbach energy tail width of Co-doped BiFeO3 is found to increase by 36%, while that of Mn-doped one is found to reduce by 15%. The optical bandgap of Co-doped and Mn-doped BiFeO3 was found to reduce by 44% and 40% respectively compared to undoped BiFeO3. A correlation between the induced defect states and the optical parameters has been observed. Analysis of J - V characteristics reveals the dependence of the current conduction upon the valence state of the dopant. In particular, the dark current density decreased by almost one order of magnitude with Mn-doping and increased by more than one order with Co-doping. A defect-dependent space-charge-limited conduction (SCLC) mechanism is proposed to understand the J - V curve in the Co-doped and Mn-doped BFO samples. A direct variation of the leakage current density with the Urbach energy suggests that Urbach energy studies could be considered as an alternative indicator of the leakage current density in thin-film BiFeO3-based devices.

Hafnium Oxide Nanostructured Thin Films: Electrophoretic Deposition Process and DUV Photolithography Patterning.

In the frame of the nanoarchitectonic concept, the objective of this study was to develop simple and easy methods to ensure the preparation of polymorphic HfO2 thin film materials (<200 nm) having the best balance of patterning potential, reproducibility and stability to be used in optical, sensing or electronic fields. The nanostructured HfO2 thin films with micropatterns or continuous morphologies were synthesized by two different methods, i.e., the micropatterning of sol-gel solutions by deep ultraviolet (DUV) photolithography or the electrophoretic deposition (EPD) of HfO2 nanoparticles (HfO2-NPs). Amorphous and monoclinic HfO2 micropatterned nanostructured thin films (HfO2-DUV) were prepared by using a sol-gel solution precursor (HfO2-SG) and spin-coating process following by DUV photolithography, whereas continuous and dense monoclinic HfO2 nanostructured thin films (HfO2-EPD) were prepared by the direct EPD of HfO2-NPs. The HfO2-NPs were prepared by a hydrothermal route and studied through the changing aging temperature, pH and reaction time parameters to produce nanocrystalline particles. Subsequently, based on the colloidal stability study, suspensions of the monoclinic HfO2-NPs with morphologies near spherical, spindle- and rice-like shapes were used to prepare HfO2-EPD thin films on conductive indium-tin oxide-coated glass substrates. Morphology, composition and crystallinity of the HfO2-NPs and thin films were investigated by powder and grazing incidence X-ray diffraction, scanning electron microscopy, transmission electron microscopy and UV-visible spectrophotometry. The EPD and DUV photolithography performances were explored and, in this study, it was clearly demonstrated that these two complementary methods are suitable, simple and effective processes to prepare controllable and tunable HfO2 nanostructures as with homogeneous, dense or micropatterned structures.

Evaporation induced self-assembly of silica nanoparticles on ITO substrates in a confined cell for vertical alignment of liquid crystals and performance analysis

The work reported herein advances the approach to achieve the vertical alignment (VA) of liquid crystals (LCs) by directly forming the multilayer self-assembly of nanoparticles (NPs) on the indium tin oxide (ITO) substrates in a confined cell. In this method, for confined evaporative self-assembly of NPs, the colloidal solution of uniformly dispersed 0.3 wt% silica NPs (SNPs) in deionized (DI) water was injected in between the two ITO coated glass substrates by capillary method. The ITO cell filled with colloidal solution was kept at a fixed temperature of 60°C for uniform thermal evaporation of water to deposit the multilayer of NPs on ITO substrates. The multilayered self-assembly of SNPs on ITO substrates was confirmed through field emission scanning electron microscopy (FESEM) and fourier transform infrared (FTIR) spectroscopy studies. The surface roughness profile of the deposited SNPs-multilayer was analysed by atomic force microscopy (AFM). Further, the contact angle (CA) and surface energy values of SNPs-multilayer deposited ITO substrates were also measured and analyzed comparatively with the values of polyimide (PI) coated ITO substrates. After complete evaporation of water, a negative dielectric anisotropy nematic LC was filled in to the cell using capillary method again and the versatility of prepared substrates was assessed for the VA of the liquid crystal (LC). Inquisitively, confirmation of VA of LC in the present approach was found similar with the PI coated VA (conventional approach) using polarized optical microscopy (POM) and conoscopy studies. In addition, effects of external applied electric field were observed well in order with the orientation of LCs to switch vertically aligned LC (VALC) cells from opaque OFF state to transparent ON state, under crossed polarizers. Also, the obtained results in terms of transmission, threshold voltage, operating voltage, and contrast ratio (CR) of VALC cell prepared with this easy and new approach were found comparable to the conventional approach.

