Abstract:
Cadmium telluride (CdTe) is a promising material for thin film solar cell applications
due to its ideal band gap of ~1.5 eV which has the ability to absorb the maximum of
the solar spectrum and higher conversion efficiency of sun light. Among the various
deposition techniques available to produce CdTe semiconductor material in
commercial quantities, electrodeposition has drawn more attention due to its
simplicity, scalability and easy control of the material properties through growth
parameters; applied potential, temperature, pH and the composition of the bath etc.
Since the reference electrode could be a potential impurity source in the conventional
three electrode electrolytic system, this study was mainly focused on the use of two
electrode electrolytic system to determine suitable deposition potential and pH
ranges for growth of CdTe thin film while avoiding the influence of impurities.
The two electrode electrolytic cell consisted of, fluorine doped tin oxide coated glass
substrate as the working electrode and 99.99% pure carbon electrode as counter
electrode was used for the deposition of CdTe thin films. The electrolyte contained
analytical grade reagents of 1.25 mol/L CdSO4 and 1.0 mmol/L TeO2 as cadmium
and tellurium precursors respectively. Prior to electrodepositions, pH of the
electrolytic baths were varied from 2.0 to 2.4 at 25 °C. While changing the cathodic
deposition potentials in the range of (1.30 - 1.37) V, the CdTe depositions were
carried out stirring the bath at 60 rpm and at the temperature of 65 °C. Following the
heat treatment of the samples for 10 minutes at 400 °C in air, the characterization of
CdTe thin films was carried out based on optical absorption, photo-electrochemical
cell, X-ray diffraction and scanning electron microscopic studies. The results of the
study indicate that, CdTe thin films can be successfully grown in the cathodic
potential range of (1.34 -1.35) V and at a pH of 2.2 using two electrode electrolytic
system.
