Bidirectional Targeted Therapy Enables Efficient, Stable, and Eco‐Friendly Perovskite Solar Cells

Perovskite solar cells (PSCs) have witnessed rapid development toward commercialization based on their superior efficiency except for some remained misgivings about their poor stability primarily originating from interfacial problems. Robust back interface for neutralization of crystal defects, depression of dopant lithium ions (Li+) diffusion, and even inhibition of toxic lead (Pb) leakage is highly desirable; however, it remains a great challenge. Herein, a cost‐effective interfacial therapy approach is developed to simultaneously alleviate the obstacles aforementioned. A small molecule, 1,4‐dithiane with unique chair structure, is adapted to interact with under‐coordinated Pb2+ on perovskite surface and Li+ from hole transport layer, neutralizing interfacial defects and suppressing Li+ diffusion. Besides, the presence of 1,4‐dithiane can efficiently modulate interfacial energetics, enhance hydrophobicity of PSCs, and anchor Pb atoms via SPb bond. Consequently, the target devices perform better than control devices when exposed to light‐soaking, moisture, and thermal stress owing to the synergistic suppression of trap‐state density, ions migration, and moisture permeation. The optimized target device delivers a champion efficiency of 23.27% with mitigated Pb leakage. This study demonstrates a promising functionalized modification strategy for constructing efficient, stable, and eco‐friendly PSCs. Herein, a cost‐effective yet robust interfacial bidirectional therapy strategy is developed to simultaneously depress dopant lithium ions diffusion, suppress defects states and inhibit toxic lead (Pb) leakage of perovskite solar cells. The unencapsulated modified devices based on formamidinium‐lead‐triiodide (FAPbI3) perform better than control devices when exposed to different harsh environments. And the modified device delivers a champion efficiency of 23.27% with mitigated Pb leakage. More importantly, the developed strategy is also adaptable to methylammonium‐lead‐triiodide (MAPbI3)‐based device for simultaneous enhancement of the device stability and efficiency (20.82%).