Air-Doctor-Blading CH₃NH₃PbI₃ Perovskite Solar Cells via a Green Cosolvent Strategy

Achieving high-performance perovskite solar cells (PSCs) under ambient conditions remains challenging due to uncontrolled crystallization in conventional solvents, often leading to defect-prone interfaces and morphological degradation. Here, we propose a green cosolvent strategy, combining high-polarity 2-methoxyethanol (2-Me) and low-polarity acetonitrile (ACN), to precisely regulate the crystallization kinetics and morphologies of perovskite films. This synergistic system effectively optimizes precursor coordination, balancing solubility and solvent polarity to meticulously control nucleation and growth of perovskite films. Furthermore, the incorporation of an ionic liquid, methylammonium acetate (MAAc), significantly facilitates intimate adhesion between the perovskite film and the underlying substrate. <i>In situ</i> characterization confirms that this approach leads to a reduced intermediate-phase lifetime and suppressed grain boundary formation. Consequently, the perovskite films processed by doctor-blading under ambient conditions exhibit remarkably enlarged grains and smooth morphology. The champion devices based on CH₃NH₃PbI₃ (MAPbI₃) thin films achieve a power conversion efficiency (PCE) of 21.94% without antisolvent treatment, while unencapsulated devices retain 96.4% of the initial efficiency after 800 h of ambient exposure.