Surface Modification with Diaza-Crown Ether for High-Efficiency and Stable Inverted Perovskite Solar Cells

The presence of positively charged cationic defects and residual PbI₂ on the perovskite surface has hindered the improvement of the device performance and long-term stability. Herein, 4,10-diaza-15-crown 5-ether (DA15C5), a diaza-crown ether featuring multiple N atom and O atom donors, is developed to modify the perovskite surface. Owing to the strong chemical interactions between DA15C5 and both Pb²⁺ and A-site cations, the positively charged cationic defects on the surface of perovskite films are effectively passivated, thereby suppressing nonradiative recombination and promoting the charge transport at the cathode interface. Furthermore, the DA15C5 treatment promotes the formation of a two-dimensional (2D) perovskite phase by reacting with residual PbI₂, which optimizes the energy-level alignment and enhances the film stability. Consequently, the open-circuit voltage (<i>V</i>_OC) and fill factor (FF) of the perovskite solar cells (PSCs) improved significantly, achieving an impressive power conversion efficiency (PCE) of 24.75%. Moreover, both the environmental and the thermal stabilities of DA15C5-treated PSCs are markedly enhanced. The unencapsulated device retains over 80% of the initial PCE after heating 1400 h at 85 °C in a N₂ atmosphere and maintains 78% of the initial PCE after 550 h in air with 40 ± 10% relative humidity (RH). This study proposes diaza-crown ether as a surface molecular modulator to achieve efficient and stable PSCs.