Effect of Seed Layer on Opto-Electronic Properties of CdS Thin Film
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Date
2019
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Uva Wellassa University of Sri Lanka
Abstract
Among different methods used to grow CdS films, chemical bath deposition (CBD) and electrochemical deposition (ED) are two of the most commonly used techniques. A novel method of growing chemical bath deposited CdS thin films (CBD-CdS) by using electrodeposited CdS (ED-CdS) as a seed layer is reported and compared with conventional ED-CdS and CBD-CdS films in this work. Conventional ED-CdS films were deposited for a duration of 60 min under potentiostatic conditions of -600 mV against the Ag/AgCl electrode at a bath temperature of 60 °C in a reaction solution of 0.05 mol dm-3 cadmium chloride, 0.05 mol dm-3 sodium thiosulfate and diluted H2SO4. Conventional CBD-CdS films were grown using 0.001 mol dm-3 cadmium sulfate, 0.002 mol dm-3 thiourea and 1.1 ml of ammonia solution for a period of 60 min. The seedassisted CBD-CdS films (ED/CBD-CdS) were grown by depositing CBD-CdS on top on an ED-CdS layer deposited for 3 min under the same conditions mentioned above. When compared, the ED/CBD-CdS system showed superior ISC (19.4 µA) performance in PEC cell (CdS/0.1 mol dm-3 Na2S2O3/Pt) compared to other two systems due to its homogeneity, enhanced majority carrier concentration, high surface roughness, and improved inter-particle connections. The ED/CBD-CdS system also showed a significant improvement in VOC (198 mV) over CBD-CdS (169 mV) and ED-CdS (168 mV) systems potentially due to higher flat band potential. Additionally, comparatively high Eg value of 2.45 eV was obtained for the ED/CBD-CdS due to lower disorder value of ED/CBD-CdS system. These results suggest that the novel method of CdS deposition, seed assisted CBD-CdS thin films demonstrate better opto-electronic properties compared to both EDCdS and CBD-CdS films alone.
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Keywords
Material Sciences, Mineral Sciences