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Improved performance of organic solar cells with solution processed hole transport layer
No full textThis work is based on Cobalt Oxide as solution processed, inexpensive and effective hole transport layer (HTL) for efficient organic photovoltaic applications (OPVs). In Organic solar cell (OSC) devices ITO coated glass substrate used as a transparent anode electrode for light incident, HTL material Co3O4 dissolve in DMF solvent deposited on anode electrode, after that active layer material (donor/acceptor) deposited on to HTL and finally Al were deposited by thermal evaporation used as cathode electrode. These devices were fabricated with PCDTBT well known low band gap donor material in OSCs and blended with PC71BM as an acceptor material using simplest device structure ITO/Co3O4/active layer/Al at ambient conditions. The power conversion efficiencies (PCEs) based on Co3O4 and PEDOT:PSS have been achieved to up to 3.21% and 1.47% with PCDTBT respectively. In this study we reported that the devices fabricated with Co3O4 showed better performance as compare to the devices fabricated with well known and most studied solution processed HTL material PEDOT:PSS under identical environmental conditions. The surface morphology of the HTL film was characterized by (AFM). Lastly, we have provided Co3O4 as an efficient hole transport material HTL for solution processed organic photovoltaic applications
Local symmetry breaking in SnO2 nanocrystals with cobalt doping and its effect on optical properties
No full textX-ray photoemission spectroscopy (XPS), X-ray diffraction (XRD) and transmission electron microscopy (TEM) have been used to study the structural and morphological characteristics of cobalt doped tin(iv) oxide (Sn1-xCoxO2; 0 <= x <= 0.04) nanocrystals synthesized by a chemical co-precipitation technique. Electronic structure analysis using X-ray photoemission spectroscopy (XPS) shows the formation of tin interstitials (Sn-i) and reduction of oxygen vacancies (V-O) in the host lattice on Co doping and that the doped Co exists in mixed valence states of +2 and +3. Using XRD, the preferential position of the Sn-i and doped Co in the unit cell of the nanocrystals have been estimated. Rietveld refinement of XRD data shows that samples are of single phase and variation of lattice constants follows Vegard's law. XRD and TEM measurements show that the crystallite size of the nanocrystals decrease with increase in Co doping concentration. SAED patterns confirm the monocrystalline nature of the samples. The study of the lattice dynamics using Raman spectroscopy and Fourier transform infrared (FTIR) spectroscopy shows the existence of many disorder activated forbidden optical phonon modes, along with the corresponding classical modes, signifying Co induced local symmetry breaking in the nanocrystals. UV-Vis spectroscopy shows that the optical band gap has red shifted with increase in doping concentration. The study of Urbach energy confirms the increase in disorder in the nanocrystals with Co doping. Local symmetry breaking induced UV emission along with violet, blue and green luminescence has been observed from the PL study. The spectral contribution of UV emission decreases and green luminescence increases with increase in doping. Using PL, in conjunction with Raman spectroscopy, the type of oxygen vacancy induced in the nanocrystals on Co doping has been confirmed and the position of the defect levels in the forbidden zone (w.r.t. the optical band gap) has been studied
Enhanced anticorrosive properties of tailored poly(aniline-anisidine)/chitosan/SiO2 composite for protection of mild steel in aggressive marine conditions
No full textPresent study focuses on the development of composite coating for corrosion protection of mild steel in marine environment. In the present work, in-situ chemical oxidative polymerization process is employed to synthesize poly(aniline-anisidine)/chitosan/SiO2 composite in aqueous medium of chitosan. The synthesized copolymer composites were characterized by FTIR, XRD, TGA, and SEM. Corrosion resistant coatings were developed by loading of the copolymer composites in the epoxy resin. Electrochemical behavior of coatings was studied in 3.5% NaCl for a span of 20 days. The electrochemical measurements have clearly demonstrated excellent improvement in the corrosion resistant properties of the substrate after application of coatings. Salt spray test (as per ASTM B117 standards) revealed that the composite coatings can withstand under accelerated corrosion conditions of high salt content and humidity for prolong periods. The improved corrosion resistance of the composite coatings is attributed to the effective combination of fillers (SiO2 nanoparticles), biopolymer (chitosan) in conducting matrix (poly(aniline-anisidine))
