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Dye-sensitized solar cells were fabricated on flexible substrate from TiO2 nanoparticles by compression at room temperature and at elevated temperature. It was found that short circuit current increases and the thickness decreases with... more
Dye-sensitized solar cells were fabricated on flexible substrate from TiO2 nanoparticles by compression at room temperature and at elevated temperature. It was found that short circuit current increases and the thickness decreases with increasing the pressure during the compression. The conversion efficiency was improved by employing hot-pressing method where the compression is done at elevated temperature. This is due to the improvement of necking between TiO2 nanoparticles.
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An intrinsic silicon nanoparticle (i-SiNP) layer was fabricated using the spin-coating technique and utilized as the active layer of a solar cell. The electrical conductivity of the i-SiNP layer was enhanced via press treatment, which... more
An intrinsic silicon nanoparticle (i-SiNP) layer was fabricated using the spin-coating technique and utilized as the active layer of a solar cell. The electrical conductivity of the i-SiNP layer was enhanced via press treatment, which increased the density and electrical conductivity of the SiNPs. Raman spectroscopy and electron-spin resonance results indicated that the SiNPs were only in contact with each other and were not bound together. To fabricate a solar cell with an i-SiNP active layer, a-Si was used to synthesize the p- and n-type doping layers. The open-circuit voltage of the cell was 140mV.
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... Cassell, N. Franklin, E. Chan, J. Han, H. Dai; J. Am. Chem. Soc., 121 (1999), p. 7959. [8]; R. Kamalakaran, M. Terrones, T. Seeger, Ph. Kohler-Redlich, M. Ruhle, YA Kim, T. Hayashi, M. Endo; Appl. Phys. Lett., 77 (2000), p. 3385. ...
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ABSTRACT This article presents the fabrication of dye-sensitized solar cells on plastic films by hot-pressing method. It is shown that the conversion efficiency is improved with increasing temperature during the compression of TiO2... more
ABSTRACT This article presents the fabrication of dye-sensitized solar cells on plastic films by hot-pressing method. It is shown that the conversion efficiency is improved with increasing temperature during the compression of TiO2 photoanode with maxima at 80 °C. The conversion efficiency of dye-sensitized solar cell by hot-pressing method is higher than that fabricated by compression at room temperature followed by sintering.
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In this paper, ZnO thin film has been synthesized on fluorine doped tin oxide (FTO) glass substrate by annealing the Zn film in air flow. The SEM image shows that the high density and thread-like ZnO nanowires could grow on the thin film.... more
In this paper, ZnO thin film has been synthesized on fluorine doped tin oxide (FTO) glass substrate by annealing the Zn film in air flow. The SEM image shows that the high density and thread-like ZnO nanowires could grow on the thin film. XRD pattern shows that ZnO was the only compound. The high-resolution transmission electron microscopy (HRTEM) results of individual ZnO nanowires show that the nanowires grown on the ZnO thin film are single-crystalline, and the selected area electron diffraction pattern (SAED) shows that the nanowires grow along the (001) direction.
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This study aims to fabricate copper oxide (CuO) nanowires by annealing a copper film formed on a charged film of fluorine-doped tin oxide (FTO). However, from the viewpoint of stress and growth of nanowires, it is difficult to... more
This study aims to fabricate copper oxide (CuO) nanowires by annealing a copper film formed on a charged film of fluorine-doped tin oxide (FTO). However, from the viewpoint of stress and growth of nanowires, it is difficult to mass-produce CuO nanowires on the entire region of the macro area on the plane substrate. In the proposed study, this was made possible by modifying the substrate’s structure.
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Single phase CuO films have been successfully synthesized by thermal oxidation of cupper foil in air with water vapor. The structural and optical properties of CuO films were investigated. It is observed that the grain size increases with... more
Single phase CuO films have been successfully synthesized by thermal oxidation of cupper foil in air with water vapor. The structural and optical properties of CuO films were investigated. It is observed that the grain size increases with increasing the oxidation temperature. The optical band gap of CuO film is determined by the transmittance and reflectance spectra.
