Enabling 95 % bifaciality of efficient TOPCon solar cells by rear-side selective sunken pyramid structure and zebra-crossing passivation contact

The bifaciality of solar cells plays a crucial role in determining their overall energy generation performance, particularly in high-reflectance environments where enhanced rear-side light absorption can significantly boost power output. Compared to silicon heterojunction solar cells, a major barrier to the further increasing market competitiveness of tunnel oxide passivated contact (TOPCon) solar cells is the lower bifaciality. In this work, we reported an excellent 94.3 % bifaciality of TOPCon solar cells by formation of rear-side selective sunken pyramid structure on the non-electrode area. The zebra-crossing passivation contact technology was developed without sacrificing the efficiency, where the passivation layers were designed as SiO₂/poly-Si/Al₂O₃/SiN_x under silver electrodes and Al₂O₃/SiN_x on rear-side texture area. The optimised rear-side short-circuit current density increased by 3.26 mA/cm² compared to the baseline, leading to a notable improvement in rear-side light absorption and current generation. As a proof-of-concept, the bifacial TOPCon photovoltaic modules were encapsulated with an impressive bifaciality of 91.7 % and a power output of 722.0 W. It is the highest bifaciality so far for TOPCon solar cells and modules to the best knowledge. Our study offers a blueprint for designing high bifaciality TOPCon solar cells and modules, making them more efficient and versatile than traditional glass/backsheet modules and accelerating practical application.