A systematic study of structural, magnetic and electric properties of perovskite-spinel composites prepared by sol-gel technique
No full textMultiferroics composite of perovskite BiFeO3 and spinel ferrites NiFe2O4/ZnFe2O4/CoFe2O4 with different composition were prepared by sol-gel method. Detailed investigations were made on the structural, magnetic and ferroelectric properties of these composites. The X-Ray Diffraction pattern confirms the formation of distorted perovskite and spinel phases of BiFeO3 and NiFe2O4, ZnFe2O4, CoFe2O4 respectively. Transmission Electron Microscopy (TEM) images reveals the particle size and the elemental idea of phase formation. The particle sizes calculated using TEM of NiFe2O4, ZnFe2O4, CoFe2O4 are 10-20 nm, 20-30 nm, 15-25 nm respectively and these are compatible with XRD results. The results of Scanning Electron Microscopy (SEM) images reveal that all the samples exhibit a very uniform distribution of perovskite and spinel phases in composites. The modified microstructure of composites is effective in reducing the leakage of electric charges which occurs due to a chain formation of the spinel-ferrite phase particle, so the electrical, magnetic and ferroelectric properties of composites may improve with spinel ferrites content
AFe(2)O(4)/(Pb0.80Sr0.20)TiO3 (A = Mn, Ni and Co): a New Room-Temperature Magnetoelectric Multiferroic Bi-layered Composite Films
No full textThe room temperature and magnetic field-dependent dielectric, impedance and magnetoelectric (ME) coupling effect of polycrystalline AFe(2)O(4)/(Pb0.80Sr0.20)TiO3 (A = Mn, Ni and Co) bi-layered composite films have been investigated. The structural and microstructural analyses using the X-ray diffraction (XRD), atomic force microscopy (AFM) and scanning electron microscopy (SEM) reveal the presence of homogenous growth of both tetragonal and spinel phases without any extra phase and diffusion in the AFO/PST20 bi-layered composite films. Our results show that all composite films exhibit ferroelectric as well as considerable magnetic, indicating magnetoelectric coupling effect. Our results show that the dielectric and impedance properties of AFO/PST20 bi-layered composite films can be manipulated by the magnetic field at room temperature, also indicating the existence of magnetoelectric coupling. The impedance (Z (') and Z (aEuro3)) Nyquist plots show distinct electrical responses with the magnetic field. The maximum magnetoelectric coefficient (alpha) is found to be alpha (ME) 239 and 195 mV/cm/Oe for the MFO/PST20 and CFO/PST20 bi-layered composite films, respectively. The above results show that the AFO/PST20 bi-layered composite films are room-temperature multiferroic material that can be potentially used in magnetoelectric devices
Reversible and fast responding ppb level Cl-2 sensor based on noncovalent modified carbon nanotubes with Hexadecafluorinated copper phthalocyanine
No full textHybrids of hexadecafluorinated copper phthalocyanine (F16CuPc) with carboxylic functionalized single walled carbon nanotubes (SWCNTs-COOH) and multi-walled carbon nanotubes (MWCNTs-COOH) have been synthesized using a solution assembly method. The resulting hybrid materials have been characterized by Transmission electron microscopy, Raman, UV-vis, X-Ray photoelectron, Fourier-transform infrared spectroscopic techniques and finally studied for gas sensing application. Cl-2 selective chemiresistive gas sensors have been fabricated using these hybrids with detection limit up to 0.27 ppb. The main characteristics of these sensors are their excellent baseline recovery and reversibility upon repeated exposure to Cl-2. F16CuPc/SWCNTs-COOH based sensors showed a gas response as large as 35.82% with a fast response time of 9 s towards 2 ppm of Cl-2. A plausible gas sensing mechanism for charge transfer in hybrids on interacting with Cl-2 has been proposed on basis of X-ray photoelectron and impedance spectroscopic studies. These outcomes clearly indicate the great potential of the low cost solution assembly approach for sensor device
Ultrafast Carrier dynamics of In(x)Ga1(-x)N nanostructures grown directly on Si (111)
