Bulk defect characterization in metalized solar cells using temperature-dependent Suns-Voc measurements

Extracting the parameters, energy level and electron-to-hole capture cross-section ratio, of efficiency-limiting bulk defects in silicon solar cells is a critical step in identifying those defects and potentially eliminating their impact. Typically, this is achieved on specially prepared test structures. However, in some cases, this is not possible, especially in mass production lines when only completed solar cells are available. In this study, a method that is based on temperature-dependent Suns-Voc measurements is introduced to extract the defect parameters in metalized solar cells. The method is validated by comparing the parameters of the boron-oxygenrelated defect extracted from cells and those extracted from wafers using the commonly used temperatureand injection-dependent lifetime spectroscopy. It is shown that this method has the benefit of a more accurate lifetime at low injection levels compared with photoconductance-based lifetime measurement since it is not impacted by minority carrier traps. The proposed technique is then applied to determine the parameters of the defect causing light-induced degradation in gallium-doped silicon solar cells. We determined an energy level, with respect to the intrinsic level, of -0.26 +/- 0.04 eV and a capture cross-section ratio of 34 +/- 2 for this defect. Finally, a sensitivity analysis is performed by considering the system's limited measurement temperature range. The findings demonstrate the potential of the temperature-dependent Suns-Voc method as a fast and easy-toapply method for defect characterization in metalized cells.

Automated summary

Extracting the parameters of efficiency-limiting bulk defects in silicon solar cells is crucial for identifying and eliminating their impact. This study introduces a temperature-dependent Suns-Voc measurement method to extract defect parameters in metalized solar cells and validates its accuracy. The method provides more accurate lifetime measurements and is fast and easy to apply for defect characterization in metalized cells.