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Bi5O7I is one of the bismuth oxyiodides family members which is commonly utilized for photocatalyst, but it has not been applied yet as a photovoltaic material. Herein, we study the effect of Bi5O7I addition to TiO2 for the photovoltaic... more
Bi5O7I is one of the bismuth oxyiodides family members which is commonly utilized for photocatalyst, but it has not been applied yet as a photovoltaic material. Herein, we study the effect of Bi5O7I addition to TiO2 for the photovoltaic device which worked based on the dye-sensitized solar cell (DSSC). A better photovoltaic performance was performed by using TiO2/Bi5O7I composite than the TiO2 based DSSC. The different ratios of Bi5O7I mixed with TiO2 resulted in the TiO2/Bi5O7I composite material films which were characterized on their structural, morphological, and optical properties. X-ray diffraction and scanning electron microscope analysis results displayed the crystal character and the morphology of Bi5O7I and TiO2 in our films. In addition, the existence of Bi5O7I in the films had an impact on the decreasing in the bandgap energy of composite materials. Moreover, the solar cell performance test with I−/I3− electrolyte solution, Pt-FTO counter electrode, and N719 dye was carried out to the composite cells. As a result, there was a slight increase in the current density and open-circuit voltage. Also, the cell efficiency could enhance up to 60% in comparison to the TiO2-DSSC in this report.
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Abstract In this paper, we report the successful synthesis of BiI3 nanofibers by using spin-coating technique for the first time. The precursor, bismuth triiodide (BiI3) and methylammonium iodide (MAI) nanopowder were treated in a N,... more
Abstract In this paper, we report the successful synthesis of BiI3 nanofibers by using spin-coating technique for the first time. The precursor, bismuth triiodide (BiI3) and methylammonium iodide (MAI) nanopowder were treated in a N, N-Dimethylformamide (DMF) solution with fixed amount while the mass of BiI3 was varied. The field-emission scanning electron microscopy (FESEM) images showed that the nanofibers were grown at larger amount of BiI3. The mechanisms for the synthesis of nanofibers were also proposed. This preliminary work results were suggested for further improvement of surface morphological and structural properties of Bi-perovskite based solar cell in future.
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In this study, short-circuit current density (Jsc) and power conversion efficiency were analyzed for dye-sensitized solar cells (DSSCs) which were prepared by electrophoretic deposition (EPD) of zinc oxide (ZnO) nanoparticles on... more
In this study, short-circuit current density (Jsc) and power conversion efficiency were analyzed for dye-sensitized solar cells (DSSCs) which were prepared by electrophoretic deposition (EPD) of zinc oxide (ZnO) nanoparticles on fluorine-doped tin oxide (FTO) glass substrates under mechanical compression and post-annealing. The JSC 12.98 mA/cm2 and power conversion efficiency 3.82% were obtained at 42 MPa mechanical pressure and 400° C post-annealing temperature. In this investigation, photoanodes were annealed at different temperatures to study the effect of the post-annealing temperature on the performance of DSSCs. The performances of the cells were analyzed by i-v, UV-Vis-NIR, and scanning electron microscopy (SEM) image. The photovoltaic performance was found to be improved with the application of mechanical compression and post-annealing temperature compared with the DSSCs without having these post surface treatments.
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Diamond-like carbon (DLC) films are prepared by a bipolar-type plasma-based ion implantation (PBII) technique using toluene and nitrogen gases (N2), and the optical and electrical properties are examined as a function of N2 flow rate. The... more
Diamond-like carbon (DLC) films are prepared by a bipolar-type plasma-based ion implantation (PBII) technique using toluene and nitrogen gases (N2), and the optical and electrical properties are examined as a function of N2 flow rate. The N concentration in the films and structural changes are also examined by Rutherford backscattering spectrometry (RBS), atomic force microscopy (AFM), and Raman spectroscopy. It is found that the deposition rate decreases, but N concentration linearly increases with increasing N2 flow rate. Granular surfaces are observed and the grains decreases in size as N2 flow rate increases. In addition, Raman analysis suggests that aromatic ring clusters and the amorphous structure increase in amount. The optical band gap and conductivity increase with increasing N concentration up to about 11 at. %, and then decrease with further increase in N concentration.
