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Fabrication of DSSCs with biebrich scarlet, alizarine cyanine green and evans blue dyes as new organic photosensitizers

Abstract

Dye sensitized solar cells are photoelectrochemical cells mimicking photosynthesis. They represent a new generation of solar cells which is intensively studied nowadays. This cell was fabricated using TiO2 nanoparticles coated on FTO glass, organic dyes as photosensitizer, PEDOT:PSS as counter electrode and iodide-triiodide as electrolyte. The present work aims at the use of low cost new organic dyes viz. biebrich scarlet, alizarine cyanine green and evans blue for DSSC as an alternative to metallic dyes. In the present work, I-V characteristics, energy or power conversion efficiencies of the dyes have been studied in different solvents. The photoelectrochemical properties of the dyes were observed under 1.5 AM condition.

Open access
Green-emitting CaF2:Ce3+,Tb3+ phosphor: selection for improving luminous flux and color quality of conformal geometry white LED lamps

Abstract

In the last decades, new solutions for improving lighting properties of white LED lamps (WLEDs) have been the main research direction in optoelectronics. In this paper, a modern approach for enhancing luminous flux and color quality of white LED lamps was presented. By mixing green-emitting CaF2:Ce3+,Tb3+ phosphor with yellow-emitting YAG:Ce phosphor compound, the luminous flux and color quality of white LED lamps with conformal phosphor geometry (CPG) increased significantly. From the obtained results it follows that, the luminous flux increased more than 1.5 times, and the correlated color temperature deviation decreased more than 4 times in comparison with the non-green-emitting CaF2:Ce3+,Tb3+ phosphor. The presented research shows that the green-emitting CaF2:Ce3+,Tb3+ phosphor could become a good candidate for enhancing luminous flux and color quality of white LED lamps.

Open access
Growth and physicochemical characterization of calcium cadmium thiocyanate CaCd(SCN)4 single crystals

Abstract

It is important to grow and characterize new bimetallic thiocyanate single crystals as they are expected to exhibit useful optical and electrical properties. In the present study, calcium cadmium thiocyanate CaCd(SCN)4 single crystals were grown by slow evaporation of solvent and were characterized chemically, structurally, thermally, optically and electrically. X-ray diffraction analysis indicates that the grown crystal belongs to the tetragonal crystal system with lattice parameters: a = b = 12.2491(7) Å and c = 15.1012(5) Å. EDAX spectral analysis confirms the expected chemical composition. Thermogravimetric (TG/DTA) measurement implies good thermal stability. Optical (UV-Vis-NIR absorption spectral and SHG efficiency) measurements suggest good optical absorption in the UV and blue regions and the SHG efficiency of 6.13 (in urea unit). The dielectric measurements carried out in the temperature range of 40 °C to 150 °C at five different frequencies, viz. 100 Hz, 1 kHz, 10 kHz, 100 kHz and 1 MHz indicate a normal dielectric behavior.

Open access
Influence of Dopants on Structure of Polycrystalline Bismuth Niobate

Abstract

Bismuth niobate (BiNbO4) has attracted attention as a low-fired ceramics with promising microwave application potential. BiNbO4 ceramics was fabricated by mixed oxide method and sintered at temperature T<1000°C. As the sintering aids a small amount of CuO oxide was used. The crystalline structure of the ceramic samples was examined by X-ray diffraction method at room temperature. The Rietveld refinement method was used for analysis of diffraction data. As a result an influence of dopants on crystal structure of bismuth niobate (BiNbO4) ceramics was revealed. It was found that fabricated BiNbO4 ceramics adopted the orthorhombic symmetry (α-BiNbO4 phase, Pnna (52) space group). Small differences in elementary cell parameters were found.

Open access
Influence of L-threonine on the growth, structural, optical, mechanical and nonlinear optical properties of tartaric acid single crystal

Abstract

Single crystals of pure and L-threonine added tartaric acid (LT/TA), organic nonlinear optical (NLO) materials were grown from their respective aqueous solution by slow evaporation method. The crystalline nature of the grown crystals was confirmed by powder X-ray diffraction analysis (XRD). UV-Vis-NIR absorption and transmission spectra revealed that the lower cut-off wavelength was around 281 nm and the crystals exhibited high transmission over visible and near IR region. The presence of the functional groups such as O–H, C–H, C–O, C=O in the grown crystals was confirmed by FT-IR analysis. CHN analysis was carried out to confirm the presence of L-threonine in the grown crystals. Microhardness study on the crystals revealed that the hardness number Hv increased with the applied load. The growth pattern of the crystals were analyzed through etching analysis from which the etch patterns in the shape of ‘step-triangle’ were observed. The second harmonic generation (SHG) properties of pure and L-threonine doped tartaric acid crystals were confirmed by Kurtz-Perry powder technique.

