A study for polymer-based passivation mechanism: Insights of island-growth crystallization and carrier dynamic in perovskite films

Polymer has been widely used for modifications in perovskite films. However, its comprehensive and complex mechanism is still lack of in-depth research. This work presents the possible mechanism for crystal growth in perovskite films under passivation circumstance. Through the crystallization and carrier dynamics analysis we establish an island-crystal growth model with low concentration precursor solution, it predicts that the curve of additive weight ratio versus film performance will reach a peak value and then decline to a mediocre level. We further set several experiment groups and test this hypothesis with a series of characterizations. For the optoelectronic performance, passivation enhances the photosensitivity (I-light/I-dark) to similar to 1020%. The aging test under an elevated relative humidity (85%) demonstrates the passivated devices extend the lifetime to 96 h, which is 3 times higher than the reference group. In addition, the encapsulated group shows a really stable performance in 240 h storage, indicating polymer passivation has a great potential for suppressing ion migration effect in the perovskite material.