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 SnO₂ electron transport layer dominate the certified high-efficiency devices. However, the defects located at the SnO₂/perovskite interface (i.e., buried interface) or inside the perovskite films impede the further improvement of power conversion efficiency (PCE). Herein, nickel acetate (NiAc₂) is introduced on buried interface as a bidirectional modifier to improve electron extraction of SnO₂ and the crystal growth of perovskite for the first time. First, NiAc₂ is chemically anchored on SnO₂ to passivate oxygen vacancies, increase conductivity, and optimize the energy level alignment of the buried interface. Second, the porous morphology of PbI₂ film deposited on NiAc₂-modified SnO₂ endows more sufficient permeation and reaction of organic amine salts (formamidinium iodide [FAI] and methylammonium iodide [MAI]), forming high-quality perovskite film with reduced PbI₂ residues. Meanwhile, NiI₂ and MAAc/FAAc may be produced via in situ reaction between NiAc₂ 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 SnO₂-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.