Thermal Processes and their Impact on Surface‐Related Degradation

• Published in: Physica status solidi. PSS-RRL. Rapid research letters 2022-02, Vol.16 (2), p.n/a
• Main Authors: Hamer, Phillip, Chen, Daniel, Bonilla, Ruy Sebastian
• Format: Article
• Language: English
• Subjects: defect engineering; degradation; photovoltaics; silicon; surface passivation
• ISSN: 1862-6254; 1862-6270
• DOI: 10.1002/pssr.202100464

Surface‐related degradation (SRD) is a phenomenon whereby recombination in the near‐surface region of silicon wafers increases under elevated temperatures with or without carrier injection. Because of its importance for solar cell processing and operation, SRD occurring under light soaking at temperatures between 80 and 200 °C has recently attracted great interest. In this work, two post‐firing processes that can affect the formation of SRD are investigated. The first is the replacement of the passivating dielectric layers and the second is the use of thermal annealing between 300 and 400 °C. Post‐firing etching and redeposition of dielectric layers have minimal impact on subsequent degradation. In contrast, a thermal anneal at 400 °C for 30 min can reduce the extent of SRD by a factor of 6. These results imply that the interface between silicon and the dielectric itself is not the critical factor in the formation of SRD. The most likely explanation is that thermal processing causes an alteration in the silicon substrate that affects the subsequent formation of SRD. Two post‐firing processes that affect the formation of surface‐related degradation (SRD) in silicon are investigated. Replacement of dielectric layers is shown to have minimal impact on degradation. In contrast, a thermal anneal at 400 °C for 30 min reduces SRD by a factor of 6. This implies that the silicon/dielectric interface is not the critical factor in SRD formation.