Grain Boundary Engineering Enables 22.2%-Efficient Inverted Wide-Bandgap Perovskite Solar Cells in Ambient Air

Wide-bandgap (WBG) perovskite solar cells (PSCs) are critical for tandem solar cells, yet their fabrication in ambient air─a critical requirement for industrial scaling─introduces grain boundary (GB) defects that impede charge transport. Here, we present a grain boundary band inversion strategy using lead dibutyldithiocarbamate (PbDBuDTC) as an interfacial passivator, which simultaneously mitigates defects and reconstructs the energy landscape in 1.68 eV WBG perovskite films. Kelvin probe force microscopy reveals that PbDBuDTC treatment reverses the work function disparity between GBs and grain interiors, transforming the inherent p-n-p junction across GBs into an n-p-n configuration, thereby facilitating charge separation. Coupled with vacancy defect passivation, the resulting inverted device achieves a power conversion efficiency (PCE) of 22.2%, one of the highest PCE for air-processed WBG PSCs. Furthermore, the reductive property of PbDBuDTC (reducing I₂ and I₃^- to I^-) and hydrophobic butyl chains confer exceptional stability, with unencapsulated devices retaining 90.7% of their initial PCE after 1000 h at 25 °C and 30% relative humidity. This work adopts a defect-engineering strategy that reconciles high efficiency with ambient-air compatibility, advancing the industrialization of perovskite photovoltaics.