Browsing by Author "Kumarage, W. G. C."

Now showing 1 - 6 of 6

Autonomous quadcopter-based intelligent irrigation system for enhancing crop care
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Vimansa, W. A. H.; Adhikari, A. M. N. D. S.; Rathnayaka, R. M. P. B.; Dilshan, P. K. S. I.; Attanayake, A. M. V. A.; Randeniarachchi, R. A. N. D.; Hemal, S. B. N. H.; Piyumal, P. L. A. K.; Kumarage, W. G. C.
Efficient crop care and high productivity are paramount to meeting global food demands amid a growing population. Leveraging advanced technologies, including precise irrigation systems conserve vital resources such as water, minimize waste, and foster sustainability. Consequently, the study presented focused on developing an intelligent irrigation system with the facility of real-time environmental monitoring to optimize water usage and increase efficiency through precise, data-driven irrigation practices. The methodology involves an autonomous quadcopter (DJI Tello) hovering over a selected land area and a weather station on the ground. The weather station was created using an ESP32 microprocessor equipped with several sensors; a DHT11 sensor, Infrared counting sensor module, Capacitive soil moisture sensor (MD0247), water level sensor (MD0207), and LDR sensor (MD0222) to monitor temperature, humidity, rainfall, wind speed, solar intensity, and soil moisture. Furthermore, a computer vision model was developed using YOLOV8 to identify the selected three crops: Arachis hypogaea, Capsicum annuum, and Antherella Sessilis. The developed irrigation system demonstrated outstanding water delivery performance by effectively reducing wastage of water by 20% and enhancing crop growth rates by 10%. This enhancement is ascribed to real-time environmental monitoring and continuous analysis of data from the sensors of the weather station. Moreover, the acquired data is stored in a database and displayed through a user-friendly web application where the data is precisely analyzed and displayed as a dashboard. Web application is aimed at user convenience providing users with location-based weather forecasts, sensor outputs and user tips while predicting the amount of water needed to be delivered in upcoming months. The findings in the presenting work highlighted significant improvements in both irrigation efficiency and crop yield. This demonstrates its potential to be applied in agriculture more extensively by adapting to different environmental conditions and crop needs. Furthermore, the developed web application integrates real-time monitoring and computer vision, providing actionable insights that democratize agricultural knowledge and improve agricultural outcomes. In conclusion, the findings signify a significant leap forward in agricultural technology, addressing inherent challenges of traditional farming with sustainable solutions. This initiative not only aims to enhance agricultural productivity but also aligns with broader goals of promoting sustainable and environmentally friendly farming practices.
Effect of substrate temperature variation on opto-electronic properties of thermally evaporated CdS thin films
(4th International Research Symposium on Pure and Applied Sciences, Faculty of Science, University of Kelaniya, Sri Lanka, 2019) Lakmal, A. A. I.; Kumarasinghe, R. K. K. G. R. G.; Maddumage, D. C.; Kumarage, W. G. C.; Munasinghe, M. A. H. M.; Seneviratne, V. A.; Dassanayake, B. S.
