Defect Passivation Enabled by Amphiphilic Polymer Additives for Perovskite Solar Cells with Suppressed Charge Recombination

Harmful defects are typically major performance and stability degrading factors in perovskite solar cells (PSCs). In order to prevent defect formation and ion migration, some small molecule additives are often used in PSCs, which, however, are highly volatile and very likely to drift. In this work, an amphiphilic polymer, p(HEMA-co-DEAMA), is synthesized and doped into organic salt solution. Through Lewis base coordination and hydrogen bonding, it can be chemically bonded to a perovskite. Further analysis reveals that trap density is significantly reduced after simple treatment with p(HEMA-co-DEAMA), suppressing charge recombination and boosting the power conversion efficiency (PCE) of PSCs. Moreover, the ordered long chain structure of p(HEMA-co-DEAMA) forms a gridlike crystal, which stitches the grain boundaries and thus modulates the growth of perovskite crystals therein. Importantly, the exposure of the long alkyl chains on p(HEMA-co-DEAMA) also provides a hydrophobic coating, which protects the perovskite film from environmental humidity and further enhances the operation stability. Therefore, the unpackaged devices modified with p(HEMA-co-DEAMA) exhibit excellent stability with retaining more than 90% of the original PCE when stored for 1000 h in an air environment, indicating the viability of our strategies.