Potential of Hawleyite Cadmium Sulphide (CdS) Nanofilms for PV Cell Applications

Abstract

The search for suitable materials as buffer layer in the development of photovoltaic cell necessitates the study. The objective is thus, to synthesize and characterize CdS nanofilm for photovoltaic cell application. Thin films of Cadmium Sulphide were deposited on degreased glass substrate, from a bath containing the precursors via Chemical Bath Deposition (CBD) technique. The Physical, Structural, and optical properties were investigated by X-Ray diffractometer, Scanning Electron microscopy (SEM), surface profilometer, Energy dispersive X-ray spectroscopy (EDX) and spectrophotometer. The 9 hours CdS sample showed peak intensities at 30.95o and 51.77o with hkl values of (1 1 1) and (2 2 0). The 12 hours sample showed peak intensities at 30.95o and 51.55o with hkl values of (1 1 1) and (2 2 0). The planes of cubic phase correspond to the mineral Hawleyites for both samples. The average Crystallite grain size for the 9 hours sample is 27.72nm and 38.99nm for the 12 hours samples. The Scanning Electron microscopy analyses illustrate the morphology and the level of uniformity of the CdS coating across the surface of the        9 hours sample and 12 hours samples. The micrographs although slightly similar, the 12 hours sample appeared to be more uniformly coated when compared to the 9 hours sample. Electron-Dispersive X-ray Spectroscopy (EDX) indicated the percentage composition of Cadmium and Sulphide present in the both 9 hours and 12 hours samples, with Cadmium having an average composition of 26.45% and sulphide 8.65% for the 9 hours sample, and 61.95% for Cadmium and 16.43% for Sulphide in the 12 hours CdS sample. The Spectrophotometer was used to investigate the behavior of both samples in the UV (≤ 400nm), Visible and part of the Infrared region. The bandgap energies of both 9 hours and 12 hours sample were 2.36eV and 2.257eV respectively. The average value for the optical conductivity for 9hours sample is 5.099 x 1013 and 7.75 x 1013 for 12 hours sample. The average values of the extinction coefficients, k  for 9 hours sample is 1.07 x 109 and 2.02 x 109 for 12 hours sample. The average thickness value of CdS Sample deposited for 9 hours is 14.10 x10-9m while that of the CdS sample deposited for 12 hours is 14.5 x 10-9m. The results affirm the choice of CdS film as buffer layer of the photovoltaic cells.