Fluorine-doped Tin Oxide Films Research Articles

Influence of Temperature on the Performance of Metal Semiconductor Metal Photodetector Fabricated by Pure and Cationic Doped (Mg2+ and Cu2+) SnO2 Nanoparticles

Research based on various temperatures always provides beneficial awareness in the fabrication of a vital photodetector for significant applications. Increasing temperature and including dopants in photodetector materials will influence the functioning of the photodetector. This study included the influence of temperature on pure and doped SnO2 photodetectors. The crystal structure of stannic oxide has been modified by adding cationic dopants, namely Mg2+ and Cu2+, through co-precipitation techniques. Various characterization techniques were employed to examine the impact of Mg2+ and Cu2+ on the Sn4+ lattice. The electrical properties of the materials were studied at different temperatures using the Hall effect. Pure SnO2, Mg-doped SnO2, and Cu-doped SnO2 nanoparticles were synthesised separately and used as photodetectors using fluorine-doped tin oxide film as a conductive medium. The fabricated photodetectors are optimized by current-voltage characteristics at different temperatures. The effects of defects in crystal structure, oxygen vacancies, carrier concentration, and temperature on the photodetectors were studied. Comparative studies of pure and doped SnO2 photodetectors revealed that temperature and crystal defects play a significant role in photoconduction.

Improving optical and electrical stabilities of fluorine-doped tin oxide films in sweat solutions with O2 addition in plasma

Abstract Recently, the use of wearable smart devices has significantly increased; however, sweat can corrode the outer-layer films, thereby decreasing their transmittance, conductivity, and overall functionality. In this study, fluorine-doped tin oxide (FTO) films for wearable smart devices were prepared via magnetron sputtering. The effects and mechanism of O2 gas flow in plasma on the properties of the fabricated films were investigated. Minor changes were observed in the film morphologies, with the preferred orientations shifting from polar (101) to nonpolar (110) and standard positions. As the O2 flow rate increased from 0 to 2 sccm, the transmittance of the film within the visible spectrum increased from 83% to 89%, with sheet resistance values in the order of 102–106 Ω·sq–1. Following immersion in an acidic sweat solution, the film without O2 peeled off, whereas several corrosion pits were observed in the films with 1 or 2 sccm O2. Conversely, following immersion in an alkaline sweat solution, several pits were observed in the films without O2, while the other films exhibited excellent corrosion resistance. The transmittance of the films immersed in different solutions did not significantly differ. Notably, the sheet resistances of the films treated with 1 sccm O2 met the industrial requirement of 3000 Ω. Moreover, the coexistence of polar and nonpolar planes provided transparency and conductive stability to the FTO films treated with 1 sccm O2. Our study aimed to not only enhance the transmittance and sweat-corrosion resistance but maintain the conductivity of the outer screen layer of a wearable smart electronic device.

Identifying Current Collectors that Enable Light-Battery Interactions.

In recent years, there has been an increased focus on studying light-battery interactions in the context of operando optical studies and integrated photoelectrochemical energy harvesting. However, there has been little insight into identifying suitable "light-accepting" current collectors for this class of batteries. In this study, fluorine-doped tin oxide, indium-tin oxide, and silver nanowire-graphene films are analyzed along with carbon paper, carbon nanotube paper, and stainless-steel mesh as current collectors for optical batteries. They are categorized into two classes - transmissive and non-transmissive, based on the orientation of the light-electrode interaction. Various methods to prepare the electrode are highlighted, including drop casting and the fabrication of free-standing electrodes. The optical and electrical properties of these current collectors as well as their electrochemical stability are measured using linear sweep voltammetry against zinc and lithium anodes. Finally, the rate performance and long-term cycling stability of lithium manganese oxide (LiMn2O4) cathodes are measured against lithium anodes with these current collectors and their performance is compared. These results show which current collector to choose depends on the application and cell chemistry. These guidelines will assist in the design of future optical cells for in-situ measurements and photoelectrochemical energy storage.

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.

