Fluorine-doped Zinc Oxide Research Articles

Effect of solutions acidity on Haacke’s Figure of Merit of ZnO and ZnO:F thin films deposited by ultrasonic spray pyrolysis

Fluorine-doped zinc oxide (ZnO:F) thin films are valued for their potential as transparent conductive materials, particularly in optoelectronic applications. In this work, the deposition of highly conductive and transparent fluorine-doped ZnO thin films, deposited by chemical spray on glass substrates is reported. The effect of acetic (AcAc) in the initial fresh solution on Haacke’s Figure of Merit (Φ) of both zinc oxide (ZnO) and fluorine-doped zinc oxide (ZnO:F) thin films was studied. The substrate temperature was fixed to 450°C, and two deposition times (8 and 14 min) were tested. Accordingly, the optical and transport properties, as well as the structural and morphological characteristics of the films were measured. The results indicate that the samples are polycrystalline in all cases and exhibit a wurtzite-type structure of ZnO. The variation of AcAc in the starting solution causes a switch in preferential growth from (002) to (001). As the AcAc content increases, the surface morphology of the films reveals the formation of well-defined hexagonal grains, and the grain size increases. Conversely, the transmittance decreases as the acetic acid increases, which can attributed to carbon incorporation into the film. In addition, the band gap values of the films varied from 3.2 to 3.4 eV. Also, as the acetic acid concentration increased, a drop in the electrical resistivity of ZnO thin films on the order of 0.016 Ω⋅ cm was found for the ZnO:F films deposited with fresh solution for 14 min. This can be ascribed to a dense acetic cloud formed during the synthesis process, trapping volatile F species that incorporate into the ZnO lattice. This enhances Haacke’s Figure of Merit of ZnO:F films deposited with a fresh solution, demonstrating their potential use for application as transparent conductive films. This contrasts with other synthesis methods that require longer aging time in the precursor solution, making these findings useful for large-scale and more efficient production of transparent conductive films.

Synergizing tin dioxide/perovskite interface with fluorine-doped zinc oxide for stabilized and efficient carbon-based perovskite solar cells

The new generation of solar cell technology, perovskite solar cells (PSCs), are the most promising candidates to meet global energy demands. In the current study, we improved the efficiency of their cost-effective type, i.e., carbon-based PSCs, by employing an interface engineering on the tin dioxide (SnO2) electron transport layer (ETL). A fluorine doped-zinc oxide material was used to treat the SnO2 layer and prepare a better substrate for perovskite fabrication. The fabricated perovskite layer on the treated SnO2 reveals better charge transfer, lower charge recombination, and lower leakage current. In addition, the fabricated perovskite layer on the modified ETL showed improved crystalline properties with passivated grain boundaries. As a result, a champion efficiency of 15.22% was recorded for the target carbon-based PSCs, referring to improved photovoltaic performance. Notably, the target devices showed a higher stability behavior against ambient air and kept 95% of their initial efficiency after 1658 h ageing time.

Comparative study of optical properties of ZnO Zinc Blend and Rock Salt structures, TB- mBJ and GGA approximations

Currently, the most used transparent conductive oxide (TCO) is the indium tin oxide (ITO). The need for a material that can replace this TCO comes in many studies. Among these materials, we have discussed zinc oxide (ZnO). This work is carried out using full-potential linear augmented plane wave (FP-LAPW) and implemented in the Wien2k. Since the ZnO alloy has different structures, this study aims to discuss the optoelectronic behavior of the F doped ZnO with its different phases and the doping concentration variation where the amount of F is 3.125%, 6.25% and 12.5%. in the visible light range. The comparison between the Rock Salt and Zinc Blend structures gives a starting point to be compared with the third structure which is Wurtzite. TB-mBJ was applied to compare the promising results found by the GGA approximation. Its optoelectronic properties make fluorine-doped ZnO a promising candidate for optoelectronic applications.