Cadmium sulfide (CdS) is a II-VI group semiconducting material which has been thoroughly investigated due to its superior optical and electrical properties that can be applicable in wide range of semiconductor devices including photonic devices. Due to its direct and wide bandgap (~ 2.42 eV), it is vastly used as the window layer in heterojunction thin film solar cells. Compared to other deposition methods such as electrodeposition, spray pyrolysis, chemical bath deposition; thermal evaporation is an attractive method of deposition due to its high deposition rate, low cost of operation, low material consumption, minimum number of impurities and straight-line propagation of vapors. In the present study, CdS thin films were deposited on cleaned FTO glass substrates using thermal evaporation technique at substrate temperatures ranging from 50 to 250 °C at a pressure of 2×10-5 torr. Deposition was carried out using CdS powder (Sigma-Aldrich, 99.995%) using an alumina boat. Deposited samples were then annealed at 300 °C for 30 minutes in vacuum (pressure of 3×10-5 torr). Structural, optical and electrical properties of annealed CdS thin films were studied by employing X-ray diffraction, UV-Vis spectrometry, I-V measurements and capacitance vs. voltage measurements. All the electrical characterizations were carried out using a photoelectrochemical cell of (CdS/0.1 M Na2S2O3/Pt). The XRD analysis shows all the grown films are preferably oriented in the direction of (002) of hexagonal CdS. The optical band gap values were found to increase with increasing substrate temperature from 50 to 175 °C. ISC and VOC values of (CdS/0.1 M Na2S2O3/Pt) cell were also found to increase up to the substrate temperature of 175 °C. The observed highest ISC and VOC values were 37.24 μA and 314.9 mV respectively. Results indicate that the CdS thin films deposited at the substrate temperature of 175 °C has yielded the best optical and electrical properties compared to the films grown at other substrate temperatures
Growth and Characterization of Seed‑Assisted, EDTA‑Treated, Chemical Bath‑Deposited CdS
(Journal of Electronic Materials, 2021) Kumarage, W. G. C.; Wijesundera, R. P.; Seneviratne, V. A.; Jayalath, C. P.; Gunawardhana, N.; Kaur, N.; Comini, E.; Dassanayake, B. S.
A simple low-cost method to enhance the electrical properties including open-circuit voltage (VOC), flat-band potential (Vfb) and short-circuit current (ISC) in the photoelectrochemical (PEC) cell of cadmium sulfide (CdS) thin films is presented. The PEC cell properties were determined using the configuration Pt/0.1 M Na2S2O3/ CdS. Three different sets of CdS thin films were grown: (a) chemical bath-deposited CdS (CBD-CdS), (b) electrodeposited seed-assisted CBD-CdS (ED/CBD-CdS) and (c) ED/CBD-CdS deposited under the presence of ethylenediaminetetraacetic acid (EDTA) in a reaction solution of CBD (ED/(CBD+EDTA)-CdS). The FE-SEM images suggested the formation of clusters with spherical shape in the presence of a seed layer. All the samples grown with seed layers demonstrated improved ISC and VOC values in the PEC cell compared to the CBD-CdS films due to better contact between the substrate and CBD-CdS. Furthermore, the carrier concentration (ND) and Vfb were also found to improve due to the introduction of the seed layer. In the case of ED/(CBD+EDTA)-CdS, the cluster size was found to be smaller, giving rise to a larger effective surface area. The improved effective surface area, interparticle connections and adhesion of CdS to the FTO substrate resulted in superior electrical properties of ED/(CBD+EDTA)-CdS compared to ED/CBD-CdS and CBD-CdS films.
Harvesting energy from human-body movements for ultra-low power appliances
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Gunarathna, T. G. L.; Rupasingha, U. S. D. B. M.; Gunasekara, H. S.; Thennakoon, S. E. R. T. M. M. I.; Senanayake, S. V.; Leanage, H. B.; Kumarage, W. G. C.; Ranaweera, A. L. A. K.
