Abstract:
Cadmium sulfide has been identified as the most promising window material for fabrication
of CdS/CdTe and CdS/CuInGaSe2 thin film solar cells. Among vast variety of commercially
available CdS fabrication methods electrodeposition (ED) is a viable technique due to its low
cost and simplicity. This study focuses a procedure followed for optimization of the three
growth parameters; pH of the bath solution, deposition temperature and deposition voltage
for ED-CdS thin films with high photovoltaic activities utilizing CdCl2 and Na2S2O3 as
cadmium and sulfur precursors respectively.
Based on the two initial leading experiments, feasible pH and deposition temperature ranges
for a stable electrolyte which does not promote chemical bath formation of CdS were
identified to be in the ranges of 1.5-2.0 and 50-70 °C respectively. Also, using cyclic
voltammetry the feasible cathodic deposition voltage was identified to be in the range of 640-
720 mV with respect to saturated calomel electrode. Consequently, the technique of the
design of experiment (DOE) was carried out to establish random combinations of levels of
the three electrodeposition parameters amid the previously identified parameter ranges for
deposition of CdS layers via the ED technique. Finally, the electrical, optical, structural and
morphological properties of the CdS thin films electrodeposited under different combinations
of parameter values were investigated using photo-electrochemical cell study, optical
absorption spectroscopy, x-ray diffraction method and scanning electron microscopy
respectively.
The results indicated that, aqueous solutions in the pH range of 1.6 to 1.8 containing 0.10 M
CdCl2 and 0.01 M Na2S2O3 at 55-65 °C can successfully be used for electrodeposition of thin
film CdS semiconductor materials over a cathodic deposition voltage range of 650 to 680 mV
with a deposition period of 20 to 40 min.
