Browsing by Author "Wijesundera, L. B. D. R. P."

Now showing 1 - 6 of 6

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 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.
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.
Investigation of electrically insulating and thermally conductive materials for a Peltier module with n-Cu2O and p-Cu2O electrodeposited semiconductors.
(International Research Symposium on Pure and Applied Sciences, 2017 Faculty of Science, University of Kelaniya, Sri Lanka., 2017) Gajanayake, G. K. U. P.; Abeywarna, U. K.; Wijesundera, L. B. D. R. P.
Thermoelectricity is a direct conversion of electrical energy into thermal energy and vice versa. Seebeck effect, Peltier effect and Thomson effect are thermoelectric effects observed for conductors during 1820-1920. After the development of semiconductors, a new era has begun in the field of thermoelectricity. Currently, the rare earth materials and their alloys are commonly used as semiconductors for constructing thermoelectric devices. In this research, copper based n-type Cu2O and p-type Cu2O semiconductors were used as thermoelectric materials. These semiconductors were deposited using potentiostatic electrodeposition technique in acetate bath. The study was carried out using two types of electrically insulating and thermally conductive material such as Thermal Heat Sink Transfer cooling pads (THST cooling pads) and mica. Multi stage Peltier modules were constructed using single stages assembling electrically in series and thermally in parallel. For the THST cooling pads, two stage Peltier module was assembled and a temperature gradient of 0.52 OC mm-1 at 2.0 V dc voltage was observed. However, the current through the module was higher and higher compared to the previous measurements when the data was repeated. It was found that the appearance of the semiconductor samples were changed when disassembling the module due to some fluid secreted from the THST cooling pads. The study was also done for both artificial and natural mica as electrically insulating and thermally conductive materials. For the artificial mica, a five stage Peltier module was built and it was observed 9.57 OC mm-1 temperature gradient for 2.0 V dc voltage. Having a three stage module of natural mica the temperature of the module decreases at the beginning and then increased while voltage was increased. A miniature temperature drop of 0.4 OC was able to achieve below the room temperature at 2.75-5.5 V range for the module with natural mica. In addition to that, a temperature gradient of 0.48 OC mm-1 was observed for this set up throughout the applied voltage. Present study demonstrated Peltier effect for both electrodeposited n-type Cu2O and p-type Cu2O semiconductors. The heating effect was always detected for the set ups with THST cooling pads and artificial mica as an insulating materials. However, the experimental data were not repeated for the semiconductor samples assembling with THST cooling pads due to some secretion of fluid. Therefore, THST cooling pads are not suitable for this kind of study. When considering artificial and natural mica as an insulating material, a higher temperature gradient was observed for artificial mica whereas a temperature drop was achieved using natural mica. Outcome of this study indicates that electrodeposited n-type and p-type Cu2O semiconductors along with mica as electrically insulating and thermally conductive materials can be used for a Peltier module.
Sulphur treated single step electrodeposited Cu2ZnSnS4
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Hetti Arachchige, K. A.; Wijesundera, L. B. D. R. P.; Kumarage, W. G. C.; Jayathilaka, K. M. D. C.; Siripala, W. P.
Solar cells, directly converting sunlight into electricity through the photovoltaic (PV) effect, is the best alternative for the global energy crisis. Among the various solar energy materials, Cu2ZnSnS4 (CZTS) is a promising material for solar cell applications due to its unique optoelectronic properties. This study studied the possibility of the growth of quaternary CZTS thin films using a single-step electrodeposition technique for applications in PV devices. CZTS thin films were potentiostatically electrodeposited at - 0.89 V vs Ag/AgCl for 4 minutes on Titanium (Ti) substrate in a three-electrode electrochemical cell containing, 0.02 M copper (II) sulphate pentahydrate (CuSO4.5H2O),0.01M zinc sulphate heptahydrate (ZnSO4 .7H2O), 0.02 M tin sulphate (SnSO4) and 0.02 M sodium thiosulphate (Na2S2O3) at room temperature. 0.2 M tri-sodium citrate (C6H5Na3O7:Na3 - citrate) was used as a complexing agent and tartaric acid (C4H6O6) was used as pH control solution. pH of the bath was maintained at 5. The counter and reference electrodes were Pt plate and Ag/AgCl respectively. Prior to the CZTS deposition, Ti substrates were initially polished with sandpaper and then cleaned with detergent, diluted HCl, and finally cleaned ultrasonically in distilled water for 15 min. Two sets of samples were prepared by annealing as grown CZTS thin films at 550 °C for 30 minutes in N2 and H2S atmospheres respectively. As grown, annealed in N2, and annealed in H2S, CZTS films were characterized and compared using dark and light Current-Voltage (I-V) and Capacitance-Voltage (Mott-Schottky) measurements in a photoelectrochemical cell (PEC) containing a 0.1 M sodium acetate aqueous electrolyte. Grown CZTS thin films did not show any photoactive properties. However, as revealed by the I-V characteristics, films annealed in N2 produced n-type photoconductivity having Voc of 204 mV and Jsc of 20 µAcm-2 in PEC while films annealing in H2S produced p-type photoconductivity having Voc of ~ 250 mV and Jsc of ~ 110 µAcm-2 in the same PEC. This finding was further studied using Mott-Schottky characteristics. Results revealed that films annealed in N2 and H2S attribute n-type and p-type photoconductivity respectively. Further, flat band potential (VFB) values of -0.066V and +0.594V vs Ag/AgCl in the same PEC exhibited for the films annealed in N2 and H2S respectively indicating the formation of a better interface between CZTS and electrolyte for the samples annealed in H2S. In conclusion, significant photoactive enhancement in single step electrodeposited CZTS can be achieved with H2S treatment.