Lead Acetate Assisted Interface Engineering for Highly Efficient and Stable Perovskite Solar Cells

High power conversion efficiency (PCE) and long-term stability are inevitable issues faced in practical device applications of perovskite solar cells. In this paper, significant enhancements in the device efficiency and stability are achieved by using a surface-active lead acetate (Pb(OAc)₂) at the top or bottom of CH₃NH₃PbI₃ (MAPbI₃)-based perovskite. When a saturated Pb(OAc)₂ solution is introduced on the top of the MAPbI₃ perovskite precursor, the OAc^- in Pb(OAc)₂ participates in lattice restructuring of MAPbI₃ to form MAPbI_3-(OAc), thereby producing a high-quality perovskite film with high crystallinity, large grain sizes, and uniform and pinhole-free morphology. Moreover, when Pb(OAc)₂ solution is mixed in the poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT-PSS) solution in the bottom way, the OAc^- in Pb(OAc)₂ improves the water resistance of PEDOT-PSS. As the OAc^- easily bonds with the Pb²⁺, the deposition of MAPbI₃ precursor onto the Pb(OAc)₂ mixed with PEDOT-PSS results in a reduction of the uncoordinated Pb, leading to strong stabilization of the perovskite layer. Both the top- and bottom-treated devices exhibit enhanced PCE values of 18.93% and 18.28%, respectively, compared to the conventional device with a PCE of 16.47%, which originates from decreased trap sites and reduced energy barriers. In particular, the bottom-treated device exhibits long-term stability, with more than 84% of its initial PCE over 800 h in an ambient environment.