Advancement of Physical and Photoelectrochemical Properties of Nanostructured CdS Thin Films toward Optoelectronic Applications

Abstract

CdS thin films were grown on an FTO substrate at different temperatures, employing the low-cost hydrothermal method. All the fabricated CdS thin films were studied using XRD, Raman spectroscopy, SEM, PL spectroscopy, a UV–Vis spectrophotometer, photocurrent, Electrochemical Impedance Spectroscopy (EIS), and Mott–Schottky measurements. According to the XRD results, all the CdS thin films were formed in a cubic (zinc blende) structure with a favorable (111) orientation at various temperatures. The Scherrer equation was used to determine the crystal size of the CdS thin films, which varied from 25 to 40 nm. The SEM results indicated that the morphology of thin films seems to be dense, uniform, and tightly attached to the substrates. PL measurements showed the typical green and red emission peaks of CdS films at 520 nm and 705 nm, and these are attributable to free-carrier recombination and sulfur vacancies or cadmium vacancies, respectively. The optical absorption edge of the thin films was positioned between 500 and 517 nm which related to the CdS band gap. For the fabricated thin films, the estimated Eg was found to be between 2.50 and 2.39 eV. According to the photocurrent measurements, the CdS thin films grown were n-type semiconductors. As indicated by EIS, resistivity to charge transfer (RCT) decreased with temperature, reaching its lowest level at 250 °C. Flat band potential and donor density were found to fluctuate with temperature, from 0.39 to 0.76 V and 4.41 × 1018 to 15.86 × 1018 cm−3, respectively, according to Mott–Schottky measurements. Our results indicate that CdS thin films are promising candidates for optoelectronic applications.

Investigating the physical and electrical properties of La2O3 via annealing of La(OH)3

“…The values for microstructural properties are summarized in Table 1 . Figure 2 displays that annealing at a higher temperature leads to fewer surface defects compared to non-annealed samples 41 .…”

“…The Nyquist curves (Z" vs. Z') were fitted using ZSimpwing software ) https://www.ameteksi.com/products/software/zsimpwin (and an electrical circuit model with the corresponding components of solution-resistance (Rs), charge-transfer resistance (RRCT), and double-layer capacitance (C dl ) 64 . The plots are composed of semicircles, and their diameters decrease as the annealing temperature increases 41 . This suggests that there is a higher rate of charge transfer and a lower rate of charge recombination 65 , 66 .…”