Interfacial carbon quantum dot thin film impacts on morphological and chemical structures of fluorine-doped tin oxide films

Morphology and chemical bonding states, including surface roughness, film density, F-doping, and oxygen vacancy (VO) concentration directly affect the electrical and optical properties of fluorine-doped tin oxide (FTO) films. In this study, morphology and chemical bonding states of FTO films are engineered simultaneously by introducing a carbon quantum dot (CQD) thin film as an interface layer during ultrasonic spray pyrolysis deposition. The abundant oxygen-containing surface functional groups and large surface free energy of the CQD thin film promoted (200) oriented crystal growth and accelerated nucleation of FTO, resulting in smooth and dense FTO film morphology. The abundant carboxyl surface functional groups on the CQDs generate active F− species that are effectively doped into SnO2. Formic acid, formed by dissociation of the carboxyl group, can serve as a strong reducing agent for extracting oxygen atoms from the SnO2 lattice, thereby increasing the VO concentration. The accelerated F-doping and VO concentration result in the generation of additional free electrons. The effects of the optimized CQD on the morphological and chemical structures of FTO films are demonstrated by their superior electrical (sheet resistance of ∼5.7 Ω/□) and optical properties (visible transmittance of ∼85.9 %) compared with bare FTO. Moreover, CQD/FTO used as transparent conducting electrodes in electrochromic (EC) application exhibited improved EC performances, including fast switching speeds (5.3 s and 2.3 s for bleaching and coloration, respectively) and high coloration efficiency (81.1 cm2/C) compared to that of bare FTO.

Magneto-optical characterization of TCO films using standard and enhanced configurations

Thin film samples like transparent conducting oxides (TCO) are typically investigated using measurements like Hall Effect and 4-point probe measurements. We use a sensitive AC Faraday rotation (FR) setup to study thin film samples for which a magneto-optic response is challenging to characterize. The experimental setup employs a stabilized He-Ne laser (633 nm) along with an AC magnetic field that enables lock-in detection. We investigate a series of TCO samples that are deposited on a glass substrate. The TCO samples include the more widely used Indium Tin Oxide (ITO) and the relatively newer Fluorine doped Tin Oxide films, usually referred to as FTO. These films have a magneto-optic response due to the presence of free carrier concentration and therefore measurement of this response (Verdet constant) could allow one to determine the carrier concentration of these films. Given that magneto optic responses like FR depend on the length of the sample length traveled by light, these sub-micron films pose considerable challenges in trying to extract the FR response of the film from that of the much thicker glass substrate. Furthermore, we present details of the design and FR characterization of samples using a Michelson interferometer-based measurement setup which enhances the Faraday rotation and affords a new means of studying harmonic peaks of the recorded optical signal in response to a sinusoidally-varying applied magnetic field. We compare some early results from this setup to the typical “single-pass” setup to highlight the difference in the recorded signals from the two setups. To showcase the advantages of the proposed measurements, we also include some early results from a very different type of sample, namely superparamagnetic nanoparticles (SNPs).

Electrical and Optical Properties of Fluorine-Doped Tin Oxide Films Fabricated at Different Substrate Rotating Speeds during Ultrasonic Spray Pyrolysis Deposition

Electrical and Optical Properties of Fluorine-Doped Tin Oxide Films Fabricated at Different Substrate Rotating Speeds during Ultrasonic Spray Pyrolysis Deposition

Femtosecond laser annealing of fluorine-doped tin oxide films towards high-performance perovskite photovoltaics

Femtosecond laser annealing preparation of a superhydrophilic FTO surface helps promote the photoelectric conversion efficiency of perovskite solar cells to 22.33%.

Enhanced nonlinear optical response by strong coupling between plasmonic antenna arrays and epsilon-near-zero film

A coupled structure of center-symmetric orthogonal nano-antenna arrays on fluorine-doped tin oxide (FTO) is designed to enhance the nonlinear response by the strong coupling. Further, we study the roles of structural and material parameters in determining the linear and nonlinear optical response of antenna-FTO metasurface. This structure shows broadband spectrum (∼900 nm) and large nonlinearity with nonlinear refractive index n 2 of 1.02 cm2/GW, which is about 400 times higher than that of bare FTO film. The results provide a promising platform for the realization of ultracompact and large nonlinear optical devices.

