IR@NPL
Not a member yet
3815 research outputs found
Sort by
Revealing charge carrier dynamics in squaraine: [6,6]-phenyl-C 71-butyric acid methyl ester based organic solar cells
Get PDFUltrafast charge carrier dynamics as well as the generation of polaron pair in squaraine (SQ) and squaraine:[6,6]-phenyl-C 71-butyric acid methyl ester (SQ:PCBM71) have been studied using ultrafast transient absorption spectroscopy (UTAS). The current study reveals that the pure SQ exhibits the creation of singlet and triplet states; however, incorporation of PCBM71 in SQ results in the formation of polaron pairs with similar to 550ps lifetime, which in turn leads to the creation of free electrons in the device. We show that the considerable increment in monomolecular and bimolecular recombination in SQ:PCBM71 compared to pure SQ which describes the interfacial compatibility of SQ and PCBMC71 molecules. The present work not only provides the information about the carrier generation in SQ and SQ:PCBM71 but also gives the facts relating to the effect of PCBM71 mixing into the SQ which is very significant because the SQ has donor-acceptor-donor (D-A-D) structure and mixing one more acceptor can introduce more complex recombinations in the blend. These findings have been complimented by the charge transport study in the device using impedance spectroscopy. The various important transport parameters are transit time (tau(t)), diffusion constant (D-n), global mobility (mu) and carrier lifetime (tau(r)). The values of these parameters are 26.38 mu s, 4.64x10(-6) cm(2)s(-1), 6.12x10(-6) cm(2)V(-1)s(-1) and 399 mu s, respectively. To the best of our knowledge such study related to SQ is not present in the literature comprehensively
Flexible and free-standing films containing cobalt-doped nanocrystalline zinc oxide dispersed in polyvinylidene fluoride matrix: synthesis and characterization
No full textSynthesis of free-standing flexible Co-ZnO/PVDF composite films is realized by sol-gel technique. Modulation of the optical and microstructural properties of the above composite films with Co-doped nanocrystalline ZnO loading in PVDF matrix was studied critically. Uniform dispersion of Co-doped ZnO in PVDF matrix was indicated by SIMS studies. Information on the bonding environment was obtained from X-ray photoelectron spectroscopy and Raman spectroscopy studies. A very strong peak at similar to 695 eV for core level spectra of F1s along with those for C1s, Zn2p and Co2p dominated the XPS spectra of the composite films. Presence of the predominant beta-phase of PVDF along with peaks related to ZnO nanocrystals in the poled sample was observed in the Raman spectra
Depth dynamics of soil N contents and natural abundances of N-15 after 43 years of long-term fertilization and liming in sub-tropical Alfisol
No full textThe aim of this study was to understand impacts of long-term (43years) fertilization on soil aggregation, N accumulation rates and N-15 in surface and deep layers in an Alfisol. Soil samples from seven treatments were analysed for N stocks, aggregate-associated N in 0-30 cm and the changes in N-15 in 0-90 cm depths. The treatments were: unfertilized control (control); recommended N dose (N); recommended N and phosphorus doses (NP); recommended N, P and potassium doses (NPK); 150% of recommended N, P and K doses (150% NPK); NPK + 10Mg FYM ha(-1) (NPK + FYM) and NPK + 0.4Mg lime ha(-1) (NPK + L). Results revealed that plots under NPK + FYM had similar to 39% higher total N concentrations than NPK + L in 0-30 cm soil layers. In NPK + L, macro-aggregates had 35 and 11% and microaggregates had 20 and 9% lower N-15 values than NPK + FYM in 0-15 and 15-30 cm soil layers, respectively. However, plots receiving NPK + FYM had similar to 39% greater deep soil (30-90 cm) N accumulation than NPK + L. These results would help understanding N supplying capacity by long-term fertilization and assist devising N management strategies in sub-tropical acidic Alfisols
Final Report CCM.V-K3: CCM Key Comparison of Viscosity
