Browsing by Author "Jayathilaka, K. M. D. C."

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Co-sensitization performance of dye sensitized solar cell based on combination of natural dyes extracted from grapes and green tea
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Shakya, M. D. P. A.; Jayathilaka, K. M. D. C.; Wanninayake, W. T. M. P. K.; Kumara, R.; Siripala, W. P; Wijesundera, L. D. B. R. P.
The global energy crisis is a pressing issue that is likely to intensify in the future. Researchers are actively exploring alternative energy sources to create a more sustainable and secure future for the world's energy needs. The advantages of Dye Sensitized Solar Cells (DSSC) include simple, easy and cost-effective manufacturing, the ability to use flexible substrate, and the possibility to attain reasonable conversion efficiency. Their unique properties make them a promising solution for addressing energy shortages and advancing renewable energy technologies. The current efficiency of DSSCs is low, however dye modification can enhance their photoactive performance. Dye modification enhances the dye's optical characteristics and photoconductivity. Co-sensitization is a chemical approach to improve DSSC performance by using two or more dyes with distinct optical absorption properties. This study explores co-sensitized DSSC using natural dyes to enhance photoactive performance. The TiO2 was prepared by mixing TiO2 powder (Titanium (IV) dioxide), Acetic acid, and Ethanol. To study the effect of natural dyes on the photoelectric conversion efficiency of DSSCs, extracts of green tea and grapes were used as sensitizers. The photovoltaic characteristics of green tea and grape dyes were studied separately and then blended in a cocktail at four various volume ratios of tea and grapes dyes 1:4, 2:3, 3:2, and 4:1 to determine the best combination. The solar cell devices were characterized using absorbance spectra, electrochemical impedance, and current density-voltage (J-V) curves. UV-visible spectra were taken from the PekinElmer Ultraviolet and Visible Spectroscopy (UV/VIS) Lambda 365. J-V and electrochemical impedance spectroscopy measurements were taken with a Gammy series G 300 potentiostat using ELS300 software. A combination of green tea and grape dyes can increase absorbance and broaden the light absorption spectrum more than a single dye. The 1:4 tea-grape mixed dye demonstrated the best DSSC efficiency value as well as the highest photocurrent value. Cosensitization resulted in a conversion efficiency of 0.0198%, photocurrent density (JSC) of 230 µA/cm2, open circuit voltage (VOC) of 0.28 V, and fill factor of 30% while efficiency also increased from 0.0058% to 0.0198%. The results show that a higher anthocyanin composition relative to chlorophyll can improve DSSC efficiency. The impedance results show that the dye mixture decreases internal resistance, which is consistent with the observed cell efficiencies. Furthermore, the best results were obtained with an acidified cocktail at pH 3 with the same volume ratio of the non-acidified cocktails. Hydrochloric acid was used for acidification. The study reveals that co-sensitization holds significant potential for the future development of DSSCs.
A Comparative Study: Sequential and Single-Step-Electrodeposited CZTS Thin Films
(Physica Status Solidi, 2022) Fernando, W. T. R. S.; Jayathilaka, K. M. D. C.; Wijesundera, R. P.; Siripala, W.
CZTS (Cu2ZnSnS4) is a relatively new and promising semiconductor material suitable for photovoltaic applications due to its favorable optoelectronic properties. Of the many techniques available for growing these films, a comparative study on sequential and single-step electrodeposition methods to grow CZTS films is carried out in this investigation to explore the possibility of improving the quality of the films using the inexpensive electrodeposition technique. Mainly in both methods, potentiostatic electrodeposition technique is adopted for growing CZTS thin films. In both methods, growth conditions of the CZTS films are optimized after measuring the photoresponses in a photoelectrochemical (PEC) cell of the films that resulted at the end of each deposition step. The observed structural and optoelectronic properties of the films reveal that, in general, structurally good and photoactive CZTS films can be prepared using both methods. Moreover, photoresponse and Mott–Schottky measurements on CZTS films in a PEC reveal that CZTS films prepared using the single-step electrodeposition have better photoactive properties and improved doping densities. This important finding shows that when developing CZTS-based solar cells using the inexpensive electrodeposition technique, single-step electrodeposition is more advantageous.
Comparison study of mechanical and chemical properties of ancient and modern clay pots
(Research Symposium on Pure and Applied Sciences, 2018 Faculty of Science, University of Kelaniya, Sri Lanka, 2018) Madhuwanthi, H. M. L. U.; Katugampola, M.; Jayathilaka, K. M. D. C.; Sumathipala, H. H.
In this study, the ancient clay pottery samples from archaeological site Devalapola, Minuwangoda, Sri Lanka (3000 years, radiocarbon age) which were found by the Department of Archaeology, University of Kelaniya, were collected and compared their physical properties with modern clay pottery samples. Also to analyze the mineralogical components and the compositions, the Scanning Electron Microscopy (SEM) coupled with the Energy Dispersive X-Ray spectroscopy (EDX) analysis were performed on the both ancient and modern clay pot samples on both side and top surfaces of them. The firing clay objects is an irreversible process, which produces ceramic materials characterized by new chemical-mineralogical composition and different physical and microstructural features. Physical properties of the shards such as pottery density and water absorption capacity were analyzed. There was no significant difference in the pottery density. The values for the water absorption of the ancient clay pot samples have a wider range than the modern clay pot samples. According to the SEM results, the grain sizes of the modern clay pot samples are comparatively larger than the ancient clay pot samples. The grain sizes of the ceramic indicate the open porosity of the matrix. Based on the SEM-EDX results, SiO2 and Al2O3 were the major components of the both ancient and modern clay pot samples while CaCO3, MgO, MAD-10-Feldspar, CaSO3, Ti, and Fe are present in trace amounts. Further albite, FeS2 and KCl were only present in the modern clay pot samples. By analyzing the EDX results it can be concluded that when the production of the ancient potteries was happening, the furnace atmosphere was filled with more CO2 and the firing temperature of the ancient clay pot samples at the production was around 850 - 9000C.
