Synergistic bimolecular erosion-healing interfacial passivation for wide-bandgap perovskite and tandem solar cells

All-perovskite tandem solar cells present immense potential due to their exceptional performance and versatility. However, their practical implementation is impeded by significant challenges, particularly in large-area devices, where interfacial inhomogeneities in wide-bandgap (WBG) perovskite subcells lead to high open-circuit voltage losses and low fill factors. Here, we introduce a synergistic bimolecular corroding-healing passivation strategy to enhance WBG perovskite films' passivation and interfacial uniformity. Unlike conventional passivation methods relying on halide ammonium salts, this approach directly employs precursor diamines to passivate interfacial defects, suppress recombination, and crucially induce mild surface corrosion, creating random openings on the perovskite surface. Paired molecules of piperazinium iodide then penetrate these openings, enabling deeper defect passivation and surface healing to form a smooth, homogeneous interface. This strategy enabled 1.78 eV WBG perovskite solar cells to achieve a power conversion efficiency (PCE) of 20.47% with an ultrahigh fill factor of 85.10%. Furthermore, when integrated with narrow-bandgap perovskite subcells, the fabricated all-perovskite tandem solar cells delivered PCEs of 28.36% (0.07 cm²) and 27.52% (1.02 cm²). This dual-molecular erosion-healing passivation strategy offers an effective and scalable solution to optimize the perovskite interface, driving advancements in the performance and manufacturability of WBG perovskite and tandem solar cells.