Substitution of DMSO for Stabilized Perovskite Solar Cells with Extended Process Window

Dimethyl sulfoxide (DMSO) is frequently employed to boost the crystal quality of solution‐processed perovskites, while it is prone to remain trapped within the films and leads to defective interface within the resultant perovskite solar cells (PSCs). Herein, a small molecule of hydroxyethyl methacrylate (HEMA) is introduced to substitute the DMSO. The hydroxyl (─OH) and carbonyl (─C═O) groups in HEMA are simultaneously associated with formamidinium (FA+) and Pb2+ via hydrogen bonds and coordination bonds, respectively, which facilitates the formation of strongly bonded FAI‐HEMA‐PbI2 complexes in the precursor solution to regulate perovskite crystallization with improved crystallinity and preferred orientation. Moreover, the solidification of residual HEMA via in situ polymerization can stabilize crystal structure with suppressed defects and released lattice strain. Consequently, PSCs based on HEMA‐treated perovskite films achieve a decent power conversion efficiency (PCE) of 25.31% with superior stability, retaining 90% of their initial PCE after 1000 h storage. Importantly, the incorporated hydrophilic HEMA can largely promote the moisture resistance of the precursor solution by preventing water molecules from direct contact with perovskite components. More than 90% of the initial efficiency is maintained by using old precursor solutions aged in ambient air for 20 days, indicating an extended process window for device fabrication.