Reduction of Thermal Caused Extra Light Induced Degradation by Redefined Regeneration Conditions

The regeneration process is a method for boronoxygen defects passivation by using heat and illumination, and its benefits have been demonstrated for efficiently reducing light induced degradation (LID) on P-type cells. It is widely used for solving LID issue on p-type PERC cells in recent year. In this paper, post-heating was used to understand the thermal influence on regenerated cells. Comparison between cell with and without regeneration process, the post-heating caused extra LID (2%) in regenerated cells is much higher than that (0.5%) in as-fired cells. The difference of extra LID between as-fired and regenerated cells indicates that the post-heating results in defect state transition from regenerated state to annealed state in regenerated cells. Based on this phenomenon, the LID test must take the impact of latent heat after regeneration process such as subsequent module process into consideration. Therefore, the regeneration process windows of temperature and light intensity need to be redefined when post-heating is introduced after regeneration process. The result of process window redefinition shows that the regeneration conditions of 1.4C suns light intensity can reduce the post-heating caused extra LID about 0.8% as compared with the regeneration conditions of 1C suns light intensity, and LID has no significant change as temperature of regeneration condition in a range from 225 °C to 275 °C. Additionally, cells with regeneration condition of 175 °C have low as regenerated efficiency, and the LID of cells with regeneration treatment at 300 °C is higher than that of cells treated with lower temperatures.