Study on the mechanism of advanced pre-degradation on hydrogenation of multi-crystalline silicon solar cells

The electrical performance of monocrystalline silicon solar cells was significantly improved under hydrogenation alone with appropriate conditions, while the similar improvements of multi-crystalline silicon (mc-Si) solar cells were relatively slight. In this paper, an advanced pre-degradation (Adv.Pre-Deg) was introduced to improve the hydrogenation effect and enhance the performance of mc-Si solar cells. Meanwhile, further studies were conducted on the influence mechanism of Adv.Pre-Deg on subsequent hydrogenation, and some microscopic detection was applied to characterize the effect of Adv.Pre-Deg on the following hydrogenation. The results indicated that Adv.Pre-Deg only slightly influenced the crystallinity, dangling bonds, and defects within the surface dielectric layer, which illustrated that Adv.Pre-Deg hardly harmed the dielectric layer. Then, Raman imaging demonstrated that Adv.Pre-Deg displayed primary assistance in stimulating impurities or defects in silicon bulk in advance. According to the detection of the Si-H bond, we also concluded that the effective performance improvement on mc-Si silicon solar cells through Adv.Pre-Deg & hydrogenation was due to the pre-activation of impurities or defects by Adv.Pre-Deg. Moreover, Adv.Pre-Deg enhanced the passivation effect of hydrogenation on interstitial ${\text{Fe}}_i^{+}$ from 30.3%_rel. to 89.1%_rel. and dislocation defects from 21.92%_rel. to 46.18%_rel., doubling the improvement of bulk passivation on mc-Si. Therefore, the method of combining Adv.Pre-Deg with hydrogenation aims to be applied to other types of solar cells and focus on improving performance and suppressing various degradations, such as TOPCon and HJT.