Benzalkonium chloride modification of tin oxide to enhance the performance of perovskite solar cells

For planar perovskite solar cells (PSCs), tin oxide (SnO2) is a perfect electron transport material. However, owing to nanoparticle agglomeration and defects, the advantages of SnO2 cannot be effectively utilized. Herein, a cationic surfactant, benzalkonium chloride (BAC) is introduced into SnO2 precursor solution to prevent the aggregation of SnO2. Thus, a uniform and free of pinhole SnO2 electron transport layer (ETL) is obtained, which supports the formation of high-quality perovskite layer (PVK). The introduction of BAC adjusts the energy level of ETL and improves the electron transport in the buried interface. Moreover, the BAC-modification reduces and passivates the defects on the surface of SnO2 and perovskite films. Consequently, BAC-modified PSCs achieves a champion efficiency of 23.49% with an impressive fill factor of 84.50%. The unpackaged device maintains an initial efficiency of 91.4% after 1000 h of storage in dark at 25±5 °C and 25±5% relative humidity.