Photocatalytic degradation of methylene blue dye using F doped ZnO/polyvinyl alcohol nanocomposites

The photocatalytic activity of fluorine-doped zinc oxide (ZnO-F) nanoparticles (NPs) is improved with the assistance of polyvinyl alcohol (PVA). ZnO-F NPs were synthesized through a co-precipitation reaction of zinc nitrate and ammonium fluoride. The obtained ZnO-F NPs were capped with various amounts of PVA, utilizing a facile solution-based approach. XRD patterns showed that PVA polymer didn’t alter the crystallinity properties of ZnO NPs and its hexagonal wurtzite structure with prominent orientations of (100), (002), and (101) was preserved. While UV–Vis spectra revealed that the optical band of nanocomposites varies with increasing amounts of PVA from 2.10 eV for ZnO-F NPs to 2.13 eV for 4% PVA loaded-ZnO-F. The data showed when the weight ratio of PVA polymer with respect to the neat ZnO NPs is fixed at 4% during the synthesis process, the highest photocatalytic activity for hybrid NPs is achieved.

Effect of trisodium citrate on morphological, structural, and optical properties of fluorine-doped ZnO structures

In this work, we present the effect of trisodium citrate (TSC) addition via a hydrothermal method on the morphological, compositional, structural, and optical changes of fluorine-doped zinc oxide (FZO) on silicon substrates. Field emission scanning electron microscopy revealed vertically aligned nanorods for FZO and pebble and block-like microstructures of different sizes upon TSC addition. X-ray diffraction analysis revealed a hexagonal structure for all the samples. Upon addition of TSC, the sample growth along the c-axis was inhibited strongly and the growth along the a-axis was developed. The crystallite size increased from 28.73 nm to 30.38 nm upon addition of TSC. The oxygen deficiency and, the presence of zinc, oxygen, fluorine, and sodium in the studied samples were confirmed by energy-dispersive X-ray analysis and X-ray photoelectron spectroscopy (XPS). Ultraviolet (UV)-visible analysis revealed the optical energy band gap increment from 3.204 eV to 3.241 eV with TSC addition. Photoluminescence (PL) analysis revealed a significant improvement in the intensity ratio of the near band emission to deep level emission from 5.44 to 12.59 upon TSC addition, indicating crystal quality improvement. Both UV–visible and PL analyses showed that the studied samples were blue-shifted upon TSC addition. The different morphologies with promising properties could be employed in different applications, eliminating the complexity and reducing cost in the fabrication of hybrid structures, and nano/microcomposites.

Structural, optical and electrical properties of F doped ZnO films: Experimental and theoretical study

In this paper, we theoretically and experimentally investigated the structural, optical and electronic properties of Fluorine-doped zinc oxide (FZO) with different concentrations of the doping element. The undoped and F doped ZnO thin films have been elaborated on glass substrate by spray pyrolysis technique. X-ray diffraction (XRD) and photoluminescence measurement are used to characterize the structural and optical properties of ZnFxO1-x films with x = 0.0, 0.02, 0.05, 0.07. The results showed that all the elaborate thin films crystallize in the hexagonal structure of the wurtzite type with a preferential orientation of the crystallites along the direction (002) along the c axis perpendicular to the surface of the substrate. All FZO thin films had relatively higher average transmittances, approximately 80–90%, in the visible region as compared to the undoped ZnO thin films. The electronic band structure, total and partial density of states of FZO were investigated studied by Density Functional Theory to examine the change in the band gap of ZnO with F doping. The results of this study indicate that with the increase of the fluorine concentration in the ZnO matrix, the band gap energy decreases which is in good agreement with the experimental results.

