Suppressing Alkyl Ammonium Deprotonation with Low‐pKa Solvent for Reproduceable and Stable High‐Efficiency Perovskite Solar Cells

Abstract Various passivation strategies have been explored to enhance the stability of the perovskite solar cells (PSCs). However, the chemical stability of passivators has received limited attention. This study investigates replacing conventional isopropyl alcohol (IPA) with hexafluoroisopropanol (HFIP) as the solvent for depositing passivation layers on perovskite films, offering a novel approach to minimizing defects and improving photovoltaic performance. The unique properties of HFIP, particularly its low pKa and strong proton‐donating ability, effectively inhibit the deprotonation of organic ammonia salts. As a result, the HFIP‐based passivation solution exhibits enhanced chemical stability, leading to highly reproducible PSCs fabrication. Additionally, perovskite films treated with the HFIP passivation solution demonstrate higher photoluminescence (PL) intensity and longer carrier lifetimes. Consequently, PSCs treated with HFIP‐based 1,3‐propanediamine dihydroiodide (PDAI) solution achieved a champion power conversion efficiency (PCE) of 26.91% (certified PCE of 26.88%) and maintained 95.9% of their initial efficiency under operational conditions for 1000 h.