The influence of A-site dipole moment on iodine migration in perovskite films revealed by transient ion drift

Ion migration is regarded as the chief culprit for the long-term instability in perovskite solar cells (PSCs), and iodine ions are the most subjects to migration in PSCs. Strategies, such as grain size engineering, chemical bonding engineering, steric impediment effect, and interface passivation, are employed to suppress the iodine migration but unfortunately are unable to completely eliminate it. Here, the influence of the dipole moment of A-site ions on iodine migration has been comprehensively investigated for perovskite films based on different A-site cations via a transient ion drift (TID) method. TID results demonstrate that the decrease in the strength of the dipole moment of A-site ions can lead to a decrease in the activation energy (EA) of iodine ions. Therefore, this work suggests that increasing the strength of dipole moment of A-site ions can be utilized as an effective strategy for suppressing iodine migration in perovskite films providing critical insight for enhancing the long-term stability for PSCs.