Structural and Electrical Properties of Glucose Biosensors Based on ZnO and ZnO-CuO Nanostructures

Background: Nanostructured metal oxides have stimulated tremendous efforts for sightseeing glucose bio-sensing applications. They have been mostly investigated to fabricate highly sensitive, stabilized and ultrafast biosensors. Objective: Fabrication and characterization of glucose biosensors based on zinc oxide (ZnO) nanostructured thin films modified by copper oxide (CuO) nanostructures in order to obtain stabilized ZnO:CuO biosensors with high sensitivity and fast response time. Methods: The components of the investigated biosensors are synthesized using the hydrothermal solgel method by dip-coating the sensing layer on indium tin oxide-coated glass substrates (ITO). The structural and electrical properties of the fabricated biosensors are investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), and I-V characteristics. Results: SEM micrographs indicate that ZnO nanostructures exhibit an interconnected sheet-like patterns. These sheets are thin and distributed randomly on the ITO substrate. SEM images of ZnO:CuO reveal that the morphology of nanostructured thin films is composed of flower-like patterns. The XRD patterns of ZnO and modified ZnO:CuO thin films subjected to thermal annealing show that thin films exhibit a high degree of crystallinity with minor traces of impurity phases. The biosensors' key parameters are calculated and interpreted by measuring the I-V characteristics to elucidate the sensitivity and reproducibility of measurements performed for various glucose concentrations. Furthermore, the electric current response of ZnO and ZnO:CuO biosensors are found to be linear and quadratic as a function of glucose concentration, respectively. The introduction of CuO into ZnO thin films leads to the enhancement of the sensitivity of the synthesized glucose biosensors for a high degree of precision in measuring glucose levels. Conclusion: Both sensors exhibit average sensitivities in the range (from 1 to 10 μA mM−1 cm−2) with quite good reproducibility. The unique property of this sensor is its ability to measure glucose concentrations at neutral pH conditions (i.e. pH = 7) using a simple, low cost and novel sensor design.

Ellipsometry Study of CdSe Thin Films Deposited by PLD on ITO Coated Glass Substrates.

Cadmium selenide (CdSe) thin films were deposited on indium tin oxide (ITO) coated glass substrates using pulsed laser deposition (PLD) technique under different growth temperatures. Samples were investigated for their structural, morphological, and optical properties through X-ray diffraction (XRD), atomic force microscopy (AFM), and UV-Vis-NIR spectroscopy. AFM analysis revealed that the surface roughness of the as-grown CdSe thin films increased with the increase in deposition temperature. The optical constants and film thickness were obtained from spectroscopic ellipsometry analysis and are discussed in detail. The optical band gap of the as-grown CdSe thin films, calculated from the Tauc plot analysis, matched with the ellipsometry measurements, with a band gap of ~1.71 eV for a growth temperature range of 150 °C to 400 °C. The CdSe thin films were found to have a refractive index of ~3.0 and extinction coefficient of ~1.0, making it a suitable candidate for photovoltaics.

Adhesive electrochromic WO3 thin films fabricated using a WO3 nanoparticle-based ink

Nanotechnology has advanced rapidly in recent years, mainly due to the unique properties of basic elements, which can be tuned by altering their chemical composition and size. Owing to their unique properties, nanoparticles (NPs) are applied in many fields, such as catalysis, electronics, and coatings. In this study, we synthesized a coatable WO3 NP dispersed ink and aimed to highlight the importance of developing an appropriate design strategy for achieving optimal physicochemical properties of the inks. Polyvinyl alcohol (PVA) was added to the WO3 NP ink to improve its adhesion to indium tin oxide-coated glass substrates. The contact angle of the inks on the substrate decreased with the addition of PVA, indicating their good wettability. Furthermore, the WO3 NP films exhibited an excellent transmittance change of 77 % at 633 nm and a coloration efficiency of 35 cm2/C. Their optical transmittance in the visible and near-infrared regions varied with the applied voltage, indicating their potential for applications in electrochromic devices and smart windows.

Fabrication and Characterisation of Organic EL Devices in the Presence of Cyclodextrin as an Interlayer.

