Research Publications
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Publication Open Access Synergistic Charge Dynamics and Light Harvesting in TiO₂/MgO Composites for Efficiency Enhancement in CdS Quantum Dot-Sensitized Solar Cells(Faculty of Engineering, 2026-01) Ajward, N.F.; Fernando,J.V.P.; Perera, V.P.S.Quantum dot-sensitized solar cells (QDSSCs) represent a promising advancement in renewable energy technologies, with recent improvements achieving power conversion efficiencies close to 6%. Structurally similar to dye-sensitized solar cells (DSSCs), QDSSCs employ quantum dots (QDs) as sensitizers that absorb photons and inject excited electrons into the conduction band of a wide-bandgap semiconductor electrode, while the redox electrolyte removes the generated holes and completes the circuit through regeneration at the counter electrode. Quantum dots composed of materials such as CdS, CdSe, PbS, and InP are increasingly studied for use in QDSSCs, offering the advantage of tunable optical band gaps through particle size manipulation. This adaptability enhances QDSSCs’ design potential, enabling the integration of third-generation solar cell configurations, including multiple exciton generation (MEG), to further improve energy conversion efficiency. Despite these advancements, QDSSC performance is currently limited by issues such as reduced photovoltage and recombination losses at the TiO₂-QD-electrolyte interface. This study investigates the effect of MgO incorporation into TiO₂ photoanodes on the photovoltaic performance of CdS QDSSCs, with particular attention to the fill factor (FF) and overall cell efficiency. MgO is expected to act as an interfacial passivation layer suppressing combination and improving charge-selective transport. In addition, MgO may enhance light scattering within the photoanode, thereby improving light harvesting and short-circuit current density. In this study, MgO powder was incorporated in specific mass ratios with TiO₂, followed by the application of CdS quantum dots (QDs) on the TiO₂/MgO composite layer using the SILAR method. Results indicated a significant improvement in the fill factor (FF) at an optimal MgO-to-TiO₂ ratio, attributed to synergistic effects of MgO on interface stabilization, reduced recombination, and enhanced charge transport. The optimized MgO-modified TiO₂ films achieved a current density of 1.95 mA cm-2, voltage of 437 mV, and power of 0.121 mW (active area = 0.49 cm²), reaching an efficiency of 0.311 % (18.7% higher than TiO₂/CdS QDSCs), with improved interfacial impedance, Incident Photon to Current Efficiency (IPCE), and FF of 0.374.Publication Open Access Synergistic Charge Dynamics and Light Harvesting in TiO₂/MgO Composites for Efficiency Enhancement in CdS Quantum Dot-Sensitized Solar CellsSynergistic Charge Dynamics and Light Harvesting in TiO₂/MgO Composites for Efficiency Enhancement in CdS Quantum Dot-Sensitized Solar Cells(Faculty of Engineering, 2025-09-09) Ajward, N.F.; Fernando, J.V.P.; Perera, V.P.S.Quantum dot-sensitized solar cells (QDSSCs) represent a promising advancement in renewable energy technologies, with recent improvements achieving power conversion efficiencies close to 6%. Structurally similar to dye-sensitized solar cells (DSSCs), QDSSCs employ quantum dots (QDs) as sensitizers that absorb photons and inject excited electrons into the conduction band of a wide-bandgap semiconductor electrode. while a redox electrolyte removes the generated holes, completing the circuit by regenerating them at the counter electrode. Quantum dots composed of materials such as CdS, CdSe, PbS, and InP are increasingly studied for use in QDSSCs, offering the advantage of tunable optical band gaps through particle size manipulation. This adaptability enhances QDSSCs’ design potential, enabling the integration of third-generation solar cell configurations, including multiple exciton generation (MEG), to further enhance energy conversion efficiency. Despite these advancements, QDSSC performance is currently limited by issues such as reduced photovoltage and recombination losses at the TiO₂-QD-electrolyte interface. This study explores the use of magnesium oxide (MgO) coatings on TiO₂ nanoparticles to address these limitations, focusing on improving the fill factor (FF) and overall cell efficiency. MgO serves as an electron-blocking layer, effectively reducing recombination and associated energy losses. Furthermore, MgO facilitates electron transport from QDs to the TiO₂ electrode, improving charge collection. The light-scattering properties of MgO also increase the photon's path length within the cell, enhancing light absorption and consequently boosting the short-circuit current. In this study, MgO powder was incorporated in specific mass ratios with TiO₂, followed by the application of CdS quantum dots (QDs) on the TiO₂/MgO composite layer using the SILAR method. Results indicated a significant improvement in the fill factor (FF) at an optimal MgO-to-TiO₂ ratio, attributed to synergistic effects of MgO on interface stabilization, reduced recombination, and enhanced charge transport. The optimized MgO-modified TiO₂ films achieved a current density of 1.946 mA, voltage of 437 V, and power of 0.121 W, reaching an efficiency of 0.311 (18.7% higher than TiO₂/CdS QDSCs), with improved interfacial impedance, Incident Photon to Current Efficiency (IPCE), and FF of 37.4%.Publication Open Access Use of Ascorbic Acid Linker in Enhancing the Photovoltaic Performance of CdS/TiO2 Quantum Dot Sensitized Solar Cells(SLIIT, Faculty of Engineering, 