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In this study, dye-sensitized solar cell (DSSC)/silicon tandem solar cells were fabricated by changing the buffer layer structure. When joining two cells, a buffer layer is important to efficiently transport electrons by suppressing... more
In this study, dye-sensitized solar cell (DSSC)/silicon tandem solar cells were fabricated by changing the buffer layer structure. When joining two cells, a buffer layer is important to efficiently transport electrons by suppressing buffer of electrons by a potential barrier. Therefore, we used PEDOT:PSS/ITO as buffer layer structures, and measured their solar cell characteristics. As a result, it was found that the structure in which both PEDOT:PSS layer and ITO layer are stacked as buffer layers is suitable for the buffer layer of DSSC/Si tandem cells. In addition, the characteristics improved each time DMSO was added to PEDOT:PSS, and as a result, the characteristics of tandem solar cells also tended to improve. The maximum conversion efficiency (Voc = 0.78 V, Jsc = 4.87 mA / cm2, FF = 0.62, Eff = 2.35 %) was obtained when the DMSO concentration was 1%. It was suggested that conversion efficiency can be improved by improving the buffer layer.
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To reduce the thickness of crystalline silicon solar cells, solar cell structures were fabricated using silicon nanoparticles (SiNPs). High resistivity of the SiNP film was achieved without any treatment because voids were located in the... more
To reduce the thickness of crystalline silicon solar cells, solar cell structures were fabricated using silicon nanoparticles (SiNPs). High resistivity of the SiNP film was achieved without any treatment because voids were located in the film. A hot press treatment was performed to increase the density of the film. After the hot press treatment at 100 °C under pressure of 30 MPa, the thickness of the SiNP film decreased from 627 to 409 nm. The resistivity successfully decreased to 0.50 MΩ/sq because its necking was improved via the hot press treatment..
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Bismuth oxyhalides are becoming a promising contender for photovoltaic applications due to its non-toxic nature and decent optical properties. This study mainly deals with clarifying the effects of phase transformations on the structure,... more
Bismuth oxyhalides are becoming a promising contender for photovoltaic applications due to its non-toxic nature and decent optical properties. This study mainly deals with clarifying the effects of phase transformations on the structure, optical, and electrical properties of BiOI thin film prepared via dip-successive ionic layer adsorption and reaction (SILAR) method at different annealing temperatures ranging from 100 to 400 °C. Therefore, significant phase transformations (i.e., the existence of Bi7O9I3 and Bi5O7I have been confirmed at 300 °C and 400 °C, respectively) appeared in the produced films, which were mainly due to the change of annealing temperatures. The experimental results confirmed that produced films achieved the maximum current density and efficiency and minimum current density and efficiency at 100 °C and 400 °C, respectively. Experimental results were also showed that with increasing the annealing temperature from 100 to 400 °C, the indirect bandgap risen from 1...
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As regards the copper oxide nanowire growth process, our experiment was consistent with the proposal of copper ions surface diffusion on a nanowire. Simply in the atmospheric pressure it is possible to synthesize CuO nanowires by... more
As regards the copper oxide nanowire growth process, our experiment was consistent with the proposal of copper ions surface diffusion on a nanowire. Simply in the atmospheric pressure it is possible to synthesize CuO nanowires by annealing a copper sheet. Under a general copper oxide nanowires occurring condition, pouring the flow rate of a slight amount of air into an enclosed electric furnace in the atmospheric pressure, copper oxide nanowires adhering copper particles were synthesized on copper sheet successfully. In the growth process of the CuO wire, when the Cu substrate was heated in the air, stresses caused grain boundaries of Cu2O and CuO layers in the Cu substrate. Ultimately Cu ions formed a wire tip diffusing on the surface of a CuO wire in the vertical direction to the top surface of the CuO layer, while assembling to the tip. In this report, we describe characteristics of the structure of the CuO nanowire obtained by lowering the air flow rate.
