Ordered Interfacial Dipole Layer Formed by Sodium Oleate to Modify Buried Interface Defects of Perovskite Solar Cells

Abstract Crystal and oxygen-related defects are present at the buried interface between the tin oxide (SnO2) electron transport layer (ETL) and perovskite layer during the solution preparation in regular perovskite solar cells (PSCs), which poses a negative effect on their photovoltaic performance. Herein, sodium oleate (NaOA) is explored as a functional interlayer to modulate the interfacial defects in PSCs. The carboxylate group (COO-) of NaOA is coordinated with Sn4+ on the surface of the SnO2 film to generate the Sn–OOC– bond. As a result, an ordered interfacial dipole layer is formed to modulate the local electronic environment on the surface of the SnO2 layer, thereby improving the energy level alignment and modifying these oxygen-related defects. Finally, the PSCs incorporated with the NaOA interlayer exhibit an improved power conversion efficiency (PCE) of 18.31%, compared with 16.53% for pristine PSCs. This study offers an interfacial dipole engineering strategy using NaOA for high-performance PSCs.