Cu2O Homojunction Solar Cells: Efficiency Enhancement with a High Short Circuit Current
(2024) Thejasiri, S. A. A. B.; Jayathilaka, K. M. D. C.; Kafi, F. S. B.; Kumara, L. S. R.; Seo, O.; Yasuno, S.; Sakata, O.; Siripala, W.; Wijesundera, R. P.
Cu2O homojunction solar cells were fabricated using potentiostatic electrodeposition technique. n-Cu2O thin films were grown in an acetate bath while p-Cu2O thin films were grown in a lactate bath. In the growth of n-Cu2O films, cupric acetate concentration, pH and temperature of the bath, deposition potential and duration (film thickness) and annealing temperature were investigated. In the growth of p-Cu2O on n-Cu2O, concentration of copper sulphate and lactic acid solutions, pH and temperature of the bath, deposition potential and duration were investigated. In addition, the procedure of sulfidation of p-Cu2O film surface using (NH4)2S vapor, before depositing Au front contact, was also optimized to enhance the photoactive performance. The structural, morphological and optoelectronic properties of the Cu2O films were investigated using scanning electron microscopy (SEMs), high energy X-ray diffraction (HEXRD), hard X-ray photoelectron spectroscopy (HAXPES), spectral response and current–voltage (J-V) measurements. The best Cu2O homojunction solar cell exhibited Voc = 460 mV, Jsc = 12.99 mA·cm−2, FF = 42% and η = 2.51%, under AM 1.5 illumination. Efficiency enhancement with the record high Jsc value for the Cu2O homojunction solar cell has mainly been due to the optimization of pH of the n-Cu2O deposition bath and lactic acid concentration of the p-Cu2O deposition bath.
Design and characterization of a tunable metamaterial absorber for efficient RF energy harvesting in the Wi-Fi frequency band
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Sahasrika, S. L. S. D.; Ranaweera, A. L. A. K.; Seneviratne, J. A.; Jayathilaka, K. M. D. C.
The pursuit of miniaturization and connectivity in semiconductor technology has led to the development of compact, interconnected devices. However, the reliance on batteries for power presents limitations. Ambient energy harvesting, particularly from radio frequency (RF) waves, offers a promising solution. This study explores the feasibility of wireless energy harvesting, especially in the context of the saturated frequency spectrum due to wireless communications. Building upon recent advancements in metamaterial technology, this study focuses on the design, fabrication, and characterization of a tunable metamaterial absorber unit cell for efficient RF energy harvesting. The aim is to exploit metamaterials, specifically tunable metamaterial absorbers (MMA), to harvest RF energy, particularly in the widely utilized Wi-Fi frequency band. To design a novel unit cell structure, simulations were conducted using the commercially available EM simulation tool CST Microwave Studio software. A novel MMA unit cell consisting of E-shaped split ring resonators, copper reflector, and FR-4 substrate layer in the middle was designed and simulated. Results demonstrated its RF energy harnessing ability, achieving peak absorptivity of 98% of incident RF energy at 2.4 GHz. The designed unit cell was fabricated using the standard PCB fabrication method. Experimental results were obtained using a network analyzer through non-contact measurement method. Results closely mirrored the simulation results, confirming a high absorptivity of 99% at 1.44 GHz. To achieve frequency tunability, an external capacitor switching circuit was integrated into the MMA unit cell. Simulation and experimental results were obtained confirming its frequency tunability. The proposed tunable metamaterial absorber unit cell offers advantages over conventional RF energy harvesting systems, including ease of implementation, a wider range of RF energy absorption, and cost-effectiveness paving the way for integration into various applications. In conclusion, this study contributes to the development of energy harvesting technologies by leveraging tunable MMA to harness ambient RF energy.
Design of novel perfect metamaterial absorber for Radio Frequency energy harnessing
(Faculty of Science, University of Kelaniya Sri Lanka, 2022) Karunathilaka, M. G. M. T.; Ranaweera, A. L. A. K.; Jayathilaka, K. M. D. C.; Seneviratne, J. A.
Due to the rapidly growing wireless communications and sensing applications, the frequency spectrum has already been saturated. Consequently, the abundance of Radio Frequency (RF) signals in the ambient environment made the concept of wireless energy harnessing to be emerged as an attractive solution to energize low-power wireless devices. In this study, a novel tuneable perfect metamaterial absorber (PMA) unit cell was designed by combining two C-shaped split-ring resonators (SRR) embedded with simple electronics circuitry. The feasibility of harnessing energy from 1.8 GHz signals was investigated through electromagnetic (EM) simulations. The design and numerical analysis of the proposed PMA structure is carried out with the aid of the commercially available EM simulation software, High Frequency Structure Simulator (HFSS). The proposed structure’s capability to absorb EM energy as a perfect metamaterial absorber is studied. According to the simulation results, it shows a high absorption coefficient of around 99%. This verifies that the proposed tuneable PMA structure encompasses a high absorption of RF energy. It can be used for the harnessing of RF energy to power up low-power devices and wireless sensor networks.
