Multi-site passivation agent for efficient tandem solar cells: Simultaneously suppressing defect recombination in NiO surface, perovskite buried interface, and silicon edge

Wide-band gap perovskites combined with silicon (Si) in tandem solar cells offer a cost-effective path to industrialization. However, surface recombination at the buried interface of perovskite solar cells (PSCs) and the edge surface of Si solar cells affects their efficiency and stability. Herein, we design a multi-site passivation agent to simultaneously suppress defect recombination in hole transfer layer (HTL) surface, perovskite buried interface, and Si edge for efficient tandem solar cells. The increased ratio of Ni 3+ /Ni 2+ reduces the nickel oxide (NiO x )/perovskite interface reaction and improves the conductivity of the NiO x HTL. The reconstructed underlayer is more propitious to the perovskite deposition, which releases the residual strain, resulting in the enhancement of the efficiency and stability of PSCs. Moreover, the multi-site passivation agent presents a distinctive passivation effect for edge surface of Si solar cells. Power conversion efficiencies (PCEs) of 21.95% and 20.01% are obtained at opaque and semitransparent PSCs, respectively. Additionally, a four-terminal tandem solar cell exhibits a PCE of 31.02% with +1.19%abs PCE increase for bottom cell by edge surface passivation. Overall, this work provides a simple and multi-site surface defect passivation strategy for obtaining high-efficiency and stable perovskite and perovskite tandem solar cells.