Evidence for a Light‐Induced Degradation Mechanism at Elevated Temperatures in Commercial N‐Type Silicon Heterojunction Solar Cells

The response of commercial n‐type silicon heterojunction (SHJ) solar cells to illuminated annealing at temperatures between 75 and 180 °C is reported on. Although a slight increase in efficiency of 0.1% absolute occurs at 75 °C under 1 sun illumination after 20 h, annealing at higher temperatures (85–180 °C) results in significant degradation in cell performance, and only occurs in the presence of illumination. At 160 °C, a loss in η up to 1% absolute is observed under 1 sun light soaking (LS) in as little as 2 min. Further illuminated annealing leads to a subsequent partial or full recovery of cell performance. At 160 °C, after an initial V OC degradation exceeding 10 mV within 3 min, a complete recovery is obtained after 60 min of illuminated annealing. The results indicate the potential presence of a light‐induced degradation mechanism in n‐type SHJ cells, suggesting care must be taken when using LS to improve efficiency. In addition, significant variability in the maximum extent of degradation indicates a high degree of cell‐to‐cell variation in expression of this degradation mechanism. The exact nature of the underlying defect mechanism(s) governing degradation and recovery dynamics remains uncertain and requires further studies.