OPTIMIZATION OF CDO LAYER IN A SE-CDO PHOTOVOLTAIC CELL

An experimental study was made on a Se-CdO photovoltaic cell of conventional structure to optimize the conditions during the de reactive sputtering of the CdO layer. The parameters varied were: sputtering current, pressure, gas flow rate, deposition time and ratio of oxygen to argon in the sputtering gas. These parameters were found to be very critical in determining photovoltaic cell performance at higher light levels. The electrical resistance and optical transparency in the CdO, are determined by its stoichiometry and this in turn was found to be controlled by the film deposition rate, through sputtering current and pressure and by oxygen content in the sputtering gas. A laboratory-fabricated Se-CdO photovoltaic cell with an optimized CdO window layer (but without an optimized collecting grid or antireflecting coating) was found to yield a conversion efficiency of about 2.5% under 100 mW/cm(2) of solar irradiance and about 5% under fluorescent room light of irradiance 0.13 mW/cm(2). For a standard commercial selenium photometry cell the corresponding efficiency values were 0.3% and 3%, respectively.