Development of tin oxide/copper(I) oxide heterojunction solar cell
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Balasuriya, B. M. U. H.; Kafi, F. S. B.; Jayathilaka, K. M. D. C.; Wijesundera, L. B. D. R. P.
The rapid expansion of the global population together with industrialization intensifies our diurnal energy need. Addressing the present energy demand is a challenging task. Solar energy stands as a pivotal solution to the global energy crisis, offering a sustainable and renewable energy source to meet the escalating demand for electricity. Photovoltaic energy emerges as a favorable substitute due to its widespread availability, free accessibility, eco-friendly nature, and reduced operational and maintenance expenses. However, the markedly available photovoltaics are unaffordable to the public due to their expensiveness. Accordingly, this study focuses on the development of a low-cost ecofriendly tin oxide (SnO2)-based heterojunction solar cell, aiming to enhance photovoltaic performance through systematic fabrication and optimization processes. The Cu/n-SnO2/p-Cu2O/Au heterojunction solar cell was fabricated using the method of electrodeposition. Tin (IV) Oxide (SnO₂) was employed as the n-type material and Copper(I) Oxide (Cu2O) as the p-type material. The fabrication process involved the electrodeposition of n-type SnO2 thin film on copper (Cu) substrates, followed by subsequent deposition of p-type copper(I) oxide (Cu2O) thin film. For making front contacts to the heterojunction, thin Au spots (area ∼2 × 2 mm2 ) were sputtered onto the p-Cu2O thin film of the bilayer. The back contact of the solar cell was the Cu substrate. The photoresponses of the Cu/n-SnO2/pCu2O/Au solar cell structure were monitored by optimizing the bath temperature of the SnO2 film deposition bath. Electrodeposition of SnO2 layers was performed on copper substrates in a threeelectrode electrochemical cell using a solution containing 30 mM SnCl2 and 150 mM HNO3 and electrodeposition was conducted at -0.85 V vs. Ag/AgCl for 2 min at temperature values of 70 ◦C, 75 ◦C, 80 ◦C, 85 ◦C, and 90 ◦C. To fabricate the device a p-Cu2O thin film was electrodeposited on Cu/nSnO2 film at -0.45 V vs. Ag/AgCl for 40 min in a three-electrode electrochemical cell containing 0.1 M CuSO4, 3 M C3H6O3, and NaOH aqueous solution. The temperature and pH of the bath were maintained at 60 °C and 13 respectively. The results of photoresponse measurements together with current-voltage measurements were used to optimize the solar cell. The highest photoresponses resulted for the SnO2 thin films deposited at a bath temperature value of 85 ◦C. This research contributes to the advancement of tin oxide-based heterojunction solar cell technology and offers insights for future optimization and development efforts in renewable energy generation.
Effect of annealing temperature on the wetting properties of electrodeposited Cu2O
(Faculty of Science, University of Kelaniya, Sri Lanka, 2021) Shakya, M. D. P. A.; Jayathilaka, K. M. D. C.; Wijesundera, R. P.; Wanninayake, W. T. M. P. K.
Surface wettability is one of the important physical parameters, which manifests the affinity of a liquid towards a solid phase. In recent years, controlling the wettability of solid surfaces has drawn significant attention due to its influence in wide range of applications. Cuprous Oxide (Cu2O) is well known as a technologically important material for various fields due to its unique advantages such as low cost, high chemical stability and remarkable electrochemical performance. This work examines the impact of the post annealing temperature on the wetting ability of Cu2O thin films. A set of Cu2O thin films was deposited on Ti substrate at a deposition potential of -200 mV vs saturated calomel electrode (SCE) in an acetate bath containing an aqueous solution of 0.1 M sodium acetate and 0.01M cupric acetate at bath temperature of 60 ºC and pH value of 6.5 for 45 min. Potentiostatic electrodeposited Cu2O films were annealed in air at 100 °C, 150 °C, 200 °C, 250 °C, 350 °C and 400 °C for 20 and 40 minute separate time intervals. The surface morphological and structural characterizations of prepared samples were studied using scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques. SEM (Zeiss evols 15) and SHIMADZU (XD-D1) X-ray diffractometer were used to study the samples. XRD spectral patterns indicated the presence of Cu2O without having any impurity phases. The water contact angles were measured using the sessile drop method in order to investigate the effect of temperature on the wettability of the Cu2O films. The contact angle of Cu2O thin film changed from 110o (non-wetting) to 10o (completely wetting) with the increase in the annealing temperature. The contact angle measurement for cuprous oxide showed a transition of cuprous oxide surface from hydrophobicity to hydrophilicity and the maximum hydrophobicity was observed at 150 ± 1 oC. Similar variation and maximum hydrophobicity of the contact angle were observed for both annealing durations (20, 40 minutes). SEM micrographs of electrodeposited Cu2O thin films indicated significant changes in the surface morphology with annealing temperature. Dimension of grains becomes smaller with increasing temperature. This suggests that higher heating temperatures lead to a decrement in the contact angle. Based on the results of the investigation, surface morphology is the primary determinant of the wettability qualities of Cu2O thin films.
Effect of temperature and pH on the wettability of electrodeposited n-type cuprous oxide films
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Kapukotuwa, K. M. V. Y.; Shakya, M. D. P. A.; Jayathilaka, K. M. D. C.; Bandara, T. M. W. J.; Wijesundera, L. B. D. R. P.
