Performance of colloidal CdS sensitized solar cells with ZnO nanorods/nanoparticles

As an alternative photosensitizer in dye-sensitized solar cells, bovine serum albumin (BSA) (a nonhazardous protein) was used in the synthesis of colloidal CdS nanoparticles (NPs). This system has been employed to replace the commonly used N719 dye molecule. Various nanostructured forms of ZnO, namely, nanorod and nanoparticle-based photoanodes, have been sensitized with colloidal CdS NPs to evaluate their effective performance towards quantum dot sensitized solar cells (QDSSCs). A polysulphide (S-x(2-))-based electrolyte and CuxS counter electrode were used for cell fabrication and testing. An interesting improvement in the performance of the device by imposing nanorods as a scattering layer on a particle layer has been observed. As a consequence, a maximum conversion efficiency of 1.06% with an open-circuit voltage (V-OC) of 0.67 V was achieved for the ZnO nanorod/nanoparticle assembled structure. The introduction of ZnO nanorods over the nanoparticle led to a significant enhancement of the overall efficiency compared to the corresponding bare nanoparticles

Localization of Dirac-like excitations in graphene in the presence of smooth inhomogeneous magnetic fields

The present article discusses magnetic confinement of the Dirac excitations in graphene in presence of inhomogeneous magnetic fields. In the first case a magnetic field directed along the z axis whose magnitude is proportional to $1/r$ is chosen. In the next case we choose a more realistic magnetic field which does not blow up at the origin and gradually fades away from the origin. The magnetic fields chosen do not have any finite/infinite discontinuity for finite values of the radial coordinate. The novelty of the two magnetic fields is related to the equations which are used to find the excited spectra of the excitations. It turns out that the bound state solutions of the two-dimensional hydrogen atom problem are related to the spectra of graphene excitations in presence of the $1/r$ (inverse-radial) magnetic field. For the other magnetic field profile one can use the knowledge of the bound state spectrum of a two-dimensional cut-off Coulomb potential to dictate the excitation spectra of the states of graphene. The spectrum of the graphene excitations in presence of the inverse-radial magnetic field can be exactly solved while the other case cannot be. In the later case we give the localized solutions of the zero-energy states in graphene.Comment: 9 pages, 6 figures, to appear in Journal of Physics: Condensed Matte

Zn2SnO4 as an Alternative Photoanode for Dye Sensitized Solar Cells: Current Status and Future Scope

Dye sensitized solar cells (DSSCs), the third generation solar cell devices have been designed to produce large-scale, inexpensive, environmentally benign solar power devices having promising efficiency and lifetime. Albeit, perfect commercialization of the devices has not been possible worldwide so far, research in this area is immensely growing with promising future. Basic principles of DSSCs along with essential characteristics of working electrode, photoanode and other major components, namely photosensitizers, electrolytes and counter electrodes, which are essential to fabricate an efficient device, are concisely highlighted in this review. In addition, successive propagation of research based on the semiconducting oxides as photoanode for the DSSC device starting from binary to ternary oxides, the perspectives, selection strategies and the status with respect to performance has also been highlighted. In an effort to introduce newer oxides as appropriate alternatives to the pioneer TiO2, ZnO-SnO2 based ternary oxide Zn2SnO4 has become successful and even better than its well-studied binary counterparts ZnO and SnO2 in a short time. Taking into account the scattered reports available, the structural, microstructural, opto-electronic and physico-chemical properties together with the performance of the newly projected ternary oxide Zn2SnO4 are discussed in this short review with a prospect of its potential as an alternative photoanode in DSSCs

Hydrothermally synthesized fluorescent Zn2SnO4 nanoparticles for dye sensitized solar cells

In this work, we have investigated the interaction of hydrothermally synthesized Zn2SnO4 (ZTO) nanoparticles (NPs) with two different commercial photo sensitizers such as N719 and N3 dye molecules and studied their performance in dye sensitized solar cells (DSSC). Interestingly, the ZTO NPs exhibited band edge emission in the mid UVA region and as a result possibility of enhanced light harvesting in the terminal UVA region was anticipated in the device due to the efficient energy transfer observed in case of the sensitizer N719 than N3. The dye sensitization property has been found to be higher for the N3 dye molecules than the N719 dye molecules as based on the time dependent dye loading study. The devices fabricated with ZTO-N719 exhibited improved photovoltaic performance compared to the ZTO-N3 based devices exhibiting an overall conversion efficiency of 2.56% by the former compared to the later (1.90%) under 1SUN 1.5AM illumination and sensitization for 12 h

