Improved prediction and analysis of cell performance at elevated temperatures

Improved modeling and analysis have been applied to data on Si solar cells made for the Magellan satellite (Venus orbits) at temperatures from -50 to 100 degrees C. Derived saturation currents for the cells have been used to calculate base minority carrier lifetimes. These rise with temperature, showing some saturation near 100 degrees C. Data are quantitatively explained by an energy band model with divacancy levels at 0.25 eV and impurity levels at 0.6 eV above the valance band. Close fits to experimental results are found for concentrations of 6*10¹²/cm³ and 1.5-2*10¹¹/cm³ for the 0.25 and 0.6 eV levels, respectively. At 100 degrees C the saturation is controlled by the latter, while divacancies affect the lifetimes at lower temperatures. It is concluded that this analysis of quite usual test data for cells, coupled with temperature variation, provides a powerful insight into basic parameters which determine the cell operational performance.