Evaluation of the Influence of Electro-deposition pH on the Physico-chemical Properties of Cadmium Sulphide for Photovoltaic Device Applications

An electrochemical set up was prepared to facilitate the deposition of cadmium sulfide (CdS) on fluorinedoped tin oxide (FTO) substrate, as all other parameters were kept constant excluding the pH. The rangeof pH variation was (2.00 to 4.00)±0.02. Due to the condition of pH variation, three samples wereproduced, which were of pH values 2.00±0.02, 3.00±0.02 and 4.00±0.02. The precursors that formed theaqueous electrolyte solution were cadmium sulfate octahydrate (3CdSO48H2O) and sodium thiosulphatepentahydrate (Na2S2O3.5H2O) and they were expected to deposit Cadmium (Cd) and sulfide (S)respectively. The optical, structural, compositional and electrical of the already deposited CdS thin filmswere determined with the use of UV-Vis spectrophotometry, x-ray diffraction (XRD), Energy dispersiveX-ray (EDX) and photochemical (PEC) cell measurements respectively. The optical absorbancemeasurement indicates the CdCl2treated samples showed different absorbance capacities, therefore,having various bandgaps. Interestingly, the bandgap of the sample of pH 2 is approximate to the standardvalue of bulk CdS, which is 2.42eV. The preferred peak of the electrodeposited thin film occurs at anangle of 28.86o along a corresponding hexagonal plane of CdS(101)H as shown by the XRD machine. Ofall the deposited thin-films, the sample with a pH of 2 has the highest peak which shortens as the pH risesup to 4. The EDX analysis portrays a decrease in the ratio of Cd to S as the pH values rises to 4. The PECmeasurement indicates that the conduction type all the samples of the electrodeposited CdS thin-films aren-type.