Fluorine-Doped Tin Oxide Thin Films with High Surface Conductance and Low Transparency for Boosting Performance in Dye-Sensitized Solar Cell Applications

Transparent conductive oxide films, like fluorine-doped tin oxide (FTO), are needed for electrochemical devices. FTO films are attractive due to their cost-effectiveness and high-temperature tolerance. Generally, solar cell fabrication requires high transmittance and low-conductivity FTOs. However, achieving both simultaneously poses a fundamental challenge. This study investigates the impact of FTO layer thickness, sheet resistance, transparency, and film morphology on optimizing the performance of dye-sensitized solar cells. To achieve this, a precursor solution containing SnCl4·5H2O and NH4F in isopropanol is sprayed onto a soda-lime glass substrate at 500 °C to form FTO films. The film thickness is varied by repeating the spray cycles. By increasing the number of spray cycles, the sheet resistance of the FTO film improves to ∼1.20 Ω □–1 with the expense of transmittance. The achieved very low sheet resistance of ∼1 Ω □–1 (∼3.54 × 10–4) Ω cm resistivity for the FTO film confirms the promise of this sequential spray pyrolysis technique in preparing highly conductive inert electrodes for various applications. Furthermore, DSCs with low transparency and sheet resistance showed higher-energy conversion efficiencies, challenging the current prerequisite of the requirement of high transmittance. The best efficiency (5.14%) is achieved with FTO films having a 34.2% transmittance and a 3.27 Ω □–1 sheet resistance, outperforming standard FTO films (4.74%) with a 10 Ω □–1 sheet resistance and an ∼83% transmittance. The results indicate that the transparency of FTO is not a dominant factor and carefully controlled light scattering and electrical properties in translucent FTO films would lead to the realization of dye-sensitized solar cells that deliver superior efficiency.

Microwave heating to form porous TiO2 layer on high-haze FTO film for dye-sensitized solar cell

A porous TiO2 layer was formed on a fluorine-doped tinoxide (FTO) film using a microwave heating technique, and applied to a dye-sensitized solar cell (DSSC). Under microwave irradiation, a self-heating process was induced in the FTO film to raise the substrate temperature up to 600 °C within a minute. After 12 min of microwave irradiation of the porous TiO2/FTO double layer, the internal resistances at the TiO2/FTO interface and the TiO2 interparticles were effectively reduced. By tuning the haze of the optical transmission through the FTO film, the photovoltaic performance was enhanced, and the conversion efficiency reached values as high as 7.2% at a haze of 31.5%, which was attributed to effective light harvesting within the cell. Unique ionic diffusion induced under microwave irradiation was detected at a lower substrate temperature, and the cell that formed at a substrate temperature of 350 °C exhibited a conversion efficiency of 6.5%, which is high for the sintering temperature. Although the photovoltaic performance was comparable to that of a general DSSC, a rapid sintering process that reduced the internal resistance within the cell was demonstrated using a microwave heating technique. Compared with a conventional electric furnace, the microwave heating technique can produce ceramics with high densities in a short time, and is an ideal tool for producing DSSCs.

A direct correlation between structural and morphological defects of TiO2 thin films on FTO substrates and photovoltaic performance of planar perovskite solar cells

Titanium oxide (TiO2) precursor is often deposited on conductive fluorine doped tin oxide (FTO) to convert into crystalline anatase phase after a thermal annealing at 400–550 °C. A higher annealing temperature can increase the crystallinity of TiO2, but it may also induce morphological changes in both TiO2 and FTO. In this work, structural and morphological changes in thermally annealed FTO and TiO2/FTO are identified and semi-quantified by X-ray diffraction, scanning electron and atomic force microscopies. 400 °C annealed TiO2 shows the lowest crystallinity and the highest dislocation density, giving a poor photovoltaic performance of planar perovskite solar cells (p-PSCs). 550 °C annealed TiO2 exhibits the highest crystallinity and lowest dislocation density, but at such temperature the FTO films undergo an increase of surface roughness by more than 25%. As a result, 550 °C annealed TiO2 coatings on FTO substrates show the highest concentration of surface fracture and a larger exposed area of FTO, permitting a direct contact of upcoming perovskite with the FTO substrate. TiO2 thin films annealed at 450 or 500 °C show a compromising between the crystalline structure and defect density, giving a better energy conversion efficiency of 16.3% of p-PSCs prepared under ambient conditions.

Electrochemical stability and corrosion mechanism of fluorine-doped tin oxide film under cathodic polarization in near neutral electrolyte

Commercial fluorine-doped tin oxide (FTO) coated glass slides were subjected to different cathodic potentials for 15 min in 0.2 M Na2SO4 of pH 6.42 to study their electrochemical stability. Results showed that FTO could maintain its electrochemical stability until -1200 mV. However, when it was cathodically polarized from -1600 mV to more negative potentials, band structure positions started to shift upwards, the electrolyte became more acidic and a porous structure appeared on the FTO surface. At -2000 mV, a layer of metallic Sn was seen deposited on the FTO surface, verified by X-ray diffraction and scanning electron microscopy – energy dispersive X-ray spectroscopy. During the cathodic corrosion in near neutral electrolyte, the reduction of SnO2 to Sn involves water oxidation as well as hydrogen evolution reaction.

