Browsing by Author "Sirimanne, P.M."
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Item 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 behaviorItem Fabrication of Solid State Dye Sensitized Solar Cell Using Red Sandalwood as Natural Sensitizer(Uva Wellassa University of Sri Lanka, 2018) Liyanage, P.L.D.R.; Etampawala, T.N.B.; Sirimanne, P.M.Commercially available dye-sensitized solar cells contain synthetic-metal centered dyes as a sensitizer. Natural dyes obtained from plants are a cheaper alternative for high cost synthetic dyes. The Main objective of this research is extraction of a natural dye which has wide availability with minimal chemical procedure to reduce cost of production and toxicity. The study intended in developing a solid-state-dyesensitized solar cell by sandwiching red-sandalwood pigments in between porous TiO2 and CuI films.Ti02 films were prepared on conducting glass substrates by using two different methods to obtain two different thicknesses and their morphologies were studied. According to the absorption spectra, presence of multiple layers increase the intensity of absorption of thicker (>10 p,m) TiO2 than thinner (<10 [tm) TiO2 film. Optical microscopic images of different TiO2 films show that thicker (>10 p.m) TiO2 film has no cracks present. Due to the absence of cracks in thicker TiO2 film, solid electrolyte cannot reach to glass substrate and therefore, no short current occurs. Red-sandalwood dye extracted to three different solvents (ethanol, acetone, acetonitrile) using soxhlet extraction and rotary evaporation. In each solvent three major electron transitions observe for redsandalwood extractions. Therefore, these three solvents are acceptable for extraction of red-sandalwood to use as sensitizer. A significant red shift in the absorption spectrum can be observed after chelating red-sandalwood pigments with TiO2 compare to that of dye in solutions. Formation of red sandalwood-Ti complex may be the reason for the observed red shift in the absorption spectrum. The bond formation between TiO2 and natural red-sandalwood pigments was confirmed by FTIR measurements. The deposition of hole-transfer (CuI) was eliminated problems encounter with the liquid electrolyte in photovoltaic cells. The morphology of CuI layer was studied. This demonstrates that triethylamine-hydrothiocyanate can control the formation of crystals of CuI by acting as a surfactant. Key words: Red-sandalwood, Solid-state dye sensitized solar cell, Ti02, Soxhlet extractionItem 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, aggregationsItem Nitrosoamine free preservative system for natural rubber latex(Uva Wellassa University of Sri Lanka, 2013) Udayangani, G.G.D.; Nilmini, A.H.L.R.; Sirimanne, P.M.colloidal dispersion of rubber particles in an aqueous medium, containing usually from about 20% to about 40% w/w rubber particles (dry rubber) and about 5% w/w non-rubber compounds, including carbohydrates, proteins, phospholipids and metal salts. Since it provides an optimum environment for microbial growth, in the absence of a proper preservation, the carbohydrates which the latex contains are oxidized in to short chain volatile fatty acids due to microbial activities. These acids destabilize the latex which results the coagulation of rubber particles (Blackley, 1997). Preservatives can effectively inhibit the bacterial growth in fresh NR latex. Hence the formation of acidic compounds resulting from bacterial activity in the latex is inhibited, which in turn inhibits coagulation. Since the most widely used preservative, Tetramethyl thiurumdisulfide (TMTD) forms carcinogenic nitrosamine, present invention is mainly focused on the provision of a nitrosoamine free preservative system for latex concentrate to stabilize the latex over a period of six months. Volatile fatty acid number is an important measure of the level of deterioration and stability of the latex. Therefore the preservative activities of new developing system (NDS) for treated latex concentrate was tested based on the measurements of volatile fatty acids (VFA) number test. The current study was carried out at the Rubber chemistry & Technology laboratories of Rubber Research Institute, Ratmalana. Three experimental trials with different treatments of NDS were conducted during this study. The trial (I) was carried out to find out the optimum concentration of NDS in preservation of natural rubber latex. In order to compare the efficiency of NDS with the conventional preservative, the VFA number of the latex, treated with ammonia/TMTD/ZnO (TZ) system and NDS was determined respectively. In trial (II), the effect of NDS on latex preservation in combination with a co-activator was determined. The effect of ammonia on the activity of novel preservative and the appropriate combination of ammonia and NDS to preserve and stabilize the latex were evaluated in trial (III).The appropriate combination was used to prepare centrifuged latex and other properties of the concentrated latex such as total solids content (TSC), dry rubber content (DRC), pH, KOH number, Brookfield viscosity were measured according to ISO standard methods and compared with the centrifuged latex preserved by adding 0.2% ammonia (NH 3), 0.025% of 1:1 mixture of tetramethylthiuramdisulphide (TMTD) and Zinc oxide (ZnO) combination as a control sample.VFA values of trial (I) and (II) were analyzed using one way analysis of variance (ANOVA) with MINITAB statistical package 16.0 version. The Experiment trials were done using complete randomized design (CRD). Means comparison of results was done by using the least significant difference (P<0.05) test (LSD).Item Red light emission from ZnO:Eu |CuCNS hetro-junction under cathodic polarization(Uva Wellassa University of Sri Lanka, 2013) Sirimanne, P.M.Recentlya considerable interest has been shown on the studies of photo-luminescence (PL) of lanthanides doped oxide ceramics. The group of rare-earth ions exhibits unique PL bands at particulate wavelengths that are highly independent from the host matrix. However, width and intensity of PL bands frequently change with the host material. ions are one of the best candidates to study luminescence properties compared to other lanthanide elements (Nogami, 2002). In this study, Eu ions were bonded to ZnO ceramic via organic molecules. Further enhancement of luminescence bands was observed by coupling with selected oligomers to Eu ions. A hetero-junction was prepared by depositing copper-thiocyanate on surface modified zinc oxide ceramic. Red light emission was observed from the surface bounded Eu ZnO:Eu |CuSCN hetro-junction under reverse bias. ions of Methodology ZnO was deposited on Fluorine doped tin oxide (FTO) coated glass substrates as previously discussed (Sirimanne et al, 2011). ZnO thin films were kept immersed in 2,2'-bipyridyl 4,4'- dicarboxylic acid (abbreviated as dcbpy, 200 μM in ethanol), EuCl3 (1 mM in ethanol) and 2- thenoyltrifluoroacetone (abbreviated as TTA, 200 μM in ethanol) for one hour in each solution in order.