Novel Interlayer Boosting the Performance of Evaporated Cu₂O Hole-Selective Contacts in Si Solar Cells

Passivating contacts based on transition metal oxides are of great interest for applications in crystalline silicon (c-Si) solar cells due to their improved optical transparency and potential cost reduction. In this work, the contact resistivity and passivation for thermally evaporated Cu₂O are investigated and optimized, with and without an Al₂O₃ interlayer, as a hole-selective contact to c-Si. Additionally, we implement an Al_yTiO_x/TiO₂ stack as a novel passivating tunnel interlayer for hole-selective contacts, achieving an implied open-circuit voltage iV _oc of 630 mV and a record-low J ₀ of 212 fA cm⁻² while maintaining a contact resistivity ρ _c of 62 mΩ cm². A record-low ρ _c of 8 mΩ cm² for Cu₂O-based contacts is also demonstrated at the expense of passivation. The addition of the interlayer resulted in a 2% absolute improvement in the efficiency of proof-of-concept c-Si cells with full-area rear Cu₂O contacts, reaching 19.1%.The demonstration of this novel interlayer stack provides new avenues to improve the performance also of other hole-selective passivating contacts.