This research considers the temperature effect on wettability properties of electrodeposited n-type cuprous oxide (n-Cu2O) thin films, having focus on the role of bath pH and annealing temperature in their different values. In this research, n-type Cu2O films were produced using a three-electrode electrochemical cell containing an aqueous solution of sodium acetate and cupric acetate at 55°C, with the change in bath pH carried out by adding diluted acetic acid and NaOH. The films were deposited on titanium substrate at -200 mV vs Ag/AgCl for 40 minutes, and after that annealed in an air atmosphere at different temperatures increasing by 50°C increments starting from 100°C. The results of the photoresponse measurements confirmed the n-type nature of cuprous oxide. Crystal structure was determined by X-ray diffraction and the detailed surface morphology of the Cu2O thin films were examined using SEMs, which relate to the wettability characteristics of this material. The sessile drop method, utilizing ImageJ software based on Young's equation, showed that the contact angle measurements of wettability in the n-Cu2O substrates greatly depended on the pH of the electrodeposition bath and annealing temperature. The results revealed that the n-Cu2O films were hydrophilic when films were prepared at pH of 5.6, 6.23, 6.4, and 6.6. Interestingly, at pH 5.8, the contact angles exceeded 90° when the surfaces were annealed in an air atmosphere at temperatures of 100°C and 150°C and then allowed to return to room temperature, indicating the formation of hydrophobic surfaces. At pH 6.0, hydrophobicity was realized under annealing temperatures of 100°C, 150°C, and 200°C. XRD crystallographic analysis supported the formation of Cu2O with a cubic structure, while SEM details gave the surface morphology of the films. It serves as a very strong demonstration of the high degree of intercorrelation between wettability, pH, and annealing temperature in cost-effective routes toward hydrophobic n-Cu2O surfaces. By varying the pH and annealing temperature, it was possible to obtain both hydrophobic and non-hydrophobic surfaces. Knowing the wetting properties of n-type cuprous oxide facilitates many applications, such as the control of corrosion in coating technology and atmospheric water harvesting.
Electrodeposited homojunction Cu2O solar cell on FTO substrate
(Research Symposium on Pure and Applied Sciences, 2018 Faculty of Science, University of Kelaniya, Sri Lanka, 2018) Kafi, F. S. B.; Jayathilaka, K. M. D. C.; Wijesundera, L. B. D. R. P.; Siripala, W.
Cuprous oxide (Cu2O), an abundant photoactive semiconducting material has optimum optoelectronic properties to develop efficient, inexpensive and eco-friendly solar cells. Even though, it is possible to fabricate Cu2O based hetero or Schottky junction solar cells, it is believed that the reduction of interface strains via application of surface treatments can produce best efficient homojunction Cu2O solar cell. Apart from the homogeneity of a p-n junction, reduction of contact resistances of a solar cell also has a great impact on its overall performance. Previous studies have shown that, annealing and/or sulphidation of thin film Cu2O enhances the surface properties while sulphided p-Cu2O/Au junction exhibits ohmic behavior as well. Thus, in this study possibility of developing efficient thin film homojunction Cu2O solar cell on FTO substrate was tested by improving the surface properties of n- and p-Cu2O thin film layers. n-Cu2O thin film was potentiostatically electrodeposited in a three electrode photoelectrochemical cell, contained 0.1 M sodium acetate and 0.01 M cupric acetate, acetic acid at bath pH value of 6.1 and then, this thin film FTO/n-Cu2O photoelectrode was annealed at temperature of 4000C to form very thin p-Cu2O layer with lower surface defects. Subsequently, for a thicker absorber layer a thin film ptype Cu2O was electrodeposited on annealed FTO/n-Cu2O photoelectrode using a lactate bath, consisted 3 M lactic acid, 0.4 M copper(II) sulphate and 4 M sodium hydroxide at bath pH value of 13.0. Finally, to form ohmic back contact this bi-layer is directly exposed to ammonium sulphide vapor for 8s and sputtered thin film of Au on it. Photoresponses and modulated light induced current-voltage characterization of this final thin film Cu2O homojunction is given the highest VOC and JSC values of 154 mV and 3.905 mA/cm-2 respectively. This result revealed that application of surface treatments to the thin film n-Cu2O and the bi-layers ameliorates surface properties, thereby the optoelectronic properties. Parameterization of surface treatments and improvements in the front contact will further improve this homojunction solar cell.
Electrodeposited p-type copper oxide for lithium-ion battery applications
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Millamadiththa, S. V.; Jayathilaka, K. M. D. C.; Wijesundara, L. B. D. R. P.