Energy harvesting from human body movements presents a promising approach to sustainably power wearable devices and sensor nodes. This study explores the potential of capturing energy from footsteps using piezoelectric technology. A critical aspect of this technology involves designing an efficient interface between the piezoelectric elements and the electrical load to maximize energy conversion. The irregular and low-frequency nature of human footsteps poses a significant challenge, resulting in low energy extraction. Moreover, achieving a self-powered circuit adds another layer of complexity. To address these challenges, a novel Parallel-Synchronous Switching Harvesting on Inductor (P-SSHI) circuit is proposed. This circuit increases the energy extraction efficiency of piezoelectric elements. Since the output of a piezoelectric element is in the form of alternating current (AC), a MOSFET-based full-bridge rectifier circuit is proposed to convert AC to direct current (DC). As proof of concept, a shoe insole integrated with multiple piezoelectric elements connected in parallel was developed, and the energy conversion circuit was rigorously validated. The system was tested at a frequency of 1 Hz, which corresponds to the typical walking frequency, using a person weighing 60 kg. Under these conditions, the proposed system achieved an average power output of 550 µW per step with a 10 kΩ resistive load and a 10 µF storage capacitor. The effectiveness of the system was further validated by demonstrating its ability to charge a 1 mF capacitor to 2.1 V in 18 steps and a 10 µF capacitor to 7.0 V in a single step. Notably, the circuit is self-powered and capable of initiating operation without the assistance of an external battery, highlighting its potential for autonomous use. The circuit was prototyped using simple discrete components, emphasizing its practicality and feasibility for real-world applications. The proposed MOSFET-based rectifier circuit offers a significant advantage in converting AC to DC with minimal voltage drop, compared to conventional diode full-bridge rectifiers. Furthermore, the system's capability to charge a Li-ion battery (3.7 V, 300 mAh) was demonstrated, showcasing the potential of the wearable piezoelectric energy harvesting system to provide a sustainable power supply for wearable wireless sensors. Future studies will focus on optimizing energy harvesting under different walking conditions, integrating energy storage devices, and enhancing durability. The proposed technology also shows promise for applications in diverse fields such as healthcare, fitness monitoring, and environmental sensing, where reliable, self-sustaining wearable power solutions are in high demand.
The role of ascorbic acid in optimizing optoelectronic performances of CdS thin films
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Danansuriya, D. B. U. I.; Hetti Arachchige, K. A.; Manilgama, T. T. D.; Kalingamudali, S. R. D.; Premaratne, W. A. P. J.; Jayathilaka, K. M. D. C.; Wijesundara, L. B. D. R. P.; Kumarage, W. G. C.
Cadmium sulfide (CdS), a widely studied (II-VI) group semiconductor, has long captivated the scientific community due to its potential applications in photovoltaic (PV) devices. However, optoelectrical properties of n-CdS, such as flat band potential, and optical band gap, are crucial for enhancing solar cell efficiency. This study explores the tunability of these properties in CdS thin films through chemical bath deposition (CBD) with a mild reducing agent ascorbic acid (C6H8O6). A series of CdS thin films were deposited on fluorine-doped tin oxide (FTO) glass substrates by using various concentrations of ascorbic acid (0, 0.1, 0.01, and 0.001 mol.dm-3). The deposition chemical bath consisted of 0.1 mol.dm-3 cadmium sulfate (CdSO4) and 0.2 mol.dm-3 thiourea (CS(NH2)2) as cadmium and sulfur sources, respectively. The deposition process was conducted at 80 °C for one hour at a pH of 11. Post-deposition, the CdS films were etched in the non-conductive side of the FTO with diluted hydrochloric acid (HCl), followed by annealing at 300 °C for one hour in air. All the electrical measurements were performed in a photoelectrochemical cell comprising a CdS/0.1 mol.dm-3 Na2S2O3/Pt half-cell with an active area of 1 cm². An Ag/AgCl electrode served as the reference for all characterizations. The short-circuit current density (JSC) has shown a significant increase with decreasing ascorbic acid concentration, achieving a 155.6% enhancement with a concentration of 0.001 mol.dm-3 compared to untreated CdS. Conversely, with increasing ascorbic acid concentration the opencircuit voltage (VOC) and the flat band potential (VFB) decreased. The highest reported photocurrent power (VOC×ISC) was observed in films deposited with 0.001 mol.dm-3 ascorbic acid, showing a 150.2% improvement over untreated CdS. Scanning electron microscopy (SEM) analysis revealed that ascorbic acid-treated CdS films exhibited aggregated nanoscale particles, whereas untreated films displayed larger clusters. Consequently, the photocurrent enhancement is attributed to these morphological changes that cause higher effective surface area in the ascorbic-treated CdS thin films compared to the untreated CdS. Furthermore, Mott-Schottky analysis confirmed that all deposited films retained n-type characteristics. This study demonstrates that the electronic properties of n-CdS can be finely tuned through ascorbic acid treatment, making it a promising approach for fabricating thin film solar cells with high light-to-current conversion efficiency. The ability to control and enhance these properties is invaluable for advancing PV applications and achieving higher solar cell performances.
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.