Silicon Solar Cell Damage from Electrical Overstress

A model for the prediction of electrical overstress failure in silicon solar cells based on bulk conduction has been developed. The model has been used to predict the threshold failure current versus pulse width for three types of concentrator cells and one flatplate cell. Threshold failure currents have been measured in each of the cell types using a high voltage pulser that was transformer coupled to the cell impedance. Threshold failure currents for a 10 μs exponential pulse of 3-15 kiloamperes were measured for the concentrator cells, in good agreement with model predictions. However, the measured reverse failure currents in the flatplate cell were 4-12 amperes for pulse widths of 10-100 μs, compared to predicted values of 200-300 amperes. The failure mechanism for the flatplate cell was related to surface or edge currents and hence would require a different model. This study was directed toward pulse widths of interest for the lightning environment but may be extended to the EMP or SGEMP environments with further analysis.