No full textWe show a flux dependence changes in structural, optical and electronic properties of InxGa1-xN nanostructures (NSs) namely nanocolumns (NCs), nanoflakes (NFs) and nanowall network (NWN) grown directly on Si(111) surface. Field emission scanning electron microscopy (FESEM) images were recorded to see morphological changes from NFs to NCs and NWNc etc, while high-resolution X-ray diffraction (HRXRD) omega - 2 theta scans were used to determine In incorporation. The maximum In incorporation was observed to be 20, 33 and 38% for the sharp transition from NFs to NCs and NWNs, respectively. The charge carrier dynamics of these grown NSs were probed using Ultrafast Femtosecond Transient Absorption Spectroscopy (UFTAS) with excitation at 350 nm pump wavelength. The UFTAS studies show the comparative charge carriers dynamics of the NWS, NCs and NFs. The charge carrier studies show a higher lifetime in NWNs as compare to NCs and NFs. Further, to examine electronic structure and level of degeneracy of these NSs, core-level and valence band spectra were analyzed by X-ray photoelectron spectroscopy (XPS), which manifest the upward band bending ranging from 0.2 eV to 0.4 eV
Star-Shaped CuS Flat Nanoflakes Reinforced Ni(OH)(2) Nanosheets for Enhanced Capacitance
No full textEnhanced electrochemical capacitance of 2D-nanosheets of Ni (OH)(2) via reinforcement of star-shaped CuS flat nanoflakes synthesized using in-situ hydrothermal root is presented. Microscopic and structural characterization suggest the inclusion of CuS nanoflakes in the films. Reinforced CuS nanoflakes offer high surface area resulting into open-sheet morphologies for Ni(OH)(2)@CuS films; contrasting with the folded sheet structures attained for the neat Ni(OH)(2) films. The remarkably high bulk (10(-3) Scm(-1)) conductivity of CuS enhances the conductivity and enable facile electron transport in the composites. Asymmetric supercapacitors constructed using Ni (OH)(2)@CuS and graphite as the electrodes is noted to show specific capacitances of 642 Fg(-1) at current density of 1 Ag-1, good rate capability and excellent cycling stability (86% capacitance retention at the end of 1000 cycles) relative to the neat Ni(OH)(2) based supercapacitor cells that shows specific capacitance of 142 Fg(-1) at the same current density. The direct contact of Ni(OH)(2) with the conductive CuS nanoflakes and highly porous structures of Ni(OH)(2)@ CuS electrodes doubles the power densities of the Ni(OH)(2)@ CuS supercapacitors than Ni(OH)(2) cells due to the low ion-diffusion resistances for charging by ions from the electrolyte, afforded by the short diffusion pathways in the composites
Structural phase transition, impedance spectroscopy and narrow optical band Gap in (1-x)KNbO3-x Ba(Sc1/2Nb1/2) O-3
No full textIn the progress of exploring lead-free ferroelectric perovskites, a new solid solution of (1-x) KNbO3-x Ba(Sci Nbl) O-3 is synthesized using solid state method. The effect of Ba and Sc codoping on structural phase transition, dielectric, ferroelectric, electrical, and optical properties is systematically studied. A narrow band gap of 1.98eV is observed at x = 0.05. On further increase in x, the optical band gap increases due to increased strain. The crystal symmetry changes from orthorhombic at x = 0.00 to tetragonal phase at x = 0.35. A new Raman active mode evolves at 180 cm(-1) at x = 0.15, which could be the TO or LO phonon of A(1) symmetry. The electrical microstructure of the prepared electroceramics at room temperature has been investigated using impedance spectroscopy. This newly synthesized ferroelectric perovskite material has promising potential applications for photocatalysis and photovoltaics, especially under the visible light spectrum
Role of National Pressure and Vacuum Metrology in Indian Industrial Growth and Their Global Metrological Equivalence
No full textThe pressure and vacuum metrology group of National Physical Laboratory (NPL) has a strong role in metrological research and development in India because of its importance to the nation's economy as well as the constitutional obligation following NPL charter of developing and maintaining national standards of pressure and vacuum measurements. Although, the group is successfully fulfilling its national duties, providing national calibration and measurement services since last 35 years, admittedly still there is lack of awareness, misinformation, and penetration of Calibration and Measurement Capabilities (CMCs) to the end users, grass root level industries, academician and Govt. laboratories. Occasionally, we are receiving feedbacks of such grey areas of awareness. Therefore, it was considered appropriate to compile the information of all these CMCs, expertise, training potential and available developed technologies in this article. The present paper also describes the summary of some of the results obtained in recent international key comparison exercises which have helped us to improve the quality in pressure metrology with a measure of technical efficiency