• S MOORTHY BABU

      Articles written in Bulletin of Materials Science

    • Electrodeposition kinetics of gallium arsenide

      S Moorthy Babu L Durai R Dhanasekaran P Ramasamy

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      A kinetic model has been developed for the electrodeposition of GaAs from solution containing reducible ions of both constituents and is based on the generalised Butler-Volmer equation. The effect of hydrogen ion concentration and activities of ions on the total current density is studied. Voltammograms corresponding to various values of hydrogen ion concentration and activities of ions are constructed by the computer simulation technique.

    • Photoconductivity studies of CdSe1−xTex thin films as a function of doping concentration

      D Ravichandran Francis P Xavier S Sasikala S Moorthy Babu

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      Thin films of CdSe1−xTex were prepared by using electro deposition with varying doping concentrations of Te(x). Photoconductive studies as a function of applied field, time, wavelength, and intensity of incident light were carried out at room temperature between 1 and 3·5 eV. After establishing that the electrode contacts made using silver paint were ohmic, it was found that as the concentration of Te(x) increases in CdSe1−xTex, the band gap of the material decreases according to the empirical relationEg = (2 − 1·5x)eV.

    • Ligand exchange in Cu$_2$ZnSnS$_4$ nanoparticles and its effect on counter electrode performance in dye-sensitized solar cells

      C IMLA MARY M SENTHILKUMAR S MOORTHY BABU

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      Ligand-exchanged Cu$_2$ZnSnS$_4$ (CZTS) nanoparticles (NPs) were successfully synthesized from colloidal NPs by replacing the long chain organic ligand from the surface of NPs via a bi-phasic method. It was found that ammonium sulphide salt ((NH$_4$)$_2$S) plays a key role in changing the surface of the NPs from hydrophobic to hydrophilic. The efficacy of the ligand exchange process over the surface of the CZTS NPs was analysed using X-ray diffraction, Fourier transform infrared spectroscopy, ultraviolet–visible spectroscopy and scanning electron microscopy with energy dispersive X-ray. The ligand-exchanged CZTS NP-based counter electrodes (CEs) were fabricated by drop casting the inorganic ligand (ammonium sulphide)-capped CZTS nanoink onto the conducting substrate. Our result indicates that dye-sensitized solar cells (DSSCs) with inexpensive CZTS NP-based CEs show 2.42% efficiency. The present result indicates that CZTS CEs will be helpful as an alternative CE to a Pt CE in DSSC application.

    • A modified high-temperature vapour deposition technique for fabricating CH$_3$NH$_3$PbI$_3$ thin films under an ambient atmosphere

      G MANOBALAJI M PANDIYARAJAN M SENTHILKUMAR S MOORTHY BABU

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      A modified two-step deposition technique was performed by vapour depositing methylammonium iodide (MAI) on lead iodide (PbI$_2$) films to fabricate good quality methylammonium lead iodide (MAPI) thin films under anambient atmosphere, and their properties were compared with conventional two-step solution processed MAPI thin films. Scanning electron microscopy results depicted that the MAI vapour-processed films have a uniform coverage and planar surface compared with the non-uniformly distributed granule-like morphology of the solution-processed MAPI film. X-ray diffraction results confirm that the vapour-processed films have better crystallinity compared to the conventional solutionprocessed MAPI thin films. An enhancement in the optical absorption and emission was observed for the vapour-processed films. The higher processing temperature of the modified-vapour deposition eliminates the effect of moisture during the ambient atmosphere processing of the MAPI films.

    • Copper indium sulphide:zinc sulphide (CIS:ZnS)-alloyed quantum dots as an eco-friendly absorber in solar cells

      M SENTHILKUMAR C IMLA MARY M PANDIYARAJAN G MANOBALAJI S MOORTHY BABU

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      Synthesis and characterization of less toxic copper indium zinc sulphide (CIS:ZnS)-alloyed quantum dots (QDs) were carried out and the ligand exchange process towards the efficiency enhancement in CIS:ZnS QD-sensitized solar cellwas demonstrated. The colloidal CIS:ZnS QDs were synthesized by an inexpensive heat up method with oleic acid as the capping ligand. The optical properties were analysed through ultraviolet–visible absorption and photoluminescence emission spectroscopy. The influence of the ligand exchange process on the CIS:ZnS QD-based solar cells was analysed with thefabrication of two batches of solar cells. The ligand exchange process was confirmed from Fourier transform infrared and thermogravimetric analyses. The QD-sensitized solar cells were fabricated using a CIS:ZnS QD-loaded titania photoanode and by employing copper sulphide as the counter electrode. The photovoltaic performance of the fabricated QD solar cells was analysed through photovoltaic characterization methods (current density–voltage characteristics of the devices under the simulated solar light conditions and external quantum efficiency measurements). The ligand-exchanged QD-loaded solar cells show enhanced power conversion efficiency compared to the long chain ligand-capped CIS:ZnS QD-sensitized solar cells.

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