Engineering Silicon Interfaces with Transparent Al_yTiO_x/ZnO/TiO₂ Stack Exhibiting Exceptional Passivating Contact Performance

Passivating contact technologies are essential for fabricating high-efficiency crystalline silicon (c-Si) solar cells, and their application and incorporation into manufacturing lines has ranked as a hot topic of research. Generally, ideal passivating contacts should combine excellent electrical contact, outstanding surface passivation, and high optical transparency. However, addressing all these criteria concurrently is challenging since it is unlikely for any single material to exhibit both efficient carrier transport and surface-defect passivation while demonstrating negligible parasitic absorption. In this work, several earth-abundant, wide-bandgap materials are combined to engineer high-quality transparent electron-selective passivating contact structures capable of overcoming these obstacles. A highly transparent Al_yTiO_x/ZnO/TiO₂ stack with a total thickness of 3 nm, prepared by atomic layer deposition, is shown to provide a close-to-ideal passivating contact to Si surfaces by enabling dual functions of remarkable silicon surface passivation (with an effective minority carrier lifetime of 12.3 ms, an implied open-circuit voltage of 730 mV, and a surface recombination current density prefactor of 2.6 fA cm⁻²), combined with efficient carrier transport with a very low contact resistivity of 3.4 mΩ cm². These results demonstrate that low-cost silicon interface-engineering strategiesbased on transition metal oxides can push c-Si solar cell performance to its theoretical limits.