Rational Design of the Electronic Structure of CdS Nanopowders

Abstract

In this study, various techniques, such as energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Raman spectroscopy, and spectrophotometry, were used to analyze the properties of nanometric CdS particles synthesized with varying precursor concentrations. EDX analysis revealed the nonstoichiometric composition manifested by an increase in the Cd/S ratio from 1.02 up to 1.43 with increasing precursor concentration. The growth of lattice parameters and unit cell volume accompanying preferential crystallization of the hexagonal phase along with an increasing Cd/S ratio was confirmed by XRD analysis. This indicated the presence of interstitial cadmium in nonstoichiometric Cd 1+x S. The formation of shallow Cd i donor levels below the bottom edge of the conduction band impacts the bang-gap energy; a decrease from 2.56 to 2.21 eV along with increasing nonstoichiometry was observed. This is accompanied by a widening of the range of absorption of light, which creates conditions that can lead to an increase in the efficiency of redox reactions in photochemical processes.

Enhanced Collection of Photocurrents Using Core–Shell Quantum Dots Decorated Polymer Composite Films

“…The SQDs employed in this study are group II–VI cadmium sulfide (Cd x S) - core and zinc sulfide (Zn 1– x S) - shell with different ratios of group II metals. The energy bandgap of CdS and ZnS bulk semiconductors are 2.4 and 3.6 eV, respectively. , SQDs of these materials, however, change properties due to the quantum size effect (QSE) as it is a well-known fact that SQD produces a broad optical spectrum with the lowest size of about 2 nm emitting blue light, while a size in the order of 10 nm gives off a red color . These combined effects of core–shell SQDs can be used to broaden optical absorption spectra and capture high photon energy, resulting in an improved solar cell performance.…”

Enhancing Photodetection Performance and Thermal Tolerance of CdS Thin Films through Cobalt (Co) Doping

“…[ 5–8 ] However, during the synthesis process, the creation of local non‐stoichiometric conditions, characterized by the presence of point defects such as sulfur vacancies (V s ) and cadmium interstitials (Cd i ), occurs within the film. [ 3,9–11 ] These defects have the capacity to influence the photo‐conducting properties of bulk CdS. [ 2,9 ] However, when CdS is at the nanoscale, these defects manifest on the surface, and the presence of surface V s adversely affects the photoresponse of CdS nanostructure‐based devices.…”

“…[ 3,9–11 ] These defects have the capacity to influence the photo‐conducting properties of bulk CdS. [ 2,9 ] However, when CdS is at the nanoscale, these defects manifest on the surface, and the presence of surface V s adversely affects the photoresponse of CdS nanostructure‐based devices. [ 10 ] This adverse effect arises from the adsorption and desorption of environmental oxygen, which results in the trapping and release of free electrons in CdS under both dark and illuminated conditions.…”