Browsing by Author "Wijesuriya, W.A.K.C."

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    Fabrication of Dye Sensitized Solar Cells on Conducting Plastic Substrates
    (Uva Wellassa University of Sri Lanka, 2016) Wijesuriya, W.A.K.C.; Senevirathna, A.J.M.H.L.; Sirimanne, P.M.
    Ninety percent of the energy consumption in the world is fulfilled by fossil fuels. As a result of unending usage, all kinds of fossil fuels will be depleted within next few decades. Therefore finding alternative energy sources is the prime scientific goal which has many challenges associated to it. In this context, solar energy has received a greater attention as an alternative and viable energy source. Several types of solar cells have been designed and fabricated by researchers to harness the solar energy. Dye-sensitized solar cell is one such device that belong to the 3rd generation solar cells and has roused significant attention due to its easy fabrication and low cost. Highest efficiency has been achieved from dye-sensitized solar cells using ruthenium based metal complexes. However, ruthenium metal complexes cause environmental issue and so does the weight of the glass substrates. Therefore reduction of the weight of the solar cells and finding an efficient organic sensitizer are essential scientific hurdles. In this study, an environmental friendly dye, 1-(2- hydroxycarbonyl-phenyl)-5-(2-hydroxy-5-sulfopheny1)-3-phenylformazan (zincon) is used as a dye (sensitizer) to fabricate a solar cell. Zincon dyes have their own conjugatedp¬orbitals with delocalized electrons in the compounds thus absorbing unique portion of the visible light and giving an intense color. Zincon dye exhibits solvatochromic behavior due to enforcement of Van der Waals interaction between dye molecules and solvents depending on their polarity. Zincon was coated on titanium coated conducting plastic substrate, which was prepared by doctor blade method and then was pressured using a hydraulic pressure instrument. Zincon dye has different surface chelating groups and making bonds easily with metal oxides. Coupling of zincon dye by COOH group with Ti4+ was confirmed by FTIR measurements. A platinum coated plastic substrate is attached to the dye coated film and the space was filed by the electrolyte by capillary action. I-V characteristics were measured under 1 Sun. Current-voltage characteristics of the cell were studied under simulated one sun. Photocurrent of 1.6 mAcni2, photo-voltage of 395 mV, fill factor 26.5 % and efficiency of 0.2 % were observed as the best performances of the cell. The photo-performances of the cell are much lower than those sensitized with ruthenium metal complexes based dyes. Keywords: Zincon, Dye sensitized solar cells, Conducting polymers, Solvatochromic behavior
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    Fabrication of Solid State Dye-Sensitized Solar Cells Using Squaraine Dyes as Sensitizers
    (Uva Wellassa University of Sri Lanka, 2016) Senevirathna, A.J.M.H.L.; Wijesuriya, W.A.K.C.; Sirimanne, P.M.
    Dye-sensitized solar cells (DSSCs) are 3rd generation solar cells combining both high efficiency and low cost of production. A solid-state dye sensitized solar cells are fabricated by using a hole-transporting p-type semiconductors replacing the liquid electrolyte used in DSSCs. Metal complexed dyes exhibit highest efficiencies over metal free organic dyes in DSSCs. However, there are several advantages of metal free organic dyes with respect to the metal centered dyes such as, low cost, and large absorption coefficients. The liquid electrolyte present in DSSCs exhibits several disadvantages such as evaporation, and degradation. Therefore, we made an attempt to produce solvent free, DSSC using two metal free organic dyes squaraine 3 (sq3) and squaraine 4 (sq4) dyes. In order to do that, a mesoporous TiO, layer was deposited on a compact layer ofTiO2 and sq3 and sq4 dyes were deposited on Ti02 by immersing them in the dye solution for 12 hours. The dye - coating process was carried out in an oil bath. Dye coated electrodes were dried in nitrogen atmosphere. Then hole conductor CuI was deposited on dye coated Ti02 films until the conductivity of the Cul film reaches 50 Qcm-I. The cell was constructed by pressing a Ni¬coated FTO glass plate on the TiO2IdyeICuI electrodes. UV-Vis spectra show both sq3 and sq4 absorb visible light in the visible region. Three different electron transitions with different intensities were observed for sq3. Broad peak over visible region was observed for sq4 when dissolved it in water. Almost constant absorption over near infrared (NIR) region was observed for sq4 when dissolved in acetonitrile and ethyl acetate. Both sq3 and sq 4 have surface chelating groups (COOH) with metal oxides. Thus, an efficient chelation was observed for sq3 and sq4 with TiO2 electrodes. sq3 and sq4 exhibit a broad absorption band in solid-state compare to liquid state because of the aggregations of dye molecules. Coupling sq3 and sq4 dyes with via COOH groups were confirmed by FTIR measurements. The current-voltage characteristics ofTi021dyelCul cells with sq3 sq4 dyes are studied under simulated one sun, the best achieved performances of the cells are sq3 dye efficiency 0.27% and sq4 dye exhibits 0.43% of efficiency which makes sq4 dye the better sensitizer than sq3 dye. Keywords: Dye sensitized solar cells, P-type semiconductors, Electrolyte, Chelation, aggregations