CdCl2-treated CdTe thin films deposited by the close spaced sublimation technique

Abstract

Cadmium telluride thin films were prepared by the close spaced sublimation (CSS) technique, using CdTe powder as evaporant and were submitted to a chemical treatment at 25°C in a saturated CdCl 2 solution (2.08 g/100 mL methanol), followed by heat treatment under vacuum $10 -3 mbar at 400°C for 30 min. The effect of chemical and thermal treatments on the crystallographic, morphological, optical, and electrical properties were studied through XRD, scanning electron microscope (SEM), spectrophotometry, and dc electrical resistivity measurements, respectively. The studies revealed that the CdTe grows in face centered cubic phase and that post-deposition treatment affects the morphology as well as the crystallographic properties. The effect on the morphology is stronger. Increase of the grain size was observed in the samples treated thermally. The electrical resistivity drops by a factor of 20 in CdCl 2 -immersed and heated samples.

Review of the CdCl2 Treatment Used in CdS/CdTe Thin Film Solar Cell Development and New Evidence towards Improved Understanding

“…In this iodine doping experiment in the presence of Cl in the bath, the electrical conductivity increased only by a factor of ~10. Shah et al [48] also reported the electrical resistivity drop by only a factor of ~20 in CdCl 2 -treated CdTe samples grown by CSS method. …”

Preparation and properties of CdS thin films deposited by chemical bath deposition

“…With pH increases to 10.5, surface of CdS is decorated and causes this absorbance curve shifting to the long wavelength direction, which indicates that the band gap decreases slightly. Based on the literatures, the decrease of the energy band gap is produced by an increase in the structural disorder induced by the change from cubic to hexagonal phase of CdS [13]. Curve d shows that although absorbance curve has a red shift, the absorption rate is too high after the wavelength 500 nm.…”

Preparation and properties of CdS thin films deposited by chemical bath deposition

“…When pH increases to 10.5, surface of CdS is decorated and causes this absorbance curve to shift to the long wavelength direction, which indicates that the band gap decreases slightly. Based on literatures, the decrease of the energy band gap is produced by an increase in the structural disorder induced by the change from cubic to hexagonal phase of CdS [13]. Curve d shows that although absorbance curve has a red-shift, the absorption rate is still high after the wavelength 500 nm.…”