Investigation of Pin-Holes Opening in Silicon Solar Cell Passivated Contacts Induced by Pulsed Laser Melting

Tunnel oxide passivating contacts (TOPCon) technology is a promising candidate for the development of high-efficiency silicon solar cells. The core structure of this technology consists of a poly-Si/SiOx/c-Si junction. The carrier transport mechanism in this junction is primarily governed by tunneling through a thin (<2 nm) SiOx layer, which passivates the Si surface and provides carrier selectivity due to the heavy doping of the poly-Si cladding. While tunneling through the SiOx layer is the main transport mechanism, direct transport through pinholes is also possible. Traditionally, high-temperature annealing induces stress deformations that lead to SiOx fracture, resulting in the formation of pinholes. In this study, pulsed laser melting (PLM) is investigated as an innovative approach for forming pinholes at the tips of pyramidal-textured solar cells, while preserving passivated contacts on the pyramid facets. AFM is used to investigate the morphological changes occurring at the pyramid tips by varying laser processing conditions. In addition, c-AFM current measurements were also performed to obtain new insights into carrier transport through pinholes.