Incorporating a Polar Molecule to Passivate Defects for Perovskite Solar Cells

The intrinsic characteristics of a ZnO electron transport layer (ETL) lead to severe charge loss in perovskite solar cells (PSCs), such as photogenerated charge accumulation recombination in the perovskite layer due to the low electron extraction capacity, and defect-induced charge recombination at the interface due to the unfavorable defects, causing efficiency loss and device hysteresis. Here, the polar molecule of (2-aminothiazole-4-yl)acetic acid (ATAA) is self-assembled onto a ZnO layer with the help of oxygen vacancy defects, combining the advantages of lowering the work function by forming the permanent interface dipole and simultaneously passivating defect states. It effectively strengthens the electron extraction capacity and reduces the density of defect states. Therefore, the resulting PSCs with a ZnO-ATAA ETL yield an enhanced efficiency of 19.74% with evidently reduced device hysteresis.