Understanding of the Influence of the Surface Defectivity on Silicon Heterojunction Cell Performance

International audienceThe fabrication process of silicon heterojunction (SHJ) solar cells can induce locally depassivated regions (so-called defectivity) because of transportation steps (contact with belts, trays, etc) or simply the environment (presence of particles embedded within surface thin films). This surface passivation spatial heterogeneity is gaining interest as it may hinder the SHJ efficiency improvements allowed by incremental process steps optimizations. An experimentally-supported simulation study is proposed and applied on full size M2 SHJ cells in order to understand how the local a-Si:H/c-Si interface passivation loss impacts the overall cell performance. A simulation framework (developed on ATLAS Silvaco) was first validated through comparisons with experimental results. This step allowed then to use simulations results further to explore and understand the physics behind the defectivity-induced efficiency loss. The cell performance drop due to depassivated regions was attributed to a bias-dependent minority carrier recombination current flow towards the depassivated region, which is shown to affect mainly the Fill Factor