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Electrical and optical characterization of SiOxNy and SiO2 dielectric layers and rear surface passivation by using SiO2/SiOxNy stack layers with screen printed local Al-BSF for c-Si solar cells
No full textIn c-Si solar cells, surface recombination velocity increases as the wafer thickness decreases due to an increase in surface to volume ratio. For high efficiency, in addition to low surface recombination velocity at the rear side, a high internal reflection from the rear surface is also required. The SiOxNy film with low absorbance can act as rear surface reflector. In this study, industrially feasible SiO2/SiOxNy stack for rear surface passivation and screen printed local aluminium back surface field were used in the cell structure. A 3 nm thick oxide layer has resulted in low fixed oxide charge density of 1.58 x 10(11) cm(-2) without parasitic shunting. The oxide layer capped with SiOxNy layer led to surface recombination velocity of 155 cm/s after firing. Using single layer (SiO2) rear passivation, an efficiency of 18.13% has been obtained with Voc of 625 mV, Jsc of 36.4 mA/cm(2) and fill factor of 78.7%. By using double layer (SiO2/SiOxNy stack) passivation at the rear side, an efficiency of 18.59% has been achieved with Voc of 632 mV, Jsc of 37.6 mA/cm(2), and fill factor of 78.3%. An improved cell performance was obtained with SiO2/SiOxNy rear stack passivation and local BS
Development and Implementation of Current Tee for AC High Current Calibration
No full textThermal current converters or thermal transfer standard with AC-DC current shunts act as the reference standards for accurate and precise measurements of low frequency current in the frequency range from 40 Hz to 10 kHz. At present CSIR-NPL, India has the AC-DC current transfer difference (delta (x)) calibration facility upto 20 A. To extend our AC current calibration range from 20 A to 100 A, a current Tee for AC high current using LC connectors has been indigenously designed and developed. This paper presents the development of current Tee for AC high current calibration. The calibration results for assigning 'delta (x)' at 30 A current shunt with respect to 20 A are shown and the same measurement technique has been used to extend the current range up to 100 A
Electrically conductive green composites based on epoxidized linseed oil and polyaniline: An insight into electrical, thermal and mechanical properties
No full textRenewable resource based electrically conductive composites were prepared using polyaniline (PANI) as a conductive filler and epoxidized linseed oil (ELO) as the matrix. Linseed oil (LO) was epoxidized to form ELO and characterized through H-1 NMR and IR spectra. Bio-based ELO/PANI conducting composites were prepared by varying the PANI concentration with an aim of attaining the electrical conductivity in the antistatic range (10(-8) to 10(-3) S/cm) to replace its petro-based counterpart. Conductivity increased with PANI upto the order of 10(-6) S/cm with percolation threshold at around 7% of PANI. The shear stress and viscosity of the uncured ELO resin and ELO/PANI resin mixture were studied as a function of shear rate. Differential scanning calorimetry (DSC) studies showed that addition of PANI had a minimal effect on ELO curing at all concentrations. Dynamic mechanical analysis indicated that PANI as a filler provided mechanical fortification in the rubbery region and increased glass transition temperature (T-g) significantly. Thermal stability of ELO remained almost unaffected with the PANI incorporation. Microscopic observation revealed good distribution of PANI in ELO matrix even at higher loading. Interestingly, tensile strength and Young's modulus increased by similar to 8 and similar to 27 folds, respectively, at 15% PANI content
Synthesis and enhancement of photoluminescent properties in spherical shaped Sm3+/Eu3+ co-doped NaCaPO4 phosphor particles for w-LEDs
No full textA series of Sm3+ doped and Sm3+/Eu3+ co-doped NaCaPO4 phosphors have been successfully synthesized via molten salt method. The structural, morphological, optical, photoluminescence and decay properties of the synthesized phosphors were investigated. Sm3+ doped phosphor exhibits excellent emission properties in the orangish-red region under n-UV excitation (403 nm), and the optimized doping concentration of Sm3+ was found to be 1.0 mol%. The excitation spectrum confirms that Sm3+/Eu3+ co-doped NaCaPO4 phosphors can be efficiently excited by both n-UV and blue LED chips. In the co-doped NaCaPO4: Sm3+/Eu3+ phosphors, the intensity of main characteristic emission peaks of Sm3+ decreased and Eu3+ increased with increasing Eu3+ ion concentration. The energy transfer (ET) from Sm3+ to Eu3+ was demonstrated to be quadrupole-quadrupole in nature by applying Dexter's ET formula and Reisfeld's approximation. Commission Internationale de l'Eclairage (CIE) chromaticity coordinates for co-doped samples lie in the red region. The decay time for the (4)G(5/2) level of Sm3+ decreases with increasing Eu3+ concentration, which also indicate the energy transfer from Sm3+ to Eu3+. These results indicate that Sm3+/Eu3+ co-doped NaCaPO4 multifunctional phosphor is a promising and an attractive potential candidate for n-UV and blue excitation based w-LEDs
Spectroscopic and electronic properties of polyallylamine functionalized graphene oxide films
No full textFunctionalization of polyallylamine (PAA) on graphene oxide (GO) surface is demonstrated using the optical spectroscopic measurements. The disappearance of C-OH and C-O vibrational modes of GO, and appearance of new N-H peak in the Fourier transform infrared spectra of PAA, indicates the chemical interaction of GO with PAA to form GO-PAA composite. The optical behavior of GO-PAA composite recorded through the UV-Vis absorption and photoluminescence for different optical excitations show individual properties of GO and PAA. The enhanced electrical conductivity through GO-PAA thin film based aluminum (Al)/GO-PAA/indium-tin-oxide (ITO) device structure is attributed to the reduction of GO sheets after functionalization with PAA
Structural and Optical Properties of Manganese-Doped NanocrystallineZinc Oxide/Polyvinylidene Fluoride Flexible Composite Thin Films Deposited by the Sol-Gel Method
