Fluorine-doped Tin Oxide Layer Research Articles

A comparative study of different M(M = Al, Ag, Cu)/FTO bilayer composite films irradiated with nanosecond pulsed laser

Aluminium (Al), silver (Ag) and copper (Cu) layers were deposited on commercial fluorine-doped tin oxide (FTO) glass by direct current (DC) magnetron sputtering, so as to form Al/FTO, Ag/FTO and Cu/FTO bilayer films. Then all the as-deposited metal/FTO films were irradiated using a 532nm nanosecond pulsed laser with a fluences of 1.05J/cm2. X-ray diffraction (XRD) analysis confirmed that all the laser-irradiated films were annealed by the laser and showed increased average crystallite size in FTO layers. Laser-induced grating structures were also obtained on the surfaces of the laser-irradiated Ag/FTO and Cu/FTO films, resulting in higher surface roughnesses and average transmittances of the films. But due to the broken continuity of the Ag and Cu layers, the sheet resistances of these two films slightly decreased as compared to that of the laser-irradiated Al/FTO film. It was also found that the laser-irradiated Ag/FTO film, whose average transmittance in 400–800nm waveband and sheet resistance was 81.5% and 6.6Ω/sq respectively, had the better figure of merit, indicating that the photoelectric property of FTO-based bilayer films could be further optimized through achieving fabrication of laser-induced grating structures and laser annealing in one step.

Electrochemical behavior of a laser microstructured fluorine doped tin oxide anode layer with a plasma pretreatment for 3D battery systems

Fluorine-doped tin oxide (FTO) films with a thickness of about 3 micrometers were prepared by electron cyclotron resonance-metal organic chemical vapor deposition (ECR-MOCVD) under 800 W of microwave power, with tetra-methyl tin (TMT) as a tin precursor. The dome-shaped micro-patterned FTO layer was prepared on a copper current collector using a KrF excimer laser micromachining system for application as an anode for 3D lithium-ion batteries. Mild ECR plasma treatment at 600 W was carried out on the surface of the microstructured FTO anode, and the electrochemical characteristics were investigated with regard to the plasma treatment effects. The results show that physical properties such as the smooth and dense surface morphology and reduced surface oxygen functional groups of the plasma-treated samples enhanced the specific capacity, rate capability, and capacity fading. This was probably due to the reduction of side reactions, which may be closely related to the plasma treatment of the microstructured FTO layer. The ECR plasma treatment plays an important role in reducing the charging transfer resistance. In the experimental range studied, a higher specific capacity of 1425 mA h g−1 at a current density of 117 mA g−1 was observed, with capacity fading of 37.8% after 100 cycles for the plasma-treated microstructured FTO anode.

Near Infrared Radiation as a Rapid Heating Technique for TiO2Films on Glass Mounted Dye-Sensitized Solar Cells

Near infrared radiation (NIR) has been used to enable the sintering of TiO2films on fluorine-doped tin oxide (FTO) glass in 12.5 s. The 9 µm thick TiO2films were constructed into working electrodes for dye-sensitized solar cells (DSCs) achieving similar photovoltaic performance to TiO2films prepared by heating for 30 min in a convection oven. The ability of the FTO glass to heat upon 12.5 s exposure of NIR radiation was measured using an IR camera and demonstrated a peak temperature of 680°C; glass without the 600 nm FTO layer reached 350°C under identical conditions. In a typical DSC heating step, a TiO2based paste is heated until the polymeric binder is removed leaving a mesoporous film. The weight loss associated with this step, as measured using thermogravimetric analysis, has been used to assess the efficacy of the FTO glass to heat sufficiently. Heat induced interparticle connectivity in the TiO2film has also been assessed using optoelectronic transient measurements that can identify electron lifetime through the TiO2film. An NIR treated device produced in 12.5 seconds shows comparable binder removal, electron lifetime, and efficiency to a device manufactured over 30 minutes in a conventional oven.

