<scp>NaHCO₃</scp>‐induced porous <scp>PbI₂</scp> enabling efficient and stable perovskite solar cells

Driven by their many unique features, perovskite solar cells (PSCs) have become one of the most promising candidates in photovoltaic field. Two-step preparation film is advantageous for its higher stability and reproducibility compared to one-step method, which more suitable practical application. However, incomplete conversion dense lead iodide (PbI2) layer during sequential spin-coating formamidinium/methylammonium (FA+/MA+) organic amine salts severely affect performance PSCs. Herein, sodium bicarbonate (NaHCO3) used induce formation porous PbI2, facilitates penetration FA+/MA+ ions a with high crystallinity large grain microstructure. Meanwhile, introduction Na+ not only improves energetic alignment PSC, but also increases conductivity via p-doping. As result, optimized NaHCO3-modified PSC achieves champion power efficiency 24.0% suppressed hysteresis. Moreover, significant reduction defect density ion migration as well mild alkaline environment enhance device. The unencapsulated PSCs maintain over 90% original upon storage ambient air (30%–40% relative humidity) 2160 h. We demonstrated an ingenious strategy controlling quality improving device low-temperature foaming simple inorganic molecules NaHCO3.