Effect of silver and cobalt on transparent conducting CdO thin films: tuning the optoelectronic properties

Abstract

Thin film technology is a crucial area of research for the advancement of modern technologies and next-generation applications. In this work, the structural, optoelectrical, and thermal properties of silver (Ag)–cobalt (Co) dual-doped cadmium oxide (CdO) thin films were investigated. Successful incorporation of the doping elements with high crystallinity (maximum value 85%) was confirmed through X-ray diffraction (XRD) analysis, and no unexpected peaks were observed. The pure and doped samples demonstrated a polycrystalline nature with FCC lattice. Scanning electron microscopy (SEM) results revealed the surface microstructures of the deposited 3% Ag–Co doped CdO thin films as spherical or round-shaped agglomerated grains with a smooth surface appearance. From the optical analysis, a maximum transmittance of 89% was observed for the 3% Ag–Co doped CdO sample, which was rarely reported in the literature. Additionally, doping altered the optical band gap from 4.09 eV to 3.88 eV, which enhanced the potential of using the transparent conductive films in optoelectronic devices. Doping CdO with Ag and Co altered its electrical properties, leading to an increase in resistivity and a decrease in carrier concentration. Hall measurements confirmed that all the samples showed an n-type semiconductor behavior. Thermal analysis results demonstrated that the 1% Ag–Co doped CdO sample exhibited the highest thermal conductivity of 2.35 W m⁻¹ K⁻¹, and further increase in the doping concentrations led to a decrease in both the power factor and figure of merit (ZT) values.