Efficient and Stable Wide‐Bandgap Perovskite Solar Cells Fabricated via Vacuum Flash

Wide-bandgap perovskite solar cells (WBG-PSCs), serving as the top cells in tandem architectures, are predominantly fabricated using antisolvent bathing or gas quenching techniques, which often suffer from stringent environmental requirements and limited scalability. Herein, we report the first successful application of vacuum flash for fabricating high-performance WBG-PSCs featuring bandgaps exceeding 1.7 eV. We demonstrate that vacuum flash at a substrate temperature (40°C) yields highly uniform, dense, and defect-free perovskite films under air conditions. Crucially, our kinetic analysis reveals a distinct crystallization pathway: unlike the antisolvent and gas quenching methods that initially form bromine-rich intermediate phases, the vacuum flash technique enables ultra-rapid solvent extraction, directly yielding a homogeneous perovskite phase free from phase separation. Building on this mechanistic insight, we further develop a humidity-adaptive strategy by elucidating the synergistic coupling among ambient humidity, additive concentration, and annealing time. The champion device achieves a remarkable power conversion efficiency (PCE) of 21.57%, ranking among the highest for WBG-PSCs, and retains 94% of its initial efficiency after 3,000 h of storage in nitrogen. This work not only bridges the gap in vacuum flash technology for wide-bandgap systems but also provides a scalable, cost-effective, and environmentally tolerant pathway for the fabrication of WBG-PSCs.