Design of experiments optimization of fluorine-doped tin oxide films prepared by spray pyrolysis for photovoltaic applications

Transparent conducting oxides (TCOs) have witnessed an ever-expanding use in our lives through many optoelectronic applications, namely photovoltaic (PV) devices. Indium-tin oxide (ITO) is the most used and studied TCO, but it lacks thermal and chemical stability and indium is a scarce and toxic element. Fluorine-doped tin oxide (FTO) emerged as the most promising alternative to ITO, presenting better thermal and chemical stability. Among the numerous techniques for depositing FTO thin films over glass substrates, spray pyrolysis is the simplest and most economical, with great potential for upscaling. However, the relative importance of the experimental variables that influence the optoelectronic properties remains barely addressed. Following this premise, the present work aimed at optimizing the deposition of FTO films on soda lime glass (SLG) substrates by spray pyrolysis following a Design of Experiments (DoE) methodology. The optoelectronic properties of FTO-SLG substrates was evaluated based on their optical transmittance and sheet resistance, both combined in a figure of merit (FoM) tailored for PV applications. It was concluded that the volume of sprayed solution and the fluorine/tin ratio in the precursor have the greatest influence in the FoM, being the optimal deposition conditions a sprayed volume of 60.8 ml and a [F]/[Sn] ratio of 0.45. FTO-SLG substrates prepared with these conditions achieved a FoM of 0.680 Ω□−1/10, corresponding to a sheet resistance of 3.40 Ω□ and a transmittance equivalent to 77% of the maximum current generated in the considered spectrum. The improved FoM was validated in dye-sensitized and perovskite solar cells (DSSCs and PSCs, respectively), assembled with in-house optimized and commercial substrates. The efficiency of DSSCs was improved by 8.9% (relative), whereas PSCs achieved a light-to-power efficiency of 17% (absolute), corresponding to an improvement of 4.7% (relative).

Femtosecond Laser Fabrication and Ultrafast Dynamics Study on FTO Film

Transparent conductive oxides (TCO) are widely used in optoelectronic devices due to their high visible light transmittance and high electrical conductivity. Fabricating micro-nano structures on TCO films with femtosecond lasers can further enhance their optoelectronic properties. However, most of the existing researches on femtosecond laser processing of TCO films focus on materials such as indium tin oxide (ITO) and ZnO, and the research on fluorine-doped tin oxide (FTO) is still insufficient. In this paper, the ablation rules of FTO film irradiated by femtosecond laser is studied in detail. When the fluence is reduced to 1/e2 of the peak value as the radius of the laser spot, the ablation threshold measured by epitaxy method is 1.27 J/cm2. The experiment explores the ablation morphology of FTO film irradiated by single femtosecond laser pulse. When the laser fluence is 2.8-8.3 J/cm2, a bowl-shaped micro-crater is ablated, and when the laser fluence is 9.6-23.4 J/cm2, a secondary crater with a vertical inner wall and a flat bottom generates in the center of the ablated bowl-shaped crater. The pump-probe technique was used to study the ultrafast dynamics of the femtosecond laser interaction with FTO film, and we found that the phase explosion was responsible for the bowl-shaped crater formation.

Growth, characterization, and photovoltaic application of copper oxide thin films

• CuO was obtained from the annealing of Cu 2 O electrodeposited on SnO 2 :F electrodes. • Optical properties were modeled in the visible and near-infrared ranges. • Photoelectrochemical measurements confirmed a possible absorber layer application. • CuO samples have presented a strong photocurrent generation. This work presents the fabrication of Cu 2 O thin films using electrodeposition at room temperature. These have been grown using a copper (II) sulfate electrolyte (pH=10) on fluorine-doped tin oxide films. Thermal oxidation at standard atmosphere was applied to obtain CuO samples from Cu 2 O. The characterization of these copper oxide samples has revealed their morphological, compositional, crystalline, vibrational, and optical properties. These results indicate the desired features for photovoltaic conversion applications. Moreover, strong photocathodic current generation in these samples has been found using chronoamperometry. In addition, first-principles calculations based on generalized gradient approximation, in a Perdew-Burke-Ernzerhof parametrization, were performed to determine the structural, electronic, and optical properties of these copper oxides to help in the interpretation of the experimental results.

