Bidirectional Modification of Buried Interface Reduces Energy Loss for Planar Perovskite Solar Cells with Efficiency >23%

Planar n–i–p perovskite solar cells (PSCs) based on a SnO 2 electron transport layer dominate the certified high‐efficiency devices. However, the defects located at the SnO 2 /perovskite interface (i.e., buried interface) or inside the perovskite films impede the further improvement of power conversion efficiency (PCE). Herein, nickel acetate (NiAc 2 ) is introduced on buried interface as a bidirectional modifier to improve electron extraction of SnO 2 and the crystal growth of perovskite for the first time. First, NiAc 2 is chemically anchored on SnO 2 to passivate oxygen vacancies, increase conductivity, and optimize the energy level alignment of the buried interface. Second, the porous morphology of PbI 2 film deposited on NiAc 2 ‐modified SnO 2 endows more sufficient permeation and reaction of organic amine salts (formamidinium iodide [FAI] and methylammonium iodide [MAI]), forming high‐quality perovskite film with reduced PbI 2 residues. Meanwhile, NiI 2 and MAAc/FAAc may be produced via in situ reaction between NiAc 2 and organic amine salts, which serve as interface modifier and crystallization regulator to further reduce defects located at the buried interface or inside the perovskite film, respectively. Consequently, an improved PCE of 23.02% for SnO 2 ‐based PSCs with an ultrahigh open‐circuit voltage of 1.17 V is obtained. In addition, long‐term storage and light stability of the optimized PSCs are improved.