Browsing by Author "Wijayaratne, W. M. K. B. N."

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Optimizing concentration of titanium dioxide nano-fillers in PEO gel-polymer electrolytes for enhanced performance of dye-sensitized solar cells
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Chandrika, R. P.; Liyanage, J. P.; Wijayaratne, W. M. K. B. N.; Bandara, T. M. W. J.
The influence of nano-composite gel-polymer electrolytes on the performance of dye-sensitized solar cells (DSSCs) has attracted significant attention recently. In this study, titanium dioxide nanoparticles (TiO2) with varying percentages were incorporated into a gel-polymer electrolyte in order to determine the optimal nanofiller (NF) concentration as well as to study the effect of NFs composition on conductivity in the polymer electrolyte and light to current conversion efficiency of DSSCs. For these purposes, TiO2 NFs with an average particle size of 13 nm were incorporated into polyethylene oxide (PEO) based gel-polymer electrolyte. The TiO2 nano-composite electrolyte series were prepared by varying the TiO2 NF composition from 0.0 to 25.0 wt.% relative to the PEO weight. The DSSCs were assembled by sandwiching NF incorporated polymer electrolyte between a multilayer photoanode sensitized with N719 dye and platinum electrode. The conductivity and light to current conversion efficiency depend on the NF composition in the polymer electrolyte. The electrical conductivity of the electrolyte and efficiency of DSSCs containing nano-composite electrolytes increases with the increase in TiO2 content up to 17.5 wt.% and then decreases with any further increase in TiO2 percentage. Temperature-dependent electrical conductivity of the prepared nanocomposite gel-polymer electrolytes was investigated by gradually increasing the temperature from 20 °C to 80 °C increments of 10 °C. The conductivity increased with rising temperature within this range, and the temperature dependence exhibited VTF (non-Arrhenius) behavior. The optimum TiO2 composition was found to be 17.5 wt.%, with a conductivity of 5.18 mS cm-1 at 20 °C, which increased to 10.43 mS cm-1 when the temperature was raised to 80 °C. Thus the highest recorded conductivity was observed at the temperature of 80 °C, testing temperature was not raised further as higher temperatures cause the release of I2 from the electrolyte. The conductivity enhancement with added TiO2 can be attributed to the change in the morphology of the polymer network. TiO2 NFs contribute to this process by inducing electrostatic interactions/Lewis acid-base interactions between O atoms of the PEO and hydroxyl group of the TiO2 particles. DSSC assembled with the polymer electrolyte containing 17.5 wt.% of TiO2 NFs (the highest conducting electrolyte) exhibited the highest photoelectric conversion efficiency of 7.30%, representing a 28.1% enhancement compared to the reference DSSCs assembled with a filler-free gel-polymer electrolyte, which had an efficiency of (5.70%).
PEDOT: PSS/GO based supercapacitor for energy storage applications
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Ravindran, N. S.; Wijayaratne, W. M. K. B. N.; Bandara, T. M. W. J.
Traditional energy storage devices like batteries and capacitors suffer from low power and poor energy densities, highlighting the need for advancements in this field. Supercapacitors offer a promising alternative as the energy and power densities of supercapacitors are comparably high. In contrast with traditional capacitors the capacitance of the supercapacitors is in the order of farad (F), higher than the electrolytic capacitors (mF) and dielectric capacitors (μF). Especially composite supercapacitors integrating carbon-based materials with pseudocapacitive components like metal oxides or conducting polymers aim to enhance energy density while preserving high power density and long cycle life. Several attempts have been made previously using different combinations of the materials mentioned above. The primary aim of this study was to fabricate a supercapacitor using electrodes made of poly(3,4-ethylenedioxythiophene) polystyrene sulfonate and graphene oxide (PEDOT: PSS/GO) to demonstrate the electrochemical properties of the nanocomposite for energy storage applications. To prepare the electrodes of the supercapacitor, first, GO was synthesized using a modified Hummer’s method. The electrode fabrication process involved depositing the PEDOT: PSS/GO nanocomposite onto a graphite sheet of dimension 1 cm × 2 cm via the drop-casting method. The supercapacitor assembly was achieved by placing filter paper soaked in a 6M potassium hydroxide (KOH) solution between two electrodes made from a composite of PEDOT: PSS and GO on a graphite base. The resulting supercapacitor exhibited a specific capacitance of 18.84 F g-1, with an energy density of 0.65 Wh kg-1 and a power density of 29.2 W kg-1, as determined from the galvanostatic charge-discharge (GCD) curve data at a current of 0.5 mA. When ascorbic acid was added to the nanocomposite, the specific capacitance dropped to 13.04 F g-1, with an energy density of 0.45 Wh kg-1 and a power density of 14.44 W kg-1. This indicates that the supercapacitor without ascorbic acid achieves the highest specific capacitance. The CV results further demonstrated that despite the presence of a polymer, the absence of visible redox peaks shows that the supercapacitor operates as an electric double-layer capacitor (EDLC).