The rapidly reversible processes of activation and deactivation in amorphous silicon heterojunction solar cell under extensive light soaking

Silicon heterojunction (HJT) solar cells use hydrogenated amorphous silicon (a-Si:H) to form passivating contacts. To obtain high performance, many crucial applications have been confirmed and introduced. In this work, extensive light soaking (ELS) was used to comprehensively investigate a-Si:H films and HJT solar cells. The enhanced effective minority carrier lifetime (τeff) for c-Si wafers passivated with a-Si:H was achieved via extensive light soaking, and the passivation enhancement can reach saturation in few seconds. It was observed that there was a significant contribution of low thermal annealing (LTA) process, excellently improving the ultimate passivation function of ELS. A comparison of c-Si wafers passivated with different a-Si stacks under various temperatures was examined, and the activation and deactivation performance during repeated extensive light soaking-low thermal annealing cycles was systematically discussed. Finally, the reversibility of efficiency enhancement and degradation in HJT solar cells related to extensive light soaking-low thermal annealing cycles was demonstrated for the first time.