Browsing by Author "Ranasinghe, J.I."

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    Dye Sensitized Solar Cells Based on TiO2 Nanotubes and Enhancement of Efficiency of Solar Cells by the Treatment of Nanotube by TiCI4
    (Uva Wellassa University of Sri Lanka, 2010) Chandrasekera, P.R.; Akilavasan, J.; Ranasinghe, J.I.; Bandara, J.M.S.
    Introduction of the Dyesensitized solar cells (DSSC) by MichealGreatzel has opened up a new way to convert light energy in to electricity with economically viable cost. DSSC was originally constructed utilizing TiO2nanocrystalline particles as an electron conducting medium. Despite of the high internal surface area, the random nature of the TiO2nanocrystalline particle network results electrons to recombine reducing cell performance. In this investigation, TiO2 nanotubes have been introduced instead of TiO2 nanoparticles as they provide straight pathway to electron transport reducing charge recombination. TiO2nanotubes were synthesized via hydrothermaltreatment.Theformation of nearly 10 nm diameter nanotubes was confirmed by Scanning Electron Microscopy analysis. TiO2 nanotube based electrode was prepared by freeze drying the nanotube precipitate and re-suspends in water by ultrasoneing followed by electrophoretic deposition onto a conducting substrate (FTO) as anode and Pt as cathode. The optimum electro deposition potential, electrolyteand time was found to be 40 V, nanotube suspension and methanol 3:1 (v/v) ratio and 7 minutes respectively. The electrode was sensitized with cis-bis(isothiocyanato)bis(2,21-bipyridy1-4,4'-dicarboxylato)-ruthenium(11) dye (N3) and iodine/triiodine redox couple was used as an electrolyte. Solar cell fabricated with TiO2 nanotubes and sensitized with N3 dye showed an open circuit voltage (V„) of 820 mV and short circuit photocurrent density (Jsc) of 0.92 mA/cm2 under 1.5 AM G irradiation. The solar cell device fabricated with TiCI4 treated nanotube electrode showed V„of 804 mV and I„of 5.44 mA/cm2. The treatment of TiO2 nanotube electrode with TiCI4 resulted in increase in solar cell efficiency from 0.52 % to 2 %. Keywords: Hydrothermal, Nanocrystalline, Nanotube, TiCI4 treatment
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    Zinc Oxide Nanorods for Hybrid Bulk Heterojunction Solar Cells
    (Uva Wellassa University of Sri Lanka, 2010) Herath, H.M.N.K.K.; Ranasinghe, J.I.; Bandara, J.M.
    Solar cells are devices which convert energy of photon to the electrical energy by photovoltaic effect. Among the different structures of solar cell devices, the demand for low cost and efficient solar cell is tremendous. Though the polymer photovoltaic devices can be easily fabricated with the available technology, increase in the device efficiency is an upward hurdle due to rapid charge recombination with the increase in thickness of the solar cell. However, this problem can be overcome by blending donor-acceptor materials together allowing better charge separation as well as transport and high cell thickness for harvest more energy from sun light. Bulk heterojunction solar cell overcome that barrier by blending donor acceptor material together which allows good charge transport and high cell thickness for harvest more energy from sun light. Introducing nanostructure inorganic charge transport material charge transport area, charge collection and transport can be enhanced. In this study, ZnO nanorods for Hybrid- bulk heterojunction(HBHJ) solar cells and their performance were studied. HBHJ solar cells were fabricated employing ZnO nanorod as electron transport media, blend of Poly(3-hexylthiopene) (P3HT) and (6, 6)-phenyl C6-butyric acid methylester (PCBM) as an light active layer and polyethylene dioxythiophene polystyrene (PEDOT: PSS) as a hole transport medium. ZnO nanorods were fabricated on fluorine doped conducting glass (FTO) by electro deposition method and on which the photoactive polymer layer was coated as a thin film using a blend of P3HT: PCBM in chlorobenzene followed by a deposition of a thin layer of PEDOT: PSS by spin coating technique. It was noticed that the performance of solar cell was highly depended on the preparation conditions and the solar cell performance optimization techniques were investigated in this study. The optimized device yielded Voc of 396 mV, photocurrentof 5. mA/cm2, a fill factor of 30% with an overall efficiency of 0.62%. Key words: ZnO nanorods, HBHJ solar cells, spin coating