Coordination‐Induced Defects Elimination of SnO2 Nanoparticles via a Small Electrolyte Molecule for High‐Performance Inverted Organic Solar Cells

Tin oxide (SnO2) is broadly used as an electron transport layer (ETL) in organic solar cells (OSCs). However, there are many hydroxyl groups and the defects of oxygen vacancy on the surface of SnO2, resulting in charge recombination. Herein, an electrolyte 4‐(dimethyl(pyridin‐2‐yl) ammonio)butane‐1‐sulfonate (PAS) is doped into SnO2 films with an appropriate proportion to improve the performance of the inverted OSCs. The PAS can coordinate with the Sn atoms in SnO2 films to reduce the surface defects, resulting adjustable work function and increased electron conductivity. Meanwhile, the PAS doping can decrease the surface energy of SnO2 layer, forming vertical phase distribution of the active layer for better exciton dissociation and charge transport. The PM6:Y6 based inverted OSC with SnO2 ETL shows a power conversion efficiency (PCE) of 14.72%, while the device with PAS‐doped SnO2 ETL demonstrates greatly enhanced PCE of 16.37%. The device performance can be further improved by using PM6:BTP‐eC9 as active layer and a PCE of 17.12% can be achieved with PAS‐doped SnO2 ETL. Furthermore, PAS‐doped SnO2 can effectively enhance the device stability under continuous illumination. These findings demonstrate that exquisite regulation of SnO2 layer via a small electrolyte molecule coordination is a promising approach to achieve efficient and stable inverted OSCs.