Micron- to submicron-scale selective crystallization of amorphous silicon for advanced passivating contacts in silicon solar cells

Amorphous silicon (a-Si) passivating contacts enable excellent surface passivation in high-efficiency silicon solar cells, but their high contact resistivity constrains further gains. Nanocrystalline silicon (nc-Si) offers lower resistivity, yet its low deposition rate limits scalability. Here, we demonstrate micron- to submicron-scale selective crystallization of a-Si via laser-induced crystallization (LIC), creating localized low-resistivity regions while retaining high deposition throughput. LIC exploits the interplay of laser irradiation, surface morphology, and thermal diffusion, with nanosecond and picosecond lasers inducing crystallization through distinct heat-transfer mechanisms. Using 532-nm nanosecond and 355-nm picosecond lasers, contact resistivity is reduced by over an order of magnitude. Integrated into a hybrid back-contact solar cell, nanosecond LIC delivers a 0.26% absolute efficiency gain, achieving a certified efficiency of 27.49%. These results establish mixed-phase a-Si/nc-Si films as advanced passivating contacts and highlight LIC as a pathway for precise laser engineering in next-generation silicon photovoltaics.