Interfacial Engineering of Cu2O Passivating Contact for Efficient Crystalline Silicon Solar Cells with an Al2O3 Passivation Layer

Passivating contacts that simultaneously promote carrier selectivity and suppress surface recombination are considered as a promising trend in the crystalline silicon (c-Si) photovoltaic industry. In this work, efficient p-type c-Si (p-Si) solar cells with cuprous oxide (Cu₂O) hole-selective contacts are demonstrated. The direct p-Si/Cu₂O contact leads to a substoichiometric SiO_x interlayer and diffusion of Cu into the silicon substrate, which would generate a deep-level impurity behaving as carrier recombination centers. An Al₂O₃ layer is subsequently employed at the p-Si/Cu₂O interface, which not only serves as a passivating and tunneling layer but also suppresses the redox reaction and Cu diffusion at the Si/Cu₂O interface. In conjunction with the high work function of Au and the superior optical property of Ag, a power conversion efficiency up to 19.71% is achieved with a p-Si/Al₂O₃/Cu₂O/Au/Ag rear contact. This work provides a strategy for reducing interfacial defects and lowering energy barrier height in passivating contact solar cells.