Lithium-ion batteries (LIBs) are considered a promising energy storage device due to their energy density, capacity, and longevity. In recent years, transition metal oxides have gained greater attraction due to their high theoretical capacity for rechargeable battery applications. The development of the anode and cathode in rechargeable batteries is crucial for enhancing overall battery performance. Among the different types of alternative anode materials for LIBs, Cu₂O is crucial due to its high specific capacity, low cost, environmental benefits, and ease of production. In this investigation, growth and characterization of p-Copper Oxide were carried out for possible anode material for rechargeable battery applications. Electrodeposition of p-Copper Oxide was carried out potentiostatically in a threeelectrode electrochemical cell containing 3M lactic acid 0.04M cupric sulfate (CuSO4) and 3M sodium hydroxide (NaOH) at - 450 mV vs Ag/AgCl for 30 min. The pH of the bath was adjusted to 12.5 using sodium hydroxide and bath temperature and stirring speed were maintained at 60°C and 200 rev./min respectively during the deposition. Titanium plate, Ag/AgCl, and platinum plate were used as working electrode, reference electrode, and counter electrode respectively. Grown materials were characterized using High Energy X-ray Diffraction (HEXRD), FTIR, Scanning Electron Microscopy (SEMs), MottSchottky measurements, and charge-discharge measurements. The HEXRD spectrum exhibited all the peaks corresponding to the reflection from Cu2O and CuO. Thus, HEXRD results revealed that the grown thin films (≈1 µm) consist of polycrystalline Cu2O with a cubic crystal structure and CuO with a monoclinic crystal structure indicating the formation of copper oxide. The FTIR spectra exhibited peaks related to Cu-O stretching vibrations and -OH groups, confirming the growth of Cu2O having proper composition. The SEM analysis confirmed the formation of uniform polycrystalline cubic grain morphology Cu2O having grain size in the order of 100-300 nm. Mott-Schottky analysis confirmed the p-type conductivity of Cu₂O having a doping density around 3.30×1016 cm⁻³ which is crucial for efficient conversion reactions during battery operation. The fabricated device using p-Copper Oxide as anode material exhibited a specific capacity of 205.4 mAh g-1. Overall results of this study reveal that electrodeposited p-Copper Oxide improves the interfacial properties between the anode and current collector and electrolyte. In conclusion, electrodeposited p-Copper Oxide can be used as a promising anode material for high-performance LIBs.
Fabrication and characterization of electrodeposited nano structured copper oxide-based supercapacitors
(Faculty of Science, University of Kelaniya Sri Lanka, 2023) Anjalika, B. R. L.; Jayathilaka, K. M. D. C.; Ranaweera, A. L. A. K.; Wijesundera, L. B. D. R. P.; Kalingamudali, S. R. D.
The increasing consumption of limited energy sources, primarily based on fossil fuels, and the resulting environmental issues, such as global warming and climate change, drive researchers to develop environmentally friendly and renewable energy conversions and storage systems. Supercapacitors (SCs) have emerged as a promising solution to meet the increasing global demand for efficient energy storage. The performance and efficiency of a supercapacitor depend directly on the electrode materials used. Nanostructured materials provide new and exciting approaches to developing supercapacitor electrodes for high-performance electrochemical energy storage applications. Interest in pseudocapacitive materials, particularly copper oxide, has grown due to its advantageous properties and application as electrode materials in energy storage devices. In this research, nano cuprous oxide thin films were used as supercapacitor electrodes, and Polyvinyl Alcohol-Potassium Hydroxide (PVA-KOH) gel polymer was used as both the electrolyte and separator for supercapacitors. The nano cuprous oxide films were synthesized on Ti substrates using the electrodeposition technique by controlling the pH of the deposition bath. For comparison, microstructured cuprous oxide thin films were also deposited on Ti substrates as electrodes using the electrodeposition technique. Structural and surface morphological properties of the fabricated electrodes were investigated using high-energy X-ray diffraction (HEXRD) and scanning electron microscopy (SEM). The HEXRD analysis showed the formation of a singlephase polycrystalline cuprous oxide film on the Ti substrate. The SEM revealed that the morphology of the electrodeposited cuprous oxide thin films strongly depends on the pH value of the deposition bath. The performance of cuprous oxide as an electrochemical supercapacitor electrode was analysed using cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS) techniques. In comparison to microstructured electrodes, the nano cuprous oxide electrodes demonstrate better electrochemical performance in terms of specific capacitance, energy density, and power density. The Cu2O//Cu2O supercapacitor with nano-Cu2O electrodes, prepared at pH 7.9, exhibited the highest specific capacitance of 176.02 mF/g, energy density of 61.4 mWh/kg, and power density of 44.23 W/kg. In contrast, the supercapacitor with microstructured electrodes, prepared at pH 6.3, exhibited a specific capacitance of 7.37 mF/g, energy density of 2 mWh/kg, and power density of 1.4 W/kg. The significant improvement is mainly attributed to the increased film surface area associated with cuprous oxide nanostructures. Therefore, nano copper oxide-based supercapacitor electrodes show great potential for supercapacitor applications.
Fabrication and characterization of sulfur-treated cuprous oxide-based supercapacitors
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Wijesinghe, W. A. N. D.; Jayathilaka, K. M. D. C.; Ranaweera, A. L. A. K.; Wijesundara, L. B. D. R. P.; Kalingamudali, S. R. D.
Supercapacitors are crucial for modern energy storage, offering high power density, fast charging, and life spans. They are widely used in various applications, meeting the need for lightweight, flexible, and eco-friendly energy solutions. Cuprous oxide (Cu2O) holds significant promise as an electrode material for supercapacitors owing to its distinctive properties. However, electrodeposited Cu2O films often have high resistivity and surface defects, hampering their electrochemical performance. To address this issue, sulfur treatment was employed to modify the surface properties of Cu2O electrodes, aiming to enhance their electrochemical performance. In this research, sulfur-treated Cuprous-oxide thin films were used as the supercapacitor electrodes, and PVA-KOH gel polymer was employed as the supercapacitor separator and electrolyte. The Cu2O films were synthesised on a Ti substrate via electrodeposition, followed by Ammonium Sulfide (NH4)2S vapour treatment for surface modification, with varying exposure times. Untreated Cu2O thin films were analysed for comparison. X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) were used to examine their structural and surface morphological characteristics. The XRD analysis showed that the Cu2O deposited on the Ti substrate treated with (NH4)2S vapour did not yield distinct CuxS peaks, indicating the formation of a very thin or amorphous CuxS layer on the film surface. SEM revealed an altered morphology of the electrodeposited Cu2O thin films after the (NH4)2S vapour treatment, with the development of a non-uniform additional layer on the surface. The electrochemical performance of sulfur-treated Cu2O electrodes for supercapacitors was studied using Cyclic Voltammetry (CV), Galvanostatic Charge/Discharge (GCD), and Electrochemical Impedance Spectroscopy (EIS). Sulfur-treated electrodes exhibited enhanced performance, showing higher specific capacitance, energy density, and power density compared to untreated electrodes. The supercapacitor utilising sulfur-treated Cu2O deposited on the Ti electrodes, treated for 10 s, demonstrated superior performance with a specific capacitance of 773.81 mF/g, energy density of 154.76 mWh/kg, and power density of 111.43 W/kg. Conversely, the untreated electrode-based supercapacitor exhibited lower values, with a specific capacitance of 23.34 mF/g, energy density of 4.67 mWh/kg, and power density of 3.38 W/kg. In summary, this study explored the impact of sulfur treatment on the electrochemical performance of electrodeposited Cu2O. CV, GCD, and EIS analyses revealed improved electrochemical performance due to the reduction of surface defects with (NH4)2S surface treatment. The results indicated that the best performance can be obtained in Cu2O with a 10 s (NH4)2S exposure duration for application in supercapacitors.
