FTO-coated Glass Substrates Research Articles

Enhanced photoelectrochemical and photocatalytic properties of 3D-hierarchical ZnO nanostructures

In the present study, highly efficient and stable photocatalysts have been developed in order to achieve both organic material degradation and sunlight-driven hydrogen generation. More specifically, we investigated the influence of the surface wettability and types of the precursor anionic species on the morphology of the three-dimensional (3D) hierarchical zinc oxide (ZnO) nanostructures. It has been observed that nitrate and acetate based anionic sources resulted with the hand fan like and nanosheet morphologies, respectively. Adhesion of the ZnO nanostructures on the FTO coated glass has been improved via potassium hydroxide treatment, which also affected the morphology of the ZnO films. Well-adhered photoelectrodes for solar water splitting on FTO coated glass substrates with high applied photon-to-current efficiency have been prepared via simple and cost effective chemical bath deposition method. Finally, ZnO nanopowders with two different morphologies have been synthesized via also chemical bath deposition. These nanopowders were used to photocatalytic degradation of methyl orange dye and very high degree of degradation (95%) was achieved using ZnO-Acetate nanopowders, which had morphology of microspheres with nanosheets.

Visible light assisted photoelectrocatalytic degradation of sugarcane factory wastewater by sprayed CZTS thin films

Highly crystalline Cu2ZnSnS4 (CZTS) thin films have been deposited onto glass and FTO coated glass substrates by simple chemical spray-pyrolysis technique. It is an important material for solar energy conversion through the both photovoltaics and photocatalysis. The effect of substrate temperatures on the physico-chemical properties of the CZTS films is studied. The XRD study shows the formation of single phase CZTS with kesterite structure. FE-SEM analysis reveals nano flakes architecture with pin-hole and crake free surface with more adherent. The film deposited at optimized substrate temperature exhibits optical band gap energy of 1.90 eV, which lies in the visible region of the solar spectrum and useful for photocatalysis application. The photoelectrocatalytic activities of the large surface area (10 × 10 cm2) deposited CZTS thin film photocatalysts were evaluated for the degradation of sugarcane factory wastewater under visible light irradiation. The results show that the CZTS thin film photocatalyst exhibited about 90% degradation of sugar cane factory wastewater. The mineralization of sugarcane factory wastewater is studied by measuring chemical oxygen demand (COD) values.

Impact of CH3NH3PbI3-PCBM bulk heterojunction active layer on the photovoltaic performance of perovskite solar cells

We report here the impact of CH3NH3PbI3-PCBM bulk heterojunction (BHJ) active layer on the photovoltaic performance of perovskite solar cells. The solar cells were prepared in normal architecture on FTO coated glass substrates with compact TiO2 (c-TiO2) layer on FTO as electron transport layer (ETL) and poly(3-hexylthiophene) (P3HT) as hole transport layer (HTL). For comparison, a few solar cells were also prepared in planar heterojunction structure using CH3NH3PbI3 only as the active layer. The bulk heterojunction CH3NH3PbI3-PCBM active layer exhibited very large crystalline grains of 2–3μm compared to ∼150nm only in CH3NH3PbI3 active layer. Larger grains in bulk-heterojunction solar cells resulted in enhanced power conversion efficiency (PCE) through enhancement in all the photovoltaic parameters compared to planar heterojunction solar cells. The bulk-heterojunction solar cells exhibited ∼9.25% PCE with short circuit current density (Jsc) of ∼18.649mA/cm2, open circuit voltage (Voc) of 0.894V and Fill Factor (FF) of 0.554. There was ∼36.9% enhancement in the PCE of bulk-heterojunction solar cells compared to that of planar heterojunction solar cells. The larger grains are formed as a result of incorporation on PCBM in the active layer.

Phase evolution during the electrodeposition of Cu–Sn–Zn metal precursor layers and its role on the Cu2S impurity phase formation in Cu2ZnSnS4 thin films

Abstract Metal precursor layers in the sequence of Cu(A)–Sn–Cu(B)–Zn (CTCZ) were electrodeposited on FTO–coated glass substrates to yield Cu2ZnSnS4, post sulphurization. Raman mapping and XRD analysis reveal the presence of Cu2S inclusions in the CZTS thin film obtained from the metal precursor in which the molar ratio of Cu(A)/Cu(B) is 0.33 (CTCZ–0.33). Such Cu2S inclusions are not present in the CZTS film obtained from the precursor with Cu(A)/Cu(B) molar ratio 3 (CTCZ–3). Systematic potentiodynamic and XRD studies of the component metal precursor layers reveals a significantly larger amount of unalloyed Sn in the CTCZ–0.33 metal precursor compared to that in the CTCZ–3 precursor. Sulphurization of the precursors thus results in a higher amount of SnS in the CTCZ–0.33 precursor. Subsequently, vaporization of SnS moves the overall composition of the sulphurized CTCZ–0.33 precursor outside of the CZTS formation window in the ternary phase diagram. This compositional shift leads to Cu2S + CZTS as the equilibrium phase assemblage for the film obtained from the CTCZ–0.33 precursor.

