The effect of permanent electric dipoles on the stability and photoelectric properties of MAPbI films

Hybrid organic-inorganic perovskites have attracted wide attention due to their excellent photoelectric properties, but their stability is still one of the main obstacles to large-scale applications. Recently, the introduction of electric dipoles has become a new strategy for improving the stability and performance of perovskites. Herein, we study the stability and the photoelectric properties of CH 3 NH 3 PbI 3 (MAPbI 3 ) films fabricated with the addition of different amounts of ferroelectric poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)). It is demonstrated that a suitable addition of P(VDF-TrFE) not only enhances the crystalline stability but also improves the light absorption, photoluminescence, and photocurrent responses of MAPbI 3 . A series of measurements were carried out to reveal that the permanent electric dipole from P(VDF-TrFE) suppresses ion migration due to the electrostatic interaction with the defects and improves the photocarrier transport because of the enhanced electrostatic screening effect, which well explains the improvement of stability and performance of MAPbI 3 films. P(VDF-TrFE) dipoles reduce ion migration and improve film stability via the interaction between ferroelectric dipoles and the ions in MAPbI 3 , and enhance the photoelectric performance of MAPbI 3 by reducing the trap-assisted capture radius.