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In this investigation, low-cost commercial Degussa P25 TiO2-based dye-sensitized solar cells (DSCs) have been fabricated using electrophoretic deposition (EPD) along with a new post-deposition treatment named hot-compression. We have... more
In this investigation, low-cost commercial Degussa P25 TiO2-based dye-sensitized solar cells (DSCs) have been fabricated using electrophoretic deposition (EPD) along with a new post-deposition treatment named hot-compression. We have optimized the number of deposition layers and found that a four layer electrophoretic deposition gives a homogeneous crack-free photoelectrode. Multilayer deposition minimizes the cracks; while to ensure the uniformity of the deposited film's surface, we introduce a four-layer four-side electrophoretic deposition (4L4SEPD) technique. Then the electrophorically deposited substrates have been post-treated by a hot-compression followed by sintering. Performance of the DSCs fabricated by this way have been compared with the conventional post-treated (sintered, compressed at room temperature) DSCs. About 16%, 39%, and 70% enhancement in power conversion efficiency has been achieved in DSC devices with compression, hot-compression, and hot-compression followed by sintering, respectively as compared to the sintered device. Several characterizations including scanning electron microscopy (SEM), photocurrent-voltage (I-V) measurement, incident photon-to-electron conversion efficiency, transmittance, and electrochemical impedance spectra (EIS) have been employed to find the nature of improvement with the post-treatments. In detail investigations reveal that hot-compression improves the surface morphology, transmittance, and electron transport which in turn lead to a substantial enhancement of photocurrent and power conversion efficiency. Under an optimized hot-compression (40 MPa compression at 70 °C heating) followed by sintering conditions, the overall power conversion efficiency of a device with P25 TiO2 photoanode has reached to 4.98% under illumination of AM 1.5 G (100 mW · cm-2). This work demonstrates that 4L4SEPD combined with hot-compression post-treatment provides a way to fabricate highly efficiency DSCs.
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A Fe2O3 nanoflakes-based solar cell was successfully prepared by thermal oxidation of iron film on FTO glass. The short circuit current density [Formula: see text] of the cell increased with annealing time while the open circuit voltage... more
A Fe2O3 nanoflakes-based solar cell was successfully prepared by thermal oxidation of iron film on FTO glass. The short circuit current density [Formula: see text] of the cell increased with annealing time while the open circuit voltage was saturated after 1 h. This enhancement was caused by the increased surface area of the nanoflakes and improved electron transfer through the (110) crystal plane in the Fe2O3-based electrochemical solar cell. The overall photovoltaic performance significantly increased with ruthenium dye, which likely suppressed carrier recombination on the Fe2O3 surface.
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Metallic Cu nanowires have been synthesized by thermal reduction of CuO nanowires in low concentration hydrogen environment. The Cu nanowires can be formed after removing oxide group from the metal oxide nanowires within temperature range... more
Metallic Cu nanowires have been synthesized by thermal reduction of CuO nanowires in low concentration hydrogen environment. The Cu nanowires can be formed after removing oxide group from the metal oxide nanowires within temperature range from 200[Formula: see text]C to 500[Formula: see text]C. These nanowires have twisted structure with 100–200 nm and average lengths of 10 [Formula: see text]m can be obtained in optimum temperature range 300–400[Formula: see text]C reduced for 30 min. The X-ray diffraction (XRD) pattern shows Cu peaks recognized at (111), (200) and (220). Scanning electron microscopy (SEM) images reveal the reduction temperatures strongly affect the nanowires formation. Transmission electron microscopy (TEM) images confirmed that Cu nanowires have single crystalline structures with 0.21 nm fringe spacing which correspond to (111) growth direction. The results indicate that thermal reduction of copper oxide nanowires in low concentration hydrogen environment can pro...
