IR@NPL
Not a member yet
3815 research outputs found
Sort by
Charge carrier dynamics in PffBT4T-2OD: PCBM organic solar cells
No full textWe investigate the charge carrier dynamics of inverted organic solar cells (OSCs) based on PffBT4T-2OD: PCBM and PTB7: PCBM - the two leading systems among the OSCs based on polymer-fullerene bulk-heterojunction - to elucidate the origin of their performance difference. Transient absorption spectroscopy (TAS) and photo-electrochemical impedance spectroscopy (photo-EIS) were employed to unravel the photo-physics that govern the cell operation of these two highly efficient bulk heterojunction OSCs. While photo-EIS indicates that the two systems under study exhibit similar behavior in terms of recombination, TAS results reveal that PffBT4T-2OD: PCBM systems not only have higher charge generation rate but also more efficient charge transfer than PTB7: PCBM systems, leading to the power conversion efficiency of PffBT4T-2OD: PCBM-based OSCs (9.16%) that is higher than that of PTB7: PCBM-based OSCs (6.44%)
Synthesis and Structural Characterization of Bulk Sb2Te3 Single Crystal
No full textWe report the growth and characterization of bulk Sb2Te3 single crystal synthesized by the self flux method via solid state reaction route from high temperature melt (850 degrees C) and slow cooling (2 degrees C/hour) of constituent elements. The single crystal X-ray diffraction pattern showed the 001 alignment and the high crystalline nature of the resultant sample. The rietveld fitted room temperature powder XRD revealed the phase purity and rhombohedral structure of the synthesized crystal. The formation and analysis of unit cell structure further verified the rhombohedral structure composed of three quintuple layers stacked one over the other. The SEM image showed the layered directional growth of the synthesized crystal carried out using the ZEISS-EVOMA-10 scanning electron microscope The electrical resistivity measurement was carried out using the conventional fourprobe method on a quantum design Physical Property Measurement System (PPMS). The temperature dependent electrical resistivity plot for studied Sb2Te3 single crystal depicts metallic behaviour in the absence of any applied magnetic field. The synthesis as well as the structural characterization of as grown Sb2Te3 single crystal is reported and discussed in the present letter
Angular and field dependent flux pinning in artificially doped YBCO films on IBAD-MgO based template
No full textThe self-organized artificial pinning structure in superconducting thin films of YBa2Cu3O6+x (YBCO) is optimized on a new type of IBAD-MgO based template by doping YBCO with non-superconducting BaCeO3 (BCO) and BaZrO3 (BZO). In these films, the YBCO is well ordered, no large angle grain boundaries are seen and the isotropic BCO particles are randomly distributed while the BZO grows as unidirectionally splayed and shortened nanorods. Additionally, the low-angle grain boundaries formed during the growth process have an impact on the flux pinning. The flux pinning behaviour can be explained by the vortex path model, where the pinning paths are shorter in BZO doped than in BCO doped films. In BZO doped films, the vortices are pinned with greater pinning force and thus the critical current density J(c) is higher than in BCO doped films, especially in high magnetic fields, where the wide peaks in J(c)(theta) were seen along the YBCO c-direction. This direction dependent pinning can be explained by the nearly similar diameters of BZO nanorods with those of vortices, thus efficiently increasing the vortex pinning in the vicinity of YBCO c-axis
Electron beam induced modifications of polyaniline silver nano-composite films: Electrical conductivity and H2S gas sensing studies
No full textThe polyaniline-silver (PANI-Ag) nanocomposite films doped with HCl were prepared on surface modified bi-axially oriented polyethylene teraphthalate (BOPET) by in-situ photo-polymerization. The grown films were modified with high energy (similar to 10 MeV) electron beam at different doses (0-100 kGy) in a Linear accelerator. After electron beam exposure the electrical conductivity of the PANI-Ag films was initially found to be enhanced by two orders of magnitude up to 30 kGy of dose and later it falls with increasing dose. Detailed characterizations of the films suggest that enhanced conductivity up to 30 kGy of electron beam dose is due to scissioning as well as additional doping of chlorine in PANI chain, through breaking of covalently bonded chlorine with PANI chain. At higher doses, cross-linking of polymer chains dominates and results in lowering of electrical conductivity. As compared to pristine film, electron beam modified PANI-Ag films exhibit higher sensitivity towards ppm level of H2S gas. The study highlights the effect of electron beam irradiation on PANI-Ag films in terms of electrical conductivity and its inferences on H2S gas sensing
Nonlinear optical single crystal of L-Cystine hydrochloride: Insights into the crystalline perfection, thermal, mechanical and optical properties for device fabrication
No full textNow days, nonlinear optical materials are subjected to extensive research owing to their versatility towards various photonic applications. In the present article, twin free L-Cystine hydrochloride single crystals were grown using conventional slow evaporation solution technique. The powder X-ray diffraction pattern confirmed that the titled compound belongs to monoclinic crystal system having space group C-2. Using FWHM of each diffracting peak, the strain present within the lattice was calculated. Through High Resolution XRD, the crystal quality was scrutinized and found that the grown single crystal is free from any type of defects and grain boundaries. For examination of optical homogeneity of the crystal, birefringence studies were conducted which revealed that there is only one fringe in the interferogram suggesting a good optical homogeneity. Further, various thermal transport parameters were calculated using Photopyroelectric technique. Apart from that, its mechanical strength was assessed at nanoscale through Nano indentation technique. Piezoelectric and ferroelectric studies were also carried out on the filed compound
Phase transition and anomalous rheological properties of graphene oxide carbon nanotube acrylonitrile butadiene styrene hybrid composites