This study examined glass-based organic electroluminescence in the presence of a cyclodextrin polymer as an interlayer. Glass-based organic electroluminescence was achieved by the deposition of five layers of N,N’-Bis(3-methylphenyl)N,N’-bis(phenyl)-benzidine, cyclodextrin polymer (CDP), tris-(8-hydroxyquinolinato) aluminium LiF and Al on an indium tin oxide-coated glass substrate. The glass-based OEL exhibited green emission owing to the fluorescence of tris-(8-hydroxyquinolinato) aluminium. The highest luminance was 19,620 cd m−2. Moreover, the glass-based organic electroluminescence device showed green emission at 6 V in the curved state because of the inhibited aggregation of the cyclodextrin polymer. All organic molecules are insulating, but except CDP, they are standard molecules in conventional organic electroluminescence devices. In this device, the CDP layer contained pores that could allow conventional organic molecules to enter the pores and affect the organic electroluminescence interface. In particular, self-association was suppressed, efficiency was improved, and light emission was observed without the need for a high voltage. Overall, the glass-based organic electroluminescence device using CDP is an environmentally friendly device with a range of potential energy saving applications.

Modification of Ag8SnS6 Photoanodes with Incorporation of Zn Ions for Photo-Driven Hydrogen Production

In this study, Zn ions were incorporated into Ag8SnS6 thin films on glass and indium–tin–oxide-coated glass substrates using chemical bath deposition. Detailed procedures for the growth of Ag–Zn–Sn–S semiconductor films and their optical, physical and photoelectrochemical performances were investigated. X-ray diffraction patterns of samples revealed that kesterite Ag2ZnSnS4 phase with a certain amount of Ag8SnS6 phase can be obtained using ethylenediaminetetraacetic acid disodium salt and trisodium citrate as the chelating agent couples. Images of field-emission scanning electron microscope showed that plate-like microstructures with some spherical aggregates were observed for the sample at low Zn content. It changed to irregular spherical grains with the [Zn]/[Sn] ratios being higher than 0.95 in samples. The energy band gaps of the samples were in the range of 1.57–2.61 eV, depending on the [Zn]/[Sn] molar ratio in sample. From the Hall measurements, the carrier concentrations and mobilities of samples were in the ranges of 6.57 × 1012–1.76 × 1014 cm−3 and 7.14–39.22 cm2/V·s, respectively. All samples were n-type semiconductors. The maximum photoelectrochemical performance of sample was 1.38 mA/cm2 in aqueous 0.25 M K2SO3 and 0.35 M Na2S solutions.

Resistive Switching Memory Performance of Two-Dimensional Polyimide Covalent Organic Framework Films.

Two-dimensional polyimide covalent organic framework (2D PI-NT COF) films were constructed on indium tin oxide-coated glass substrates to fabricate two-terminal sandwiched resistive memory devices. The 2D PI-NT COF films condensated from the reaction between 4,4',4″-triaminotriphenylamine and naphthalene-1,4,5,8-tetracarboxylic dianhydride under solvothermal conditions demonstrated high crystallinity, good orientation preference, tunable thickness, and low surface roughness. The well-aligned electron-donor (triphenylamine unit) and -acceptor (naphthalene diimide unit) arrays rendered the 2D PI-NT COF films a promising candidate for electronic applications. The memory devices based on 2D PI-NT COF films exhibited a typical write-once-read-many-time resistive switching behavior under an operating voltage of +2.30 V on the positive scan and -2.64 V on the negative scan. A high ON/OFF current ratio (>106 for the positive scan and 104-106 for the negative scan) and long-term retention time indicated the high fidelity, low error, and high stability of the resistive memory devices. The memory behavior was attributed to an electric field-induced intramolecular charge transfer in an ordered donor-acceptor system, which provided the effective charge-transfer channels for injected charge carriers. This work represents the first example that explores the resistive memory properties of 2D PI-COF films, shedding light on the potential application of 2D COFs as information storage media.

In-situ synthesis of covalent organic polymer thin film integrates with palladium nanoparticles for the construction of a cathodic photoelectrochemical cytosensor

Sensitive detection of cancer cells is essential to early clinic diagnosis, and the photoelectrochemical (PEC) sensors with high sensitivity and good selectivity may provide new approaches for cytosensing. Herein, we demonstrate the development of a new cathodic PEC cytosensor based on the integration of covalent organic polymer (COP) with palladium nanoparticles (PdNPs). The COP films are in-situ grown at room temperature on the transparent indium tin oxide-coated glass substrates, and they subsequently assemble with PdNPs to immobilize aptamers via palladium-sulfur chemistry. PdNPs can catalyze the oxidation of dopamine to produce aminochrome and its derivative, which may function as the electron acceptors of COP for the generation of an enhanced photocurrent. In the absence of cancer cells, the electrons on the conduction band of COP on the electrode transfer to the aminochrome and O2, while the electrons on the electrode transfer to the hole of valence band, resulting in a high cathodic photocurrent. In the presence of cancer cells, the trapped cancer cells efficiently cover the electrode to reduce the surface of COP/PdNPs, resulting in the decrease of catalytic precipitation on the electrode and consequently the generation of a low PEC signal. This PEC cytosensor exhibits high sensitivity with a detection limit of 8 cells mL−1 and a large dynamic range from 10 to 106 cells mL−1. Moreover, this PEC cytosensor has distinct advantages of high selectivity, good reproducibility and excellent stability, and it can be extended to directly detect various cancer cells through the integration with corresponding specific aptamers.