Enhanced sensitivity of low-cost fabricated fluorine doped ZnO metal semiconductor metal photodetector

The literature mostly reports on thin-film fluorine-doped zinc oxide (FZnO) and has yet to fabricate metal semiconductor metal (MSM) photodetectors (PDs) based on FZnO nanostructures for the enhancement of photoresponse parameters despite their huge potential. In this work, ZnO film of 32 nm-thick was deposited and used as a seed layer on silicon (Si) substrates with the aid of the radio frequency (RF) magnetron sputtering method. Vertically well-aligned FZnO nanorods (NRs) were later grown on the seeded substrates via a hydrothermal method and annealed for 1 h at 400 °C. The formation of well-aligned hexagonal NRs at low fluorine doping was revealed by field emission scanning microscopy (FESEM), and energy-dispersive X-ray (EDX) analysis confirmed the presence of fluorine doping. X-ray diffraction (XRD) investigation confirmed the growth of good crystal quality hexagonal wurtzite F–ZnO NRs along the (002) direction, and bandgaps were estimated using UV–Vis–NIR spectroscopy. Photoluminescence (PL) measurement has revealed the main emission peak for ultraviolet (UV) is centered at 375 nm and a red-shifted emission with fluorine doping has been identified. An F2 UV MSM PD device is fabricated. Upon exposure to UV light (395 nm) at 4 V, it displayed a high sensitivity of 1.1 × 105%, responsivity of 0.66 A/W, detectivity of 1.30 × 1010 Jones, a response time of 90 ms, and recovery time of 110 ms.

Effect of fluorine doping concentration on efficiency of ZnO/p-Si heterojunction solar cells fabricated by spray pyrolysis

The paper reports the fabrication of fluorine-doped zinc oxide/p- silicon (ZnO/p-Si) heterojunction solar cells and the effects of fluorine content on efficiency of these solar cells. Fluorine-doped zinc oxide nanoparticles (FZO) were synthesized using sol–gel method and heterojunctions of n-FZO/p-Si solar cells were fabricated by the spray pyrolysis technique. FZO thin films were also deposited on the glass substrate under the same conditions for the investigation of their optical properties. The structural characterizations of FZO films were investigated using scanning electron microscopy (SEM) and X-ray diffraction (XRD). Optical characterization of these thin films was studied by UV–Vis spectroscopy and transmittance values of over 84% were obtained at the visible region. The current–voltage characteristic of the n-FZO/p-Si heterojunction solar cells was measured at room temperature in the dark and under illumination (90 mW/cm2). Series resistance (Rs) values obtained from solar cells were found between 5.52 and 10.12 Ω. The conversion efficiency of the fabricated solar cell of between 3.82 and 6.74% was obtained.

Enhanced photovoltaic performance and stability of dye-sensitized solar cells by utilizing manganese-doped ZnO photoanode with europium compact layer

Zinc oxide (ZnO)-nanoparticles based photoanodes are one of the most important photoanodes in dye-sensitized solar cells (DSSCs). However, ZnO-based photoanodes have disadvantages such as low photovoltaic performance and low stability compared to titanium dioxide (TiO2)-nanoparticles based photoanodes. In this current work, two different strategies have been simultaneously applied to eliminate these disadvantages of ZnO photoanodes and to prepare more efficient photoanode for DSSCs applications. In the first strategy, europium (Eu) compact layer has been deposited between fluorine-doped tin oxide (FTO) substrate and ZnO paste in order to increase the current density of DSSCs by benefiting down-conversion and photoluminescence properties of Eu. In the second strategy, manganese (Mn) ions have been doped into the ZnO structure at different ratios in order to enhance the electron transport mechanism of the ZnO photoanode and to increase the stability of the obtained DSSCs. As a result of these two strategies, the obtained DSSC performance with 1.0 mol% Mn doping and Eu compact layer showed a conversion efficiency of 4.20%, which is much higher than pure ZnO DSSC photoanode employing (1.45%). More importantly, the device showed considerable stability and repeatability under the constant light for 3000 s. Considering this improved performance and stability of DSSCs, this work may guide different lanthanide compact layers and different doping sources in order to further improve the performance and stability of DSSCs.