No full textMn-doped nanocrystalline ZnO (MnxZn1-xO) was incorporated in the polyvinylidene fluoride thin film for obtaining the free-standing flexible film by the sol-gel technique. The effect of Mn-ZnO loading on the optical and microstructural properties of the Mn-ZnO/polyvinylidene fluoride (PVDF) composite films was studied critically for the as-deposited and the poled samples. X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy were carried out to study the bonding environment. The XPS spectra recorded for poled samples from the fluorine-terminated surface showed a very strong peak at approximate to 695 eV for F1s arising due to C-F bonds. Raman studies showed the presence of the predominant phase of PVDF in the sample. Peaks related to ZnO nanocrystals were also observed in the Raman spectra. Photoluminescence spectra indicated a strong emission band at approximate to 2.79 eV in the ultraviolet region arising out of near band edge emission of free excitons
Naphthalene diimide self-assembled ribbons with high electrical conductivity and mobility without doping
No full textThe thermally activated electrical conductivity and charge transfer properties of self-assembled naphthalene diimide molecule have been studied with N,N'di(hexadecyl)naphthalene tetracarboxylic diimide (HD-NDI) derivative. The self-assembly of HD-NDI has been resulted in one-dimensional large micron-size ribbons. The aggregate formation and self-assembling property have been extensively studied by absorption, fluorescence and X-ray diffraction analysis. Absorption and fluorescence measurements were taken in variety of solvents in fresh and aged samples, and the study suggested J-type aggregation for self-assembly formation. The electrical conductivity of self-assembled HD-NDI material was measured as a function of temperature where the conductivity increased with temperature and the highest conductivity (1 x 10(-5) S/cm) was obtained at 250 A degrees C. SEM images clearly show the formation of ribbons of micron size. Further the electron transport property of HD-NDI was also evaluated by SCLC method at room temperature by fabricating electron-only devices with annealing the film at similar to 200 A degrees C. HD-NDI shows excellent electron mobility (1.8 x 10(-3) cm(2) V-1 s(-1)) because of effective channel formation due to self-assembly of HD-NDI molecules, and this material may find potential application in variety of electronic devices
Crystal structure, dielectric, magnetic and magnetoelectric properties of xNiFe(2)O(4)-(1-x)Na0.5Bi0.5TiO3 composites
No full textMagnetoelectric (ME) composites xNiFe(2)O(4)-(1-x)Na0.5Bi0.5TiO3 (x = 0.10,0.30,0.50) were synthesized by conventional solid state reaction method. Crystal structure and microstructural characteristics of these composites were investigated by XRD and SEM respectively. Rietveld analysis of XRD pattern confirms the coexistence of cubic (Fd3m) and rhombohedral (R3c) symmetry simultaneously in these composites. The microstructural evaluation discloses the effect of constituent phases on the average grain size of a composite. The dielectric constant (epsilon') and dielectric loss (tan delta) were examined as a function of frequency within range (100 Hz to 7 MHz) and at different temperatures. The magnetic behavior of composites was determined by MH hysteresis loop which reveals their soft magnetic behavior. ME voltage coefficient was determined to study the coupling between ferrite and ferroelectric phases. The maximum value of ME coefficient alpha approximate to 223 mu V/cmOe was observed for 0.10NFO-0.90NBT sample
Enhanced electrocatalytic activity of reduced graphene oxide-Os nanoparticle hybrid films obtained at a liquid/liquid interface
No full textHybrid films of reduced graphene oxideosmium nanoparticles (rGO-Os NPs) synthesized at a liquid/liquid interface are explored for their electrocatalytic activity towards the oxidation of rhodamine B (RhB), a popular colourant found in textile industry effluents and a non-permitted food colour. The freestanding nature of the films enables them to be lifted directly on to electrodes without the aid of any binders. The films consist of aggregates of ultra-small Os NPs interspersed with rGO layers. The hybrid film exhibits enhanced RhB oxidation when compared to its constituents arising from the synergic effect between rGO and Os NPs, Os contributing to electrocatalysis and rGO contributing to high surface area and conductance as well as stabilization of Os nanoparticles. The electrochemical sensor based on rGO-Os NP hybrid film on pencil graphite electrode shows a remarkable performance for the quantitative detection of RhB with a linear variation in a wide range of concentrations, 4-1300 ppb (8.3 nM-2.71 mu M). The modified electrode presents good stability over more than 6 months, reproducibility and anti-interference capability. The use of developed sensor for adequate detection of RhB in real samples such as food samples and pen markers is also demonstrated
Synthesis & characterization of poly (o-phenitidine)/SiO2/Epoxy for anti-corrosive coating of mild steel in saline conditions
No full textCorrosion is one of the biggest problems faced by the society in the present world. It causes economical loss as well as degrades the service life of the materials. In present study we demonstrate synthesis and characterization of corrosion resistant coating Poly (o-phenitidine)/SiO2/Epoxy. The polymer composite was synthesized by chemical oxidative polymerization of o-phenitidine and silica nanoparticles. The composite coating was synthesized using FTIR and XRD. The morphological analysis was carried out by Scanning Electron Microscope (SEM) and Transmission Electron Microscope (TEM). All Electrochemical Studies was carried out in saline condition (3.5 wt% NaCl). The Electrochemical Impedance Spectroscopy (EIS) and Tafel analysis results demonstrate good inhibition properties of coatings. The salt spray test results show no extension of corrosion around Cut Mark Scribed on epoxy coatings loaded with Poly (o-phenitidine)/SiO2 composites. The results demonstrate the synergistic combination of polymer and nano filler material that causes improvement in corrosion resistant properties