Metal (Cu, Ag, and Au) Doping-Induced Tunable Optical Properties of Cadmium Hydroxide for Optoelectronic Applications

We examine the electronic, optical, and dielectric properties of Cu-, Ag-, and Au-doped and undoped cadmium hydroxide [Cd(OH)₂)] using first-principles density functional theory. The electronic investigations show the semiconducting characteristics of Cd(OH)₂ with a band gap of about 1.83 eV. These properties were investigated along two mutually perpendicular directions of light polarization and as a function of the incident light energy (photon energy). The frequency-dependent dielectric function is obtained from the electronic structure calculations. The optical quantities, such as absorption, transmission, refractive index, etc., are also calculated to investigate the optical behavior. The metal doping (Cu, Ag, and Au) significantly affects the properties of Cd(OH)₂ in the infrared and low-energy visible regions of the electromagnetic spectrum. For photon energies greater than 4.0 eV, the effect of these doping elements on the optical and dielectric properties is negligible. These materials exhibit negative dielectric permittivity, which is one of the fundamental features of a photonic crystal. The low-energy absorption spectrum of the doped material shows a shift towards the longer wavelengths compared to the undoped Cd(OH)₂. This shift is maximum (minimum) for Cu (Au)-doped Cd(OH)₂, whereas Ag-doped Cd(OH)₂ has an intermediate shift compared to Cu- and Au-doped Cd(OH)₂. This relative shift may be attributed to their atomic radii. These are good candidates for the absorption of UV radiation. The calculated static refractive index of Ag-doped Cd(OH)₂ is comparable to SiO₂. These electronic and optical investigations reveal that the considered materials are excellent candidates for optoelectronic device applications.