Modification of SnO2 by acidic FAAc-HI solution for efficient and stable perovskite solar cells with a multifunctional interface

Tin oxide (SnO2) offers unique advantages as the electronic transport layer (ETL) of perovskite solar cells, such as low-temperature preparation and excellent electron extraction capability. However, the SnO2 semiconductor process is prone to forming a hydroxyl group enrichment at the interface, resulting in insufficient stability. Furthermore, the potassium hydroxide stabilizer in commercial SnO2 can degrade the perovskite layer. Herein, acidic formamidine acetate and hydroiodic acid (FAAc-HI)-mixed solutions are added into a commercially SnO2 aqueous to alleviate hydroxyl enrichment and neutralize the OH− in SnO2-ETL. As a result, the modified SnO2/perovskite interface exhibits faster charge extraction in comparison with that of the primeval interface. The as-prepared device achieves a champion power conversion efficiency (PCE) of 21.25%, with a Jsc increasing from 23.84 mA cm−2 in the untreated device to 24.71 mA cm−2. When stored in an air environment (40% RH, 25 °C) for 600 h, it retains 90% of its initial efficiency compared to 80% of the control group.Graphical abstract