Effect of anionic fluorine incorporation on structural, optical and electrical properties of ZnO nanocrystalline films

ZnO and ZnO:F (fluorine doped Zinc oxide) films have been deposited on glass substrates at 325 ± 5 °C through ultrasonic spray pyrolysis method (USP). X-ray diffractometer (XRD) has been utilized to determine the crystal structural and some structural parameters such as lattice constants, texture coefficients TC (hkl), crystallite size and dislocation densities of all the ZnO films. The XRD results have revealed that all the ZnO films have the hexagonal wurtzite structure and F incorporation shows no significant effect on the crystal structure. X-ray photoelectron spectroscopy (XPS) measurements have confirmed the presence of fluorine atoms in the ZnO lattice and also the existence of Zn–F bonding states. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) measurements have been carried out to investigate the effect of F doping on the surface morphology of the ZnO films. The optical properties of the films have been analyzed by utilizing transmittance, absorbance and reflectance measurements. Some optical parameters such as extinction coefficient (k), refractive index (n) and optical conductivity have been determined depending on the change in F incorporation. Increasing the F doping initially led to a decrease in the optical band gap, but later increased. Electrical resistivity and carrier concentration values of the deposited films have been determined with Hall effect measurement system and it has been detected that 6% F-doped ZnO film has the minimum resistivity and maximum carrier concentration.

Solar photocatalytic degradation of diclofenac aqueous solution using fluorine doped zinc oxide as catalyst

The photocatalytic degradation of a sodium diclofenac (DCF) solution (10 mg/L) under simulated solar radiation was evaluated using a ZnO semiconductor modified by the incorporation of 10, 15, and 20 wt.% fluorine (ZnO-F10, ZnO-F15 and ZnO-F20). The ZnO-F catalysts were synthesized by the sol-gel method using zinc acetate as a precursor of zinc oxide and NH4F as a fluorine source. The photocatalytic performance of the F-doped ZnO material was compared to that of bare ZnO. The obtained photocatalysts were characterized using X-ray diffraction (XRD), Scanning electron microscopy with Energy dispersive spectroscopy (SEM-EDS) and X-ray photoelectron spectroscopy (XPS) techniques. The Brunauer-Emmett-Teller (BET) surface area, pH of zero charge (pHpzc), and band gap of the solids were also evaluated. An experimental Box-Behnken design combined with response surface methodology was applied to establish the optimal conditions for the photocatalytic degradation of the DCF solution. Complete DCF degradation, total release of chloride ions, and approximately 90% mineralization were achieved during degradation of the drug at an accumulated energy of 400 kJ/m2 under the optimized experimental conditions (1 g/L of ZnO-F20 catalyst with the pH of the DCF solution maintained at 6.5).

Transparent Conductive Oxide Thermoelectric (TCO-TE) Generators: Fabrication and Comparing of ZnO, SnO2, Fluorine Doped Tin Oxide and Fluorine Doped Zinc Oxide Materials as TCO TE Generators

Transparent Conductive Oxide Thermoelectric (TCO-TE) Generators: Fabrication and Comparing of ZnO, SnO₂, Fluorine Doped Tin Oxide and Fluorine Doped Zinc Oxide Materials as TCO TE Generators

Optimization of a Hydrothermal Growth Process for Low Resistance 1D Fluorine-Doped Zinc Oxide Nanostructures

Design of Experiment (DOE) has been used for the optimization of a hydrothermal growth process of one-dimensional fluorine-doped zinc oxide (1D-FZO). Box-Behnken design was used in the DOE which includes three design points on each of the synthesis condition parameters. The condition parameters were the gold sputtering time (10 s, 15 s, and 20 s), hydrothermal reaction time (3 hours, 6.5 hours, and 10 hours), and hydrothermal temperature (50°C, 75°C, and 100°C). This statistical method of DOE was used to study the effects of these hydrothermal conditions on the quality of 1D-FZO produced. Au nanoparticles were used as the catalyst to enable the growth of the 1D-FZO. The XRD and EDX analysis confirmed the formation of polycrystalline FZO with the presence of fluorine, zinc, and oxygen elements. SEM observations indicated that the sputtering time of the Au nanoparticles has significant effect on the morphology and growth process of 1D-FZO. The lowest resistance value of 22.57 Ω was achieved for 1D-FZO grown with the longest Au sputtering time at growth temperature below 100°C.