Thin films of SnO2:F by reactive magnetron sputtering with rapid thermal post-annealing

Thin films of fluorine-doped tin oxide (FTO) are transparent conducting oxide (TCO) layers that exhibit excellent corrosion and mechanical resistance and are typically produced by high temperature (>400°C) spray pyrolysis. Magnetron sputtering is another industry relevant method for large area FTO deposition where a low temperature process can be used although the electrical properties of sputtered FTO are currently inferior to those of spray pyrolysis. Here reactive sputtering of FTO is investigated in order to optimize the sputter and post-treatment parameters for achieving high quality TCO layers. FTO layers are deposited by reactive DC magnetron sputtering of metallic tin targets in an atmosphere of Ar/O2/CF4 or CHF3. Post-deposition rapid thermal processing (RTP) for a short annealing time of less than 5min at 450°C is sufficient to lower electrical resistivity down to ~2×10−3Ωcm as a result of the increased carrier concentration and mobility while keeping the average optical transmittance above 79%. The free carrier concentration can be controlled by changing the fluorine doping via the CF4/CHF3 flow, as determined by Rutherford backscattering spectrometry and elastic recoil detection analysis. The electrical activation of the fluorine dopant is found to be low, on the order of 4%. Based on temperature-dependent Hall measurements we show that the electrical conductivity in RTP-annealed FTO is primarily limited by ingrain scattering.

Nanoporous TiO2 aerogel blocking layer with enhanced efficiency for dye-sensitized solar cells

TiO2 aerogel film possessing nanoporous feature was used as the blocking layer between fluorine-doped tin oxide (FTO) substrate and mesoporous TiO2 layer in dye-sensitized solar cell (DSSC). TiO2 aerogel film was deposited on FTO glass via sol–gel and ambient drying processes and sintered at 500 °C, which exhibited the crystallite size of 5–25 nm, the pore size of 3–10 nm, and the thickness of ∼320 nm. Brunauer–Emmett–Teller (BET) analysis confirmed its nanoporous feature and average pore size of 3.8 nm after annealing at 500 °C. In addition, TiO2 aerogel film showed good interfacial adhesion with FTO and mesoporous TiO2 layer, high transmittance over 70% in the visible-near infrared band, and large band gap of 3.67 eV. The DSSC device based on this aerogel blocking layer showed obviously enhanced photocurrent density (Jsc) and open-circuit voltage (Voc) compared with the cell without blocking layer. The highest conversion efficiency of 6.0% was achieved for P25 TiO2 mesoporous photoanode based on the aerogel blocking layer, improved by 36% than the control cell. The much decreased recombination frequency (aerogel cell: 11.9 Hz; control cell: 31.5 Hz) observed in Nyquist plots, together with the much prolonged electron lifetime (aerogel cell: ∼1 s; control cell: 0.02–0.1 s at 0.2–0.55 V) obtained from open-circuit voltage decay curves, indicated that the increased electron life and retarded recombination at FTO/electrolyte interface were primarily responsible for the efficiency improvement in the aerogel blocking layer based DSSC.

Fundamental Electrochemiluminescence Characteristics of Fluorine-Doped Tin Oxides Synthesized by Sol–Gel Combustion

Fluorine-doped tin oxide (FTO) materials synthesized by sol-gel combustion method were investigated for electrochemical luminescence (ECL) application. Effects of sol-gel combustion conditions on the structures and morphology of the porous FTO (p-FTO) materials were studied. ECL efficiency of p-FTO-based cell was about 251 cd/m2 at 4 V bias, which is higher than the sell using only FTO electrodes (102.8 cd/m2). The highest intensity of the emitting light was obtained at the wavelength of about 610 nm. The porous FTO layer was effective for increasing ECL intensities.

Fabrication of a double layered FTO/AZO film structure having enhanced thermal, electrical and optical properties, as a substitute for ITO films

An ideal transparent conducting oxide (TCO) should possess high optical transparency and electrical conductivity along with good chemical and thermal stabilities while it is subjected to high temperature processes. In the present study, a novel TCO film which possesses good figure of merit (ϕ) (i.e. good optical transparency and electrical conductivity) along with good chemical and thermal stabilities and especially which can acts as a substitute for ITO has been realized. To achieve the combined unique characteristics of ZnO (thermal stability) and SnO2 (chemical stability), a double layered structure which consists of fluorine doped tin oxide (FTO) as the top layer on AZO layer, has been deposited using a simplified spray pyrolysis technique. In order to optimize the thickness proportions of FTO/AZO double layer for obtaining improved quality factors, five sets of samples were fabricated with different thickness proportions (1:5, 1:2, 1:1, 2:1 and 5:1) of AZO and FTO layers. Then, for the better understanding of physical properties of FTO/AZO double layered films, structural, optical and electrical studies were carried out and the results are reported. The minimum electrical resistivity of 9.141×10−3Ωcm with 80 % of optical transparency obtained for the FTO/AZO bilayer film having 5:1 thickness proportion, prompts us to conclude that this thickness proportion is suitable to achieve improved quality factor (1.185×10−3 (Ω/□)−1). The quality factor is found to be increased nearly four times after annealing (3.965×10−3 (Ω/□)−1).