No full textThis report describes the third CCM key comparison in capillary viscometry at twelve National Metrology Institutes (NMIs), which was carried out between October 2012 and February 2013. Seven NMIs, which do not maintain an independent viscosity scale, also took part in this comparison. Three samples of Newtonian liquids with nominal kinematic viscosities of 6 mm(2)/s at 15 degrees C and 5 mm(2)/s at 20 degrees C, 2000 mm(2)/s at 20 degrees C and 500 mm(2)/s at 40 degrees C, and 160000 mm(2)/s at 20 degrees C and 25000 mm(2)/s at 40 degrees C prepared by NMIJ were provided to each of the NMIs. For each of these liquids at two temperatures, total number of 98 measurements was carried out and from the results of viscosity measurements, the key comparison reference values (KCRVs) for six data sets were determined. The degrees of equivalences was evaluated by difference from the KCRV and, with a few exceptions, these differences were almost equal to or less than expanded uncertainties, showing a good equivalencies of capabilities at the participating NMIs for the viscosity measurements in wide range of viscosities covered from 5 mm(2)/s to 160000 mm(2)/s
Photoluminescence investigations on Sm3+ ions doped borate glasses for tricolor w-LEDs and lasers
No full textThis work describes mainly the optical absorption, photoluminescence (PL) and decay spectral properties of Sm3+ ions doped borate glasses to understand their possible usage in tricolor w-LEDs and lasers. The XRD spectrum recorded for an un-doped glass confirms glassy nature of the as prepared glass. The Judd-Ofelt (J-O) intensity parameters evaluated from experimental oscillator strengths were used in estimating the various radiative parameters. Under 402 nm excitation, the PL spectra exhibit intense emission at 600 nm for which the decay spectral profiles were recorded. The decay profiles are converting from single exponential to non-exponential with increase in Sm3+ ion concentration ensuing decrease in experimental lifetimes which may be attributed to the efficient energy transfer through cross-relaxation process. The non-exponential decay curves fitted to I-H model reveals the interaction between the Sm3+ ions as dipole-dipole in nature. From the evaluated emission cross-sections, quantum efficiency, branching ratios and CIE co-ordinates, it is concluded that 1 mol% Sm3+ ions in these glasses are aptly suitable to fabricate reddish-orange luminescent devices
High-Field Magneto-Conductivity Analysis of Bi2Se3 Single Crystal
No full textWe report the high-field (up to 14 Tesla) magneto-conductivity analysis of Bi2Se3 topological insulator grown via the self-flux method. The detailed experimental investigations including crystal growth as well as the electrical, thermal, and spectroscopic characterizations of the resultant Bi2Se3 single crystal are already reported by some of us. The current letter deals with high-field magneto-conductivity analysis in terms of Hikami Larkin Nagaoka (HLN) model, which revealed that the electronic conduction is dominated by both surface state-driven weak anti-localization (WAL), as well as the bulk weak localization (WL) states. Further, by applying the HLN equation, we have extracted the fitting parameters, i.e., phase coherence length (l(phi)) and the pre-factor (). Here, the magneto-conductivity data is fitted up to +/- 5 Tesla, but in order to extract reliable fitting parameters, the same is fitted at much lower magnetic fields, i.e., up to +/- 1 Tesla. The value of the HLN coefficient (), extracted from the HLN equation exhibited values close to - 1.0, indicating both WAL and WL contributions. On the other hand, the extracted is seen to decrease from 11.125 to 5.576 nm as the temperature is increased from 5 to 200 K, respectively. Summarily, the short letter discusses primarily the temperature-dependent magneto-conductivity analysis of pristine Bi2Se3 single crystal by the HLN model
Negative-capacitance and bulk photovoltaic phenomena in gallium nitride nanorods network
