Recently, the Guangzhou Energy Research Institute of the Chinese Academy of Sciences, together with the Research Center for Chemical Physics and Pharmaceutical Chemistry of the Russian Academy of Sciences, the Zhengzhou Research Institute of Harbin Institute of Technology, and the Institute of Microfabrication of Louisiana University of Technology in the United States, have made progress in the research of interface defect passivation mechanism and flexible calcium titanium ore solar cells.

The trap state on the surface and grain boundaries of perovskite is one of the main obstacles to the further commercialization of flexible perovskite solar cells (FPSCs). This study introduces two novel multifunctional fluorinated propylamine salts, 2,2,3,3,3-pentafluoropropylamine hydrochloride (PFPACl) and 3,3,3-trifluoropropylamine hydrochloride (TFPACl), in situ into the light absorption layer to passivate surface and grain boundary defects of perovskite and improve the performance of FPSCs. The nuclear magnetic resonance results confirmed the strong interaction between PFPACl and TFPACl with the precursor components of perovskite. This study derived the supramolecular complex structure formed by the two additives and methylamine iodide from two-dimensional nuclear magnetic resonance data, and proposed the importance of hydrogen bonding between the passivation agent molecule and its pre structure before the formation of perovskite film. Experiments and density functional theory calculations indicate that due to the high electronegativity of fluoroalkyl groups, PFPACl may be more inclined to dissociate into the form of R-NH3+- Cl -. Therefore, the binding of 2,2,3,3,3-pentafluoropropylamine salt to methylamine vacancy defects is stronger than its binding to 3,3,3-trifluoropropylamine salt. At the same time, the anion Cl - has a strong interaction with methylamine iodide vacancy defects and uncoordinated lead ions in FPSCs, resulting in PFPACl uniformly covering the entire surface of the perovskite film and more effectively matching the energy levels of the hole transport layer. Research has found that FPSCs modified in situ with PFPACl achieve a photoelectric conversion efficiency of 23.59% and still maintain an initial efficiency of 89.8% after 1000 hours, demonstrating excellent operational stability.

The relevant research results have been published in Advanced Functional Materials and have applied for a national invention patent. The research work was supported by the Ministry of Science and Technology and the Chinese Academy of Sciences.

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Schematic diagram of flexible perovskite solar cell device structure and PFPACl passivation perovskite defect mechanism diagram