Fabrication of inverted organic solar cells on stainless steel substrate with electrodeposited and spin coated ZnO buffer layers
(Journal of Polymer Engineering, 2022) Namawardana, D. G. K. K.; Wanigasekara, R. M. G.; Wanninayake, W. T. M. A. P. K.; Jayathilaka, K. M. D. C.; Wijesundera, R. P.; Siripala, W.; Malik, M. I.
Polymer based organic solar cells (OSCs) are of tremendous interest as suitable candidates for producing clean and renewable energy in recent years. In this study, inverted OSCs on stainless steel (SS) substrate with zinc oxide (ZnO) as the electron selective transport layer (ESTL), are investigated, occupying bulk heterojunction blend of regioregular poly(3-hexylthiophene) (P3HT) and phenyl- C61-butyric acid methyl ester (PCBM) as the active material and poly-(4,3-ethylene dioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) as the hole transport layer (HTL). The device structure is SS/ZnO/P3HT:PCBM/PEDOT:PSS/Au. ZnO films are prepared by spin coating and electrodeposition techniques, followed by annealing under ambient conditions. The insertion of ZnO layer between the SS substrate and active layer has improved short-circuit current ( Jsc), open-circuit voltage (Voc), fill factor (FF), and power conversion efficiency (PCE) compared to those of the reference cell without ZnO layer, achieving the highest efficiency of 0.66% for the device with spin coated ZnO from sol–gel technique. This enhancement can be attributed to the effective electron extraction and the increased crystallinity of ZnO after annealing treatments at higher temperatures as further confirmed by X-ray diffraction (XRD) and scanning electron microscope (SEM) analyses.
Fabrication of natural dye sensitized solar cells with eastern black nightshade extract.
(4th International Research Symposium on Pure and Applied Sciences, Faculty of Science, University of Kelaniya, Sri Lanka, 2019) Kulathilaka, D. S. V.; Wanninayake, W. T. M. A. P. K.; Jayathilaka, K. M. D. C.; Wijesundera, R. P.
Energy crisis is one of the biggest challenges for the humans in the world today. Considerable efforts have put by many researchers to tackle this issue. Solar cells represent critical role for extracting energy from the sun which is the most promising natural energy source. The dye-sensitized solar cells (DSSCs) have attracted much attention owing to their simple structure, transparency, flexibility, low production cost, and wide range of application. The function and structure of the dye-sensitized solar cells are based on the sensitization of the wide band gap semiconducting materials which are arranged as a sandwich-liked structure that consists of a photo-sensitized semiconductor formed between an anode and a cathode (an electrolyte). The essential sensitization of wide bandgap semiconductor electrodes is achieved by incorporating dye molecules in its structure. In this study, we focused on the Eastern black nightshade (Solanum ptycanthum) natural dye as the sensitizer of TiO2 photoelectrode. The power conversion efficiency of the Eastern black nightshade dye incorporated solar cells was 0.00616%. It was a clear improvement of the power conversion efficiency of the reference solar cell which was made up with the Grapes dye under the same experimental conditions. The power conversion efficiency of the reference solar cell was 0.00265%. These results reveal that the Eastern black nightshade natural dye has improved the power conversion efficiency of dye-sensitized solar cells compared to those with Grapes dye which is one of the most popular dye among the researches.
Mosquito detection and repellent system using acoustics signals for household use.
(Faculty of Science, University of Kelaniya Sri Lanka, 2023) Senanayake, S. V.; Warnakulasooriya, C. B.; Ranaweera, A. L. A. K.; Jayathilaka, K. M. D. C.