Structural, optical and electrical properties of Aluminum doped ZnO, CuO and their heterojunction fabricated using spin coating and Rf-Sputtering techniques

Objectives: The aim of this work is to fabricate and analyze the Aluminum Doped ZnO, Copper Oxide CuO and their heterojunction CuO/ZnO:Al using Spin Coating and Rf-Sputtering techniques. Methods: ZnO:Al was synthesized from a sol-gel precursor and deposited on Indium Tin Oxide-coated glass substrate ITO using spin coating. CuO thin films, on the other hand, were elaborated by RF-sputtering. The characterization of both thin films was performed by means of X-ray diffraction, scanning electron microscopy and UV-visible-NIR double beam spectrophotometer. The CuO/ZnO: Al heterojunction was fabricated and characterized using current voltage, capacitance-voltage and conductancevoltage measurements. Findings: The collected results confirm the rectifying nature of the junction with a built-in voltage Vbi of about 1.6 V. Keywords: Copper oxide; Aluminum doped Zinc oxide; RF sputtering; spin coating; heterojunction

Hole trap, charge transfer and photoelectrochemical water oxidation in thickness-controlled TiO2 anatase thin films

Despite the symbolism of TiO2 in photoelectrochemistry, its fundamental nanoscale properties in oxidation reaction have often reported inconsistent results. We demonstrated the simple model of TiO2 thin films (TFs) for photoelectrochemical (PEC) oxidation reaction (OR) of water, which is constituted of Indium Tin Oxide (ITO) and TiO2 TFs, by depositing it directly onto ITO coated glass substrates through Atomic Layer Deposition (ALD). Using ALD with a sub-nanometer thickness control, 9 to 90 nm in thickness (200 to 2000 in no. of ALD cycles) of TiO2 TFs were fabricated and annealed for crystallization into anatase phase. Anatase TiO2 TF photoanodes showed an optimum PEC OR performance at the thickness of 45 nm (corresponding to around 1000 ALD cycles) in the electrolyte solution of 0.1 M NaOH (pH = 12.9) under UV light illumination of 365 nm in wavelength. Different thicknesses of TiO2 TFs were characterized by electrochemical and optical measurements. Increasing bulk traps in TiO2 TFs up to the critical thickness improved charge transfer and PEC OR by increasing holes’ lifetime. However, it was found to be detrimental when it became dominant along with the increase of TFs’ thickness. This work provides insight in designing highly efficient TiO2 photoelectrodes with the precisely controlled thickness that can have a significant effect on charge transfer kinetics and thus PEC performances.

Significant effect on annealing temperature and enhancement on structural, optical and electrical properties of zinc oxide nanowires

This paper focused on the growth of zinc oxide nanowires on unannealed and annealed indium tin oxide-coated-coated glass substrates on the structural, optical, and electrical properties towards surface acoustic wave (SAW) piezoelectric nanodevices. Zinc oxide nanowires (ZnO NWs) were grown onto Indium Tin Oxide (ITO)-coated glass substrates by a chemical bath deposition method. The growth of ZnO NWs carried onto unannealed and annealed Indium Tin Oxide-coated glass substrates. Substrates were annealed at 400 °C for 90 min at ambient using a horizontal furnace. This work also focused on the effect of annealing condition of ITO-coated glass substrate on nanowires morphology, crystal phase, optical band gap, and electrical properties. Substrate annealing was found to have a significant effect on the nanowires dimension. The nanowire's morphology was obtained by FESEM which the average diameter and length found on unannealed ITO-coated glass substrate were 674.18 ± 26.75 nm and 3.107 ± 0.446 μm. However, the nanowire's average diameter and length on annealed ITO-coated glass substrate were 393.50 ± 27.02 nm and 3.175 ± 0.321 μm. XRD analysis confirmed that ZnO nanowires on substrates with both conditions were able to promote the growth of crystal structure with crystal plane orientation of (1 0 1) and (1 0 0) belongs to hexagonal wurtzite structure. The near-band-edge (NBE) emission of ZnO nanowires obtained by using Photoluminescence which grown on unannealed and annealed ITO-coated glass substrates were observed at 380 nm (3.20 eV) and 384 nm (3.23 eV). FTIR analysis showed that ZnO absorption bands in the region between 450 and 500 cm−1 had arisen from interatomic vibrations due to the stretching of the ZnO bond. The resistivity of ZnO nanowires obtained by using the four-point probe method on unannealed and annealed substrates was found to be 2.0675 × 10−7 Ω cm and 2.0494 × 10−7 Ω cm.

