Enhancing performance and stability of perovskite solar cells through interface dipole engineering with perfluorinated ammonium salts

The introduction of PFDAI passivates the surface defects of the perovskite and induces the formation of a spontaneous interfacial dipole layer via its fluoride groups. This effectively adjusts the dielectric properties of the perovskite surface, reducing the exciton binding energy and resulting in an improved power conversion efficiency of 25.15%, with a high open-circuit voltage of 1.171 V and a short-circuit current density of 25.73 mA cm−2. [Display omitted] •PFDAI passivates the perovskite surface defects and simultaneously induces the formation of an interfacial dipole layer.•PFDAI effectively adjusts the perovskite surface’s dielectric properties, reducing the exciton binding energy.•A downward shift of the Fermi energy level is achieved, improving the charge-carrier dynamics within the PSCs.•The resultant PSC exhibits a champion power conversion efficiency of 25.15%. Despite significant progress in perovskite solar cells (PSCs), non-radiative recombination losses caused by deep energy level defects in perovskite films and energy barrier between the perovskite layer and the hole transport layer remain the primary obstacles limiting further enhancement of their power conversion efficiency and long-term stability. In this study, by employing density functional theory calculations, we investigated the impact of the number of fluorine groups on the electron cloud distribution and dipole moment within passivated molecules, specifically methylammonium with varying perfluoroalkyl chain lengths (CH2NH3(CF2)nCF3, n = 2,5 and 7). The results demonstrate that 1,1-H-perfluorodecyl iodide ammonium (PFDAI) exhibits the optimal dipole moment and serves as a passivating agent for the perovskite film, possessing exceptional defect passivation capability and significant hydrophobicity. The synergistic effect of perfluorocarbons and ammonium groups on FA+ and uncoordinated Pb2+ serves to adjust the Fermi level of the perovskite film and the energy barrier for hole transition, thereby promoting charge carrier migration. As a result of these enhancements, the efficiency of the solar cells ultimately increases significantly to 25.15 %. Under conditions of 20 % relative humidity and a temperature of 25 °C, the retention rate of the PCE remains as high as 90 % after 1000 h of aging tests.