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Abstract
The idea of thin films is relatively simple, we can produce truly a low-cost solar cell by using pennies worth of active semiconductor materials rather than the larger quantities required for crystalline-silicon cells but the efficiencies of these cells are low. So we use multijunction (tandem) solar cell to improve the efficiency. Cadmium-Zinc Telluride (CdxZnl_xTe) is investigated as an absorber layer material for the wide bandgap top cell in tandem thin film solar cells. The composition is varied in order to optimize the bandgap of the absorbing layer. To match the current in both bottom and top cells, CuInSe2 is chosen as an absorber layer material for the bottom cell in tandem cells.
The effects of series resistance, shunt resistance, absorber thickness, doping concentration, light concentration and temperature on the performance of tandem solar cells are carried out using adapted PC-I D program. The results indicate that series resistance and shunt resistance have a significant effect on the performance of the top cell compared to their effects on the bottom cell. In addition, under high illumination levels, the series resistance has a tremendous effect on deteriorating the cell efficiency compared to low concentration conditions. Also, the temperature variations greatly affect the bottom cell more than the top cell. Finally, the effect of illumination levels on the performance of a triple junction solar cell for different series resistance is studied showing that the series resistance has critical effect at high concentration