Get PDFAn enhanced self-powered near-ultraviolet photodetection phenomenon was observed in epitaxial gallium nitride (GaN) nanorods network grown on an intermediate layer of N:GaN on a nitridated HfO2(N:HfO2)/SiO2/p-Si substrate. The fabricated Au/GaN/N:GaN/N:HfO2/Ag heterostructure exhibited a giant change (OFF/ON ratio > 50 without applying any external electrical field) in its conductance when illuminated by a very weak (25 mW cm(-2)) near-UV monochromatic light with a low dark current (nearly 20 nA). The presented near-UV photodetector offers photoresponsivity of approximate to 2.4 mA W-1 at an applied voltage of 1 V. We observed an optically generated internal open circuit voltage of approximate to 155 mV and short circuit current approximate to 430 nA, which can be attributed to the quantum confinement of free charge carriers in the nanorod matrix. Interestingly, it also shows a negative capacitance after near-UV illumination. It has great potential as a self-powered UV photodetector and in metamaterial applications
Optimization of Ni2+ /Ni3+ ratio in reduced graphene oxide/nickel oxide nanohybrids for platinum free dye sensitized solar cells
No full textA strategy has been explored to design a novel network of reduced graphene oxide (rGO)/nickel oxide (NiO) nanohybrids with optimized Ni2+/Ni3+ ratio for the fabrication of compact, flexible, and large area Pt-free dye sensitized solar cells (DSSCs). The rGO/NiO nanohybrids were synthesized by a hydrothermal method and characterized by field emission scanning electron microscopy, Brunauer-Emmett-Teller analysis, X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, Fourier transform infrared spectroscopy, cyclic voltammetry, and electrochemical impedance spectroscopy. These studies demonstrate that the rGO/NiO nanohybrids with Ni2+ rich species show high catalytic activity toward the I/I-3(-) redox reaction. This led to the fabrication of improved DSSCs with power conversion efficiency as high as 3.69% with these nanohybrids as counter electrodes in comparison with DSSC devices containing counter electrodes based on rGO (1.71%) and NiO (0.75%)
Edge enriched cobalt ferrite nanorods for symmetric/asymmetric supercapacitive charge storage
No full textFor maximum and efficient charge storage and delivery, porous nanorods with active sites can offer a unique set of advantages. Herein, hierarchically porous (0.2-200 nm) cobalt ferrite (CoFe2O4) nanorods are hydrothermally prepared by tuning oleic acid concentration (100-500 mu L with subsequent annealing (400 degrees C). These hierarchical pores (with edges and cavities) raise the specific surface area of CoFe2O4 nanorods to 154 m(2)g(-1). In addition, 80% of CoFe2O4 sites become accessible boosting the capacitance to a high value (460.5 Fg(-1) at 1.0 Ag-1), while retaining excellent cyclic stability (95.8% for 5000 cycles). Maximum pseudocapacitive contribution from these electrochemically active sites is ensured by rapid diffusion of electrolytic OH- ions (5.8 x 10(-8)cm(2)s(-1)). Moreover, on assembling these nanorods as a positive electrode in asymmetric configuration (graphene nanoribbons as negative electrode), the cell exhibits an outstanding energy density (33.5 Wh kg(-1) at 727.8 W kg(-1)), almost double of its symmetric (16.5 Wh kg(-1) at 288 W kg(-1)) counterpart
Enhanced thermomechanical and electrical properties of multiwalled carbon nanotube paper reinforced epoxy laminar composites
No full textThermomechanical and electrical properties of multiwalled carbon nanotubes (MWCNTs) bucky paper reinforced epoxy laminar composites have been studied. Incorporation of bucky paper in epoxy matrix led to improvement in thermomechanical properties but it reduced through-plane electrical conductivity. Therefore, 0.05 wt.% of MWCNTs is incorporated as secondary network in epoxy matrix to improve the electrical conductivity. The storage modulus for a 0.05 wt.% dispersed MWCNTs in epoxy resin impregnated 20 plies of bucky paper based composites (20Ply.05) was 4.84 GPa as compared to 2.24 GPa of pure epoxy. The glass transition temperature of 20Ply.05 laminar composite reaches to 191.6 degrees C as compared to pure epoxy (168.5 degrees C). The increment in electrical conductivity (792%) is reflected in improved electromagnetic shielding effectiveness (SE) over a wide frequency range of X & Ku band. The SE of more than 50 dB for 20Ply.05 laminar composite in both the bands was obtained