Structural and Optoelectronic Characterization of Synthesized Undoped CZTS and Cd-doped CZTS Thin Films

Copper zinc tin sulfide (CZTS) thin films with different doping ratios of Cadmium (Cd) were successfully fabricated using the sol-gel method by dip-coating technique. The surface morphology, the crystal structure properties as well the optical properties of undoped CZTS thin film and Cd- doped CZTS thin films wereinvestigated using scanning electron microscopy (SEM), x-ray diffraction (XRD), and UV-Vis spectrophotometer. SEM micrographs demonstrated that the size and morphology of the particles improve due to increasing the Cd concentration in CZTS thin films. In addition, the XRD patterns exhibited the crystalline nature for CZTS thin films with kesterite crystal structure and showed improvement in some crystal structure properties such as crystal size and volumeof unit cell with the incorporation of Cd into CZTS thin films. Moreover, optical bandgap energy 𝐸_g, in addition to several optoelectronic parameters such as refractive index (𝑛), extinction coefficient (𝑘), dispersion energy, high-frequency dielectric constant, density of state,Plasma frequency, and relaxation time have been estimated. Remarkably, the bandgap energy of CZTS thin films ranges from 1.594 𝑒𝑉to 1.529 𝑒𝑉 depending on the Cd content; it increases with increases the concentration of Cd into CZTS thin films.