Humidity sensing properties of fluorine doped zinc oxide thin films

In this study, the effect of fluorine (F) doping on the humidity sensing properties of F doped zinc oxide structures was investigated. Undoped zinc oxide (ZnO) and F doped zinc oxide (FZO) nanoparticles were synthesized by sol gel method. The synthesized nanoparticles were coated on glass substrates by dip coating method. In the coating process, the glass substrates were immersed in undoped ZnO and FZO solutions and withdrawn at a rate of 25 cm/s at room temperature. Then, the thin film coated glasses are annealed in a square furnace at 500 °C for 1 h. Structural analyzes of the produced thin films were performed using X-ray diffraction and scanning electron microscopy. The thin film nanostructures were placed in the homemade system in order to investigate the humidity sensing characteristics such as relative humidity dependent resistance change, sensitivity, hysteresis, stability, response and recovery times and reproducibility. As a result, it is predicted that the FZO structures can be used in the humidity sensing applications and it is determined that the optimal F additive amount for application is 2 mol%.

Effect of doping concentration, solvent proportions and solution aging on the figure of merit of chemically sprayed ZnO:F thin films

Undoped zinc oxide (ZnO) and fluorine doped zinc oxide (ZnO:F) thin films were deposited on sodalime glass substrates by the ultrasonic chemical spray technique. The effect of the relevant deposition variables, namely, doping concentration, solvent proportions and solution aging on the Haacke´s Figure of Merit, φM, of ZnO:F thin films, is reported for the first time. φM was evaluated from the optical and electrical characteristics of the films. A wide range of F/Zn doping from 5 to 90 at%, in the starting solution, was used due to the high volatility of F during the deposition process and the concomitant poor incorporation into the ZnO lattice. In order to have F-doped solutions with high chemical stability, a mix of acetic acid:water:methanol, at different volume proportions, were tested as solvent; nevertheless the φM magnitudes remain unchanged, irrespective of solvent proportions. Regarding solution aging, despite it is a deposition variable that no plays any role in similar wide band gap semiconductor oxides, in the case of ZnO:F films, φM was significantly influenced through the electrical transport properties. Complementary information on structural and morphological characteristics of deposited ZnO:F thin films, for films with high φM, is also reported. From the results, optimization of deposition variables was achieved, as highly conductive and transparent ZnO:F thin films with a maximum, φM = 7.57 × 10−3 (Ω/□)−1, were deposited with a doping concentration of 30 at%, solvent proportion of 50:50:900, and an aging of 37 days. The obtained results show that ZnO:F thin films are potential candidates for transparent conductive oxide applications.

Controlled defects and enhanced electronic extraction in fluorine-incorporated zinc oxide for high-performance planar perovskite solar cells

Oxygen-related defects in the intrinsic metal-oxide films restrict the transportation and collection processes of photogenerated carriers from the perovskite film to charge transport layers, which obstruct the applications of metal-oxide films in perovskite solar cells (PSCs). In this study, fluorine as an anion dopant was introduced to modify the oxygen-related defects in the intrinsic zinc oxide (ZnO). The impact of fluorine concentration on the structural, electrical, and optical characteristics of solution-processed ZnO films was systematically investigated. When the fluorine concentration was optimized to 15%, fluorine-doped ZnO (ZnO:F) film exhibited multiple advantageous effects, such as large crystalline size, low oxygen-related defect state density, good hydrophobic surface, and high conductivity. Furthermore, ZnO:F films with various fluorine concentrations as electron transport layers (ETLs) were introduced into the PSCs. The PSCs based on the ZnO:F ETL with the fluorine concentration of 15% yielded a maximum power conversion efficiency of 16.23% owing to the improvements of short-circuit current and fill factor. Meanwhile, the thermochemical stability of the device based on the ZnO:F ETL was also significantly improved.

