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 MAPbI3-x(OAc)x, 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.
Keywords: Pb(OAc)2; high efficiency; long-term stability; perovskite solar cells; top and bottom ways.