2025-01) Ajward, N.F.; Davisan, S.; Perera, V.P.S.This study explores the use of ascorbic acid to enhance the photovoltaic performance of CdS/TiO2 Quantum Dot Sensitized Solar Cells (QDSSCs). Ascorbic acid acts as a mild reducing agent, donating electrons to Ti atoms on the TiO2 film, effectively filling oxygen vacancies known to act as recombination centers for photogenerated charge carriers. By passivating these detrimental sites, ascorbic acid facilitates improved carrier transport and reduces recombination, ultimately boosting photocurrent and overall efficiency. QDSSCs fabricated via the Successive Ionic Layer Adsorption and Reaction (SILAR) method were characterized using I-V measurements, Incident Photon to Current Conversion Efficiency (IPCE), Impedance Spectroscopy (IS), and overall power conversion efficiency. The optimized cell incorporated with ascorbic acid demonstrated a remarkable improvement compared to the control, achieving a short circuit current density (Jsc) of 4.863 mA/cm², open circuit voltage (Voc) of 446.1mV, efficiency of 1.368%, fill factor of 24.6%, and maximum power of 0.342mW. Optimization of ascorbic acid absorption time and precursor concentrations resulted an impressive 68.26% enhancement in efficiency (from 0.813% to 1.368%) and increase in maximum power from 0.163 mW to 0.342 mW for 0.64 cm². cell. This study highlights the potential of ascorbic acid as a simple and effective strategy for enhancing the performance of CdS/TiO2 QDSSCs, paving the way for further developments in low-cost and efficient solar cell technologies.Publication Open Access Fabrication, Characterization, and Gas Sensing Properties of Different Semiconductor Metal Oxide Nanostructures for LPG Detection: A Comparative Study(SLIIT, Faculty of Engineering, 2025-01) Bandara, A.H.M.N.N.; Senadeera, G.K.R.; Bandara, K.N.D.; Perera, V.P.S.The research explores how the structural, morphological, and electrical properties of nanostructured semiconductor metal oxides (SMOs), including Cu2O, ZnO, TiO2, and reduced graphene oxide (rGO), synthesized via electrochemical deposition and doctor blading techniques, influence their effectiveness in sensing liquid petroleum gas (LPG). Scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis were used to assess the chemical composition and structure. Cu2O, ZnO, and TiO2 were found to exhibit significant polycrystalline structures, with increasing average crystallite sizes of approximately 42.8 nm, 70.1 nm, and 87.78 nm, respectively. The dominant (111) Cu2O phase displayed a homogeneous cuboid morphology. rGO exhibited a singleplane (002) microstructure with a crumpled paper texture and an average crystallite size of ~85.3 nm, indicating a successful hydrothermal reduction of graphene oxide (GO). UV-vis absorption spectra in the range of 200 – 800 nm revealed the presence of different energy bands in ZnO, TiO2, and rGO, alongside their major band energies of 3.2 eV, 3.3 eV, and 1.9 eV. Cu2O thin films, with the lowest band energy gap of 2.5 eV, exhibited high photocatalytic activity, potentially enhancing chemical reaction rates during gas sensing under light exposure. Additionally, alternating current (AC) impedance spectra of SMO indicated increased film conductivities with positive bias voltages. ZnO films showed the most significant gas response (~27%) for LPG sensing at 70 ℃, with response and recovery times of less than 20 seconds. A stable and considerably high LPG sensitivity of ~11% was discovered with Cu2O. This finding underscores the significance of its relatively small grain size in influencing its sensitivity to LPG.Publication Embargo Efficiency Enhanced by Chelation of Al3+ Metal Ions with Erythrina Fusca Flower Dye Harnessing Bathochromic Shift(SLIIT, Faculty of Engineering, 2024-10) Mannawadu, M.W.M.K; Perera, V.P.S.Utilization of natural dyes in dye-sensitized solar cells (DSSCs) presents a sustainable approach towards enhancing photovoltaic efficiency. This study explores the bathochromic shift exhibited by Erythrina fusca (Erabodu) flower dye upon chelation with Al3+ ions, offering an innovative strategy for improving DSSC performance. 20g of chopped flower petals was boiled with 50ml of ethanol until flower petals become pale in colour in the dye extraction process. After that, 0.1 M, AlCl3 solution was added dropwise to 2ml of dye solution until the colour changed to purple. The pH value of Erabadu bare dye was recorded as 5.47 and with the Al3+ ion addition it was changed to 4.49. Through spectroscopic analysis and electrochemical characterization, the chelation mechanism and its impact on dye absorption spectra and electron transfer dynamics was elucidated. The Dye was coated on a thin film of TiO2 nanoparticles deposited on fluorine-doped tin oxide (FTO) glass plates. FTO glass which coated with platinum was used as the counter electrode and iodin/triiodide (I2 / I3 -) was used as the electrolyte. Solar cell was tested with a light source with an intensity of 100 mW/cm2. Al3+ ion chelated Erabadu dye exhibited higher efficiencies than bare dye which was 1.627%. The open circuit voltage (Voc) of this cell was 470mV, short circuit current density (Jsc) was 4.00 mA/cm2 and the fill factor of DSSC’s was 0.553. The Incident Photon to Current Conversion Efficiency (IPCE) of the cell further revealed the action spectrum was broadened between 300 nm – 500 nm enhancing the efficiency. Our findings unveil the potential of Al3+ ion chelated Erythrina fusca dye as a promising sensitizer for DSSCs, paving the way for eco-friendly and efficient solar energy conversion.