Silicon solar cells with hybrid back contacts

Silicon solar cells are essential for sustainable energy but remain limited by efficiency losses, particularly in the fill factor^1-3. Here we develop a hybrid interdigitated back-contact solar cell that combines advanced all-surface passivation with laser-treated tunnelling contacts. This approach achieves a power conversion efficiency of 27.81%, approaching 95% of the theoretical limit⁴. By integrating high- and low-temperature processes, we suppress recombination and enhance contact performance, achieving a fill factor of 87.55%-nearly 98% of the theoretical limit. A model links the ideality factor to carrier loss mechanisms, elucidating carrier recombination in both the bulk and the surface and clarifies key fill factor losses owing to recombination. These innovations provide both experimental and theoretical advances towards scalable, high-efficiency silicon photovoltaics.