Dual Surface Passivation Strategy for Enhanced Performance and Stability of Perovskite Solar Cells

Inverted perovskite solar cells (PSCs) have gained significant attention due to their ease of fabrication and superior stability. Surface passivation has proven to be an effective strategy for mitigating defect densities and suppressing non-radiative recombination at the perovskite-electron transport layer (ETL) interface. However, conventional single-passivant strategies often fail to simultaneously enhance both efficiency and long-term stability. Here, we introduce a dual-passivation approach using ethylene diammonium diiodide (EDAI) and dimethyl ethylene diammonium diiodide (DEDAI) to achieve improved device performance and durability. This synergistic passivation not only addresses undercoordinated lead ions and halide vacancies but also leverages the methyl-functionalized groups in DEDAI to create a moisture-resistant barrier, thereby enhancing the stability of the underlying perovskite layer. Photoluminescence (PL) and electrochemical impedance spectroscopy (EIS) measurements confirm that the dual-passivated perovskite surface exhibits superior defect passivation compared to single-molecule treatments. Furthermore, this approach promotes enhanced crystallinity and smoother surface morphology, facilitating more efficient electron transport toward ETL and ultimately boosting device performance. With this strategy, the power conversion efficiency (PCE) of our inverted PSCs improved significantly, rising from 17.6% in control devices to 18.4% with single passivation, and further to 19.5% with dual passivation. The shelf life of the solar cells also enhanced upon dual passivation.