A Rapid Deposition of Fluorine Doped Zinc Oxide Using the Atmospheric Pressure Chemical Vapour Deposition Method

Fluorine-doped zinc oxide (FZO) (ZnO:F) thin films were manufactured by atmospheric pressure chemical vapor deposition (APCVD) on glass substrates using zinc acetate dihydrate [C4H6O4Zn·2H2O, ZnAc] and ammonium fluoride (NH4F) as the source of fluorine with deposition duration of only 120 s for each sample. The effects of different amounts of fluorine as the dopant on the structural, electrical and optical properties of FZO thin films were investigated. The results show a polycrystalline structure at higher temperatures compared to amorphous structure at lower temperatures. The x-ray diffraction patterns of the polycrystalline films were identified as a hexagonal wurtzite structure of zinc oxide (ZnO) with the (002) preferred orientation. Also, the sheet resistance decreased from 17.8 MΩ/□ to 28.9 KΩ/□ for temperatures 325°C to 450°C, respectively. In order to further decrease the sheet resistance of the undoped ZnO thin films, fluorine was added using NH4F as the precursor, and again a drastic change in sheet resistance of only 17.7 Ω/□ was obtained. Based on the field emission scanning electron microscopy images, the fluorine concentration in CVD source is an important factor affecting the grain size and modifies electrical parameters. Ultraviolet–visible measurements revealed reduction of transparency of the layers with increasing fluorine as the dopant.

Ethylzinc‐ and Zinc–bis–fluoroalkoxides

AbstractWe describe synthesis routes from fluorinated ethylzinc alkoxides to ether adducts of fluorinated binary homoleptic zinc alkoxides with fluorinated residues such as ORF (OC(CF3)3), ORHF (OC(H)(CF3)2), ORHT (OC(CH3)(CF3)2), ORAF (perfluoroadamantoxy) and ORCY (OC(CF3)(CF2)5). Their structures depend on the nature of the fluorinated residue: perfluorinated alkoxides ORXF tend to give monomeric ether adducts (ether)2Zn(ORXF)2, while partially fluorinated residues ORYF lead to dimers of type (ether)(YFRO)Zn(μ‐ORYF)2Zn(ORYF)(ether). The monomeric (Et2O)2Zn(ORF)2 was tested for its possibility to form fluorine doped zinc oxide upon thermal decomposition in inert atmosphere. Indeed, upon thermal degradation, homogenously doped materials (EDX mapping) with fluoride contents of 5.5 to 6 weight‐% form (EDX, ion chromatography).

Numerical Simulation of CuInSe<sub>2</sub> (CIS) Thin Film Solar Cell with (ZnO, ZnO:F) Buffer Layers

This study focuses on the solar cells based on CIS simulation with buffer layer zinc oxide (ZnO) and fluorine-doped zinc oxide (ZnO:F). ZnO is a multifunctional material with several applications in electronics and photovoltaics, with multiple possibilities of synthesis involve inexpensive methods. ZnO (ZnO:F) is a prominent candidate to be an alternative buffer layer to so-called toxic cadmium sulphide (CdS) in CIS based solar cells. A promising result has been achieved with an efficiency of 22% with Voc = 0.565 V, Jsc = 45 mA/cm² and fill factor = 82% by using ZnO (ZnO:F) as a buffer layer. It is also found that the high efficiency of CIS absorber layer thickness is between 1500nm and 2000nm. Our results are in good agreement with those reported in the literature from experiments.

Highly improved photo-induced bias stability of sandwiched triple layer structure in sol-gel processed fluorine-doped indium zinc oxide thin film transistor

In order to improve the reliability of TFT, an Al2O3 insulating layer is inserted between active fluorine doped indium zinc oxide (IZO:F) thin films to form a sandwiched triple layer. All the thin films were fabricated via low-cost sol-gel process. Due to its large energy bandgap and high bonding energy with oxygen atoms, the Al2O3 layer acts as a photo-induced positive charge blocking layer that effectively blocks the migration of both holes and V o2+ toward the interface between the gate insulator and the semiconductor. The inserted Al2O3 triple layer exhibits a noticeably low turn on voltage shift of −0.7 V under NBIS as well as the good TFT performance with a mobility of 10.9 cm2/V ⋅ s. We anticipate that this approach can be used to solve the stability issues such as NBIS, which is caused by inescapable oxygen vacancies.