Electrodeposition of CdS thin-films from cadmium acetate and ammonium thiosulphate precursors

Cadmium sulphide (CdS) thin-films have been electrodeposited using two electrode system to be used as the hole back diffusion barrier (hbdb) layer for graded bandgap solar cells with p-type windows. Cadmium acetate dihydrate [Cd(CH₃COO)₂·2H₂O] and ammonium thiosulphate [(NH₄)₂S₂O₃] have been used as the cadmium (Cd) and sulphur (S) precursors respectively. In this work, CdS layers have been grown on glass/FTO (fluorine doped tin oxide) substrates at cathodic potentials ranging from 1300 to 1460 mV in order to find the best growth voltage. N-type conductivity is observed for all the layers and band-gap ranged between ~ 2.36 and ~ 2.40 eV for as-deposited layers and ~ 2.31 and ~ 2.36 eV for air-annealed layers. X-ray diffraction (XRD) analysis revealed cubic/hexagonal mixed crystallinity for the as-grown layers which indicates a tendency of transiting towards hexagonal structure upon annealing. Compositional and morphological characteristics of the layers have been investigated with energy dispersive X-ray (EDX) and scanning electron microscopy (SEM) respectively.