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 AlyTiOx/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 rho(c) of 62 m Omega cm(2). A record-low rho(c) of 8 m Omega cm(2) 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.