Influence of SnO2:F/ZnO:Al bi-layer as a front electrode on the properties of p-i-n amorphous silicon based thin film solar cells

The effect of aluminum doped zinc oxide film used between a fluorine doped tin oxide layer and a hydrogenated amorphous silicon carbide layer to improve the open circuit voltage (Voc) and fill factor (FF) for high efficiency thin film solar cells. The efficiency enhancement was accomplished by the insertion of high work-function layers engineered in the interfaces to raise FF as well as Voc. Therefore, we were able to obtain the conversion efficiency of 10.34% at 16.14 mA/cm2 of the current density (Jsc) and 70.37% of FF.

Effect of Annealing Temperature on Electrochemical Luminescence Properties of Nanoporous Fluorine-Doped Tin Oxide Films

Nanoporous Fluorine-doped tin oxide (FTO) materials were synthesized by sol-gel combustion method for electrochemical luminescence (ECL) application. The influence of annealing temperature on the structures and morphology of the nanoporous FTO films was examined by X-ray diffraction (XRD), atomic force microscopy (AFM), optical transmittance and BET specific surface measurements. The naoporous FTO-based ECL cell is composed of FTO glass/nanoporous FTO/Ru(bpy)2+ electrolyte/FTO glass. The peak intensity of emitting light from the cell was obtained at the wavelength of about 615 nm, which corresponds to dark orange color. At 5 V bias, ECL efficiency of the cell using the 550 degrees C annealed FTO was about 975 cd/m2, which is much higher than those of other cells. The result shows that the nanoporous FTO layer was more effective for increasing ECL intensities. The sol-gel combustion method at annealing temperature of 550 degrees C could be employed to synthesize the nanoporous FTO materials with high porosity and ECL performance.

Rapid radiative platinisation for dye‐sensitised solar cell counter electrodes

ABSTRACTThe successful transition of dye‐sensitised solar cell (DSC) manufacture from laboratory to factory requires new thinking in terms of lowering cost and removing time consuming manufacturing process. Platinisation of the fluorine doped tin oxide (FTO) glass counter electrode is essential for the operation of a conventional DSC and is usually carried out by thermal decomposition of chloroplatinic acid at 385 °C for 30 min. Here, near infrared radiation is used to directly heat the FTO layer resulting in full platinisation in 12.5 s. These platinised electrodes behave identically to those produced via conventional static thermal treatment in assembled DSC devices. Copyright © 2013 John Wiley & Sons, Ltd.

Dense CdS thin films on fluorine-doped tin oxide coated glass by high-rate microreactor-assisted solution deposition

Continuous microreactor-assisted solution deposition is demonstrated for the deposition of CdS thin films on fluorine-doped tin oxide (FTO) coated glass. The continuous flow system consists of a microscale T-junction micromixer with the co-axial water circulation heat exchanger to control the reacting chemical flux and optimize the heterogeneous surface reaction. Dense, high quality nanocrystallite CdS thin films were deposited at an average rate of 25.2nm/min, which is significantly higher than the reported growth rate from typical batch chemical bath deposition process. Focused-ion-beam was used for transmission electron microscopy specimen preparation to characterize the interfacial microstructure of CdS and FTO layers. The band gap was determined at 2.44eV by UV–vis absorption spectroscopy. X-ray photon spectroscopy shows the binding energies of Cd 3d3/2, Cd 3d5/2, S 2P3/2 and S 2P1/2 at 411.7eV, 404.8eV, 162.1eV and 163.4eV, respectively.

Porous FTO thin layers created with a facile one-step Sn4+-based anodic deposition process and their potential applications in ion sensing

Porous fluorine-doped tin oxide (FTO) thin layers were created from commercial FTO glass with a novel, facile, one-step Sn4+-based anodic deposition process. The Sn2+ necessary for the anodic deposition of SnO2 was generated in situ from the starting Sn4+ such that a comparable competition between deposition and acid-etching of SnO2 became possible, leading to a rich morphological evolution of the deposit. The fluoride ions released from the acid-etching of the starting FTO layer were later incorporated into the newly deposited SnO2 to make it fluorine-doped, resulting in the formation of a conductive, porous FTO layer. This unique FTO product may find a wide range of applications in processes requiring large surface areas for the accommodation of active sites to host functional interfacial events and excellent electric conductivities for charge transfer/transport involved in the interfacial events. To demonstrate its applicability, this conductive porous FTO thin layer was applied to the sensing of nitrate ions, which play a fundamental role in a wide range of environmental and biological processes. A simple device was developed for the sensing of nitrate ions based on surface charge-modulated adsorption of nitrate ions and measurements of consequent currents. At 0.5 M HNO3, the porous FTO showed a 55 fold sensitivity improvement over the commercial FTO. In buffer solutions of a specific pH value, the cation effects on ion sensitivities were also discussed. A low detection limit of 10−8 M was achieved for nitrate ion sensing with the present porous FTO layer.

