Deciphering the Role of Hydrogen in the Degradation of Silicon Solar Cells under Light and Elevated Temperature

In recent years, significant attention has been paid to the research of light- and elevated-temperature-induced degradation (LeTID) in silicon solar cells due to the substantial power loss and instability it causes. It has been discovered that the presence of hydrogen is closely linked to the occurrence of LeTID. In this study, a thorough review and re-assessment of previously published results is conducted and connected with newly obtained data. The findings indicate a complex interaction between different hydrogen complexes and the LeTID defect states. The precursor of LeTID is connected to molecular hydrogen (H₂), while the LeTID degradation and regeneration are related to the binding of atomic hydrogen to the precursor and defect, respectively. A detailed description of the various reactions that occur under illumination and in the dark is provided. Additionally, explanation is given on how pre-annealing can significantly affect the kinetics of LeTID during subsequent light soaking. Furthermore, a comprehensive hydrogen model that incorporates these various reactions and demonstrates an agreement between simulation and experimental results is developed. Finally, the implications of the findings on strategies for mitigating LeTID are discussed.