Sunlight assisted photoelectrocatalytic degradation of benzoic acid using stratified WO3/TiO2 thin films

Abstract The stratified WO 3 /TiO 2 thin films have been deposited onto glass and FTO coated glass substrates using simple chemical a spray pyrolysis method. The structural, morphological, compositional and photoelectrocatalytic properties of the stratified WO 3 /TiO 2 thin films are studied. The photoelectrochemical (PEC) study shows that, both short circuit current (I sc ) and open circuit voltage (V oc ) are (I sc =1.192 mA and V oc =0.925 V) relatively high at 50 ml spraying quantity of TiO 2 solution on pre-deposited WO 3 . XRD analysis confirms that films are polycrystalline with monoclinic and tetragonal crystal structures for WO 3 and TiO 2 respectively. Specific surface area of 72.14 m 2 g −1 is measured by Brunauer-Emmett-Teller (BET) technique. Photoelectrocatalytic degradation of benzoic acid (BA) dye in aqueous solutions is studied. The end result shows that the degradation percentage of benzoic acid (BA) using stratified WO 3 /TiO 2 photoelectrode has reached 66% under sunlight illumination after 320 min. The amount of degradation is confirmed by COD analysis.

Solution process for fabrication of thin film CdS/CdTe photovoltaic cell for building integration

A low-cost, scalable chalcogenide semiconductor thin film deposition process, Chemical Bath Deposition, is used to fabricate semi-transparent TiO2/CdS/CdTe solar cells. Cadmium telluride (CdTe) acts as an absorber and cadmium sulphide (CdS) is the window layer with band gaps of 1.45eV and 2.45eV, respectively. In this work, about 400nm thick p-CdTe and ~200nm n-CdS films are deposited on titanium dioxide (TiO2) coated substrate. Insertion of TiO2 layer at front contact between FTO coated glass substrate and CdS; improved CdS/CdTe PV cell performance by reducing the leakage current. This resulted in increase of short circuit current in the device. At the initial stage of development the cell exhibits a voltage of 100.53mV and photocurrent of 14.7mA/cm2, illustrates the potential of the process. The devices are characterized using FE-SEM, UV–Visible spectroscopy, XRD and AFM. The fabricated PV cells are around 43% transparent and these semi-transparent cells can be used as windowpanes for building integrated photovoltaic applications.

Hydrothermal Growth of Hierarchical NiO Nanostructures and Their Application in a Complemetary Electrochromic Device

NiO is one of the most popular electrochromic (EC) materials due to its high EC efficiency, good cyclic reversibility and low material cost. As an anodic EC material, NiO can be used as a complementary electrode with WO3, where the optical modulation increases due to the simultaneous modulation of both electrodes. We have demonstrated that porous NiO nanostructures film can be grown directly on FTO-coated glass substrates using a template-free hydrothermal technique. A variety of NiO nanostructures, including nanoflake array, nanorod-based networks, hexagonal nanoplates and hierarchical microflakes, could be obtained by tuning the composition of the precursor solution. Among the obtained NiO nanostructures, hierarchical structure holds the advantages of both nanometre-sized building blocks and microsized assemblies. Thus, the complementary EC device based hierarchical NiO microflake and self-weaving WO3 nanoflake film shows a high optical modulation (73.2% at 550 nm), large coloration efficiency (146.9 cm2 C-1 at 550 nm) and fast switching responses with a coloring time of 1.8 s and a bleaching time of 3.2 s, making it attractive for practical applications.

