Interface and Grain Boundary Passivation by PEA-SCN Double Ions via One-Step Crystal Engineering for All Air-Processed, Stable Perovskite Solar Cells

The degeneration of organic–inorganic hybrid perovskite solar cells (PSCs) under ambient air is a serious challenge that prevents the commercialization of PSCs. The introduction of hydrophobic long-chain organic cations into the perovskite film is a promising way to improve the long-term stability of devices. However, this approach always comes with the sacrifice of the power conversion efficiency (PCE). In this work, we introduce a novel one-step double ion passivation route together using phenylethylamine ion (PEA⁺) and SCN^– to passivate the grain boundary and surface of the perovskite polycrystalline film by crystal engineering to fabricate all air-processed, stable PSCs. Compared with three-dimensional (3D) MAPbI₃ perovskite films, the PEA⁺ and SCN^– codoped MAPbI₃ perovskite films from the single crystal engineering have a larger grain size and better stability with a longer carrier lifetime and lower electron trap state density. The champion PCE of 18.04% with negligible hysteresis was achieved for the 0.05 M PEA⁺ and SCN^– codoped PSCs, which exhibit 25% higher efficiency than the MAPbI₃ solar cell fabricated using the traditional precursor solution mixing method. The devices without encapsulation still maintain 82% of their original PCE when stored over 750 h under ambient air conditions with a relative humidity of 50%.