Impact of transition metal doping on the optical and electrical properties of zinc sulfide: advancing photovoltaic performance

This study explores the impact of cobalt (Co²⁺) and nickel (Ni²⁺) doping on the structural, optical, and electrical properties of ZnS thin films synthesized via the SILAR technique. X-ray diffraction (XRD) confirmed a cubic polycrystalline structure with lattice distortion more pronounced in Co-doped films due to ionic radius differences. SEM and EDX analyses showed uniform elemental distribution and improved grain growth with increasing dopant content. Optical measurements revealed a tunable band gap, decreasing from 3.73 eV (undoped) to 3.51 eV (6% Co) and 3.54 eV (6% Ni), accompanied by reduced transmittance. While both dopants influenced the optical behavior, cobalt doping resulted in more significant changes. Electrical measurements performed on Co-doped samples revealed enhanced conductivity and carrier mobility, attributed to donor-like states near the conduction band minimum. These results position Co-doped ZnS as a promising material for optoelectronic and photovoltaic applications, with doping levels up to 6% offering optimal performance without compromising structural integrity.