Role of defects in one-step synthesis of Cu-doped ZnO nano-coatings by electrodeposition method with enhanced magnetic and electrical properties

We report the growth of flower-like ferromagnetic Cu-doped ZnO (CZO) nanostructures using electrochemical deposition on FTO-coated glass substrates. X-ray photoelectron spectroscopy studies affirmed the presence of Cu in ZnO with an oxidation state of 2+. In order to find the optimized dopant concentration, different Cu dopant concentrations of 0.28, 0.30, 0.32, 0.35, 0.38, and 0.40 mM are applied and their magnetic, optical, and electrical properties are studied. Magnetic moment increased with the increasing dopant concentration up to 0.35 mM and then decreased with further increase in the concentration. Diamagnetic pure ZnO showed ferromagnetic nature even with a low doping concentration of 0.28 mM. Band gap increased with the increasing Cu concentration until a value of 0.35 mM and then remained the same for the higher dopant concentrations. It is ascribed to the Burstein–Moss effect. Defect-related broad photoluminescence (PL) peak is observed for the pure ZnO in the visible range. In contrast, Cu-doped samples showed a sharp and intense PL peak at 426 nm due to increased Zn interstitials. Kelvin probe measurements revealed that the Fermi level shifts toward the conduction band for the Cu-doped samples with respect to pure material. Electron transport mechanism in the samples is observed to be dominated by space charge-limited current and Schottky behavior with improved ideality factor up to 0.38 mM Cu.

Synthesis of Hierarchical SnO2 Nanowire\u2013TiO2 Nanorod Brushes Anchored to Commercially Available FTO-coated Glass Substrates

Growth of single-crystal SnO2 nanowires using a fluorine-doped SnO2 (FTO) thin film as both the source and substrate is demonstrated for the first time at relatively low temperature (580 °C) which preserves the integrity of the underlying glass support and improves scalability to devices. Furthermore, a microwave hydrothermal process is shown to grow TiO2 nanorods on these nanowires to create a hierarchical nanoheterostructure that will lead to efficient photogenerated charge carrier separation and rapid transport of electrons to the substrate. This process simplifies nanowire growth by using commercially available and widely used FTO substrates without the need for an additional upstream Sn source and can be used as a high surface area host structure to many other hierarchical structures.

Schottky diode behaviour with excellent photoresponse in NiO/FTO heterostructure

Delocalization of charge carriers through formation of native defects in NiO, to achieve a good metal oxide hole transport layer was attemted in this work and thus a heterojunction of p-type NiO and n-type FTO have been prepared through sol-gel process on FTO coated glass substrate. The synthesis process was stimulated by imparting large number of OH− sites during nucleation of Ni(OH)2 on FTO, so that during oxidation through annealing Ni vacancies are introduced. The structural properties as observed from X-ray diffraction measurement indicate formation of well crystalline NiO nanoparticles. Uniform distribution of NiO nanoparticles has been observed in the images obtained from scanning electron microscope. The occurrence of p-type conductivity in the NiO film was stimulated through the formation of delocalized defect carriers originated from crystal defects like vacancies or interstitials in the lattice. Ni vacancy creates shallow levels with respect to the valance band maxima and they readily produce holes. Thus a native p-type conductivity of NiO originates from Ni vacancies. NiO was thus obtained as an auspicious hole transport medium, which creates an expedient heterojunction at the interface with FTO. Excellent rectifying behavior was observed in the electrical J–V plot obtained from the prepared heterojunction. The results are explained from the band energy diagram of the NiO/FTO heterojunction. Remarkable photoresponse has been observed in the reverse characteristics of the heterojunction caused by photon generated electron hole pairs.

An Electrochemical Method for Fast and Controlled Etching of Fluorine-Doped Tin Oxide Coated Glass Substrates

Fluorine-doped tin oxide (FTO) coated glass substrates are etched by a mixture of Zn and HCl for solar cells, flat panel displays, and related applications. However, this chemical etching method has its own limitations, and the most important limitation is no control on the etching process. Here, we report a controlled etching of FTO-coated glass substrate by a chronoamperometric method. In this method, optimized step potentials, −3 V for 10 s, −5 V for 80 s and −9 V for 10 s are applied between the FTO substrate to be etched and a counter electrode dipped in acidic 0.1 M FeCl3 (aq) electrolyte. The etched FTO was characterized by the energy dispersive X-ray spectroscopy showing complete removal of conducting FTO layer that was further studied by current-voltage characteristics. The chemical reaction involved in this etching process was investigated by the X-ray photoelectron spectroscopy that reveals similar chemical reaction as reported for the chemical method.

