Abstract
The study reports the influences of altering
of Cd/S molar ratio on some physical properties of hydrothermal grown CdS
nanospheres. Cd/S molar ratios were chosen as 1:0.5, 1:1, 1:2, 1:3 and 1:4 in the stock
solution. X-ray diffraction (XRD) data showed the occurrence of nano-amorphous
CdS structure. Scanning electron microscopy (SEM) conclusions illustrated that
increasing Cd/S molar ratio up to 1:3 caused a growth in the sphere size
whereas further rising of Cd/S molar ratio led to smaller sphere size. The
presence of Cd and S atoms in CdS structure was approved by Energy dispersive
x-ray spectroscopy (EDS) analysis. Optimum transparency was found by Cd/S molar
ratio of 1:3. Band gap scores of CdS nanospheres were determined to be above
2.60 eV that was bigger than bulk CdS (2.42 eV) because of quantum confinement
effect. Photoluminescence (PL) results showed that a gradual decrease in each
peak was attained upon increasing Cd/S molar ratio, which could be due to the
formation non-radiative recombination phenomenon. Electrical data demonstrated
that CdS nanosphere having Cd/S molar ratio of 1:1 exhibited the best carrier
density (1.48´1015cm-3)
and resistivity (1.27´103
Ω.cm) values. Thus, it can be deduced
that Cd/S molar ratio of 1:3 was obtained to be optimum one since it possesses
both bigger sphere size and better transparency, facilitating the effective use
of CdS nanospheres in the solar cells.