Annealing-Driven Enhancement of Charge Storage Behavior in Electrodeposited CdTe Thin Films

In this study, cadmium telluride (CdTe) thin films were prepared by electrodeposition on fluorinated tin oxide (FTO) glass substrates using cadmium acetate and tellurium dioxide as sources of Cd 2+ and Te 4 , respectively. The films were then annealed at 200, 300, and 400 ℃ after deposition to enhance their crystal structure and eliminate defects. X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), and Raman spectroscopy were used to analyze the morphological and structural characteristics of the films. The results indicated that the crystallinity and grain size increased steadily with increasing annealing temperature. The absorbance was measured, and the band gap was calculated, showing that the optical properties of the unannealed samples were 1.74 eV, and those treated at 400 ℃ were 1.59 eV. This was attributed to grain growth and improved composition. The electrochemical behavior was assessed using Mott-Schottky analysis, electrochemical impedance spectroscopy (EIS), and galvanostatic charge-discharge (GCD) tests. The 400 ℃ annealed film demonstrated the best charge storage performance, with reduced charge-transfer resistance, a specific capacitance of 484.97 F g -1 , and a coulombic efficiency of 99%. These results indicate that thermal annealing enhances the structural and electrical properties of CdTe, making it a promising material for energy storage and supercapacitor applications.