Laser scribing of fluorine-doped tin oxide coated on glass substrate in air and water

Fluorine-doped tin oxide (FTO) is one of the conductive layers used in the emerging perovskite solar cell technology, and the layer is typically scribed by a laser beam. However, thermal damage induced by laser deteriorates the scribe quality and in turn reduces the efficiency of the solar panel. This paper compares five different laser scribing techniques for isolating the FTO on the film and substrate sides both in air and water environments. The width and depth of laser-scribed channels, as well as burrs height, produced by using the different techniques were examined and compared. A clean and consistent scribe with negligible burrs was achievable by ablating the FTO film in the flowing water layer. Using this technique, its burr height index was found to reduce by 62.5% compared to the laser scribing of FTO film in air. A three-dimensional transient heat transfer model was also developed in this study to simulate the temperature field of workpiece subjected to the laser scribing in air and in flowing water environments. The thermal damage region was substantially small when the ablation was performed in the flowing water film. This could be a promising technique for the P1 scribing step in the manufacturing of emerging perovskite solar modules.

Measurement of the Surface Electrical Resistance of SnO2:F Thin Films

In this work, thin films of tin oxide doped with fluorine and of nominal surface resistance between 30 Ω and 40 Ω were deposited by RF sputtering in a plasma deposition system and their surface electrical resistances were evaluated for different conditions. To measure the resistivity of the fluorine-doped tin oxide film using an aluminum PAD with the same thickness and the same width as the film, a Minipa digital multimeter acting as an ammeter, a DC voltage source, and wires with banana-alligator connectors were used at six intervals (between the aluminum measuring tips and the PADs). Thus, a linear approximation and verification of the resistance value for each measured distance were undertaken. Resistances ranging from 44.10 Ω/ to 88.10 Ω/ for separations of 6 and 1 cm, respectively, were found. With the values obtained, the respective graphs were plotted for the six separations. The four-point method was employed to obtain four measurements (M1 to M4), and the curves of voltage as a function of the current were obtained. Values of resistance ranged from 11.4 Ω (M4) to 29.1 Ω (M3).

Definition of the influence of pulsed deposition modes on the electrochromic properties of Ni(OH)2-polyvinyl alcohol films

In this work, the influence of some types of the pulsed deposition mode of electrochromic films from aqueous solutions of nickel nitrate with the addition of polyvinyl alcohol was investigated. Glass coated with a fluorine-doped tin oxide film was used as the basis for deposition. The deposition of nickel (II) hydroxide – polyvinyl alcohol electrochromic films was carried out in three pulsed modes: –0.2 mA/cm2×5 s, 0 mA/cm2×5 s (10 minutes); –0.5 mA/cm2×2 s, 0 mA/cm2×8 s (10 minutes); –1 mA/cm2×1 s, 0 mA/cm2×9 s. In this case, the amount of electricity used for the formation of thin-film electrodes was the same for all samples. The resulting films showed dramatic differences in electrochemical, optical, and quality characteristics. The sample obtained in the mode of the highest cathode current density and the duration of the no-current condition (1 mA/cm2×1 s, 0 mA/cm2×9 s) had the worst specific capacity and optical characteristics. This sample was characterized by the highest number of coating defects and color non-uniformity as well. The sample, which was obtained at average current densities (–0.5 mA/cm2×2 s, 0 mA/cm2×8 s), had the highest specific characteristics among the electrodes in the series. The coating was uniform and solid. Also, this sample had the greatest stability of the coloration depth value, which varied from 79.1 to 78.1 % (first to fifth cycles). The sample obtained in the mode –0.2 mA/cm2×5 s, 0 mA/cm2×5 s showed moderate specific indicators, however, there were some coating defects. According to the results obtained, a mechanism was proposed that explained the differences in the characteristics of thin-film electrodes formed in different modes. This mechanism consists of changing the time of non-stationary processes and the distribution of the current density with a change in the value of the deposition current density, the duration of the cathode period, and the no-current condition.

Synthesis and optical characterization of nanocrystalline fluorine-doped tin oxide films: conductive window layer for optoelectronic applications

Synthesis and optical characterization of nanocrystalline fluorine-doped tin oxide films: conductive window layer for optoelectronic applications