Photovoltaic and photocatalytic performance of electrospun Zn2SnO4 hollow fibers

The phase pure hollow Zn2SnO4 and green emitting ZnO-SnO2-Zn2SnO4 composite fiber have been prepared by post calcining the as formed fiber by electrospin technique. Depending upon the calcination temperature, the as prepared fiber exhibited a striking variation in composition, microstructure, optical and photo-electrochemical properties. The composition dependent dissimilarity in photovoltaic performance and photocatalytic activity has been established in this work. A relatively enhanced open circuit voltage (Voc) of 0.76 V, fill factor (FF) of 59.78%, short circuit current Qsc) of 4.2 mA/cm(2) and an overall conversion efficiency (n) of 1.93% have been achieved for the phase pure Zn2SnO4 porous fiber obtained at the elevated calcination temperature of 1000 degrees C. On the contrary, a relatively reduced Voc, FF, J(sc) and n of 0.70 V, 42.54%, 3.8 mA/cm(2) and 1.17%, respectively, have been achieved for the 800 degrees C calcined dense fiber consisting of a mixture of three distinct phases ZnO, SnO2 and Zn2SnO4. Unlike photovoltaic behaviour the trend in photocatalytic performance interestingly got reversed for the ZnO-nO(2)-Zn2SnO4 composite fiber owing to its superior photo-induced charge separation ability followed by generation of larger amount of active hydroxyl radicals (OFF). Our results establish the composite fiber as a preferred photocatalyst in comparison to phase pure Zn2SnO4 towards the textile dyes Methylene blue and Congo red and non absorbing organic pollutants such as Phenol and Bisphenol A under UV illumination. (C) 2016 Elsevier B.V. All rights reserved

Enhanced stability of Zn2SnO4 with N719, N3 and eosin Y dye molecules for DSSC application

In view of the increased prospects of Zn2SnO4 as an alternative photoanode for dye sensitized solar cells (DSSCs), we synthesized phase pure Zn2SnO4 nanostructures by a cost effective sonochemical technique. In order to establish the stability of this alternative photoanode in DSSCs, we further explored the interaction of the synthesized Zn2SnO4 with commonly used photosensitizers in DSSCs, such as N3, N719 and eosin Y. Based on the time dependent optical studies we could establish the prominence of anchoring groups in controlling the dye loading. Optical studies confirmed an enhanced stable interaction of Zn2SnO4 with all the studied sensitizers which could be beneficial in designing DSSC devices in future. In addition, we also established contact angle measurement as an indirect tool to understand the surface characteristics and thereby optimize the dye loading and stability of the photoanode surface. With the help of contact angle data, we could unequivocally establish the stability of the Zn2SnO4 photoanode surface modified with N3 and N719 dye molecules. Our studies further suggest the enhanced and superior stability of the prepared Zn2SnO4 compared to ZnO in different chemical environments. The quenching of the fluorescence and the abrupt decrease in the contact angle owing to an increase in the surface roughness further strengthen the above conclusion. To our best knowledge, this probably is the first report on the synthesis of Zn2SnO4 by a sonochemical process and its interaction with various photosensitizers. An exceptionally high open circuit voltage of >0.8 V was observed for all the devices fabricated with the synthesized ZTO as a photoanode. Our studies could pave way to future developments in the area of DSSCs using Zn2SnO4 as a photoanode

Iron antimonate quantum dots exhibiting tunable visible light emission

In this paper, we report for the first time tunable visible light emission from FeSbO4 quantum dots prepared by combustion synthesis, a property hitherto unknown for this oxide. The auto-combustion process results in the formation of quantum dots of rutile FeSbO4 of 3-6 nm in size exhibiting tunable visible blue light emission in the 350 to 550 nm wavelength range with quantum yields of 2.74 and 2.03, respectively, in solid form. These fluorescent quantum dots could form a new series of semiconducting quantum dots for various biosensing, imaging and photovoltaic applications

Multiband Fluorescent Graphitic Carbon Nanoparticles from Queen of Oils

Here, we report a facile and rapid approach for the synthesis of multiband fluorescent graphitic carbon nanoparticles (CNPs) from queen of oils exhibiting multifarious applications. The as-prepared and calcined CNPs exhibited excitation dependent multiband emission that has been explored for detection of deoxyribonucleic acid (DNA) and removal of water pollutant cationic dye. We report here selective detection of Escherichia coli (E. coli-DNA) using fluorescent graphitic carbon nanoparticles through fluorescence enhancement of the nanoparticle. On the basis of thermal melting, CD and calorimetric studies, we could conclude that the interaction of CNPs are stronger with E. coli-DNA resulting in preferential selectivity for E. coli-DNA. The as-derived CNPs could be an emerging cost-effective material for the selective detection of E. coli-DNA and a sorbent for removal of basic pollutant dyes from water