International Research Symposium on Pure and Applied Sciences (IRSPAS)

Permanent URI for this communityhttp://repository.kln.ac.lk/handle/123456789/15650

Browse

Author: search.filters.author.Pathiratne, K. A. S.

Search Results

Now showing 1 - 2 of 2
  • No Thumbnail Available
    Item
    Evaluation of solution parameters for CdCl2 solutions to be used in post-deposition treatments of CdTe thin films in CdS/CdTe solar cells.
    (International Research Symposium on Pure and Applied Sciences, 2017 Faculty of Science, University of Kelaniya, Sri Lanka., 2017) Atapattu, H. Y. R.; Silva, D. S. M. D.; Pathiratne, K. A. S.
    Owing to its high absorption coefficient and the near ideal band gap, CdTe has become one of the topmost solar energy materials available for conversion of solar energy into electricity. It exhibits excellent power conversion efficiencies, when coupled with the CdS window material to form CdS/CdTe heterojunction solar cells. Further, CdCl2 treatment has been identified as one of the promising post-deposition treatments available for achieving drastic improvements in the performance of CdTe material. However, no extensive investigations have yet been carried out to identify suitable solution parameters for the CdCl2 solutions used in the post-deposition treatment process. Hence, the present study was designed to investigate the effect of concentration and pH of CdCl2 solutions used for post-deposition treatments of CdTe material grown on glass/FTO/CdS surfaces. In this study, CdTe layers were potentiostatically electrodeposited on glass/FTO/CdS substrates in electrolytic baths containing 1.0 mol/L CdSO4 and 1.0 mmol/L TeO2 at pH 2.3. A cathodic deposition potential of 650 mV with respect to saturated calomel electrode and temperature of 65 °C at a continuous stirring rate of 60 rpm were maintained through the deposition. At the end of electrodeposition process, all the glass/FTO/CdS/CdTe samples were rinsed in de-ionized water and dried under a high purity nitrogen gas stream and conveyed for the CdCl2 treatment followed by air annealing at 390 °C for 15 min. For CdCl2 treatment, three different CdCl2 concentrations (1.0, 0.5 and 0.1 mol/L) were used. For each concentration, three different pHs; as prepared (5.6, 6.3 and 7.1 for 1.0, 0.5 and 0.1 mol/L CdCl2 solutions respectively), 2.0 and 6.5 at 25 °C were selected. Hence, nine sets of samples with two replicates in each were subjected to the CdCl2 treatment. Once the treatment process was over, samples were inspected for their optical, electrical and morphological properties using the techniques of optical absorption spectroscopy, photo-electrochemical cell studies and scanning electron microscopy. The results revealed that, two solutions; one with 1.0 mol/L CdCl2 solution at pH of 5.6 and the other with 0.1 mol/L CdCl2 solution at pH of 2.0 can be effectively used for the post-deposition treatment of CdTe material for improving its properties and eventually to produce power efficient CdS/CdTe based solar cells with ~80 % efficiency improvement compared to the untreated devices.
  • No Thumbnail Available
    Item
    Intrusion of Cd, As, Cr, Pb & Hg into selected rice varieties (Oryza sativa L.) in relation to their status in two different agricultural management systems.
    (International Research Symposium on Pure and Applied Sciences, 2017 Faculty of Science, University of Kelaniya, Sri Lanka., 2017) Navarathna, N. M .C. M.; Pathiratne, K. A. S.; De Silva, D. S. M.
    Five traditional varieties (TRV) and five newly improved hybrid varieties of paddy (NIRV) were cultivated under both conventional and organic farming conditions during Yala and Maha seasons at selected areas in Anuradhapura district where chronic kidney disease was prevalent and Kurunegala districts where chronic kidney disease was not known to exist at the time of the study. The area used for cultivation under each organic and conventional farming condition in each district was approximately 11 m x 11 m and was well separated from each other. The contents of each of the selected toxic elements; Cd, As, Cr, Hg, and Pb in the soil, irrigation water, conventional and organic fertilizers and pesticides used for cultivation together with the relevant physicochemical parameters for soil were estimated before the beginning of the cultivation while the required physicochemical parameters and contents of the elements in irrigation water were estimated regularly during the cultivation. After the maturity periods at each cultivation, paddy were harvested and the contents of the elements in rice grains, straws and roots were determined. All samples for determination of the elements were processed and microwave acid digested according to US EPA 3052 method and analyzed using atomic absorption spectrometer. (Hitachi ZA3000 Zeeman Polarized). Analytical methods were validated using either standard reference materials or recovery tests. The study revealed that, the contents of any of the selected elements in any of the rice varieties grown did not exceed the safe limits of 200 μg kg-1 for Cd, 200 μg kg-1 for As, 300 μg kg-1 for Pb, 2000 μg kg-1 for Cr and 20 μg kg-1 for Hg recommended by the World Health Organization (WHO) and Food and Agricultural Organization (FAO) for milled rice. Hg, As and Pb were not detected in any of the rice varieties grown. The highest content of Cr detected was one tenth of the allowable WHO limit of 2000 μg kg-1. The contents of cadmium were in the range below the detection limit of 159 μg kg-1. Arsenic was below the detection limits in agrochemicals, soils and irrigation waters. Pb and Cr were present in fertilizers below the SLSI limits of 10 mg kg-1 and 250 mg kg-1, respectively. Slightly elevated levels of cadmium (1.80 mg kg-1 to 3.44 mg kg-1) were detected in Muriate of Potash (MOP) and Triple Super Phosphate (TSP) respectively. The green fertilizers contained Cd in the range from 0.44 mg kg-1 to 1.67 mg kg-1 . Irrigation water did contain Cd below the detection limits of 0.2 ± 0.0 μg L-1, while Cr contents were in the range of 13.8 ± 1.9 μg L-1 to 157.9 ± 22.7 μg L-1. The Cd contents in paddy soils were in the range 0.41 ± 0.02 mg kg-1 to 0.75 ± 0.03 mg kg-1 and while the Cr contents were in the range 1.33 ± 0.15 mg kg-1 to 1.63 ± 0.09 mg kg-1. Cd was detected in rice straws along with roots in the range, 12.2 ± 2.6 μg kg-1 to 1582 ± 74.3 μg kg-1.