Anodic Deposition of Ultrathin TiO2 Film with Blocking Layer and Anchoring Layer for Dye-Sensitized Solar Cells

Ultrathin anatase TiO2 films were coated on the fluorine-doped tin oxide (FTO) glass by anodic electrodeposition followed by annealing at 450°C before the formation of thick TiO2 layer. The electrodeposited TiO2 films were more compact structure near the FTO surface (inner layer), and became less compact further away from the surface (outer layer). The outer layer of film deposited at 10 μA cm−2 was composed of granular nanoparticles and that of film deposited at 5 μA cm−2 was composed of short nanorods. The inner compact layer could act as a blocking layer to suppress the charge recombination. The outer loose layer could provide an anchoring layer for a better electrical contact between FTO and thick TiO2 layer. The photoelectron conversion efficiency (η) of dye-sensitized solar cell (DSC) using TiO2-coated FTO deposited at 10 μA cm−2 was 6.9%, which is higher than that of DSC using bare FTO (6.5%). The outer anchoring layer composed of short nanorods deposited at 5 μA cm−2 could significantly reduce the interfacial contact resistance between FTO and main TiO2 layer. Therefore, η of DSC was further increased to 7.1% after employing the TiO2-coated FTO deposited at 5 μA cm−2.

Au Nanoparticles as Interfacial Layer for CdS Quantum Dot-sensitized Solar Cells

Quantum dot-sensitized solar cells based on fluorine-doped tin oxide (FTO)/Au/TiO2/CdS photoanode and polysulfide electrolyte are fabricated. Au nanoparticles (NPs) as interfacial layer between FTO and TiO2 layer are dip-coated on FTO surface. The structure, morphology and impedance of the photoanodes and the photovoltaic performance of the cells are investigated. A power conversion efficiency of 1.62% has been obtained for FTO/Au/TiO2/CdS cell, which is about 88% higher than that for FTO/TiO2/CdS cell (0.86%). The easier transport of excited electron and the suppression of charge recombination in the photoanode due to the introduction of Au NP layer should be responsible for the performance enhancement of the cell.

UV-reduction of graphene oxide and its application as an interfacial layer to reduce the back-transport reactions in dye-sensitized solar cells

A mixture of graphene oxide (GO) and TiO 2 nanocomposites was reduced photocatalytically by UV-irradiation and applied as interfacial layer between a fluorine doped tin oxide (FTO) layer and a nanocrystalline TiO 2 film. Impedance spectra implied a decreased back-transport reaction of electrons. The graphene–TiO 2 interfacial layer effectively reduced the contact between I 3 - ions in the electrolyte and FTO layer, which inhibited back-transport reaction. The introduction of graphene–TiO 2 increased V oc by 54 mV and the photoconversion efficiency was improved from 4.89% to 5.26%.

Comparative study of ITO and FTO thin films grown by spray pyrolysis

Tin doped indium oxide (ITO) and fluorine doped tin oxide (FTO) thin films have been prepared by one step spray pyrolysis. Both film types grown at 400 °C present a single phase, ITO has cubic structure and preferred orientation (4 0 0) while FTO exhibits a tetragonal structure. Scanning electron micrographs showed homogeneous surfaces with average grain size around 257 and 190 nm for ITO and FTO respectively. The optical properties have been studied in several ITO and FTO samples by transmittance and reflectance measurements. The transmittance in the visible zone is higher in ITO than in FTO layers with a comparable thickness, while the reflectance in the infrared zone is higher in FTO in comparison with ITO. The best electrical resistivity values, deduced from optical measurements, were 8 × 10 −4 and 6 × 10 −4 Ω cm for ITO (6% of Sn) and FTO (2.5% of F) respectively. The figure of merit reached a maximum value of 2.15 × 10 −3 Ω −1 for ITO higher than 0.55 × 10 −3 Ω −1 for FTO.

Diffusion barrier of sol-gel derived silica for sprayed tin oxide film on soda-lime glass

Diffusion barriers of silica were deposited on soda-lime glass using a sol-gel technique. The migration of sodium from the glass through these layers and into a spray-pyrolyzed layer of fluorine-doped tin oxide was studied by SIMS depth profiling. The silica layer reduced sodium in the tin oxide overlayer by two orders of magnitude.