Effect of water on structural, optical and hot carrier cooling properties of MASnI3 perovskite

Understanding the stability, carrier transport and relaxation of Sn based perovskites CH3NH3SnI3 are of high interest to develop lead free perovskite solar cells. In this study, we performed first principles and non-adiabatic molecular dynamics simulations to address the electronic, optical, and hot carrier relaxation dynamics of the pristine CH3NH3SnI3 and its monohydrated phase CH3NH3SnI3.H2O. Our results show that the water molecule interacts strongly with the organic cation by forming hydrogen bonding, while having also an interaction with the iodide ions. Our study also indicates that the water molecule has in general a negative impact on the optical properties of perovskite materials. In fact, the water molecule reduces the absorption of the system mostly in the visible range of the solar spectrum, and it leads to a faster hot-carrier cooling and to an increase in the polarization of the material.