Enhanced Optoelectronic Behaviour of Potassium-Doped CdS Thin Films: Effect of Doping Concentration

In this study, the structural, morphological, optical, and electrical properties of potassium (K)-doped cadmium sulfide (CdS) thin films were systematically investigated. Undoped CdS thin films were initially deposited on fluorine-doped tin oxide (FTO) substrates via the chemical bath deposition (CBD) method and served as reference samples. Potassium doping was achieved by incorporating potassium chloride (KCl) into the chemical bath at concentrations of 20 mM, 30 mM, 40 mM, and 50 mM. Potassium incorporation, achieved by introducing KCl at varying concentrations, significantly enhanced film homogeneity, crystal quality, and optoelectronic performance. Among the doped samples, K30 exhibited high phase purity and uniform morphology, while K40 displayed a compact structure and increased carrier density. These improvements are expected to minimize recombination losses, reduce current leakage, and enhance charge transport, highlighting the potential of optimally K-doped CdS films for high-efficiency photovoltaic applications.