There are over 130 mosquito species in Sri Lanka, and this abundance may be the reason for the spread of several critical diseases. Therefore, an effective mosquito repellent system, including a mosquito detection mechanism, is essential for daily life. Using acoustic signals is a harmless and cost-effective method for detecting and repelling pests compared to other visual or thermal processes. Therefore, this research investigates a novel approach for detecting mosquitoes and creating an effective mosquito-repellent mechanism based on acoustic signals. A system capable of distinguishing mosquitoes from other sound sources based on their unique wing flapping frequency was built and repelling them using specific ultrasonic frequencies was realized. The system consists of several components, including microphones, amplifiers, and filters, tested in both simulations and experiments. The methodology involved in determining the wing flapping frequency of mosquitoes by concentrating mosquitoes in a soundproof container, which was found to be within the 800-900 Hz range, with slight differences between male and female mosquitoes. Additionally, the effect of ultrasound in repelling mosquitoes was explored, discovering an effective frequency range of 42 kHz to 44 kHz. The system was subjected to numerous iterations and improvements to enhance mosquito detection sensitivity and the band of repellent frequencies. The final design includes an instrumentation amplifier for cancelling the noises and a second order Sallen-Key bandpass filter for filtering the flapping frequency of mosquitoes. However, due to the limitations of conventional condenser microphones, the discrepancy between simulations and physical implementations appeared. Further, the interference from surrounding noise caused some complications. Despite these obstacles, the results showed the system's potential in detecting and repelling mosquitoes. The system can be improved further by incorporating more sensitive microphones and filter circuits. By providing power with rechargeable batteries, it can be made portable. The flexibility and adaptability of the system design offer exciting possibilities for future enhancements and optimizations. In conclusion, this research advances the field of mosquito detection and repellence, providing new insights into the potential of acoustic signal processing in pest detection and control. Future improvements to the system could significantly contribute to mitigating the risks associated with mosquito-borne diseases.
Optimization of growth parameters of electrodeposited tin oxide thin films for PV Applications
(Faculty of Science, University of Kelaniya Sri Lanka, 2023) Kafi, F. S. B.; Gunaratne, B. H.; Jayathilaka, K. M. D. C.; Wijesundera, R. P.
Tin oxide (SnO2) is a promising photoactive semiconducting material due to its optoelectronics properties. Even though, growth of SnO2 using the method of electrodeposition is advantageous, it has paved low attention among semiconductor researchers. In this study, well-adhered photoactive SnO2 thin film was successfully electrodeposited on Cu substrates. The growth parameters, such as film deposition potential, bath temperature, and duration of deposition were optimized. Electrodeposition of SnO2 layers was performed on copper substrates in a threeelectrode electrochemical cell using a solution containing 30 mM SnCl2 and 150 mM HNO3 at a deposition potential of -0.85 V vs. Ag/AgCl. The fabricated best thin film resulted JSC value of 410 �A cm-2 and VOC value of 113 mV in 0.1 M NaNO3 electrolyte. The best thin film obtained at a bath temperature of 85◦ C for a deposition time of 120 seconds. The Mott-Schottky analysis revealed that the fabricated SnO2 thin film exhibits n-type conductivity, and it has a flat band potential of -0.51 V vs. Ag/AgCl.
Optimization of growth parameters of photoactive Cu2ZnSnS4.
(International Research Symposium on Pure and Applied Sciences, 2017 Faculty of Science, University of Kelaniya, Sri Lanka., 2017) Fernando, W. T. R. S.; Jayathilaka, K. M. D. C.; Wijesundera, R. P.; Siripala, W.
Cu2ZnSnS4 (CZTS) is a promising candidate for application in low-cost and environmentally friendly thin film solar cells due to its optoelectronics properties. It is a perfect absorber material for photovoltaic applications due to its high absorption coefficient (>10-4 cm-1) and direct optical band gap (1.4 - 1.5 eV). Among the CZTS preparation techniques, electrodeposition of Cu, Sn and Zn stack layers followed by sulphurisation in H2S is an attractive technique because of its simplicity, low cost and easy to control stoichiometry. In this investigation, optimization of growth parameters in order to obtain photoactive CZTS thin films by sulphurisation of electrodeposited Cu, Sn and Zn stack layers has been investigated. Cu thin film was electrodeposited on Mo substrate at –0.89 V Vs Ag/AgCl electrode in an electrochemical cell containing 0.4 M CuSO4, 3 M lactic acid and NaOH at pH 11. Deposition of Sn thin film on Mo/Cu electrode was carried out at -1.2 V Vs Ag/AgCl in an electrochemical cell containing 0.055 M, 2.25 M NaOH and 8 ml of sorbitol. Zn thin film was electrodeposited on Mo/Cu/Sn at -1.2 V Vs Ag/AgCl in an electrochemical cell containing 0.2 M ZnSO4. Deposition parameters of Cu, Sn and Zn have been obtained by voltammograms. In order to grow CZTS, Mo/Cu/Sn/Zn thin film electrodes were annealed at 550 oC for 60 min in H2S. Sulphurisation process was carried out at different temperatures and durations using set of identical Mo/Cu/Sn/Zn thin film electrodes and thereby optimized temperature and duration of the sulpurisation. Atomic ratios of initial Cu, Sn and Zn layers could be crucial parameters in determining properties of CZTS thin films. Therefore, atomic ratios of Cu/Sn/Zn layers were optimized by changing Cu, Sn and Zn deposition duration. Various combinations of deposition durations were carried out and optimized by monitoring the dark and light I-V measurements in a PEC containing 0.1 M sodium acetate. Dark and light I-V characteristics revealed that the best photoactive CZTS films can be grown by depositing Cu for 20 min, Sn for 10 sec and Zn for 10 sec. Results further showed that photoconductivity of CZTS thin films is p-type. It is evident from reflectance measurements that the band gap of the CZTS films is 1.5 eV. In conclusion, it is found that the highest photoactive p-CZTS thin films can be grown by sulphurisation of electrodeposited Cu, Sn and Zn stack layers on Mo substrate using H2S at 550 oC for 60 min. Cu: Sn: Zn ratios of the stack layers are the crucial parameters in determining photoactive CZTS thin films. The methodology developed in this study will be further investigated in order to develop the materials for wider applications.
