Browsing by Author "Dassanayake, B.S."

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Effect of film thickness on characteristic properties of thermally evaporated cadmium sulphide thin films
(Faculty of Science, University of Kelaniya, Sri Lanka, 2020) Lakmal, A.A.I.; Kumarasinghe, R.K.K.G.R.G.; Seneviratne, V.A.; Dassanayake, B.S.
Cadmium sulphide (CdS) thin films are regarded as one of the most promising materials for heterojunction solar cells. Due to its wide bandgap (~ 2.42 eV), CdS thin films have been used as the window material together with several semiconductors such as InP, CdTe, Cu2S, and CuInSe2. For the future development of photonic devices based on above materials comprehensive studies on CdS window layer throughout all aspects such as deposition technique, temperature, duration, and post-heat treatments, etc. are highly required. In this study, CdS thin films were deposited on the cleaned FTO glass substrates using vacuum thermal evaporation technique by varying the deposition duration to have different layer thicknesses. The temperature of the substrates and the chamber pressure were maintained at 175 °C and 2×10-5 torr respectively. The deposition was carried out using CdS powder (Sigma-Aldrich, 99.995%) containing in an alumina boat. Deposited samples were then annealed in vacuum (pressure 3×10-5 torr) at 300 °C for 30 minutes. The bandgap and optical transmittance of the deposited thin films were studied using UV-Visible spectrophotometry. The surface topology analysis of the deposited thin films was carried out using Atomic Force Microscopy (AFM). A photoelectrochemical cell of (CdS/0.1 mol L-1 Na2S2O3/Pt) was used to investigate electrical properties such as short circuit current (JSC), open circuit voltage (VOC), carrier concentration, and majority carrier type of the semiconductor with the aid of I-V measurements and Mott–Schottky measurements. The structural and crystal properties such as preferred orientation, phase distribution, crystallite size, microstrain, and lattice parameters were studied by employing the grazing incident X-ray diffraction. The calculations were done using the profile fit, Rietveld refinement, and Pawley refinement techniques. All the results revealed that there exists a correlation between the film thickness and the above-considered properties of the CdS thin film. The highest bandgap of 2.43 eV and optimum JSC and VOC of 113 µA/cm3 and 341 mV respectively were observed for the photoelectrochemical cell made by 210 nm thick CdS thin film.
Effects of NH3 concentration and annealing temperature on CBD CdS thin films
(Postgraduate Institute of Science Research Congress, Sri Lanka, 2014) Kumarage, W.G.C.; Wijesundera, R.P.; Seneviratne, V.A.; Jayalath, C.P.; Dassanayake, B.S.
Influence of Bath Temperature on CBD-CdS Thin Films
(ScienceDirect, 2016) Kumarage, W.G.C.; Wijesundera, R.P.; Seneviratne, V.A.; Jayalath, C.P.; Dassanayake, B.S.
CdS thin films were grown on conducting glass substrates at different bath temperatures in order to investigate their influence on opto-electrical properties of the chemical bath deposited (CBD) CdS thin films. The CBD-CdS process was carried out with 0.001 M CdSO4, 0.002 M CS(NH2)2 and NH3 solution at different bath temperatures from 40 to 80 0C for one hour. Fabricated films were characterized using UV-Vis spectrometry, SEM, PEC cell and Profilometer. The optical transmittances of the films decreased with increasing bath temperature due to the increase of the film thickness. CdS cluster size of the thin films grown in the bath at a temperature of 60 0C was considerably larger compared to the films fabricated at other bath temperatures. The variation of optical band gap (Eg) was found to be in good agreement with cluster size variation while electrical characterizations reveal considerably high Voc and Isc values for the films fabricated at a bath temperature of 80 0C.
A study on solution grown CdZnS as a window layer for solar applications
(The U.S. Workshop on the Physics and Chemistry of II-VI materials, 2013) Dassanayake, B.S.; de Silva, D.S.M.; Pathiratne, K.A.S.; Colegrove, E.; Zheng, X.; Dhere, R.; Sivananthan, S.
Tunable optoelectronic properties of CBD-CdS thin films via bath temperature alterations
(2016) Kumarage, W.G.C.; Wijesundera, R.P.; Seneviratne, V.A.; Jayalath, C.P.; Dassanayake, B.S.
The tunability of the band-gap value and electron affinity of the n-CdS by adjusting the growth parameters is very important as it paves the way to improve the efficiency of CdS-based solar cells by adjusting the band lineup with other p-type semiconductors. In this respect, polycrystalline n-CdS thin films were grown on FTO glass substrates at different bath temperatures (40–80 °C) by the chemical bath deposition technique. The structural, morphological and optoelectronic properties of CdS thin films were studied using x-ray diffraction, scanning electron microscopy, UV-Vis spectrometry, profilometry, atomic force microscopy, photoelectrochemical and Mott–Schottky measurements. Absorption measurements reveal that an energy-gap value of n-CdS can be adjusted from 2.27 to 2.57 eV and Mott–Schottky measurements indicate that the flat-band potential is increased from −699 to −835 V with respect to a Ag/AgCl electrode by decreasing the deposition bath temperature from 60 to 40 °C. This tunability of optoelectronic properties of n-CdS is very useful for applications in thin film solar cells and other devices.