Recycling of Waste CdS Film Solar Cells by Different Depositions

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صبيح, مجد إبراهيم راشد
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An-Najah National University
Nano-sized CdS films were deposited onto ITO/Plastic substrates for the first time by different techniques, namely: electrochemical (ECD), chemical bath (CBD) and electrochemical followed by chemical bath (ECD/CBD) deposition techniques. Scanning electron microscopy (SEM), X-Ray diffraction (XRD), and electronic absorption spectra confirmed the presence of CdS in the films. Photo-electrochemical (PEC) characteristics of different films, such as photo (J-V) plots, conversion efficiency and stability, were all investigated. Method of deposition and treatment affected the CdS film characteristics. PEC characteristics of different films showed different behaviors. ECD films gave a CdS film that was too thin to be characterized. ECD/CBD films showed lower light-to-electricity conversion efficiency than CBD films. Moreover, the CBD films, which were prepared through the fourth cycle of deposition showed higher values of conversion efficiency and stability than other counterparts. This shows how advantageous the new described films are. Coating the CBD-CdS film with multi-wall carbon nanotube (MWCNT) did not improve its PEC characteristics. XVIII The effect of redox couple on the photo J-V plots was measured for fresh CBD- CdS thin film electrodes. The most efficient redox couple was the Poly-Sulfide system, which showed higher efficiency than the iron redox couple. Therefore, the Poly-Sulfide redox couple was used throughout this work. Due to the hazardous nature of Cd ions, and their negative impact on the environment, this work described how the waste CdS films can be recycled into useful films. Again ITO/Plastic substrates were used for recycling the CdS films using CBD. The effect of annealing (125 ºC), and cooling rate (slow & fast), on fresh CdS film characteristics, such as electronic absorption spectra was studied. Different film PEC characteristics, such as photo (J-V) plots, open circuit voltage (Voc), short photo-current density (Jsc), efficiency and stability, were also studied. Films treated by annealing & fast cooling showed higher conversion efficiency and stability than non-annealed ones. The recycled CdS film showed lower PEC efficiency when annealed 125 ºC under N2, despite the cooling rate.