Recently, a team led by Dr. Xu Xueqing from the Guangzhou Institute of Energy Research, Chinese Academy of Sciences, in collaboration with partners, has made new advancements in the field of defect passivation mechanism and flexible perovskite solar cells. The related research has been published in "Advanced Functional Materials," and the outcomes have been applied for a national invention patent.
Schematic diagram of the device structure of flexible perovskite solar cells (FPSCs) and defect passivation mechanism of PFPACl on perovskite. Image provided by the research team.
The trap states at the surface and grain boundaries of perovskite are among 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 chloride (PFPACl) and 3,3,3-trifluoropropylamine chloride (TFPACl), into the light-absorbing layer to passivate surface and grain boundary defects of perovskite, thereby enhancing the performance of FPSCs. NMR results confirm the strong interaction of PFPACl and TFPACl with the precursor components of perovskite, deriving for the first time the supramolecular complex structures of the two additives with iodomethane from 2D NMR data, highlighting the importance of the preorganization of passivator molecules through hydrogen bonding before perovskite film formation.
Experimental and density functional theory calculations suggest that due to the higher electronegativity of the fluoroalkyl group, PFPACl may preferentially dissociate into the form of R-NH3+-Cl-. Consequently, the binding of 2,2,3,3,3-pentafluoropropylamine salt with methylammonium vacancy defects is stronger than its binding with 3,3,3-trifluoropropylamine salt, while the anion Cl- interacts sufficiently strongly with iodomethane vacancy defects and under-coordinated lead ions in FPSCs, allowing PFPACl to uniformly cover the entire surface of the perovskite thin film and more effectively match the energy levels of the hole transport layer. Ultimately, FPSCs modified in situ with PFPACl achieve a photovoltaic conversion efficiency of 23.59%, retaining 90% of the initial efficiency after 1000 hours, demonstrating excellent operational stability.
This research was a collaborative effort by the team led by Dr. Xueqing Xu from the Guangzhou Institute of Energy Conversion, Chinese Academy of Sciences, in cooperation with researchers from the Federal Research Center "Crystallography and Photonics" of the Russian Academy of Sciences and the Zhengzhou Research Institute of Harbin Institute of Technology. The study received support from the Foreign Expert Program of the Ministry of Science and Technology of China, the International Exchange Program of the Chinese Academy of Sciences, and the Strategic Priority Research Program of the Chinese Academy of Sciences.
For more information, refer to the related paper: https://doi.org/10.1002/adfm.202405078
