Light enhanced moisture degradation of perovskite solar cell material CH3NH3PbI3

Abstract

To understand the light enhanced moisture degradation of CH₃NH₃PbI₃ (MAPbI₃) material, we carry out a series of first principles calculations and find the decisive role played by the giant photostriction effect. The photostriction effect in MAPbI₃ material changes the charge distribution and thus the bonding interactions between atoms. This effect enhances the adsorption and penetration of H₂O molecules nearby the MAPbI₃ surface after the above band gap illumination, which is ascribed to the alternation of bonding interactions between MA molecules, H₂O molecules and PbI networks. Owing to the straightening of the PbI networks induced by the photostriction effect, the band gap of MAPbI₃ decreases, leading to more photon absorption and thus self-accelerated photostriction processes. Hence the photostriction effect could accelerate the moisture decomposition of MAPbI₃ perovskite under illumination. Therefore, to develop perovskite solar cells with strong moisture resistance, an effective strategy is to develop perovskite materials with no or a minor photostriction effect.