Fluorine-containing Cyclic Surface Passivators for Perovskite Solar Cells with Improved Efficiency and Stability

Surface defects induced non-radiative recombination is one of the major limitations to realize high-performance perovskite solar cells. Here, we develop a novel cyclic molecular material with fluorine moieties to passivate the surface defects and retard the water corrosion of perovskite films. The interaction of difluorotrimethylenimine hydrochloride (DFZCL) with residual lead iodide on the surface of perovskite films through N-H inhibits the formation of surface defects without affecting their crystal structure and reduces the film defect density, thereby enhancing the fluorescence intensity and carrier lifetime of perovskite films. Simultaneously, the employment of double fluorine atoms achieves a strong intermolecular linkage and constructs a moisture-resistant barrier on the surface of perovskite films. Consequently, the DFZCL-based perovskite cell yields a maximum power conversion efficiency of 22.4% with 13.7% enhancement compared with those of control devices. Moreover, the PCE keeps 68.3% of its initial efficiency and maintains outstanding stability under air conditions for up to 720 h. These preliminary results demonstrate the fluorine cyclic surface passivators is a promising for future high-performance perovskite solar cells.