Electrochemical behavior of spray deposited mixed nickel manganese oxide thin films for supercapacitor applications

The relatively low energy density is a crucial issue obstructing the growth of supercapacitors as energy storage devices. Various tactics have been developed to enhance the energy density. Nickel manganese oxide thin films have been synthesized by spray pyrolysis on preheated amorphous and FTO coated glass substrates. These films are characterized for structural, morphological and optical properties using X-ray diffraction, scanning electron microscopy and UV–Vis spectrophotometer. XRD study illustrates formation of spinel cubic NiMn2O4 as prominent phase with crystalline size 11 nm. SEM shows fractured surface morphology; wherein small pores on the surface are covered by the particles. Optical band gap of 1.98 eV is observed. The electrochemical performance of NiMn2O4 electrode is studied by cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy measurements. The maximum specific capacitance is found to be 460 Fg−1 at scan rate of 5 mVs−1. The excellent rate capability and long term stability suggests NiMn2O4 thin film to be good candidate for electrochemical supercapacitors.

Electrochemical synthesis and physical properties of Sn-doped CdO nanostructures

Un- and Sn-doped CdO thin films were deposited on FTO-coated glass substrates using electrodeposition method. Crystalline study revealed a cubic phase for all samples. SEM images showed flower- and rod-like morphologies for the Sn-doped samples in nano-dimensions. Optical energy band gaps of 2.70, 2.79, and 2.84 eV were obtained for Sn0, Sn1, and Sn2 samples, respectively. Electrical investigations indicted that CdO thin films revealed n-type conductivity with high density of donor levels, which exceeded by corporation of Sn cations in the crystalline structures of CdO thin films.

Assembling tungsten oxide hydrate nanocrystal colloids formed by laser ablation in liquid into fast-response electrochromic films

High-performance electrochromic films based on tungsten oxide hydrate ([WO2(O2)H2O]·1.66H2O) colloidal nanocrystals with fast switching speed were fabricated by laser ablation in a mixture of water and hydrogen peroxide followed by electrophoretic methods. Through electrophoretic deposition, the nanoparticles in the colloids synthesized by laser ablation aggregated onto the FTO coated glass substrate forming a lager cell with a uniform size of around 200nm, which subsequently self-assembled into a porous tungsten oxide hydrate film. By optimizing the electrophoretic time (800s) and voltage (−0.5V), the mesh-like porous tungsten oxide hydrate film achieved a wide optical modulation of 32% at 632nm, fast coloration and bleaching response speed of 7.8 s and 1.7s respectively due to the synergetic effect of the unique atomic structure of [WO2(O2)H2O]·1.66H2O and porous structure with large surface area that facilitates the ion insertion/extraction. Thus the tungsten oxide hydrate can be a promising electrochromic material for practical applications.

Enhanced visible light photocatalytic activity of pristine and silver (Ag) doped WO3 nanostructured thin films

In this report, pristine and silver (Ag) doped tungsten trioxide (WO3) thin films were deposited on FTO-coated glass substrate by using simple chemical bath deposition method for the first time. The structural, morphological, and optical properties of pure and Ag-doped WO3 thin films have been systematically studied. The as-deposited films were annealed at 600 °C for 2 h in the ambient atmosphere in order to improve the crystallinity. The structural properties revealed that both pure and Ag-doped WO3 films exhibited the monoclinic phase of WO3. The surface morphology revealed that pure films showed the dense surface and films contained agglomerated grains which were uniformly distributed on the surface of the substrate. The optical transmittance decreased from 95 to 85 % for pure and Ag-doped WO3 films, respectively. The photocatalytic activities of the films were evaluated by degradation of methyl orange and Phenol in an aqueous solution under visible light irradiation. The photocatalytic activity of WO3 nanostructures could be extremely improved by doping with Ag. The improved photocatalytic mechanism by Ag also discussed. The films were further characterized by Fourier Transform Infrared (FTIR) spectra and photoluminescence spectra analysis.

Seeded growth of WO3 film on FTO substrate with tunable structures for stable electrochromic performance

ABSTRACTIn this work, tungsten trioxide (WO3) film was prepared on FTO-coated glass substrates using a facile hydrothermal method. Detailed studies revealed that a variety of WO3 nanostructures-including nanosheets, nanoflakes, nanocuboids and 3D nanowire flowers could be obtained by tuning the composition of the precursor solution, where the additive ((NH4)2C2O4 and CO(NH2)2-(NH4)2C2O4)) content and solvent composition played important roles in controlling the shape and size of the WO3. These nanostructure films exhibited good electrochromic performance. The transmittance spectra showed that WO3 film displayed 50% and 70% in the range of visible light at the colored and bleached states (S2) and a potential of ±1.0 V. There is no significant degradation of the electrochromic properties after 1000 continuous coloration/bleaching cycles, making it attractive for practical applications.