Open access
Influence of magnetron powering mode on various properties of TiO2 thin films

Abstract

In this paper, comparative studies on the structural, surface, optical, mechanical and corrosion properties of titanium dioxide (TiO2) thin films deposited by continuous and sequential magnetron sputtering processes were presented. In case of continuous process, magnetron was continuously supplied with voltage for 90 min. In turn, in sequential process, the voltage was supplied for 1 s alternately with 1 s break, therefore, the total time of the process was extended to 180 min. The TiO2 thin films were crack free, exhibited good adherence to the substrate and the surface morphology was homogeneous. Structural analysis showed that there were no major differences in the microstructure between coatings deposited in continuous and sequential processes. Both films exhibited nanocrystalline anatase structure with crystallite sizes of ca. 21 nm. Deposited coatings had high transparency in the visible wavelength range. Significant differences were observed in porosity (lower for sequential process), scratch resistance (better for sequential process), mechanical performance, i.e. hardness:elastic modulus ratio (higher for sequential process) and corrosion resistance (better for sequential process).

Open access
Influence of modulation frequency on the synthesis of thin films in pulsed magnetron sputtering processes

Abstract

The research on the influence of modulation frequency on the properties of films synthesized using a unique pulsed power supply combined with a standard unbalanced circular magnetron was conducted in the process of pulsed magnetron sputtering (PMS). It was shown that by using different levels of modulation, the composition of plasma (measured by optical emission spectroscopy, OES) as well as film growth rate and morphology (observed with scanning electron microscope, SEM), can be changed. The impact of modulation is related to the used materials and gases and can vary significantly. It was concluded that modulation frequency can greatly influence the synthesis of materials and can be used as an additional parameter in PMS. Specific relations between modulation frequency and synthesized material require further investigation.

Open access
Influence of molar concentration and temperature on structural, optical, electrical and X-ray sensing properties of chemically grown nickel-bismuth-sulfide (NixBi2−xS3) thin films

Abstract

In this report, ternary semiconducting NixBi2−xS3(x = 0.2 M and 0.5 M) thin films were synthesized in situ for the first time by a chemical bath deposition technique at different bath temperatures (60 °C, 70 °C and 80 °C). The effects of concentration and deposition temperature on the deposited films were studied by combining the results of structural, morphological, optical and electrical analyses. The growth of NixBi2−xS3 films with good crystalline nature and interconnected grain arrangement takes place due to increasing the concentration of Ni2+ ions in bismuth sulfide matrix. EDS result confirmed the stoichiometry of NixBi2−xS3 formation. Wettability test demonstrated that the surface of the film was hydrophilic in nature. The optical absorption spectra revealed that the bandgap Eg of the x = 0.5 M film deposited at 70 °C was about 1.36 eV. Current-voltage (I-V) characteristics of the x = 0.5 M film deposited at 70 °C were studied under X-ray radiation and dark condition. An X-ray detection sensitivity analysis showed that the detection sensitivity is optimum when the bias voltage applied across the film is low (~0.9 V). These findings reveal that the film with x = 0.5 M deposited at 70 °C can be used as an efficient low cost X-ray sensor.

Open access
Investigation of Mechanical and Anti-Corrosion Properties of Flame Sprayed Coatings

Abstract

This article presents the results of an examination of the properties of thermal flame sprayed coatings produced by material in the form of four powders (two polymers: PA11 and PA12 CastoPlast, and two high purity: tin and aluminum) on the substrate of the unalloyed structural steel of S235JR grade. Investigations of coating properties are based on metallography tests (SEM and CLSM), measurement of microhardness (acc. to PN-EN ISO 6507-1:2007), anticorrosive (acc. to PN-EN ISO 9227:2017-06) and bend testing. Results demonstrate properties of flame sprayed coatings that are especially promising in the industrial applications where corrosion-resistant coating properties are required. Consequently, performed experiments show that the highest corrosion resistance is demonstrated by steel samples with a polyamide anti-corrosion system. Accelerated corrosion tests showed the lowest corrosion resistance of the tin coating system, however, they do not fully correspond to the corrosion processes in operating conditions.

Open access
Linear-nonlinear optical, dielectric and surface microscopic investigation of KH2PO4 crystal to uncover the decisive impact of dopant glycine

Abstract

Present investigation has been started to perform the comparative study of pure and glycine doped KH2PO4 (KDP) single crystals grown by most commercial slow solvent evaporation technique. The grown crystals were subjected to single crystal X-ray diffraction analysis to determine their structural parameters. The linear optical studies of pure and glycine doped KDP crystal have been undertaken within 200 nm to 1100 nm wavelength range by means of UV-Vis studies. The enhancement in second harmonic generation (SHG) efficiency of glycine doped KDP crystal has been determined using a standard Kurtz-Perry powder test. The dielectric measurements have been carried out to explore the impact of glycine dopant on dielectric constant and dielectric loss of KDP crystal. The surface growth habitat and etch pit density of glycine doped KDP crystal have been evaluated using the results of microscopic etching studies. In light of obtained results the suitability of glycine doped KDP crystal for device applications has been discussed.

Open access