Passivating Defects via Retarding the Reaction Rate of FAI and PbI Enables Stable Perovskite Solar Cells.

The two-step sequential deposition strategy has garnered widespread usage in the fabrication of high-performance perovskite solar cells based on FAPbI. However, the rapid reaction between FAI and PbI during preparation often leads to incomplete reactions, reducing the device efficiency and stability. Herein, we introduced a multifunctional additive, 2-thiophenyl trifluoroacetone (TTA), into the FAI precursor.