Sanhita Majumdar

Optical and electrical effects of thin reduced graphene oxide layers on textured wafer-based c-Si solar cells for enhanced performance

Photoluminescence active amine-functionalized reduced graphene oxide (af-RGO) has been synthesized at room temperature with prolonged sonication to obtain a free floating, hexagonally arranged carbon network having larger dimensions ∼(20 μm × 15 μm) in aqueous medium. The presence of amine in an RGO network has been confirmed by Raman, FTIR and photoluminescence (PL) studies. It has been used as the top layer on c-Si solar cells. Its effect on solar cell parameters was investigated. The effect of dilution (10% to 90%) of aqueous af-RGO and its coverage on c-Si solar cells leading to optimum cell parameters has been studied. The respective reflected and transmitted photon fraction through the af-RGO thin film obtained from a spectral response graph was estimated. The suitability of the synthesized material for c-Si cells has been established through different characterization supports, like height profile and the surface coverage on a polished silicon surface, analysed by atomic force microscopy (AFM) and field emission scanning electron microscopy (FESEM). It was observed that the 50% diluted sample shows the best performance with respect to the baseline parameters of solar cells. An enhancement of 4.6% in short-circuit current density (JSC) and 4.8% in fill factor (FF) was achieved over the baseline parameters of the cell, while dip coating the baseline cell in the optimized dilution of af-RGO.

Precursor dependent tailoring of morphology and bandgap of zinc oxide nanostructures

Zinc oxide (ZnO) nanoparticles have been synthesized by wet chemical processing from four different zinc precursor materials at room temperature. Synthesis of phase pure material with four different morphologies and orientations have been confirmed through different characterization techniques like, X-ray diffraction, field emission SEM, fourier transformed IR etc. The band gap energies of the synthesized materials were within specific semiconductor limits and the same have been determined from UV–Visible and photoluminescence spectra of the synthesized nanostructured ZnO materials. Thus it is possible to control ZnO nanostructures and morphologies through facile room temperature synthesis and tailor their band gaps for different application purposes.

Switching of selectivity from sulfur dioxide to butane: The role of V2O5 concentration in nanostructured SnO2 sensors

Vanadia (V₂O₅) doped tin dioxide (SnO₂) nanocrystallites were synthesized by sonication assisted simultaneous precipitation method, keeping in view their application for LPG (n-butane) gas sensor. The best sensing conditions were determined by studying the sensors under different operating temperatures with different vanadium loading (in the form of V₂O₅), in presence of 60-65% ambient humidity. 0.50 wt% V₂O₅ loaded SnO₂ exhibits the best sensitivity against butane at 4500C operating temperature, without using any expensive nobel metal catalyst. The same material exhibited a switching in selective sensing of SO₂ at a different V₂O₅ concentration (0.15 wt%), operated at lower temperature (3500C). The nanocrystalline powders were characterized by X-ray powder diffraction (XRD), scanning electron microscope (SEM) and current-voltage (I/V) measurement studies. The morphology of V₂O₅-doped SnO₂ nanocrystalline powder is elongated spherical in shape and the distribution of particle size is uniform, having the range of 70-90 nm, as confirmed by SEM and Brunauer-Emmett-Teller (BET) observations.