Simulation-Driven Insights into the Structural, Electronic, and Optical Properties of x:CdS (x = Mg, Ca, and Sr) for Enhanced Optoelectronic Performance

Abstract

Zinc blende cadmium sulfide (CdS), a direct bandgap II–VI semiconductor holds immense potential for optoelectronic applications. However, challenges such as limited light absorption and stability often hinder its performance. This study, employing density functional theory (DFT) via CASTEP, investigates the effects of alkaline earth metals doping on the structural, electronic, and optical properties of CdS. Doping modifies lattice constants and bond lengths, resulting in notable bandgap enhancements: Mg (1.331 eV), Ca (1.399 eV), and Sr (1.366 eV), attributed to the Burstein–Moss effect. Optical analyses reveal enhanced dielectric constants, with static values increasing to 5.14 (Mg), 4.88 (Ca), and 4.34 (Sr) compared to 4.56, the dielectric constant of undoped CdS. Elevated absorption across the UV-visible spectrum and shifts in photoconductivity peaks to higher energy regions underscore their capacity for superior light interaction. Moreover, photoconductivity and dielectric loss analyses highlight Mg’s pronounced impact on carrier dynamics. These findings demonstrate that alkaline earth metal doping effectively tailors CdS for advanced optoelectronic applications, providing a pathway to high-performance semiconductors in energy and light technologies.