Beneficial effects of cesium acetate in the sequential deposition method for perovskite solar cells

The cesium cation (Cs+) is widely used as a dopant for highly efficient and stable formamidinium lead tri-halide perovskite (FAPbX(3), X = I, Br, Cl) solar cells. Herein, we introduce a small amount of cesium acetate (CsAc) that can effectively stabilize FAMAPbI(3) under thermal- and light illumination-stress. We show that incorporated Cs+ leads to relaxation of strain in the perovskite layer, and that Ac- forms a strong intermediate phase with PbI2, which can help the intercalation of the PbI2 film with Cs+ and cation halide (FAI, MAI, MACl) in the sequential deposition process. The addition of CsAc reduces the trap density in the resulting perovskite layers and extends their carrier lifetime. The CsAc-modified perovskite solar cells show less hysteresis phenomena and enhanced operational and thermal stability in ambient conditions. Our findings provide insight into how dopants and synthesis precursors play an important role in efficient and stable perovskite solar cells.

Automated summary

The addition of cesium acetate (CsAc) effectively stabilizes FAMAPbI(3) perovskite, reduces trap density, extends carrier lifetime, and improves the performance and stability of perovskite solar cells in ambient conditions. The study provides insights into the crucial role of dopants and synthesis precursors in the efficiency and stability of perovskite solar cells.