No full textAcrylonitrile butadiene styrene (ABS) nanocomposites with multiwalled carbon nanotubes (MWCNTs), reduced graphene oxide (RGO) and graphene oxide-carbon nanotubes (GCNTs) reinforced acrylonitrile butadiene styrene (ABS) composites were prepared using twin screw extruder. The effect of these reinforcements on dynamic rheological properties of composites was studied. Different carbon nanofillers significantly enhanced the viscoelastic properties of nanocomposites. The rheological studies showed that the material undergoes viscous to elastic transition for 5 wt % MWCNTs, 10% RGO and 7% GCNTs reinforced in ABS matrix. GCNTs hybrid composites show a higher dispersion as well as effectiveness for increased filler amount as compared to RGO and MWCNTs based ABS composites. The dynamic intersection frequency of GCNTs-ABS composites indicates its superiority over MWCNTs and RGO based ABS composites by solving the problem of restacking of graphene and agglomeration of MWCNTs. Modified Carreau-Yasuda model and Hershcel-Bullrey model have been used to determine the yield stress of the composites and van Gurp-Palmen plot to determine the viscoelastic properties. These models were used to compare the theoretical results with experiment data. Dynamic rheological measurements revealed the viscous-like (G '' > G') behavior at the lower loading of filler and elastic like (G' > G '') behavior at higher loading of carbon nanofiller
Proximity-induced supercurrent through topological insulator based nanowires for quantum computation studies
Get PDFProximity-induced superconducting energy gap in the surface states of topological insulators has been predicted to host the much wanted Majorana fermions for fault-tolerant quantum computation. Recent theoretically proposed architectures for topological quantum computation via Majoranas are based on large networks of Kitaev's one-dimensional quantum wires, which pose a huge experimental challenge in terms of scalability of the current single nanowire based devices. Here, we address this problem by realizing robust superconductivity in junctions of fabricated topological insulator (Bi2Se3) nanowires proximity-coupled to conventional s-wave superconducting (W) electrodes. Milling technique possesses great potential in fabrication of any desired shapes and structures at nanoscale level, and therefore can be effectively utilized to scale-up the existing single nanowire based design into nanowire based network architectures. We demonstrate the dominant role of ballistic topological surface states in propagating the long-range proximity induced superconducting order with high IcRN product in long Bi2Se3 junctions. Large upper critical magnetic fields exceeding the ChandrasekharClogston limit suggests the existence of robust superconducting order with spin-triplet cooper pairing. An unconventional inverse dependence of IcRN product on the width of the nanowire junction was also observed
Silicon Wafer Surface Reflectance Investigations by Using Different Surface Texturing Parameters
No full textThis paper discusses surface texturization of monocrystalline silicon wafer by using a very simple and cost effective technique consisting of a combination of mechanical grinding and chemical etching, to achieve desired surface reflectance for solar cell applications. The abrasive used for mechanical grinding is aluminum oxide powder with different grain sizes. Potassium hydroxide-isopropyl alcohol solution (with different molar concentrations) is used as alkaline etchant. The change in surface reflectance may be correlated with the change in surface roughness parameters of silicon wafer after texturing. The roughness measurements are performed by using white light interferometry based three dimensional optical profiler. Reflectance measurements of texturized silicon wafer samples are carried out by ultra violet visible spectrophotometer. A comparative reflectance study of silicon wafer samples after using these methods reveals that the combination of mechanical grinding and alkaline etching is more effective for surface texture modification in terms of significantly reduced surface reflectance as compared to a single texturization technique. After reflectance data analysis of texturized samples, correlations have been established for percentage reflectance versus abrasive grain size and percentage reflectance versus molar concentration of etchant. These correlations provide a combination of abrasive grain size and etchant molar concentration to achieve desired value of percentage surface reflectance of silicon wafer from 23.97 to 11.85% at 800nm wavelength, which is significant for solar cell applications
X-ray photoelectron spectroscopy study on adsorption property of harmful air pollutants on zeolite prepared from fly ash
No full textThe present study focuses on the adsorption property of zeolite material prepared from fly ash for NOx, CO and other harmful air pollutants. X-ray diffraction (XRD) pattern of zeolite shows formation of two phase namely, Analcime and Na-Pl (Na6Al6Si10O32 center dot 12H(2)O). X-ray photoelectron spectroscopy (XPS) study reveals the adsorption of NO2, NO, N2O and CO pollutants on zeolite which are confirmed by core level XPS spectra of N 1s, O 1s and C 1s peaks. The two-zeolite phases have low silica content having acidic and thermal resistivity properties. These properties can be exploited in internal as well as external building environment for adsorption of harmful air pollutants
Signature of a Griffiths phase in layered canted antiferromagnet Sr2IrO4
No full textThe complex magnetic nature of 5d layered iridate Sr2IrO4, owing to Ir0 6 octahedral rotation has triggered great interest in recent years. In this article, we investigated the magnetic excitations in layered canted antiferromagnet Sr2IrO4 via dc magnetization measurements and report the Griffiths phase (GP) signatures above the magnetic ordering temperature T-N. The non-analytic nature of GP leads to unique critical exponent, beta = 0.75(1) extracted from modified Arrott plot, in corroboration with magneto-caloric study. However, the analysis by Bray model in GP regime yields a reliable critical exponent value of beta = 0.18(1), belonging to two-dimensional XYh(4) universality class. The study also suggests a new picture of largely debated insulating nature of Sr2IrO4 in context of GP above T-N