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Abstract For Chemical Vapor Deposition (CVD) grown graphene on Cu substrate, deviation from atomic orientation in crystals may be resulted from diffusion of abnormalities in the form of Cu nanoparticle (NP) formation or defects and... more
Abstract For Chemical Vapor Deposition (CVD) grown graphene on Cu substrate, deviation from atomic orientation in crystals may be resulted from diffusion of abnormalities in the form of Cu nanoparticle (NP) formation or defects and affects graphene quality and properties drastically. However, for the uniform graphene deposition, mechanism of nanoparticle formation and its suppression procedure need to be better understood. We report growth of graphene, affected by Cu nanoparticles (NPs) emergence on Cu substrates. In the current study, growth of these nanoparticles has been suppressed by fine tuning of carrier gas by two-fold gas insertion mechanism and hence, quality and uniformity of graphene is significantly improved. It has been also observed that during the deposition by CVD, Cu nanoparticles cluster preferentially on wrinkles or terrace of the Cu surface. Composition of NP is extensively studied and found to be the oxide nanoparticle of Cu. Our result, controlled NP growth affecting deposition of graphene layer would provide useful insight on the growth of uniform and high quality Single layer or bilayer graphene for numerous electronics applications.
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Pre-annealing as part of a two-step thermal oxidation process has a significant effect on the growth of hematite ([Formula: see text]-Fe2O3) nanowires on Fe foil. High-density aligned nanowires were obtained on iron foils pre-annealed at... more
Pre-annealing as part of a two-step thermal oxidation process has a significant effect on the growth of hematite ([Formula: see text]-Fe2O3) nanowires on Fe foil. High-density aligned nanowires were obtained on iron foils pre-annealed at 300[Formula: see text]C under a dry air flow for 30[Formula: see text]min. The X-ray diffraction (XRD) patterns indicate that the nanowires are transformed from the small [Formula: see text]-Fe2O3 grains and uniquely grow in the (110) direction. The formation of a high-density of small grains by pre-annealing improved the alignment and density of the [Formula: see text]-Fe2O3 nanowires.
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Abstract Iron oxide nanowires, nanoflakes and film were successfully synthesized by two-step thermal oxidation process by changing oxidation temperatures. Highly aligned and high quantity nanowires and nanoflakes were obtained at 550 °C... more
Abstract Iron oxide nanowires, nanoflakes and film were successfully synthesized by two-step thermal oxidation process by changing oxidation temperatures. Highly aligned and high quantity nanowires and nanoflakes were obtained at 550 °C and 450 °C respectively. Their structural properties were characterized by SEM, XRD and photovoltaic performance by solar simulator. Results show that different structures of Fe 2 O 3 used will influence the photovoltaic performance by the effect of surface area. Fe 2 O 3 in nanowires shape gives the highest efficiency of 0.04% with short circuit current, open circuit voltage and fill factor of 0.25 mA/cm 2 , 0.42 V and 0.38 respectively. More efficient photoanodes were obtained in Fe 2 O 3 nanowires in dye sensitized solar cells (DSSC) as compared to nanoflakes and films due to the high surface area with smaller diameter and high distribution.
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Aligned high-density Fe2O3 nanowires were successfully obtained by thermal oxidation of Fe foil, with pre-annealing at 300 °C for 30 min. Pre-annealing in this two-step oxidation process improved the nanowire alignment and increased the... more
Aligned high-density Fe2O3 nanowires were successfully obtained by thermal oxidation of Fe foil, with pre-annealing at 300 °C for 30 min. Pre-annealing in this two-step oxidation process improved the nanowire alignment and increased the density from 5.0 × 108 to 2.5 × 109 nanowires cm−2. The X-ray diffraction pattern of the Fe2O3 nanowires had a dominant (110) peak, with crystalline Fe and iron oxide phases. The improved properties are the result of formation of smaller grains during the first oxidation step.
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Carbon films were grown on single crystal silicon substrate by XeCl excimer pulsed laser deposition (PLD) and fullerene (C60) is used as a target. A detailed Raman analysis is presented here to investigate the structural change of the... more
Carbon films were grown on single crystal silicon substrate by XeCl excimer pulsed laser deposition (PLD) and fullerene (C60) is used as a target. A detailed Raman analysis is presented here to investigate the structural change of the film and hence the result is compared with those of the films produced from graphite and camphor (C10H16O) targets deposited in the