Mitigating parasitic absorption in Poly-Si contacts for TOPCon solar cells: A comprehensive review

Owing to their rapidly rising market share, TOPCon (poly-Si/SiOx passivating contact or POLO contact) solar cells, which are projected to surpass PERC as the dominant solar cell technology within the next decade. The TOPCon structure exhibits exceptional passivation and conductivity properties for both n+ and p + polarities, while also being compatible with conventional industrial production processes. However, a limit upon implementing poly-Si/SiOx passivated contacts is the potential for optical losses caused by parasitic absorption in the poly-Si layer, particularly when placed at the front of solar cells or at the back of bifacial solar cells in bifacial modules where light can be absorbed from both the front and the backside. This review paper provides a comprehensive review of innovations aiming to mitigate these losses. These include thinning, employing transparent conductive films, light element doping, and localizing poly-Si contacts. Through an exploration of these methods, the paper endeavours to offer valuable insights into optimizing the performance of solar cells utilizing the TOPCon structure.