Photocurrent improvement in grape dye sensitized solar cells by in cooperation of electrodeposited Cu particles in TiO2 photoanode
(Faculty of Science, University of Kelaniya Sri Lanka, 2023) Shakya, M. D. P. A.; Jayathilaka, K. M. D. C.; Wanninayake, W. T. M. P. K.; Kumara, R.; Siripala, W. P.; Wijesundera, R. P.
A worldwide effort is currently underway to address the world's energy crisis by finding sustainable energy alternatives. The Dye-Sensitized Solar Cell (DSSC) is a type of solar cell device that functions based on electrochemical principles and uses light sensitive dyes within its TiO2 photoelectrode layer to absorb light. The DSSC, one of the potential solutions, appears to be the most viable option for a future renewable energy source due to its sustainability and environmental friendliness. In cooperation of metal particles like Au or Ag in nano scale to the photoanode is one of the promising methods to improve the efficiencies of these DSSCs. Among these metal particles Cu has some distinct properties such as abundance, low toxicity, low cost and it undergoes Localized Surface Plasmonic Resonance (LSPR) effect like Au nanoparticles. Therefore, to improve the DSSC performances, in this study, Cu particle incorporation to the TiO2 electrode was carried out by electrochemical deposition method. Homogeneous TiO2 paste prepared by mixing appropriate amount of TiO2 powder (Titanium (IV) dioxide), ethanol, and acetic acid was deposited on a transparent Indium-doped Tin Oxide (ITO) conductive glass substrate by doctor blading method. Electrodeposition of Cu particles were potentiaostatically grown in the TiO2 electrode at -700 mV vs Ag/AgCl reference electrode using a three electrode electrochemical cell configuration with Pt as the counter electrode and 0.1 M sodium acetate and 0.01 M cupric acetate electrolyte at room temperature. Natural dye grapes have been used as sensitizer in the study. DSSCs were fabricated by sandwiching above TiO2 films with a C coated counted electrode using KI/I2 based electrolyte. The devices were characterized by analysing the UV – vis absorbance spectra and current density-voltage (J-V) curves and controlled potential coulometry measurements. The UV – vis absorbance spectrum revealed that the light absorption of DSSCs enhanced due to the incorporation Cu. The power conversion efficiency of 0.10%, photocurrent density (JSC) of 501 μA/cm2, open circuit voltage (VOC) of 0.47 V, and fill factor (FF) of 42% were achieved after the Cu incorporation in the photoanode. It is found that due to the incorporation of Cu particles, a slight voltage drop was visible, but there was a significant increase in the photocurrent density (JSC) from 308 μA/cm2 to 501 μA/cm2. The efficiency also increased from 0.07 to 0.10%. DSSC with the incorporated Cu particles showed 62% enhancement in the photocurrent compared to the DSSC without Cu particles.
Photoelectrolysis of water using electrodeposited Cu2O electrodes.
(International Research Symposium on Pure and Applied Sciences, 2017 Faculty of Science, University of Kelaniya, Sri Lanka., 2017) Silva, A. G. T. D.; Jayathilaka, K. M. D. C.; Wijesundera, R. P.; Siripala, W.
At present, fossil fuels are the main energy contributor of the world’s energy needs but gradually depletion of fossil fuels is heading towards an energy crisis. Therefore it is very important for us to find out a renewable clean energy source to minimize the use of fossil fuels and environmental problems created by the burning fossil fuels. Among the suggested alternative fuels, hydrogen is one of the best and it can be produced by photoelectrolysis of water. Finding correct semiconducting materials and techniques are the key areas of research in the development of an efficient photoelectrolysis device. Ultra low cost electrodeposited cuprous oxide (Cu2O) is a good candidate material because it has required semiconductor properties for the process. p-Cu2O electrode electrolyte system requires external bias to produce photocurrent and this can be overcome by using n-Cu2O. However, in our previous studies, we have observed the possibility of enhancement of photocurrent at zero bias using double electrode system (electrodeposted n-Cu2O, thermally grown p-Cu2O, electrolyte system). In this investigation it was studied the possibility of photoelectrolysis of water using electrodeposited n- and p-Cu2O thin film electrodes as a double photoelectrode system in a 0.1 M sodium acetate photoelectrochemcal cell. n-Cu2O thin films on Ti substrates were potentiostatically electrodeposited at −200 mV Vs Ag/AgCl for 60 minutes in an aqueous solution containing 0.1 M sodium acetate and 0.01 M cupric acetate. The initial pH of the deposition bath was adjusted to 6.1. The temperature of the electrolyte was maintained at 55 °C and counter and reference electrodes were a platinum plate and a Ag/AgCl electrode, respectively. p-Cu2O thin films were electrodeposited on Ti substrate at -400 mV Vs Ag/AgCl for 40 min in a three-electrode electrochemical cell containing a 3 M sodium lactate and 0.4 M CuSO4 solution at pH 11. During the electrodeposition, the baths were continuously stirred using a magnetic stirrer. Prior to the film deposition, substrates were cleaned with detergent, dilute HCl, distilled water, and finally ultrasonicated in distilled water. Electrolytic solutions were prepared with distilled water and reagent-grade chemicals. n-Cu2O thin films are annealed at 150 oC for 10 min in air. Possibility of photoelectolysis using electrodeposited Cu2O has been investigated using dark and light current–voltage measurements in a three-electrode electrochemical cell containing 0.1 M aqueous sodium acetate solution. Results reveal that photoelectrolysis process is enhanced by 380% when n- and p-Cu2O double electrode system was operated compared to the n-Cu2O single electrode system.