Enhanced Resistive Switching Effect in Ag Nanoparticles Embedded in Graphene Oxide Thin Film

In this paper, the effect of different concentrations of Ag nanoparticles embedded in graphene oxide (GO) for resistive random-access memory (RRAM) has been investigated. The spin-coating method was used for the deposition of a GO-Ag layer on indium tin oxide-coated glass substrate. The structural studies of the samples were carried out using x-ray diffraction. The morphology of the as-deposited layer was determined using scanning electron microscopy and atomic force microscopy. It has been observed that Ag-doped memory devices require low voltage to switch from OFF to ON and vice versa. The switching voltage was reduced by half in Ag-doped devices as compared to undoped devices with a high OFF/ON current ratio of ∼ 103. The electrical stability of Ag-doped devices was tested for 4 × 103 s. Also, the SET/RESET behavior was tested for up to 60 cycles at a read voltage of 0.2 V. It was observed that both electrical stability and SET/RESET behavior did not exhibit excessive degradation. The switching speed of the RRAM device was calculated using an oscilloscope and found to be ∼ 200 ns for the low-resistance state (LRS) and ∼ 1 μs for the high-resistance state (HRS). The capacitance in Ag-doped GO devices was recorded and found to be ∼ 400 pF in the HRS as compared to 20 pF in case of undoped GO devices. It has been concluded that the charge trapping and de-trapping mechanism in case of Ag-doped GO is responsible for the enhanced properties of fabricated RRAM devices.

Effect of Solution pH on Properties of Cuprous Oxide Thin Films Prepared by Electrodeposition from a New Bath

Cuprous oxide (Cu2O) thin films have been successfully electrodeposited onto indium tin oxide-coated glass substrates from copper acetate solution and characterized by x-ray diffraction analysis, scanning electron microscopy, ultraviolet–visible (UV–Vis) spectroscopy, and photoelectrochemical (PEC) and electrical Hall-effect measurements. The effect of the solution pH on the structural, morphological, optical, PEC, and electrical properties of the deposited Cu2O thin films was investigated. The x-ray diffraction results indicated that the prepared Cu2O films exhibited good crystallinity with pure cubic structure, while the crystallite size increased with increasing solution pH. The preferential orientation of the deposited films also changed with the pH value. When the solution pH was changed, the surface morphology changed from spherical to pyramidal shape with increasing grain size. The optical characteristics of the Cu2O thin films were not significantly affected by changing the solution pH value. PEC measurements revealed that Cu2O thin films prepared at pH 6.2 exhibited n-type conductivity, while those obtained at pH 11 showed p-type conductivity. These results were confirmed by Hall-effect measurements. The obtained Cu2O thin films would be promising semiconductor materials for use in various applications such as PEC cells and photovoltaic solar cells.

Electrochromic Properties of Graphene Doped TiO2 Layer Deposited by Thermionic Vacuum Arc

Electrochromic (EC) device has been widely used many applications and TiO2 is a popular electrode material. Graphene doping affects Li+ ion intercalation/deintercalation mechanism in positive way for energy storage devices. So high performance devices can be manufactured by doping graphene. In this study, graphene doped TiO2 layers have been deposited by thermionic vacuum arc system. According to AFM results, mean height of the grains for the graphene doped TiO2 layer deposited onto fluorine tin oxide (FTO) and indium tin oxide (ITO) coated glass substrates were measured 10 nm and 100 nm, respectively. Anatase TiO2 and graphene bands were determined in Raman analyses. Refractive index of graphene doped TiO2 layer was found approximately 1.80 @ 550 nm. Optical modulation values for the FTO and ITO coated glass substrates were calculated as 25% and 11% @ 420 nm, respectively. Coloration efficiencies were obtained as 28 and 77 cm2/C for the graphene doped TiO2 layers deposited onto FTO and ITO coated glass substrates, respectively. Maximum transparency value was 85% in optical region. According to the coloration efficiency, it found that graphene dopant is proper and promising two dimensional material to improve TiO2 performance in EC device application.