Photoelectrocatalytic activity of Mn2O3–TiO2 composite thin films engendered from a trinuclear molecular complex

Newly synthesized trinuclear bimetallic precursor [Mn2Ti(μ3−O) (TFA)6 (THF)3] (1) (where TFA = trifluoroacetato and THF = tetrahydrofuran) was successfully used to develop Mn2O3–TiO2 (MT) composite thin films by aerosol assisted chemical vapour deposition (AACVD). The Mn2O3–TiO2 composite thin films developed at four different temperatures of 400, 450, 500 and 550 °C were characterized by X-ray diffraction (XRD) and their elemental composition was affirmed by energy dispersive X-ray spectroscopy (EDX). Further field emission gun-scanning electron microscopy (FEG-SEM), atomic force microscopy (AFM), UV–visible absorption spectrophotometry and photoelectrochemical properties were investigated to compare the properties and efficiency of thin films fabricated at 400, 450, 500 and 550 °C. The FEG-SEM and AFM analyses illustrated that the morphology and surface roughness of the thin films significantly depend on the deposition temperature. Films deposited at 500 °C shows agglomerated spinal column scattered vertically on the FTO-coated glass substrate. The direct optical band gap energies of 2.80, 2.52, 2.75 and 2.90 eV for the films fabricated at 400, 450, 500 and 550 °C respectively were found. Photo-oxidation of water via Mn2O3–TiO2 thin films was carried out under simulated solar irradiation of AM 1.5 G (100 mW/cm2) in 0.5 M Na2SO4 using three-electrode photoelectrochemical cell. The films deposited at 500 °C exhibited a better photocurrent density of ∼1.3 mA cm−2 at 0.7 V as compared to the rest of the films grown at different temperatures.

Synthesis of novel Cu2S nanohusks as high performance counter electrode for CdS/CdSe sensitized solar cell

An important component of quantum dot sensitized solar cells (QDSSC) is the counter electrode which mediates the regeneration of oxidized quantum dots by reducing the polysulphide electrolyte. However, design and synthesis of an efficient counter electrode material is a challenging task. Herein, we report the synthesis of a unique Cu2S nanohusks directly on FTO coated glass substrates by electrodeposition and used as a counter electrode in QDSSC. When these electrodes are used for the reduction of polysulfide electrolyte in QDSSC, they exhibit higher catalytic activity and photovoltaic performance as compared to the Platinum counter electrode. The power conversion efficiency of about 4.68% has been achieved by optimizing the deposition time of Cu2S.

Effect of Tl+ Intercalation on Electrochromic Behavior of Tungsten Heteropolyoxometalate Polymeric Thin Films

SummaryTungsten oxide (WO3) and molybdenum oxide (MoO3) are an extensively studied EC materials due to its outstanding electrochromic properties. Hence in present investigation Tl+ intercalated tungsten heteropolyoxometalate polymeric thin films have been successfully deposited on the FTO‐coated glass substrates using low cost chemical bath deposition technique. The films formed were uniform and well adherent. For the electrochemical characterization, the standard three‐electrode electrochemical cell was used. The polymeric thin films show good EC properties. By observing various parameters obtained from cyclic voltammetry, chronoamperometry and iono‐optical studies of tungsten heteropolyoxometalate thin films it is clear that, reversibility of phosphotungstic acid (PTA) increases after intercalation of thallium but coloring efficiency (CE) decreases.

Fabrication of Morphology Controllable Vertically Aligned TiO<sub>2</sub> Nanorod Arrays for Dye-Sensitized Solar Cells

In this work, vertically aligned TiO2 nanorod arrays (NR) are synthesized directly on FTO coated glass substrate by hydrothermal method. The samples are characterized by XRD, SEM, TEM and the results indicate that the 1-D nanorods are of single crystal rutile structure with growth direction along the [001] direction. The morphology (diameter, thickness and density) of the nanorods can be adjusted by changing the precursor amounts. The possible growth mechanism of TiO2 nanorods on FTO substrate has also been briefly discussed in this work. For dye-sensitized solar cells (DSSCs) fabricated of different thickness nanorods, a power conversion efficiency (PCE) of 1.74% has been achieved by using ~3μm nanorod arrays under simulated AM 1.5 illumination (100 mW cm-2). It is expected that the 1-D nanorods can be composited with other nanomaterial of different structures and morphologies to enhance the efficiency of DSSCs.