Development of Polyaniline Using Electrochemical Technique for Plugging Pinholes in Cadmium Sulfide/Cadmium Telluride Solar Cells

Polyaniline (PAni) thin films were prepared by using an electrochemical polymerization technique on glass/FTO substrates by varying the deposition potential, deposition time, pH concentrations and heat treatment conditions. The structural, morphological, optical and electrical properties of electrodeposited PAni films were characterized using x-ray diffraction, scanning electron microscopy, UV-VIS spectroscopy, optical profilometry and D.C. conductivity measurements. Structural analysis shows the formation of the highest crystallinity for PAni thin film grown at V (g) 1654 mV. Optical absorption measurements have demonstrated a wide variety of energy band gaps (E (g)), varying from similar to 0.50 eV to 2.40 eV for PAni grown by tuning the pH value during the deposition. The electrical resistivity showed an increase from 0.37 x 10(6) a"broken vertical bar cm to 3.91 x 10(6) a"broken vertical bar cm when the pH increased from 2.00 to 6.50. The diode structures of glass/FTO/CdS/CdTe/PAni/Au were fabricated incorporating PAni as a pinhole plugging layer, and assessed for their photovoltaic activities. The results showed the enhancement of all device parameters, especially of open circuit voltage and fill factors. This improvement offers a great potential for enhancing solar cell performance and the device lifetime, and the latest results are presented in this paper.